Talk:Mass-to-charge ratio

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[edit] Real Discussion Here

This article is way too opinionated and carries way too much of someone's POV rather than presenting an issue of some debate in a balanced fashion. It would be nice to see it present the strong arguements for change while fairly representing m/z as a widely accepted standard that has great utility.--134.9.228.11 18:40, 3 April 2006 (UTC)

  • m/q is more original than m/z. People that want to change to a so called m/z are the ones that should present some strong arguments. 195.186.150.165 14:41, 4 April 2006 (UTC)
  • there is no utility in m/z that the traditional m/q would not have. 195.186.150.165 14:41, 4 April 2006 (UTC)

I have made great effort to accurately and fairly represent all points of view and the support for each viewpoint while accurately representing reality. If you are going to cover a specific POV please do it within the context of representing the POV not as advocacy. There is room for all POV's just don't represent opinion as fact. Yes, there are lots of facts that can add to make a good arguement but that doesn't mean that it changes the nomenclature conventions. You may be of the opinion that the nomenclature should change to be more logical and consistent with physics but that does not mean that it has changed already. Also please discuss what might be more balanced if you disagree with the balance. Wholesale deletion of comments is vandalism. Wholesale deletion (or reversion) of articles without discussion or consideration of other POVs is also vandalism. Notice that all of the facts previously presented are for the most part intact or even improved. --134.9.228.11 22:09, 3 April 2006 (UTC)

  • Whereas m/q is well defined and clear people favoring m/z do not even agree if m/z has a dimension or is dimensonless. You, for example, claim that m/z is both with and without dimension (???). Does that not bother you? A physical quantity can't have both, a dimension and no dimension. This is absolute nonsense and your own POV. Unless you show a reference that states that a physical unit can have both, a dimension and no dimension, you have to decide on one way. IUPAC orange book clearly states that m/z is dimensionless. Hence, remove all the units from your writing or show a reference where some official entity says that m/z has the dimension mass/charge. (And please, do not mix up dimension with units again). Your writing shows once more that the concept of m/z is completely confused. Please read below why m/z is wrong. 195.186.150.165 14:41, 4 April 2006 (UTC)
  • Cite: m/z is used nearly exclusively in mass spectrometry ... - so why does the mass spec community need a special symbol and cannot use what is widely used by the rest of the scientific community?
  • ... and carries essentially the same meaning and scales identically as m/q when used in the sense of u/e, Da/e or Th above. - so why cant you just use the traditional m/q then?
  • The use of m/z, however, implies this specific non-SI scale not the SI kilogram/coulomb (kg/C) scale sometimes meant by m/q. - Well, that contradicts the IUPAC green book chapter 1.1 where it is stated that a symbol for a physical quantity DOES NOT IMPLY ANY UNITS. So please remaove this sentence unless you show a better reference.
  • The units of m/z are most often omitted. - Most people learn in kindergarten that if you omit the units from a result, the result is wrong. The IUPAC clearly states in the green book: a physical quantity consists of a numerical factor and a unit. The notion that units can just be omited is your POV unless you show a reference.
  • This implies that it is either unitless or a unit itself. - wow, I really like this one. You can't even decide if m/z is a unitless physical property or a unit? This is what I call confused. Please figure this one out before you write about it.
  • It is argued that since all masses are relative to the atomic mass constant (1/12 of a carbon 12 isotope) that the m in m/z is truely unitless. - my dear, all measurements are made relative to a standard! For example, the Eiffel tower relative to the standard meter stored in Paris is 300 times larger. So is the Eiffel tower length l= 300 ? NO! It is l = 300 m.
  • When you consider that any mass spectrometer is calibrated relative to a standard- well, EVERY measurement system is calibrated to a standard. Otherwise people at NIST would be jobless.
  • So what is really being measured is a relative mass-to-charge. - exactly - like in any other measurement too. The height of the Eiffel tower is also measured relative to a meter stick. This really is not an argument for omitting the units. With this argument you would have to omit all units! Now, please show me the reference where it says we don't need units. My dear, you have a very deep lack of understanding in the nature of measurments. PLEASE READ THE IUPAC GREEN BOOK. It is all in there.
  • Now here is a good one: In analytical chemistry, which includes mass spectrometry, .... Do you really think just because analytical chemists sometimes use a mass spectrometer, the whole field of mass spectrometry is included in analytical chemistry? What about those nuclear physicists, cosmologists, historians, biologists, MDs, ... that use MS ? Do they all become analytical chemists?
  • it is common practice to report results in units which are consistent with what is actually being measured - ah, you do try to use consistent units? That is good to hear. Unfortunately m/z is not one of them.
  • Advocates of m/z usage argue: why not call the new unit m/z as has been essentially the case in common usage for decades? - Well, because most m/z advocates argue that m/z is dimensionless which means it does not have a unit (see IUPAC orange book), but you argue that m/z IS a unit. Maybe m/z advocates should first get their act together and decide what m/z really is before they try to persuade the rest of the scientific community to change to m/q. Is that an idea?
  • BTW: if m/z IS a unit, how come some m/z users still combine it with the unit Th? Wouldn't this amount to square thomson? - Fact is: with m/q you don't have any of these problems. Everything is logic, clear, well defined, and according to the IUPAC standart. So why do you not just use the m/q instead of confusing yourself with the m/z?


Well, thanks for respecting the space and the criticism. A couple of pointers though. The entries are supposed to written in a factual, encyclopedic style. I have edited your editorial, argumentative style in a few places. Please refrain from editorializing in the article. Do it here. A not necessary but perhaps helpful piece of advice for you: If you are arguing a point (here on the discussion page) it is not effective rhetoric to insult those who you are trying to convince. I personally ignore insults and look for your argument; however even so I find that it contains a lot of rhetoric and is more interested in winning an argument than in accurately representing the facts. I have no interest in an argument. In fact I really don't care about what should be done only about facts. I have searched for constructive criticism in your long critique here and have made some improvements to the article based on them. --Thanks In terms of criticism I can offer you (other than style and avoiding combativeness) I am actually very concerned that your usage of m/q is incorrect or at least slightly misrepresentative. I actually have a signifcant physics background and I have never once used m/q in the units that you are using. They seem entirely mass spectrometry specific. I think it is great to present how some have proposed changing the mass spectrometry specific units to be more consistent with physics, but let us not forget about the physicists and engineers who use exclusively kms or gms units for the most part. This brings up a point that you are free to dismiss but thinking as a physicist I never really considered the mass-to-charge ratio to be anything other than just the mass divided by the charge and of no particular importance over any other ratio and thus not worthy of it's own wikipage. It was simply the necessary solution to some physical problems. It held just as much importance to me as say the charge-to-mass ratio and less importance than the distance-to-time ratio. Velocity was worthy of it's own word. I also believe from my limited understanding of other spectroscopies where m/q plays a role that kms or gms units are used. The m/q section seems to pass over this fact very briefly and could be misleading. Perhaps a separate sections for "m/q" and "m/q (mass spectrometry)"? Remember we are presenting facts and are not advocates. We can present factual representations of contraversies and how and why change has been proposed, but keep it real.--134.9.228.11 19:00, 4 April 2006 (UTC)


I did not know that Th is commonly used in physics? Is this true? I certainly understand that is could be used but I am unaware that it is in common usage. From your edits thus far I tend to think that you think it should be, but that does not make it true. My understanding is that it is not even an accepted unit, only a proposed unit. Also the use of m/q in at atomic units??--134.9.228.11 19:18, 4 April 2006 (UTC)

  • What do you mean with "... that Th is commonly used in physics?" Th is used in mass spectrometry and mass spectrometry is physics. Analytical chemists are users of mass spectrometers. My mother is also user of a car, but that does not make her a technician or a mechanic. Analytical chemists should write articles about the great work they do using mass spectrometry, but not about mass spectrometers. In return I will not write about results you guys get with mass spectrometers. It would be a mess, too. Thanks for understanding. Kehrli 19:32, 4 April 2006 (UTC)


Th is not commonly used in mass spectrometry. --134.9.228.11 19:52, 4 April 2006 (UTC)


  • Maybe not by by you. The thomson was proposed by Cooks, R. G. and A. L. Rockwood (1991). "The 'Thomson'. A suggested unit for mass spectroscopists." Rapid Communications in Mass Spectrometry 5(2): 93. These are two of the brightest mass spectrometrists of our time. Do you think there could be a reason that those two proposed the thomson or do you think these great scientists are just nuts?

You take me all wrong. I understand perfectly well why they recommended the change. I've talked to Graham Cooks about it myself and heard his spiel many times. I am not opposed to the idea either. It however simply is not true that it is in common usage. It is a proposed unit. Btw if you ask Graham cooks what field he is in he says that he is an analytical chemist and will veheminantly reject any other labels.--134.9.228.11 20:18, 4 April 2006 (UTC)

  • Ok, you are right, Cooks may be an analytical chemist, but he is a smart one. He proposed the Th. You, however, don't get it. The m/z and the Th are incompatible. m/z is dimensionless, therefore it cannot have the unit Th. m/q, however, has the right dimension. m/q and only m/q is compatible with Th.

I "get it" and I think he makes a compelling point. There are some definate advantages, consistency and clarity to come from such a definition. It is, however, a proposed unit which is not in common usage. That seems to be what you do not get. The fact is that m/z is the law of the land from IUPAC and every MS journal. I'm not arguing what is the better definition simply reporting the fact that there is an established accepted system and a proposed system. I think it is great that you are so enthusiastic about contributing to the justification of the proposed system but it doesn't mean it's day has come and the wiki page should be changed to reflect a decision by IUPAC or all of the MS journal simulataneously switching to Graham Cook's proposed definition.--134.9.228.11 20:43, 4 April 2006 (UTC)

  • you should not distort history. Here is how it really was: first was the mass-to-charge ratio m/q which worked fine for many many years. Then there came some confused analytical chemist and for some unknown reason introduced a flawed new quantity m/z which is ill defined and from which we only know that it is dimensionless and therefore cannot be a mass-to-charge ratio because mass-to-charge raton per definition is not dimensionless. The smarter part of the mass spec community has realyzed the mess and just never changed to m/z and kept quiet. This turned out to be a mistake because in the mean time some journals (mainly journals in analytical chemsitry) require the m/z. The m/z has gotten way too much inertia. Therefore it is big time put a stop on it. I feel that you slowly begin to realyze that m/z is a misconception and that your only defense for m/z is that it is widely used. Here is what Giordano Bruno would has said about this attitude: Truth does not change because it is, or is not, believed by a majority of the people. Once you understand this, you will be free to help me in the fight for the mass spec community. I'll be waiting for you. 83.77.121.120 11:04, 5 April 2006 (UTC)

Maybe you should detail that (with references) in the history section. I think much of what you just said is true minus the editorializing. No amount of logic will make me believe something that isn't true. It might convince me personally of the logic behind the proposed new unit, which I am to begin with (no convincing required) but it won't make me believe that it is in common usage today or has the support of IUPAC. Maybe it could be included in the article as something like.

"A small but vocal group of mass spectrometrists, primarily of a more physical background, advocate the change to the proposed Th unit as standard based on logic and consistency with other unit systems; however, with ubiquitous use, IUPAC support, a long history of use and significant interia such a change away from m/z has not occured to any significant degree. Currently all major mass spectrometry journals require m/z as standard and the definition of Th remains as a proposed definition without the support of any governing bodies."

--134.9.228.11 23:39, 5 April 2006 (UTC)


The use of m/q in mass spectrometry in SI units is common when adressing physical problems such as instrument design.

  • that is neither true nor important. Please remove it.

I have moderated it to sometimes. It is important for exactly the reason that m/q does not indicate units and it is common for students to make the mistake of mixing units or using physics constants in SI units. I don't have a table of physical constants in anything except SI units. Well I do have them in grams-centimeters-seconds come to think of it but those are SI just not standard SI.--134.9.228.11 20:34, 4 April 2006 (UTC)

I think you may have misread the IUPAC definition it says that m/e not m/z is not recommended. m/e was used (probnably moreso than Th) at one point and is not recommended.--134.9.228.11 20:03, 4 April 2006 (UTC)

  • Jesus: m/e is a quantity - NOT a unit. Th is a unit, nor a quantity. Please stop mingeling those.

I never said it was a unit I only quoted IUPAC "The use of m/e is not recommended". May be it is not recommended for exactly that reason. --134.9.228.11 20:18, 4 April 2006 (UTC)

  • of course e is not recomended, because it is a constant rather than a unit. However, Thomson himself used m/e. That was probably before q was introduced as the symbol for charge. BTW: the official symbol for charge is Q, hence according to the IUPAC green book it shoud be m/Q and not m/q. But this would be too frightning for guys like you.

I still don't get your use of atomic mass units as a acceptable unit of m/q??--134.9.228.11 20:29, 4 April 2006 (UTC)

  • where is the problem? There are quantities, dimensions, and units.

Take mass: mass is a quantity for which the symbol m should be used. The dimension of m is mass. The units of m can be any unit of dimension mass, e.g. kg, lb, ounce, amu, Me, whatever you want. m does not imply a unit, but it implies a dimension. Now lets take speed: symbol v, dimension is L/T which stands for length/time. Units can be km/h, m/s, mm/s, c, whatever. Now same for mass-to-charge ratio: symbol m/q (or m/Q is even more correct), dimension is M/Q, and unit can be anything with the correct dimension, e.g. amu/C, kg/C, u/e, Th, whatever.

The problem is that you are saying that the mass-to-charge ratio can have the units [u], which is toatlly and completely inconsistent with everything you've said and is wrong IMO too. I think it may just be a typo?? Maybe you ment to say "with" atomic units rather than "in" atomic units.--134.9.228.11 21:30, 4 April 2006 (UTC)

  • where did I say that? I suppose you are confusing atomic units with the atomic mass unit. Atomic units is a system of units where the electron mass is used as the mass unit, the electron charge is used as the charge unit, and so on. The atomic mass unit amu, however, is just a unit for mass and not a system of units. Note that the amu is not part of the atomic unit system. This makes it very confusing and that is probably the reason why people started to use dalton in place of u or amu. A good decision, in my view.

[edit] Argument for m/z below this line

[edit] Argument for m/z (and replies) below this line

m/z is the currently accepted IUPAC nomenclature for mass-to-charge ratio in the field of mass spectrometry. Nothing more to do but define it, demonstrate its usage and address its history so that those who are interested can understand it. End of argument.

  • is it? So why does the gold book then say
It has long been called the mass-to-charge ratio although m is not the ionic mass nor is z a multiple or the elementary (electronic) charge, e.
To me that very much says that m/z no longer should be called mass-to-charge ratio.
  • Mass-to-charge ratio does have the dimension mass/charge. Therfore, by definition, if m/z is unitless, it has the dimension 1 and hence cannot be a quantity for the mass-to-charge ratio. The quantity mass-to-charge ratio MUST HAVE the dimension mass/charge. There is no choice here. Please read dimensional analysis for more details.

I think you may have misread the IUPAC definition it says that m/e not m/z is not recommended. m/e was used (probnably moreso than Th) at one point and is not recommended.--134.9.228.11 20:03, 4 April 2006 (UTC)

  • no, I did not misread. If IUPAC would think that m/z is a mass-to-charge ratio, they would have written: It IS called the mass-to-charge ratio although m is not the ionic mass nor is z a multiple or the elementary (electronic) charge, e.
  • Jesus: m/e is a quantity - NOT a unit. Th is a unit, nor a quantity. Please stop mingeling those.

"The abbreviation m/z is used to denote the dimensionless quantity formed by dividing the mass number of an ion by its charge number." There is your is'. There is no thomson definition in the gold book at all.--134.9.228.11 20:26, 4 April 2006 (UTC)

  • where did you get this is from? is it really somewhere in an IUPAC document?
  • fact is: There is a long, nicely written and carefully thought out green book from the IUPAC. Read it, it is excellent. Then there is the gold book and the orange book which are badly written, full of contratictions and do not even comply to the green book. They should never have been released. And guess what - they were written by the Analytical Chemsitri Group of the IUPAC. It is because of them that we have this mess.


Here is how th orange book defines mass-to-charge:

"Mass/charge ratio

(m/z) ratio."[1]

Why don;t you show me where the green book defined mass to charge ratio?? I understand that the green book defines mass and charge and as I said before as a physicist mass-to-charge is just a ratio of these two. The green book says nothing about thomsons or "mass-to-charge". It is a reference for physical chemistry and does not have a section on mass spectrometry. Physically it is logical to have the mass-to-charge be the mass divided by the charge but the thomson isn't exactly that either it is the mass divided by the number of charges and incorporating the value e into it's definition as a scaling factor. It effectively makes e=1 and it disappears. As I have said before there is room for unit thomson in this page just don't missrepresent it as common or official. It has a very good supporting argument for adoption.--134.9.228.11 21:01, 4 April 2006 (UTC)

  • Hey, you are starting to understand. The green book defines mass and it defines charge and therefore there is no need to further define the mass-to-charge ratio. I know that the green book is drafted by physical chemists, and that is probably the reason why it is so good. These guys understand physics and don't confuse units with quantities and all that stuff. They are also aware that physicists have defined mass and charge and that there is absolutely no need to redefine mass-to-charge ratio in a new way that is completely inconsistent with all prior science. These guys know what they are doing. BTW: if you think that mass spectrometry is not part of physical chemsitry you may be wrong. I am just now sitting beside a physical chemist who wrote his thesis about mass spectrometry. It would peobably be a very good idea to remove mass spectrometry, the gold book and the orange book from the analytical chemists and put it in the physical chemists hand. I am sure they would do the job much better ond they would not create such a mess. It has come to the point wehre I have to be ashamed to be involved with mass spectrometry. With our m/z we look absolutely stupid in the scientific community.
  • Now about the thomson: the thomson is a unit compatible with the dimension mass/charge and not mass/(charge number). It has nothing to do with what you call charge number and which is the basic reason of the m/z mess. Look, I build mass spectrometers for a living and I can assure you that there are not any dwarfts in there that count either nucleons or charges. Instead there are only fields that influence particles according to their mass/charge. These fields do not care how the charge is divided among internal elementary particles. So please, all analytical chemists, stop with this mass number and charge number mess. Not that these would be inherently bad concepts, but they are completely useless in mass spectrometry. They are not only useless, they are even dangerous in that respect that they confuse some people, especially those analytical chemists. Just forget mass number, charge number, and z and you will see your life becomes really simple. Leave your predjudices behind and try it.

Again you are advocating rather than reflecting reality. I may think that we should base our mass scale on hydrogen and I may have a compelling case but that doesn't make it so. You may disagree with IUPAC but that doesn't change what the universally accepted international governing body of chemical nomenclature says. You may think that analytical chemists are a bunch of hacks and that everything is actually physics and that chemistry does not really exist but that does not make it the prevailing consensus. I would also like to point out that the 45.5 Th is just as much a (physically defined) mass-to-charge ratio as m/z 45.5. The unit thomson does not exist in physics. If you think it does I would like to see the IUPAP definition. It is an invention of an analytical chemist! It is not even an accepted unit in analytical chemistry, although it is occasionally used. The only time I have seen it used is by Graham Cooks himself (an analytical chemist). The only truely correct and consistent use of m/q in physics is to use SI units, as SI units are always prefered over non-SI units. If you were a true purist you would be arguing for SI units. After all they are accepted and used by every scientific field all over the world and are specifically designed to unify the units used throughout diverse fields.--134.9.228.11 20:48, 5 April 2006 (UTC)

  • "The only truely correct and consistent use of m/q in physics is to use SI units ..." No, you are completely 100% wrong. Read the IUPAC: not the name nor the symbol of a quantity does imply a unit. Please, please, start to accept this. It is only your predjudice that makes you beleive that m/q has any favoring for SI units implemented. READ THE GREEN BOOK.
  • Frankly, I don't care if you use hydrogen as a reference as long as you openly declare it. H as a reference might be unusual, but it is still correct. Different from what you think I am not a purist. The reason why I am against the DIMENSIONLESS m/z is that it is wrong, nothing else. It is a misconception.
  • "I would also like to point out that the 45.5 Th is just as much a (physically defined) mass-to-charge ratio as m/z 45.5". No, this is not true. If m/z is really dimensionless, then IT CANNOT BE A MASS-TO-CHARGE RATIO because it then has the wrong dimension. It is just a ratio of some numbers. The physical quantity mass-to-charge ratio requires a unit of the dimension mass-to-charge. End of story. - If, however, m/z is used as a mass-to-charge ratio, then it has the dimension mass/charge and it NEEDS A UNIT. m/z = 45.5 is as wrong as m = 4.5, where you also don't know if the units are kg or lb or g or Da or whatever. READ THE IUPAC GREEN BOOK. EACH PHYSICAL QUANTITY WITH A DIMENSION NEEDS A UNIT. You learned that back in high school.
  • Do you really believe that Cooks is an idiot that he comes up with some redundant unit? I can assure you that he had a good reason, otherwise he would not have proposed it. And the good reason is that he realized that m/z is a mess. Please, please, believe the man, he is a very good mass spectrometrist and he deserves your trust. I trust him. That, by the way, shows that I have nothing against analytical chemists. I am just amused about those analytical chemists that think they are mass spectrometrists and don't even understand the concept of mass-to-charge ratio (Cooks is not one of them). I know, this may again be too harsh against you, but it is symply true. What is the definition of a scale? It is an instrument that measures a weight which is not dimensionless. What is the definition of a speedometer? It is an instrument that mesures speed which is not dimensionless. What is the definition of a mass spectrometer? It is an instrument that measures mass-to-charge ratio which is not dimensionless. But some analytical chemists try to tell us that it actually measures m/z. That makes my laugh and cry simultaneously.

Look, I'm tired of your circular argument. I've told you several times that I understand the argument for Th. I understand how m/z has inconsistencies, blah, blah, blah. I'm not advocating anything, except to accurately represent the factual truth, not what is "right". You seem to want to represent a half-truth. I agree 100% that there are problems with m/z wrt its definition and consistency and I think this should be accurately represented. It is true that people have pointed this out and there are real inconsistencies. It is also true that Graham Cooks has proposed the unit thomson, and you have properly cited it. It is also true that certain recommendations of IUPAC are inconsistent and these inconsistencies can be accurately represented, as facts. I think that Cooks has made a very salient point, but my opinion does not matter and neither does yours. We are here to represent facts not opinion, nor are we here to advocate. FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS FACTS. The language used can represent accurately and fairly two sides of a debate but not advocate. Also we should accurately represent the state of the debate. This is not the place for such a debate to take place. You seem deadset on debating the merits of the Th with me. This is not the place for that sort of thing. We should be debating what the state of the debate is and how to accurately represent it. You seem to think each time I say something like "m/z is recommended by IUPAC" you seem to think that I personally believe that IUPAC is correct in recommending it. What I or you personally thinks is way beyond what an encyclopedia is about. For that matter what is "right" is also outside the scope. What you are doing is like saying that "the US did not invade Iraq, because there were not weapons of mass destruction to begin with." What I am saying is equivalent to "The US invaded Iraq. After several years of searching for weapons of mass destruction little evidence of their existance has been found and the general consensus today is that they did not exist at least in any quantity. Because of this the justification for the invasion remains a contentious issue..." An encyclopedia is not a place for debate but a place for generalized facts. I can only reach a consensus with you if you can bring yourself within the scope of writing an encyclopedia entry. If you are going to persist I do not see that you are contributing to wikipedia.

"NPOV (Neutral Point Of View) is a fundamental Wikipedia principle which states that all articles must be written from a neutral point of view, representing views fairly and without bias. This includes reader-facing templates, categories and portals. According to Wikipedia founder Jimbo Wales, NPOV is "absolute and non-negotiable"." "NPOV says that the article should fairly represent all significant viewpoints, in proportion to the prominence of each."

Failure to comply with wikipedia policies and guidelines is serious and can get you banned. I think I am done with negotiation. I will contact a mediator unless you would like to start debating the facts. I know you feel that there are many facts on your side and that you are trying to state them but you need to parse what are facts and what is an argument. Realize that I agree with most of your facts. E.g. --Cooks proposed the unit thomson, based on logic and consistency with the rest of the scientific community. But I disagree with opinion such as --m/z should not be used. And I strongly reject falsehoods such as the unit thomson is commonly used in physics. This is the last time I will address this issue with you without a mediator unless you choose to adhere to the letter and spirit of the wikipedia policies and guidelines.--134.9.228.11 23:40, 6 April 2006 (UTC)


[edit] Negotiation

  • Now we are talking. Excellent. So let us figure out the facts and get rid of the opinions:
  1. I agree that "m/z should not be used" is an opinion and it should be deleted
  2. I agree that thomson is not widely used and I think I never said so. If I did it should be deleted.
  3. I agree that it is a fact that m/z is wiedely used in mass spec
  4. Since today I also agree that m/z can be used if used consitently. I did some more thinking about it and came to conclusion which I will elaborate later. (this is my POV)
  5. However, it is a fact that m/z is not a mass-to-charge ratio because it does not have the dimension of a mass-to-charge ratio and it is a fact that IUPAC does not explicitly state it is.
  6. it is a fact that the IUPAC m/z definition is shaky, inconsistent, and not very useful and should be improved to be useful. (They know this and they are currently in the process of improving it).


Based on our agreement "The use of m/q with Th, atomic units, SI units is common in physics and related fields." has been changed to "The use of m/q in atomic units and SI units is common in physics and related fields."--134.9.228.11 18:18, 7 April 2006 (UTC)

I disagree with: "Whereas m/q is used as a symbol for the well defined physical quantity mass-to-charge ratio" I don't think that m/q is well defined when including Th and m/e. I think the physics definition is well defined: the mass divided by the charge in units of mass over units of charge. The MS usage is mass-to-"number of elemetary charges" even with Th, that is what the number represents. In MS usage the mixing of units and constants makes it poorly defined. I think that this could be stated as a position or an opion but not in the factual way that it is stated here. --134.9.228.11 18:18, 7 April 2006 (UTC)

  1. Unfortunately I do not have the Cooks/Rockwood article at hand. Are you really really sure that they define the Thomson for a dimension mass/(charge number)? I must say that I would be very surprised if this were the case. I always thought the Thomson is a unit for mass/charge.
  2. m/q is well defined: it is a physical quantity for the dimension mass/charge. The units don't really matter. You can use SI units kg/C, atomic units Me/e, mass spec units amu/e, and, it Th has dimension mass/charge, you can use it too. You are even free to create your own units as long as you explain what you do. Of course this is nor nice and it may not be recomended, but it is consistent and correct. The fact that there are several units in use does not disqualify for well defined. Otherwise mass m would also be ill defined because some people still use lb.
  3. the m/z, however, is not well defined because there is no agreement about it's dimension. Some think it is dimensionless, some think it is mass dimansion, and some think it is mass/charge dimension. That is why it is ill-defined. This, however, could be solved quickly.
  4. the MS usage of m/q is not mass-to-"number of elemetary charges", it is mass-to-charge with units u/e = Th.
  5. above you use m/e as a unit. m/e was never used as a unit. e is the ancient symbol for charge, thats all. Not e is used as a unit and as a constant, this is probably why you confuse m/e with a unit.

I have made several changes to the article that I hope you see as improvements and consistent with your statements above. SOme reorganization as well.--134.9.228.11 18:42, 7 April 2006 (UTC)


Think about what the Th represents. By incorporating the constant e into its definition the net result is that the number represents the mass divided by the number of elemetary charges.

  • no, it represents the mass divided by charge where the charge is in units of the elementary charge. Your conclusion that using e as the reference standard would turn charge into a charge number is wrong. By the same argument the length of the Eiffel tower would be turned into a dimensionless length number by using the meter reference standard. Your POV is completely against all metrology rules. Please read the green book.

Therefore it is a unit that represents the mass per elemetary charge.

  • No, it represents mass/charge. You still have not understood what is in the IUPAC green book. First: e is not a numerical constant (as you treat it), instead it is a physical constant, i.e. it is a constant physiscal quantity. This means e has a numerical factor and a unit, not just a numerical factor. Therefore e = 1.6E-19 is wrong. Correct is e = 1.6E-19 C or e = 1 e. Hence, the numerical factor 1.6E-19 only belongs to e if e is expessed in coulombs. If e is expressed in another unit of charge, this factor changes. For example, if using atomic units, the factor is 1 and the physical constant e becomes 1 e (in the later case e represents a unit). If you consider this fact (read the green book) your formulas become quite different.

Here is a formalized derivitzation since you are of that mindset:

1 Th = \frac{1}{1.602177x10^-19} (\frac{Da}{C})=\frac{1}{e}(\frac{Da}{C})

  • correctly this would read 1 Th = \frac{1}{1.602177x10^-19}(\frac{Da}{C}) = \frac{1 Da}{1.602177x10^-19 C} = 1 (\frac{Da}{e}). Because of this error all your formulas below are completely wrong and you better delete them.

So to compute whatever Th represents you divide the mass by the number of elementary charges that the ion is carrying:

Th = \frac{[mass]}{[number of elementary charges]}\times (\frac{1}{e}\frac{Da}{C})

  • this notation is against all IUPAC rules. I think what you would like to say is:

m/q = n [m/q] = n Th

Why do you think that m/z is numerically identical? The unit Th is a unit of mass per charge number not mass per charge.

  • you are quite wrong. m/z is a quantity and Th is a unit. Therefore your question does not even make sense. Your question should be: Why has m/q expressed in Th always the same numerical factor as m/z expressed in Da? The answer is: since z = q/e and Th = Da/e
m/q = n (Th)
m/(z*e) = n (Da/e)
m/z = n Da ==> the numerical factor n has not changed

It is very confusing and you are confused because they are folding a constant into a unit which is technically very uncool. The true units are Da/"the number of elementary charges". Why are you always dividing your masses by whole numbers? Because it is the charge number!

  • it is obious that you still have not understood the difference between the Th and the mass-to-(charge number) m/z. This difference is very subtile and though very important because m/z is of dimension mass and Th is of dimension mass/charge.

Also, you are a very good example for eliminating the z. z is so easy to mix up with q that it would be better to drop the z entirely. z just confuses those analytical chemists that are not so used tp coping with units. This, of course, is my POV, but you very much back this POV. Here are the facts: Th = Da/e with dimension mass/charge. (as stated above, e has the dimension charge) and not mass/(charge number) which would have the dimension mass (since charge number is dimensionless).

Another deritivation:

m/q=\frac{[mass]}{[charge]}=\frac{[mass]}{[number of elementary charges][charge of one elemetary charge]}=\frac{[mass]}{[charge number]\times e}

  • m/q = [mass]/[charge] is wrong. [] means "units of" and your sybtax does not make sense. Correct would be: m/q is of dimension of mass/charge and [m/q] can be any units of mass/charge, e.g. Th, u/e, amu/e, Da/C, Da/e, u/C, and so on. All those dimensions are correct, even though they may not be very practical.

=\frac{[mass]}{[charge number]}\times \frac{1}{e}(\frac{Da}{C})=\frac{[mass]}{[charge number]}(Th)

Therefore:

\frac{[mass]}{[charge number]}(Th)=\frac{m}{q} NOT Th=\frac{m}{q}

I apologize for the slopiness of units and constants but that is your source of confusion.

  • In this discussion we can not tolerate any sloppyness, because they would confuse analytical chemsists. Therefore please keep to the notations in the green book in this discussion or give references for your notations.

The unit Th times the mass/charge number is equal to the mass to charge. Not the unit Th nor the mass/charge number is the true (physics defined) mass to charge ratio.

  • Th is just a unit for the mass-to-charge ratio, not the mass-to-charge ratio itself.

The unit Th is a unit with dimensions [mass]/[charge number] but since the charge number is unitless its units are (Da/C) since the constant e=1.602177x10^19 C is hidden in the Th.

  • Gee - you are a confused analytical chemist. If the Thomson would be defined as Da/C (which of course it is not) then its dimension would be mass/charge, not mass/(charge number).


I know this is a very confusing explanation ...

  • it is so confusing because it is wrong

... but that is what you get when you start mixing units and constants.

  • Whereas I agree that constants and units should be kept separate, I also strongly state that the two are very simillar. Every physical constant can be used as a unit, too. The original meter that is stored in Paris is used as a reference for all length measurements, but it is also a physical constant. This is why they try to keep the temperature the same, so it stays constant.

The bottomline intuitive explanation is that in the end the number before the Th is the mass divided by the charge number!!!

  • no that is wrong again. Strictly speaking this number is the number in front of the Da divided by the number in front of the e

I think what would be correct from your philosophy would be to report every number as, for example:

m=91, number of elementary charges=2

\frac{m}{q}=\frac{45.5}{e}(\frac{Da}{C})

  • correctly this would read the following: assume you have an ion with 91 Da and charge of +2 elementary charge units (note that the number of elementary charges in this ion is roughly 88, say 45 protons and 43 electrons. The charge of the ion is +2 e).

that way we would not mix units and constants and it would be a mass to charge. This is however unwieldy and all of it is implied in both m/z and Th. Any way this arguement is moot except in regard to charcterizing the unit Th, which you imply is a unit of the physics defined mass to charge. --134.9.228.11 22:55, 7 April 2006 (UTC)


I also disagree that m/z is not a mass-to-charge ratio while m/q in Th is. (m/q in units of mass and charge clearly is) They are numerically and dimensionally identical.

numerically they are, dimensionally they are not. m/q is mass/charge and m/z is mass only.

If you have a case and an issue it is about units not dimensions. The charge number has the dimension of charge!

  • No, not at all. Read your IUPAC documents. charge number is dimensionless.

It is however unitless because it is just a number.

  • if it is just a number then it has no dimension. The definition of dimensionless is: just a number.

Charges are quantized. What are the units of "there are five fingers on my hand"? You could call it "number of fingers" but that is not necessary.

  • you can either create a unit "finger" or you can define as it dimensionless, but you have to be aware. However, if you want to confuse analytical chemists you should do both and they will be confused for a couple of 100 years :-)

They are either both a mass-to-charge ratio or not.

  • No, m/q is mass-to-charge ratio and therefore has dimension mass/charge. m/z is mass-to-(charge number) and therefore has dimension mass.

They are after all interchangeable and numerically identical.

  • They have the same numerical value, but they are not interchangable since they don't have the same dimension.

I would vote for are. Numerically they are both the mass divided by the number of charges and as the number of charges is representative of the total charge it is a form of a mass to charge ratio. You can argue about units but if they are the same numbers they represent the same thing.

  • No, only one of them is a mass/charge. Sorry to be so picky, but if you want to operate with the dimensionless z then do it correctly.

I hope we can clear this up soon. It is about the silliest argument to be talking about two completely interchangeable systems both of which have essentially the same problems hidden in different ways.

  • I completely agree. This is why I keep saying that we should get rid of the m/z. It is not necessary to have m/z and it is a completely redundant term for m/q measured in Th. On the other hand we cannot get rid of the m/q because:
  1. it is older and more traditional
  2. it is necessary for people outside MS
  3. it necessary for doing physics and ion optics
  4. it is consistently defined

One mixes constants with units and the other gives up and leaves off the units all together.

  • No, correct usage of m/z still requires the units Da

But they represent exactly the same thing in exactly the same way. One just happens to be the officially accepted notation.--134.9.228.11 01:41, 8 April 2006 (UTC)

  • they represent almost the same thing but not exactly. mass/charge is not the same as mass/(the net number of elementary charges). If you were a physicist then I would ask you to imagine what would happen if a particle were discovered with an uneven charge. Then, the charge number concept fails more obviously. You could no longer count charges. In this case the concept of charge number would imply to get rid of all units whatsoever. The Eiffel tower would then be 300, and everybody would be confused because it is no longer clear what units are used. In contrast, m/q is much more universal. It is useful for all science, not just MS, and it is usefull without the e charge quantization (which we now know is not universal because quarks have charge 1/3 and 2/3). Finally m/z has no advantge over m/q in Th. m/z is a ill defined term for narrow minded analytical chemists that do not know about the wider concepts of science and are sufficiently stubborn not to care either. Sorry to put it so harsh, but this is a very objective conclusion from our discussion. You yourself talk about the "real m/q".

[edit] How is the Th defined?

"Are you really really sure that they define the Thomson for a dimension mass/(charge number)?"--------------------- Yes the proposed definition is "1Th == 1 u/atomic charge"--134.9.228.11 01:50, 8 April 2006 (UTC)

  • in this case the Th is defined for mass/charge not for mass/(charge number). This is what I suspected.
  • What??? By atomic charge they clearly mean the number of atomic charges. Read the paper. Which is the charge number.--134.9.228.11 17:01, 10 April 2006 (UTC)
  • No!!!! "atomic charge" is not the same as "number of atomic charges". The first has the dimension charge, the later is dimensionless. If physical quantities have different dimensions they cannot be the same. E.g. 1 kg is not the same as 1 rad, even though the numerical factor is the same. They are not the same because they have a different dimension.
  • Atomic charge = number of atomic charges x size of one atomic charge (units: charge = dimensionless x charge).

[edit] let us define m/z

let us start with the following equation on which we hopefully can agree: 1 Th = \frac{1}{1.602177x10^-19}(\frac{Da}{C}) = \frac{1 Da}{1.602177x10^-19 C} = 1 (\frac{Da}{e}).

Now it is you turn to

  1. define m/z in a consistent way, including the dimension and the units,
  2. show that Th has the dimension mass/(charge number)

good luck. (Hint: you are allowed to use all my formulas - this should make it easy for you)

m/z can be defined identically.

m/z is almost: \frac{mass in Da}{integer number of elementary charges}(\frac{Da}{e})

however, since the "units" are not units they are dropped by convention and you get

m/z is: \frac{mass in Da}{integer number of elementary charges}

Wrong:
  • You write: "since the "units" are not units" ??? Units are units and you are not allowed to just drop the units. Units are an essential part in a physiscal quantity and it is not correct to just drop them.
  • Example: "the Eiffel tower is 300 m" is a correct statement. If you drop the unit you get "the Eiffel tower is 300" and it becomes wrong, because now nobody knows what you are talking about.

A more complete definition of Th:

m/q (Th) = \frac{mass in Da}{integer number of elementary charges} (\frac{Da}{e})

The thomson is a unit and its definition is 1Th = 1Da/1e. Your definition is the definition of a physical quantity mass-to-charge ratio measured in thomson, which is not the same. A physical quantity includes (1) a numerical factor, and (2) a unit. The thomson is just a unit. Your mixing up of quantity and unit is the equivalent of mixing up car and steering wheel. Each car has a steering wheel, but a steering wheel does not make a car, and they are not identical.

Again the numbers are identical.

So what? See this example: 1 kg = 1 km. The numerical factors are the same. Still there is a big difference. These are not identical quantities. The same is true for 1 u/e and 1 u and 1. They are not the same quantities even though the numerical factor is the same everywhere.

There is simply a difference in notation.

Wrong: it is a different quantity. m/z = 1 Th and m/q = 1 Th are just different notations.

m/q (Th) creates a new unit to deal with needing to extricate the number e from the final number and m/z just drops units all together

Wrong: it is not allowed to just drop units

and extricates the number e in the process. As I have said before my personal opinion (and you seem to only care about what should be done, not what is convention) is that there should be a unit e. with the following definition:

1e = 1.602177x10 − 19C

Wrong: This unit does indeed exist. It is the unit of charge in the atomic units system.


However e is not a unit but a constant. But again my opinion does not matter. --134.9.228.11 17:59, 10 April 2006 (UTC)

Your opinion is wrong: it is both, a unit and a constant. Read atomic units

Conclusion: you still failed in giving a solid definition of m/z! Please try again without illegal unit dropping.

[edit] Purpose of this article

I strongly object to your making this a purely mass spectrometry article. There are other uses of mass-to-charge that are the physically defined mass-to-charge (which you mistake m/q in Th to be). Please stop with your agenda and represent the facts, apropriately and proporitonally. Mass spectrometry is not the only usage of this phrase! Please give appropriate room to the much more common m/q. I don't think that it requires alot simply a clear separation between the usages and clear definition. The MS part requires much more explanation whereas the physical part is intuitive and obvious but don't mix the two.--134.9.228.11 18:14, 10 April 2006 (UTC)

[edit] how the m/z does make sense

Here I would like to elaborate how m/z can be made consistent. Start with a quantity:

m/q = n Da/e = n Th (units and constants are in bold)
m*(e/q) = n Da

now, we set z = q/e and we get

m/z = n Da -> voila

here are the facts:

  1. m is a symbol for mass, recomended by IUPAC
  2. above z is in line with the IUPAC gold book charge number definition
  3. m/z has the dimension mass
  4. m/z therefore needs a unit, choose whatever mass unit you want: Da, amu, u, kg, lb
  5. many people already label their mass spec x-axis with: m/z (Da) -> that is correct and consistent

Big advantage of this approach: a mass spectrum is indeed a mass spectrum, not a mass/charge spectrum. Disadvantage: z is known only in the small mass spec community.

My POV: this is probably how m/z was originaly meant, before the wrong definition in the IUPAC gold book confused everyone. Many people still use it in exactly this way. m/q (Th) is probably still better, but m/z (Da) is also very good. m/z should also get a good name. I envision something like "mass per net charge carrier" or "mass per charge number".

What do you think? Can you live with that?

To Do List:

While I disagree with your to do list. (We should discuss first.) In terms of your personal POV I personally agree very much with your thinking, but that is irrelevant. One point you should think about more is "Big advantage of this approach: a mass spectrum is indeed a mass spectrum, not a mass/charge spectrum." No it still is a mass-to-"number of elemetary charges" spectrum. Your doubly charged ion will not show up at its mass in Da. There is simply no way to make things nice and clean and useful. Even the Th approach has its stickiness and it is a stretch to claim that it is consistent with the rest of science (incorporating a constant into a unit). I personally think that we should redefine the SI unit of charge to be one elemetary charge and create the unit e to replace C (or redefine C==e*mol), solving our problem and solving some others as well. While we are at it some other changes that would be good are to make the mole == 10^24 exactly, adopt the gram as the primary SI unit and make it equal to one (new) mole of hydrogen. It's fun to dream.--134.9.228.11 18:58, 7 April 2006 (UTC)

The thomson does not have any stickyness and its definition is consistent and rock solid, whyle the m/z promoters cannot even agree on the dimension of m/z. BTW: it is VERY usual to derive a unit from a natural constant. In the system of atomic units for example ALL units are derived from natural constants. One can even go further and argue that the the original meter in Paris also represents a constant (a constant length, not a natural constant). This means ALL units are derived from constants. 85.0.31.211 18:01, 12 April 2006 (UTC)

[edit] Argument against m/z below this line

The concept of the dimensionless mass-to-charge ratio m/z is a misconception and should no longer be used. Use m/q instead.

[edit] Physical quantities

The IUPAC green book about Quantities, Units and Symbols in Physical Chemistry explains:

Any value of a physical quantity Q can be expressed as the product of a numerical value {Q} and a unit [Q].
Q = {Q} x [Q]
Neither the name of a physical quantity nor the symbol used to denote it, implies a particular choice of unit.

some examples:

  • l = 3 m (the physical quantity length is three meters)
  • m = 5 kg (the physical quantity mass is 5 kilograms)
  • m = 5 u ( the physical quantity is 5 unified atomic mass units)
  • q = 3.5 C ( three and a half coulombs)
  • q = 2 e (two elementary charge units)

In the following it will be demonstarted that the m/z used by so many mass spectrometrists does not comply to above fundamental instruction about the measurement of physical quantities.

In this article symbols for a physical quantity are written in italics (e.g. q), units are written in bold (e.g. kg). n represents a numerical value that is a real number and z represents a numerical value that is a whole number.

[edit] What the IUPAC says

Current IUPAC definition

The abbreviation m/z is used to denote the dimensionless quantity formed by dividing the mass number of an ion by its charge number. It has long been called the mass-to-charge ratio although m is not the ionic mass nor is z a multiple or the elementary (electronic) charge, e. The abbreviation m/e is, therefore, not recommended. Thus, for example, for the ion C7H72+, m/z equals 45.5.

Critique
  • why should dividing a mass quantity by a dimensionless quantity yield a dimensionless quantity?
  • why is m not a mass and what is it then?
  • if z is not a multiple of the elementary charge what is it then?
  • the quantity mass number has the official symbol A - why is it not used?
  • everyone knows that mass spectrometers measure the mass to charge ratio - so why the fuss about mass numbers and charge numbers instead of just using plain mass and charge?
  • how can you conclude from m is not the ionic mass nor is z a multiple or the elementary (electronic) charge, e that therefore m/e is not recomended? Where is the logic?
  • why should anyone substitute z (a physical quantity) with e (a unit)?
  • why does IUPAC issue a definition that completly contradicts it own green book?


[edit] Three reasons why m/z is wrong

1) Mass spectrometers measure the physical quantity mass to charge ratio which is not dimensionless. This is a simple fact.

2) There are some dimensionless physical properties. The most famous one is the Reynolds Number Re and the most common in mass spectrometry is the mass resolving power R = m/dm. The characteristic of such dimensionless properties is that it does not matter what system of units you use: whether you use kg or Da, m/dm will be the same. This is not the case for the mass-to-charge ratio: whether you use kg or Da makes a big difference.

3) If a non-dimensionless physical quantity is measured we should use units. This is exactly what units were invented for. Units are a cultural achievement like the wheel or the language and they should be used.

[edit] What went wrong

Let us investigate where the z is coming from: start with Q = n x [Q] and use it for a charge:

q = n x [q]

Now, if [q] is the elementary charge, n will always be a whole number. Whole numbers are often indicated with z. Therefore in this special case we could write:

q = z x e

This means z is not the symbol of charge as it is used by mass spectrometrists (m/z), it is only the numerical factor belonging to the unit to form a quantity. Hence z is the number that you read from the x-axis and should not appear in the label. Compare this with a charge measurement:

q = n [l] or, when measuring in coulombs: q = n C, and when measuring in elementary charge units: q = z e.

Now, if you label a x-axis that represents a charge, do you label it with “z” ? No! It is labeled with q (C) or q (e). Consequently we should eliminate the z because it is the source of the whole confusion.

[edit] A correct approach

[edit] What symbol to use?

Here are the basic facts:

  1. mass spectrometers measure the physical quantity mass/charge
  2. the symbol for mass is m
  3. the symbol for charge is q (it is actually Q, but q is also often used).
  4. we need to choose a symbol for the mass to charge ratio. Possible choices are m/q, m/z, and it would actually be even more correct to have a single symbol like μ or mQ but this is to far ahead of the mass spec community.

Note: as stated above, the symbol m/q is completely independent on the units [m/q] that are being used. Analogously it is common to use the the symbol for mass m with kg as well as with lb:

m = 3 kg
m = 6 lb

[edit] what units to use

Now we have settled the question of the symbol. Let’s turn to the second part, the units to be used. Obviously, everyone in MS wants to measure the mass in u and the charge in elementary charge units. Therefore

m = n [m]
q = n [q]

becomes:

m = n u
q = n e

Hence, the unit mass spectrometrists use is [m/q] = u/e. That is by the way what everyone uses, even when they claim to a dimensionless m/z.

m/q = n u/e

Note how clumsy it is to say: "the ion C7H72+ has a mass-to-charge ratio of 45.5 atomic mass units per elementary charge units".

[edit] A better approach

The problems with above approach are:

(A) e is not an official unit and therefore cannot be used
(B) "atomic mass unit" is a very clumsy name and is gradually replaced by dalton (Da)

(A) is a severe problem: everyone uses a unit that does not exist officially. There are four ways out:

  1. we make e official (in which case we should not call it e, but for example millikan (Mi).
  2. we create the Th (which de facto creates e through the back door)
  3. we use kg/C

(3) is unpractical, (2) requires (1), therefore there is no way around (1)!

Problem (B) is best solved by adopting the dalton Da

So we end up with:

m = n Da
q = n Mi
m/q = n Da/Mi

[edit] An even better approach

m/q = n Th

where 1 Th (thomson) = 1 Da/Mi

[edit] The correct approach

mQ = n Th

but this is too far ahead for the mass spec community

[edit] Conclusion

Say:

the ion C7H72+ has a mass-to-charge ratio of 45.5 Th
the peak at 45.5 Th is probably C7H72+

[edit] See also

[edit] Nominated for POV Check

It is great to see this debate, but the main article needs a neutral point of view. Please outline the facts in the main article and editorialize in the Talk/Discussion page. In particular, it would be useful to get some details of the shift from e/m to m/e to m/z, which must have happened in the early to mid 20th century. Many of the critical papers are now on-line. Yes, m/z is a clunky notation, but if you want to change it, you will need to do some research and lay out some solid arguments. I'm willing to listen and carry any reasonable arguments forward.

Here's a starting point:

-- Kmurray 02:12, 11 April 2006 (UTC)
  • In your opinion, where is the neutral POV missing in the main article? Could you please give a detailed list instead of just placing a POV check? 85.0.31.211 15:01, 12 April 2006 (UTC)
  • in one of the articles in your link it is Thomson himself who uses m/e, not m/z. And his e is not dimensionless. 85.0.31.211 18:16, 12 April 2006 (UTC)


As the "counterpoint" to the m/q (Th) argument I would like to say that being a logical, reasonable and consistent notation is not enough to make it the accepted standard and worthy of dominant or even substantial representation in the article. I (personally) generally agree with the argument for change to a "better" notation/unit system; however, the only factual representation of this is that m/q (Th) is a logical and well thought out alternative to m/z but is extremely rare in usage and not recognized by most people, journals, governing bodies. m/z is close to universal in its domain. An important point that also needs to not be misrepresented is that m/q (Th) is computed in an identical way to m/z, and they only differ in notation. They are both the mass in Da divided by the number of elementary charges. This differs from the physics and most other usage which is the mass divided by the charge in accepted units of mass and charge. Let's try to inform the casual (scientific) reader with factual information rather than convince the expert to reasess convention.--Nick Y. 17:30, 11 April 2006 (UTC)

Nick:

  1. m/z is far from universal. It is used by only one of many scientific communities that use mass-to-charge ratio: the mass spectrometrists. Most other scientific fields dealing with mass-to-charge ratio (lithography, electron microscopy, Auger spectroscopy, nuclear physiscs, cosmology, ...) use predominantly m/q.
  2. even in the mass spec communitiy many people use m/q or m/e.
  3. m/q follows directly from the Lorentz and Newton formula, whereas m/z confuses the fact that the mass-to-charge ratio is coming from those formulas
  4. m/q is well defined whereas for m/z people do not even agree what dimension it has
  5. as long as some people regard m/z as dimensionless it is not even clear that m/z is a mass-to-charge ratio.
  6. Thomson himself used m/e (or e/m). This means m/z is not original.
  7. if you think that m/z is a mass divided by a number, m/z would be of dimension mass and therefore it should not even be on the mass-to-charge ratio page because mass-to-charge ratio has dimension mass/charge, not mass. We should move it to the mass page or make an own page. (the physiscal quantity length is also not discussed on the speed page - to make an anology). m/z should only stay on the mass-to-charge ratio page if people using it can agree that it has mass/charge dimension, e.g. it must have units u/e or amu/e or Da/e or Th or kg/C. Otherwise it would not be a mass-to-charge ratio and it would have to be moved.

Considering all this, m/z is already overrepresented in the mass-to-charge page. Science does not exclusively consist of mass spectrometry. If the mass spectrometry community wants to go a separate route than everyone else, they may do this but they should not pretend it is the only way, and they should stop enforcing their opinion on everyone else in the scientific community. 85.0.31.211 10:05, 12 April 2006 (UTC)

Alright here is my repsonse to each point, please understand what I am saying and don't assume that I disagree:

  1. I agree %100 with your first point. No question, never has been.
  2. I also agree that in mass spectrometry some people use m/q (as the x-axis), but this is a small group. I can also agree with that most people in mass spectrometry use m/q as the physical quantity (mostly in SI units, mass divided by charge) not as the x-axis but as the physical quantity, for solving physics problems (not chemical problems). m/e is very rare in modern usage and primarily exists in very old literature or in speaking about old literature.
  3. I agree that m/q (the physical quantity) derives directly from the Lorentz equation and the physical solution of a charged particle. The second half of your statement is unclear but I think that it is mistaken. m/z is the solution to exactly that same set of equations only q has been separated into teh number of charges z and the elemetary charge e(q=z*e):
\frac{m}{z}= e \times \frac{\mathbf{E}+ \mathbf{v} \times \mathbf{B}}{a}

Of course this is most often computed by dividing the mass by the number of charges.

(4)

I agree 100% that m/q is well defined, when used in the physics sense only. m/q is well defined until you start using it in the sense of a mass spectrometry x-axis ala m/z and using Th. Then it becomes poorly defined or at least as poorly defined as m/z. There is an authoritative definition of m/z in IUPAC. Again some people do not conform with the m/z standard by using non-standard units, just as some people advocate the use of m/q (Th) (a non-standard unit for the x-axis) as the x-axis in mass spectrometry.

(5)

m/z is the mass divided by the number of elementary charges and is called the mass-to-charge ratio weather you like it or not. btw m/q in Th is the mass divided by the number of charges as well.

(6)

I agree. Irrelevant. m/z is the standard (for the x-axis of a mass spectrum, not the physical quantity.

(7)

I would be willing to make a separate "mass-to-charge ratio (mass spectrometry)" and have disambugation but the unit Th will have to come with it since it is used exclusively in MS.

Points I would like to get consensus on (a short list to start to make it tractable):

(A) There is only disagreement in mass spectrometry usage. There is consensus of the physics meaning of m/q.
(B) m/q (Th) (mass spectrometry usage) is computed identically to m/z as the mass in Da divided by the number of elementary charges.
(C) m/z is recommended by IUPAC as standard notation in mass spectrometry (for the x-axis or when refering to that scale)
(D) The unit Th is not recognized by IUPAC, IUPAP or any governing body that recommends nomenclature. It is a unit proposed more than a decade ago by Cooks, who we all respect, but it is not in particularly common usage today. It is however used by some. Additionally its limited usage is confined almost exclusively to mass spectrometry.

--Nick Y. 21:06, 12 April 2006 (UTC)

Here are my comments to your points, where I disagree:

(3)

your formula for m/z is finally coherrent and when you check the dimension on the right side you will see that it has dimension mass. Therefore (your) m/z also is a mass. Therefore, (your) m/z should not be on this mass-to-charge ratio page. Thanks for proving this point. (BTW: I hope that you realyze that this formula is much more complicated than the formula using m/q and that therefore all textbooks use the m/q formula and that no textbook and no paper ever used your m/z formula and that it is therefore original research, which is not really wellcome on Wikipedia.)

(4)

I strongly disagree that m/q becomes ill defined on an x-axis. m/q is well defined, also and specially, on an x-axis. An x-axis can hold any well defined physiscal quantity and I can assure you that an x-axis does not somehow misteriously turn a well defined quantity into an ill defined quantity. m/q is also well defined for usage by chemists. I do not understand why analytical chemist think the m/q is not good enough for their use. I have never seen an argument. If you have one, please let us know. It is my POV that analytical chemists should ask their IUPAC body to set them free to use the well defined m/q instead of the flawed m/z.

(6)

m/z is the standard set only by IUPAC which is a body of chemists. Those scientists from other fields have no obligation to follow IUPAC rules nor should they as long as IUPAC sets standards that are impractical for their work and also ill defined. If IUPAC wants to make rules for the whole mass spec community they better include some delegates from other fields in the cometees that help them coming up with coherrent definitions, or they better listen to smart members like Cooks.

(7)

The Th is a unit for mass/charge and can be used by anyone dealing with mass-to-charge ratios q/m. The Th, however, does not have the dimension mass that you claim in your definition for m/z. Therfore your m/z is incompatible with Th. The IUPAC definition of m/z is also not compatible with Th because according to their definition m/z is dimensionless (which, according to my POV and the IUPAC green book, is flawed, but this is another story).

Then my comments to your points of consensus:

(A)

There is no difference (concerning mass-to-charge ratio) between MS and physics, since MS is a part of physics. The separation of MS and physics is very artificial and random. I agree to the following: whereas in physiscs the mass-to-charge ratio is well defined, analytical chemists have incoherrent usage of a term m/z, which is used by some as a dimensionless quantity, by some as a mass quantity and by some as a mass-to-charge ratio quantity.

(B)

You are wrong:
  • m/q (Th) is the mass in Da divided by the charge in elementary charge units.
  • m/z is the mass in Da divided by the net number of elementary charges.
  • whereas the numerical factor in both quantities are equal, the units are different.
There is a difference: with m/q the division is by a charge, with m/z the division is by a number.

(C)

m/z is recommended by IUPAC as standard notation in mass spectrometry for chemists. (Please note that thier definition of m/z is incompatible with yours, which means your m/z is a completely different quantity as their m/z. In other words: my m/q is as different from the IUPAC m/z as your m/z is.) This also means that non-chemists are free to use the well defined and coherrend m/q if they prefer.

(D)

I agree except that the Th is useful not only for mass spectrometrists but for all scientists dealing with charged atoms and molecules.

-- 195.186.211.54 07:52, 13 April 2006 (UTC)


(A) You do not seem to get the distinction between the physics of mass spectrometry and the chemistry of mass spectrometry. As long as you try to include the chemistry part of mass spectrometry in the physics part of mass spectrometry you will not understand the distinction. In physics as in the physics of mass spectrometry m/q is used. In the chemistry of mass spectrometry (interpretation of data) m/z is used, m/q in Th is used by some but is not common or accepted. The point I was trying to reach consensus on is that the physics usage is clear and we can agree, this includes the physics of mass spectrometry because it is physics. I am of the impression that you are going to fail to make this distinction and argue for unification, however the facts are that no matter what you think is right it is convention to use m/z in the chemistry of mass spectrometry and m/q in the physics of mass spectrometry and we should represent facts not arguments for change. "The separation of MS and physics is very artificial and random." maybe so however it exists and we all have to live with it. It is not for you and I to decide how to partition science. I think you should recognize that it is a field at the interface of physics and chemistry that paritially includes both disciplines. I will reword it so that we might reach consensus:

"There is agreement on the usage of m/q or m/Q in physics (excluding mass spectrometry). We also agree that within the field of mass spectrometry the physics usage is used for physical problems."

I think we should also agree that the m/z convention is used with chemical problems within mass spectrometry. But you seem to disagree. Be aware that by agreeing with this you are not saying m/z should be used simply that it is.

(B)You retort is not relevant to what I was proposing we agree upon which only concerns how they are computed from the mass and charge of a given molecule. We can deal with units next. What I am proposing we agree on is that they are computed in the same way regardless of units. They are both the mass in Da divided by the number of elementary charges (please, please, please do not become semantical about this). They are the same number because they are the same ratio of numbers.

(C) So you agree. "m/z is recommended by IUPAC as standard notation in mass spectrometry"

(D) I agree. Restating to include your input and qualify it:

"The unit Th is not recognized by IUPAC, IUPAP or any governing body that recommends nomenclature. It is a unit proposed more than a decade ago by Cooks, who we all respect, but it is not in particularly common usage today. It is however used by some. Additionally its limited usage is confined almost exclusively to mass spectrometry. There is no reason why this proposed unit could not be useful in other fields. However the traditional m/q or M/Q notation in accepted units is near universal outside of mass spectrometry."

--Nick Y. 17:25, 13 April 2006 (UTC)

Nick, of course I agree that m/z is used by some mass spectrometrists. This is why I included a lengthy section about m/z in the mass-to-charge article even though the definition of m/z is unclear and it is not even sure that m/z is a mass-to-charge ratio. This long discussion, by the way, is now the reason why Kmurray thinks m/z is over represented (he is right, but shortening would make people like you mad).

I never disputed that m/z is being used in chemistry. Your claiming so is outrageous.

(B) You still seem not to understand the concept of a physiscal quantity and you treat it as a numerical value. Fact is: if you compute physiscal quantities this includes both, the numerical factor and the units. Therefore, when you say" computing the mass-to-charge ratio (in Th) of a molecule and computing the m/z value of a molecule yields the same result", then you are definitely wrong. Correct would be: "the mass-to-charge ratio (in Th) of a molecule and the m/z value of a molecule are different physiscal quantities which, however, always have the same numerical factors". (Note: this, of course, is only valid under the assumption that m/z is defined according to your or IUPAC definition. If m/z is defined as a mass-to-charge ratio with units u/e, amu/e, Da/e, as many people do, then m/q and m/z are indeed identical. Once more we have the problem that m/z is ill defined and used inconsistently.)

(D) I propose: "The unit Th is a synonym for Da/e and is not recognized by IUPAC, IUPAP or any governing body that recommends nomenclature. It is a unit proposed more than a decade ago by Cooks, who we all respect, but it is not in particularly common usage today. It is however used by some. The composed notation amu/e, u/e, Da/e, which represent the same unit as the Th, are much more widely used. Additionally its limited usage is confined almost exclusively to mass spectrometry. There is no reason why this proposed unit could not be useful in other fields. However the traditional symbols m/e, m/q or m/Q for the quantity mass-to-charge ratio is near universal outside of mass spectrometry."

(E) the m/z notation is not endorsed by the International Bureau of Weights and Measures which is the standards Organization for units, and nor the General Conference on Weights and Measures, nor the International Committee for Weights and Measures have endoresd the m/z notation.

[edit] References

[edit] famous books on ion optics

Electron and Ion Optics by Miklos Szilagyi, Plenum Press, ISBN 0-306-42717-6.
This book about ion optics and electron optics uses m for mass, Q for charge, and m/Q for the mass-to-charge ratio.
Introduction into optics of charged particles by J. Grosser, Teubner, ISBN 3-519-03050-0.
This book about particle optics uses m for mass, q for charge, and m/q for the mass-to-charge ratio.
Applied charged particle optics, edited by A. Septier, Academic Press, ISBN 0-12-014574-X.
This book uses m for mass, Q for charge, and m/Q for the mass-to-charge ratio.

In ion optics m/q or m/Q is used. We all agree. No deabte here.--Nick Y. 21:14, 12 April 2006 (UTC)

Please give us one reason why chemists cannot use what everyone else uses. --195.186.211.54 07:56, 13 April 2006 (UTC)

I do not have to. It is irrelevant. Nor do I care. If they can or should is not relevant to this article (or any wikipedia article) that is the reason for the POV check. I have never advocated should or could and have not taken a position except for the purpose of letting you know that my position is irrelevant too. The point of wikipedia is to represent what is. If you can not get this point and stop being an advocate I think that is grounds to ban you from wikipedia. --Nick Y. 19:55, 13 April 2006 (UTC)

Nick, fact IS that m/z even among mass spectrometrists is not as predominant as you suggest it is. Your claim is only based on your personal POV. Look at the links below, if you don't believe it. Both, m/q and m/e ARE USED by mass spectrometrists. Thomson, the inventor of mass spectrometry, used m/e with dimension mass/charge. These are the facts and your coninuing statement that m/z is almost exclusievely used is POV with no bases on references. The reference below prove this fact. Please accept what is, not what you wish to be true.

--81.62.126.160 09:34, 14 April 2006 (UTC)

I don't know who you are but I assume you are the same guy as before. Yes, yes, yes, yes ,yes for thelast time the use of m/q is absolutely and undeniably common and near universal within the field of mass spectrometry when directly addressing physical problems, instrument design, explanations of the physics of mass spectrometers etc. I have never ever said anything else. It is however an undeiable fact that in the non-physical aspects of mass spectrometry, data collection, data interpretation, gas phase chemical reactions and the like m/z is near universal. My references are the entire volumes of all major mass spectrometry journals: [www.asms.org journal of the american society of mass spectrometry], European Journal of Mass Spectrometry,International Journal of Mass Spectrometry and Ion Processes, Journal of Mass Spectrometry and more. As well as IUPAC, the nomenclature governing body for chemistry.--Nick Y. 17:48, 14 April 2006 (UTC)

[edit] WWW pages about mass spectrometers

[2] uses m/e
[3] uses m/q
[4] uses m/e
[5] uses m/q
[6] uses m/q
[7] uses m/q
[8] Thomson used m/e with dimension mass/charge when he determined m/e of an electron in 1897.
[9] Thomson used m/e with dimension mass/charge in his 1913 article presentng the first ion mass spectrometer (ref.: Kmurray).

In the physics of mass spectrometry m/q is used we are all agreed. It is only in the x-axis usage that there is any debate.--Nick Y. 21:13, 12 April 2006 (UTC)

Please give us one reason why x-axis should be labeled differently from what the physical mass spectrometers actually measure? -- 195.186.211.54 07:55, 13 April 2006 (UTC)

See above.--Nick Y. 19:57, 13 April 2006 (UTC)

[edit] POV Check

85.0.31.211 said:

In your opinion, where is the neutral POV missing in the main article? Could you please give a detailed list instead of just placing a POV check?

Kermit Murray responds:

The article is in large part an editorial on m/z and why it is wrong. That is an important discussion to have, but it should not be on the main page.
--Kmurray 14:11, 13 April 2006 (UTC)

I completely agree. If you check the history of the article you will see that this m/z discussion is relatively new. An even more lengthy m/z discussion was added by someone who thought m/z should be there exclusively. Recently I considerably shortened the m/z discussion but it is still too long. Unfortunately m/z is used in completely different ways and to have a neutral POV all those must be addressed. Also, the mass spec part in general is too long. All that should be there is one line explaining that mass-to-charge ratio is measured with instruments called mass spectrometers. However, I do not see any section where it says that m/z is wrong. I can see sections where it is stated that m/z is used in different ways and that these do contradict each other, which, however, is not POV. I cannot see any section where it says that m/z is wrong. Could you please indicate what section you mean?

--195.186.211.54 15:43, 13 April 2006 (UTC)

I agree with Kermit Murray too. I also agree with "195.186.211.54" that m/z should not be present to the exclusion of others. I think that the true physics definition (not Th or m/z) should come first and foremost. In terms of proportion the physics definition is so obvious and straight forward that it barely needs a definition, much less significant explanation. There isn;t much that is confusing about it. Mass-to-charge ratio in physics isn't its own entity separate from other quantities but simply a ratio of two quantities. If mass spectrometry did not exist with its unconventional definition this page would not exist. It think part of the POV check is the disproportionate advocacy of the unit Th which is very obscure, mass spec only and not accepted by any body of authority. Again I would propose disabiguation. Put the one line in the physics article (exclude all other references to Th in non-mass spectrometry sense) have a disambiguation page. On the mass spectrometry page there should be a lengthy explanation of m/z and how it relates to m/q with a one line reference to Th with the proposed definition. That would be representative of proper proportions. Th is not used in physics and is rare in mass spectrometry and is not an accepted unit at all. The only problem I see with disambiguation is that the physics page will be about two sentences, but I would be happy to see a long physics page, let's just not mix things up and confuse everyone.--Nick Y. 18:06, 13 April 2006 (UTC)

[edit] Cabal Mediation

I have requested mediation due to ongoing and unrelenting advocacy. Please check the mediation page:

[10]

Based on the response of the mediator and your continued beligerant advocacy I am inclined to proceed more aggressively for disciplinary action against you. I would prefer that you understand how your opinion, as mine, does not matter. We are here to represent facts not advocate.

--Nick Y. 20:20, 13 April 2006 (UTC)

[edit] Kerli contribution

I have changed the article according to proposals of mediation and Kmurray.

--Kehrli 11:47, 14 April 2006 (UTC)

I'm not sure about the path of forging ahead. I however welcome your changes and think it is a great improvement. The only major problems left are a couple of sentences and organization: misrepresentating Th and the derision of m/z left over from before. Since I have another level headed editor, who has chosen to try to improve the article I will make an effort to improve while trying to approach consensus. I think that the article is pretty close to being complete and accurate as of now and if it remains approximately as is (with improvements) then I think the POV check could be removed (what do you think Kmurray?). Please note that by complete and accurate I do not mean that I agree with any of it on a fundamental, philosophical or personal level. It is an accurate representation of facts. In terms of proportion it is fairly close with some over representation of m/z and even more over representation of Th. It however seems as I said before that the problem of proportional representation is more that there is not a hell of a lot to say about the physical m/q. If the physical m/q could be expanded about 10 fold and the m/z section expanded about 2 fold and the Th sentence remains then that would be about proportionate. Alternatively we could shorten the Th section but then we would have a sentence fragment and not explain it well.--Nick Y. 16:42, 14 April 2006 (UTC)

Nick, your definition is in contradiction with the IUPAC definition of m/z. Therefore it is your POV and I had to remove it. If you put it back I will ask for a mediator. Also, mass spectrometry is only one of many fields using mass-to-charge ratio. As Kmurray correctly stated, mass spec does not deserve as much space in the article and especially not two titles.

--85.1.30.127 13:29, 15 April 2006 (UTC)

[edit] POV

"In mass spectrometry, when presenting data, it is common to use the symbol m/z. Unfortunately the m/z is not clearly defined and it is even controversal wether it denotes a mass-to-charge ratio."

This should not be here. I think the History section should be moved to the top, and the history of m/z, along with a brief discussion of its problems, should be at the end of that section. Ryan4 16:53, 15 April 2006 (UTC)

[edit] Much Better

If everyone's happy, I'd like to propose that I close the mediation case and take the POV warning from the top. Ryan4 17:17, 15 April 2006 (UTC)

That is fine with me. I have not yet included any discussion about the problems of m/z, as you suggested. I will let you do it, otherwise Nick will go ballistic. --Kehrli 17:47, 15 April 2006 (UTC)

As a mediatior I don't think I should be editing the page myself, only proposing edits that will be a compromise for both parties. How about we let Nick write a sentence or two on the problems of m/z here, then if we all agree on it, add it to the article and then be done with it! :) Ryan4 18:06, 15 April 2006 (UTC)

I am still not satisfied. However I think that we are closer now that we have removed most of the POV from the article and that the Th proponents are no longer editorializing. There is now only misrepresentation of facts. The remaining issues:

  • The implication that Th is an accepted unit
  • The implication that Th is used in areas outside mass spectrometry
  • The disproportionate representation of Th (over m/z, not to mention the physics usage) (Th is a proposed unit for the replacement of the standard mass spec m/z notation)
  • The complete lack of m/z. And I can provide plenty of references saying that "to compute the m/z divide the mass in Da by the number of charges" this in addition to the IUPAC definition, which are in no way incompatible. Is there any other way to compute it? I wonder if any of the people constantly deleting the m/z section have ever done any mass spectrometry other than the physics of mass spectrometry. There seems to be a vast misunderstanding of practice here. If the only thing that holds weight are IUPAC or IUPAP definitions than Th should not be mentioned at all.

To correct this in a way that is not reverting and hoepfully approaching consensus I have included the only thing we can agree on regarding m/z and given Th appropriate weight ( only a reference). Perhaps this is leading to disambiguation?? Maybe the one m/z line should link to a "mass-to-charge ratio (mass spectrometry)" article?? I can live with the article with one m/z sentence and only the Th reference. Any more inclusion of an obscure unaccepted unit is not acceptable to me. The fact that mass spectrometry is a relatively minor area in which the mass to charge is used is fine with me. I will not debate this.

I wonder who else here other than me has actually read Cook's article. Has anyone here other than me had a conversation with the man? I've had dinner with him and partied with him as well. He's not a friend or anything but I've heard him explain his position and respect him greatly. I think everyone else here misunderstands his intentions.

I have added a sentence to the end of the history section as suggested by Ryan4. It does seem to me that the history section is for the most part about mass spectrometry, not that I object. I have always said that m/q is simple and mass spectormetry nomenclature requires much more explanation. Again another argument for disambiguation. I think a whole article could be written about mass spectrometry usage of mass-to-charge ratio, since it is confusing. It could use a more thorough explanation, with examples etc. How it is spoken etc. With this we could be more inclusive of Th too.

I would like to offer to write a more extensive section on mass spectrometry usage with m/z including some of it's short comings and criticisms. I would also like to offer to include Th in this appropriately. However this would take a dispropotionate amount of space according to some, which I can not completely disagree with based purely on proportion. If the physics section was vastly larger maybe we could cover the nuances of mass spectrometry usage in a thorough, clear and inclusive way.

--Nick Y.21:47, 15 April 2006 (UTC)

Nick writes:

"And I can provide plenty of references saying that "to compute the m/z divide the mass in Da by the number of charges" this in addition to the IUPAC definition, which are in no way incompatible."

Nick, please read the IUPAC orange book. Their definition is different from yours. Their definition of m/z is "mass number divided by charge number" which is indeed dimensionless. Your definition (mass divided by charge number), however, is not dimensionless but of dimension mass. Even though I agree that your definition is better than the IUPAC definition, it is your POV and should not be here. I have in the mean time realized that your knowledge about metrology is too superficial to understand the difference, but I will call a mediator if you include your wrong definition in any article. Ryan, please explain to Nick the difference between his m/z and the IUPAC m/z. I tried it for week and failed to explain him.

--Kehrli 09:25, 16 April 2006 (UTC)

[edit] Mass Spectrometry

There is an article on mass spectrometry already. So, if you want to add something to this article, then make sure you're not just being redundant. I don't think any more discussion on Th is needed since it is non-standard. More emphasis should be placed on the fact that m/z is the IUPAC standard, and sentence with the link to IUPAC needs to be cleaned up (formatting-wise). Also, someone should clean up the math so that the article is consistent. E.g. in some places there is [m/q] written out like that, in other places the correct (m / q) is used.

Ryan4Talk 00:31, 16 April 2006 (UTC)

Ryan, [m/q] means "units of the quantity m/q". This is the notation given by ISO 31-0 and accepted by IUPAC. [Q] means "unit of quantity Q", and {Q} means "numerical factor of quantity Q", . You find this in the IUPAC green book. There is no cleanup needed, the notation is consistent. Also, units are not in italic fonts, therfore should not be within a math brackets. This is also following IUPAC and ISO. I had to change back your corrections.

--Kehrli 09:27, 16 April 2006 (UTC)

Sounds good. I agree whole-heartedly on thomsons. My suggestion of more m/z discussion and examples and the original intention of including it in this artiicle is for the benefit of people new to mass spectrometry. A more detailed look for those that are confused. To me all of this is obvious and simple but I think the issue of mass spectrometry notation of mass-to-charge is confusing to the mass spectrometrist in training. I think the mass spectrometry article is in good shape (I've done a lot of editing myself) but it is so varied and complex of a field that including everything in one article is not helpful, especially if you look at all of the mass analyzers imagine it with a full physics explanation of each. I find that even the scientific community is unaware of many critcal nuances. I find that top notch scientists are unaware of things like that multiply charged ions are common in some forms or that giant 300,000 Da protein complexes are studied whole with mass spectrometry or that mass spectrometry is not necessarily quantitative. This particular article was intended (wrt to mass spectrometry) to be explanatory and informative to those needing a little more help. The basic definition of m/z is in the MS article, but will the novice really get it without a little more help?? It is their loss that a more complete explanation can not be included as an aside since we are arguing over things they could care less about. At least they won't be misled, just ill-informed.

--Nick Y.04:20, 16 April 2006 (UTC)

Nick, I completely agree with your statements, but you are definitely not the right person to educate people about m/z, because you don't understand it either. I am not saying this to offend you, it is just my observation. You constantly mix up units and quantities and you still have not understood that a quantity requires a unit, that a quantity does not imply a specific unit, and that quantities should be computed without th eunits incorporated (all this according to IUPAC). Your writing will confuse any mass spectrometrist, because it is full of errors. For example, see your m/z definition which is not in line with the IUPAC definition.

--Kehrli 09:34, 16 April 2006 (UTC)

Ryan, please tell Nick that he should stop vandalyzing the article. Especially he should let the definition of the Th in there, including the reference. He may not like it, but the thomson is in a officialy referenced paper.

--Kehrli 09:54, 16 April 2006 (UTC)

Kehrli- "an officially refernced article" An officially referenced article about a non-official, unaccepted suggestion to mass spectrometrists from 15 years ago. A suggestion does not a standard make. And yes it was to mass spectrometrist specifically. Again have you read the article?

Kehrli- removing non-standard unaccepted notation from the article, at least unitl we can agree on its proper place, is not vandalism. Ryan4 has already indicated that its inclusion any more than I gave it in its last edit would be misleading and disproportionate, given that it is an obscure non-standard notation. "I don't think any more discussion on Th is needed since it is non-standard. More emphasis should be placed on the fact that m/z is the IUPAC standard" I have given thousands upon thousands of references for the use of m/z from twenty years ago to the present day and offical sanction from the nomenclature governing body. You have given one article which I have read and have personally spoken to the author about but is simply a "suggestion" only to the small group that comprises analytical mass spectrometrists. I personally like the idea, but it is only that at this phase. Any greater inclusion is misleading and confusing.

Kehrli- I would like to invite you to write a short explanatory parargraph which will be helpful to the practicing mass spectrometry novice. It needs to be non-editorial and not advocate the unit Th which I hope we have all agreed is a minor footnote (no matter how appealing or potentially useful or consistent). It should explain to the novice how to compute an m/z ratio from the expected mass and charge of an ion and how it is written in the overwhelming majority of mass spectrometry literature. In what circumstances m/z is used. Also how it is spoken in speaking to an audience. This should reflect common usage and help the novice to effectively use the current standard notation according to current usage. The issue of to what or if we should all change to something different is beyond the scope of this page. Simply let the casual (scientific) reader effectively use this standard. I do not object to a small discussion of units as long as it is helpful to the novice reader to gain some sort of greater understanding of how to effectively use the standard. I would ask that you do it here on the talk page and that we discuss it thoroughly before putting it on the article page. Efforts to undermine the standard are not helpful to the novice reader. This includes references to non-standard usage or presentation of conflicts that will only confuse the reader. Later we might talk about a small section on some of the conflicts etc. on some sort of advanced area but not in this section. This one is informative and about use of the standard MS notation. Perhaps you can do this more effectively do this than me?? From your statements above you seem to be unwilling to make sense of the current standard, only to male it look as incomprehensible as possible, accentuating its shortcomings (which it does have) at every possible point.

--Nick Y.Nick Y. 10:20, 16 April 2006 (UTC)

Nick, the ISO is the organisation that can set up standard units. The IUPAC does not have this authority. It ony can give recommendations to its members, the chemists. The ISO has not endorsed the Th. Nor has it endorsed m/z, nor the unit e. Unforunately, mass spec faces the situation where it has to use non-endorsed units, unless m/q is indicated in kg/C which, we agree, is endorsed but unpractical. There are many units in Wikipedia which are not endorsed. There is even a page against using endorsed unit (anti-metrisaton). Fact is: Th is used by some people and therefore it should be mentioned. I suggest you and I do no longer change the article without Ryan's permission.

--Kehrli 12:27, 16 April 2006 (UTC)

Nick, your suggestion about me making a page about m/z in mass spectrometry: I appreciate your suggestion and I will love to do it. However, you have to realize that the issue is more complicated as you think it is. The problem is that the orange book m/z contradicts to both, the IUPAC green book and the ISO standards, which both are more important documents than the orange book. The deeper reason is that m/z is a misconception, and this misconception is the only reason why m/z seems so complicated. In a fair discussion I would have to mention that fact. I would have to say that m/z very widely used, but it contradicts to ISO and IUPAC green book. And I know that you don't want to hear this and you would be very unhappy with my writing. Look, we are in a dead lock, and the origin of the dead lock is that IUPAC has published a orange book that contradicts both, its green book and the ISO standards. We won't be able to resolve this dead lock, because it is beyond our scope. What we can do is the following: we can show to the Wikipedia readers exactly what is going on, we can show them: here is this quantity, it is widely used and it is even recomended by some mass spectrometrists organization, but it contradicts to the larger picture given by by ISO and the IUPAC. And I can show them in detail where the contradiction is. This will help all mass spec people to understand why m/z is so confusing. I am ready to make such a document with you, but it is only possible if you open your mind and if you read the literature and if you dive into the formalisms required by ISO. Otherwise it is just a waste of my time.

--Kehrli 12:27, 16 April 2006 (UTC)

[edit] the thomson is widely used

Nick, the thomson is widely used even by people that use m/z. Look here for examples:

Removing widely used units from Wikipedia is vandalism. People that are not familliar with the thomson should be able to look it up on wikipedia, even if it is not recomended by IUPAC. Please accept the fact that the thomson is used by a lot of chemists because it makes sense and because it complies to the procedures of ISO, even though it is not recommendet by IUPAC. For some people complying with ISO is more important than complying with IUPAC. Accept this, please.

--Kehrli 14:03, 16 April 2006 (UTC)

Nick - you wrote:

There have been several suggestions (e.g. the unit thomson) to change the official mass spectrometry nomenclature m / z to be more internally consistent and compatible with the broader scientific unit system.

This is missleading: the Th does not change the "m/z nomenclature". It changes m/z from a dimensionless quantity into a well behaving quantity with dimensions. This is more than just nomenclature. Please correct your scentence to be less missleading.

-- Kehrli 14:30, 16 April 2006 (UTC)

[edit] new m/z definition

I just found that IUPAC is drafting a new definition of m/z. Here it is:

m/z – The three-character symbol m/z is used to denote the dimensionless quantity formed by dividing the mass of an ion by the unified atomic mass unit and also by its charge number (regardless of sign). The symbol is written in italicized lower case letters with no spaces.

My critique:

  1. the m/z quantity is not defined according to the IUPAC green book
  2. the m/z is not defined according to the ISO 31-0 standard on quantity and units

Well that seems like a quite sensible definition that they are drafting. As I have said many times I would like to include Th. I however strongly object to the way in which you choose to include it. It amounts to advocacy. I have consistently mentioned it and given it significant room (for a non-standard, unexcepted unit). You want to include it within the main explanatory text. That is simply wrong and misleading. I would like to propose some priorities:

  • 1) The physics, SI definition and explanation
  • 2) The physics, Da/e definition and explanation
  • 3) As a field specific section the definition of m/z and a sensible as possible explanation of this standard (without derision or confusion)
  • 4) As a separate section with relatively lesser weight, non-standard and proposed definitions and usage with an explanation of why they are proposed. This should include the new proposed IUPAC m/z definition which honestly I think will be very helpful to the understanding of novices, as well as the Th. This section must be constrained and made clear that they are non-standard uses that are not IUPAC recommended.

I think there should be no doubt about the order of these priorities. First SI, second non-SI accepted units, third MS specific standard, lastly and least completely unofficial non-standard notation. Please consider if this is a reasonable priority list to you.

I would point out to you that the Th references you have given do not conform to your standards, they are m/z in Th. I have seen many non-standard combinations such as this. That does not mean it should take priority. It is an interesting and even important side notet that people do not alway comply to the standards. I would also point out that your references are MS specific and therefore should at the veryleast only be mentioned within the context of MS. Again I have given tens of thousands of references of the standard usage of m/z. Try finding tens of thousands of references for Th.

--Nick Y. 00:39, 17 April 2006 (UTC)

Nick, look, the discussion with you is quite useless since you mix up the things. Th is a unit and can be used with any quantity of dimension mass/charge. Wether you call the the quantity m/q, m/e, m/z, m/Q really does not matter. Your remarks are embarassing. It is the equivalent of arguing wether the unit meter can be used with symbol l (for lenght), d (for distance), r (for radius), x (for spacial dimension). Your claim that Th should only be used with m/z is like claiming that the unit meter should only be used with l, but not with r and x. It is a ridiculous discussion on a Kindergarten level. You obviously have no knowledge about metrology and the concepts of quantities and you have painted yourself into a circle that does not allow you to give in.

I did not say that it could not be used with m/z. It is you who said that the correct usage was m/q (Th). As a matter of fact that is what Cooks suggested. I personally don't have any more problems with this particular usage than any other. I was only pointing out that your call for using m/q or even better m/Q seems to be taking second place to Th. I thought the best part of your argument (which is completely irrelevant to writing an encyclopedia entry as I have emphsized endlessly) was the use of a standard accepted symbol for charge not the use of a non-standard obscure unit that seems less useful than Da/e. --Nick Y. 17:13, 18 April 2006 (UTC)

[edit] Edit War

Kehrli- What you are doing is called an edit war. The mediator has specifically indicated to us that any further inclusion of Th would be disproportionate. You are specifically ignoring his very specific conclusion. It is fine to try to argue with him about it but my reverting the article to what he said was correct, proportionate and acceptable is in no way vandalism. Your intial editing of it back to what was deemed by him to be disproportionate is closer. If you are unwilling to participate in this mediation we can elevate this to official action where you may be banned and not have the opportunity to try to sway anyone. Again I recognize that there is a place for your minority view but it is not in the main body of this page above and beyond the accepted standard. As you pointed out I personally have included the unit Th. I am only interested in accurately representing the facts. For the hundreth time I will say again: I personally am an advocate of change and sympathitic to your cause, but that does not change our responsibility as editors not to advocate or misrepresent. If you want to add the misrepresentative text please ask the mediator first and propose it here. I am getting closer to elevating this dispute because you have proven to be unrelenting in your advocacy, just a little slicker.

--Nick Y. 00:58, 17 April 2006 (UTC)

Nick - fact is: if someone reads an article that includes the Th and he does not know what it is and wants to look it up on Wikipedia, he NEEDS the definiton 1 Th == 1 u/e. Hence leave it there. Exactly because the thomson is not widely used it needs to be there. If it were very common, everyone would know it and there would be no need to define it.

-- Kehrli 08:56, 17 April 2006 (UTC)

As I have said I am absolutely willing to include it but it must be proporitonate to the current standard m/z. (again not that I am a big fan of m/z, but that is irrelevant) As long as you will not allow the standard to represented any more than it is now the non-standard unaccepted unit Th needs to be proportionate which in this case is just a footnote.

--Nick Y. 17:16, 18 April 2006 (UTC)

Nick, the Th needs to be defined so that people who come here understand what it is. The m/z, however, is not even a mass-to-charge ratio. Therefore it does not deserve any mentioning on this page. The only reason it is here is because there are some people who wrongly believe it is a mass-to-charge ratio. Therefore the Th deserves much more representation than the m/z.

-- 81.62.126.189 20:35, 18 April 2006 (UTC)

[edit] Recommend Merging this Entry with "Mass Spectrum"

IUPAC is indeed drafting a new set of mass spectrometry terms and definitions. Here is a link to the project page: Standard definitions of terms relating to mass spectrometry. I am chair of the task group that is assembling the updated glossary and I am interested in any constructive comment on this issue.

The article is improved from a previous version I read, but it is not neutral. The point of the first paragraph seems to be that the field of mass spectrometry stands apart from others in their use of the m/z designation. The remainder of the article discusses only mass spectrometry and none of the techniques parenthetically mentioned in the first paragraph. Thus the article is not about the measurement of mass and charge in physics and physical chemistry, but it is about what to call the x axis of a mass spectrum. Therefore, I suggest that the mass spectrum entry, rather than being merged with mass spectrometry, be kept and the mass-to-charge ratio entry be merged with the mass spectrum entry. A good discussion of the elements of a mass spectrum will naturally include a discussion of mass-to-charge ratio.

The current IUPAC Gold Book Definition is also recommended by the American Society for Mass Spectrometry (Price 1991):

Mass-to-charge ratio (in mass spectrometry) m/z: The abbreviation m/z is used to denote the dimensionless quantity formed by dividing the mass number of an ion by its charge number. It has long been called the mass-to-charge ratio although m is not the ionic mass nor is z a multiple or the elementary (electronic) charge, e. The abbreviation m/e is, therefore, not recommended. Thus, for example, for the ion C7H72+, m/z equals 45.5.

David Sparkman in his Mass Spectrometry Desk Reference (ISBN 0966081323) has a good critique of m/z, m/e and the thomson unit (p 27 and 28). He calls m/z a symbol and not an abbreviation (as IUPAC does) and notes that m/z is a “mass spectrometry neologism” that he finds “unfortunate.” In his view, the correct notation would be u/z, but he doesn’t show much hope of it being adopted. He objects to a unitless thomson, which he describes as “having caught on with a fringe faction of the mass spectrometry community.” He objects to the m/e notation as archaic and implying that the mass be divided by the unit charge.

On the other hand, McLafferty in his Interpretation of Mass Spectra (ISBN 0935702253) considers the Thomson an acceptable unit and merely notes that m/e has also been used in place of m/z.

The bottom line is that most everyone in the mass spectrometry community agrees that the m/z terminology isn’t the greatest, but we are probably stuck with it. An NPOV article will acknowledge that m/z is the accepted standard and that the thomson unit is accepted by some, rejected by others and not widely used.

-- Kermit Murray - Kmurray 03:58, 17 April 2006 (UTC)

Kermit: if everyone agrees that the m/z terminology isn't the greatest then, in your position, you should do something about it and draft a better definition that is according to ISO 31 and the IUPAC green book. I can help you in doing this. The current definition is just not good enough. Please look how other fields of science define their quantities: they use formulas. Using just words is not up to a scientific standart.

Kermit: the IUPAC definition says explicitly that m/z denotes a quantity. Hence it needs to keep to the rules of IUPAC green book, even if m/z is a abbreviation.

Kermit: the IUPAC definition says explicitly that m/z has been called mass-to-charge ratio. This means that it is no longer considered a mass-to-charge ratio. Therefore, and here I agree with you, m/z should no longer be in the mass-to-charge ratio article. It should be moved somewhere else. Your suggestion is ok with me. Your current draft also does not mention that m/z is a mass-to-charge ratio. The fact that m/z is dimensionless (according to your definition) actually excludes it from being a mass-to-charge ratio, because mass-to-charge ratio is per defintion not dimensionless, but has mass/charge dimension.

Kermit: I don't know what Sparkman means with a unitless thomson, but I can hardly believe that he said such a contradictionary thing. The thomson is a unit, not a quantity and therefore per definition cannot be unitless. Only a quantity can be unitless. If Sparkman would have said that, it would show his complete ignorance about the ISO 31 terminology, and I don't think he is that ignorant.

Kermit: I would like you to understand that your comitee is not working in empty space. There is the ISO 31 and the IUPAC green book to which your definitions should comply. I am well aware this would mean some bigger changes and it might even offend some (less flexible) people in the mass spec community, but please, please, bring mass spectrometry back in line with the bigger picture of metrology. Please, go and get advice from one of the ISO 31 cometee members, they will help you drafting a modern, consistent definition of m/z which complies with international standards. In the long run this will help mass spectrometry tremendously.

Kermit: the mass spec community indeed stands appart from the other scientific communities using the mass-to-charge ratio. Most other communities use the symbol m/q or m/Q for this quantity, and all agree that it is not domensionless but of dimension mass/charge. The reason why they use the sumbol m/q instead of m/z is because the m and the q symbols directly follow from the Lorentz and Newton equations, which are always written with the internationally accepted symbol q or Q for charge. The m/z is almost exlusivley used in mass spec. This is unfortunate, since obviously it would be better if the mass spec community would keep to the international standarts established by ISO and IUPAC which clearly recommend m/Q for mass/charge. Since the instrument used to actually measure mass-to-charge ratios are called mass spectrometers, MS needs a significant representation in the mass-to-charge article. This is why there is so much MS in the article and, for example, so little REM. Electron microscopists use the quantity mass-to-charge ratio, but they do not measure the mass-to-charge ratio. This is why MS needs to have a larger representation. (Side note: It is very unfortunate that the mass spec community decides to use a dimensionless quantity instead of the mass-to-charge ratio, which to measure they were invented for, but we cannot change this (well, in fact you could, but it seems to me you don't want to). Hence we need to live with this.

Kermit: mass-to-charge ratio cannot be merged with mass spectrum, because mass-to-charge ratio is a quantity that is used by many different scientific fields, whereas mass spectrum is specific for mass spectrometry. For example someone working on electron microscopy uses the mass-to-charge ratio, but never uses or sees a mass spectrum. Claiming the mass-to-charge ratio exclusively for mass spectrometry would not be neutral, it would be POV.

Kermit: I think the article is very neutral, because it does not favor the mass spectrometry notation over the notation of the many other users of mass-to-charge ratio. Please explain in more detail why in your POV the article is not neutral.

--Kehrli 08:49, 17 April 2006 (UTC)

Kehrli,

If you will formulate your suggestion as a concise glossary entry according to IUPAC Guidelines [11] I will be happy to circulate it among the mass spectrometry terms Task Group.

Regarding NPOV, I stand by my above comments, which are intended as constructive criticism. The salient issue is what you call the x-axis of a mass spectrum.

-- Kermit Murray -- Kmurray 16:11, 17 April 2006 (UTC)


Kermit - you wrote:

An NPOV article will acknowledge that m/z is the accepted standard and that the thomson unit is accepted by some, rejected by others and not widely used.
  • different as you imply, m/z and Th do not exclude each other. Many people use the quantity m/z with the unit Th. This m/z also complies much better with the ISO 31 standart than the dimensionless m/z.
  • it is acknowledged in the article that m/z is wiedely used in the mass spec community
  • I personally have never seen a rejecting statement against the thomson. Could you please cite one?
-- Kehrli 07:40, 19 April 2006 (UTC)



Kehrli & Kermit,

Kehrli here is your great opportunity to advocate. I agree with everything that Kermit Murray said. And I agree with Kehrli's sentiment of disdain for m/z. I support him 100% in presenting his ideas to the mass spectrometry terms Task Group. In the search for improvement all ideas are welcome. Kmurray's comments about the state of the debate is very accurate. Kehrli's comments about the state of the debate are way out there in some fantasy world. The point that Kehrli is advocating is not an unreasonable point to advocate and his support is reasonable. As I have said I sympathize if not agree. The problem here in this article is that Kerhli chooses to advocate his POV rather than give an accurate reporting of the state things. He should advocate to the mass spectrometry terms Task Group and NOT HERE. If his POV is or is not correct is irrelevant here. I think Kmurray's suggestion about separating the physical and mass spectrum usage by merging the MS part with mass spectrum is a good one. (btw the inclusion of things other than MS was just a retorical device used by Th advocates to some end?? That is why there is nothing more on it) We will need a link to it from this article and disabiguation of some sort. Please can we do a good job of writing an encyclopedia entry. There is no hope of doing this until advocacy stops.

--Nick Y. 17:02, 18 April 2006 (UTC)


I have done all of tha work needed to merge this article with mass spectrum except deleting this article. Mass spectrum now adresses all of the mass spec issues that used to be covered here. I am in favor of deleting this article since I see it as redundant; however I do not wish to invite advocacy at Mass spectrum so if there is a desire to keep this article as a physics article that is fine with me. As a physicist it seems unnecessary and irrelevant as well. Just my input.

--Nick Y. 19:13, 24 April 2006 (UTC)

Comments on merge: I support merging Mass-to-charge ratio in with mass spectrum. However, I think the mass spectrometry page is quite long enough covering just the technique itself, and there is enough on the subject of the mass spectrum to justify having a separate article. MS is an important analytical technique in chemistry, and in the mass spectrum article I can see lots of room for discussing spectral analysis (not as a textbook, but giving the general principles). So I recommend keep mass spectrum separate. Walkerma 05:39, 26 April 2006 (UTC)
On merge: Do not merge mass-to-charge ratio into mass spectrum. If anything, mass spectrum should be merged into mass-to-charge ratio because mass-to-charge ratio is a much more basic concept. Better is not merging at all. It would be like merging car and wheel. Wheels are not only used for cars, and cars are more than just wheels.
62.203.121.14 14:30, 26 April 2006 (UTC)

[edit] I'm done with this disingenuous debate

Kehrli- This article is now yours to mislead as many people as you would like. The only thing I ask is that you not remove the diambiguation to mass spectrum. I will also insist on the biased article tag remain. I am reporting your behavior to the authorities. Remember that the history is all saved with your blatant bias as well as your disingenuous slick rhetorical changes. Please constrain your advocacy to this one page.

--Nick Y. 21:54, 18 April 2006 (UTC)

Nick, - the mass spectrum article is quite good, you have done a good job. The only thing that you should improve is to state that the m/z as defined by IUPAC does not comply with ISO 31 nor with the IUPAC green book nor with the IUPAP red book. If you would include these facts, it would be a very neutral and balanced article.

-- 83.77.125.177 07:20, 19 April 2006 (UTC)

Done, no problem.

--Nick Y. 20:36, 19 April 2006 (UTC)

[edit] M/Z suggestion for IUPAC

[edit] Current M/Z

In order to avoid confusion, the mass spectrometry M/Z is written in capital letters in the following. For the same reason, units and constants are written in bold font, quantities are written in italic font.

Currently the IUPAC orange book defines M/Z the following way: M is the mass number, defined by the mass m divided by the mass unit dalton:

M = m/Da

Z is the charge number, defined by the charge q divided by the elementary charge unit e.

Z = q / e

and therefore M/Z becomes:

\frac{M}{Z} = \frac{\frac{m}{Da}}{\frac{q}{e}}

or, when sorting quantities and units:

\frac{M}{Z} = \frac{m}{q} \div \frac{Da}{e}

[edit] ISO and Quantities

The ISO established quite strict rules for dealing with quantities. These rules are listed in the document ISO 31 on quantities and units, which by large parts is based on the Document IUPAP-25 published by the IUPAP. IUPAC adopts the same rules in its IUPAC green book.

This means all three organizations agree with the following notation of the quantity mass:

m = n × Da

This means a mass quantity has the symbol m and consists of a pure numerical factor n and a mass unit like for example Da. (Da, though not a SI unit, is accepted by ISO.) The same for charge would yield:

q = z × e

This means a charge quantity has the symbol q and consists of a numerical factor z and a unit e. We use z to indicate that the numerical factor is always a whole number when using the elementary charge unit e. Here we have the problem that the elementary charge unit e is not directly accepted by ISO. (However, ISO accepts eV, therefore e is semi-allowed by the construct eV/V.)

In general, ISO wants quantities to be expressed as a product of a numerical factor and a unit, which is written as:

A = {A} × [A]

where {} means "numerical factor of" and [] means "unit of".

Note that a mass-to-charge ratio quantity according to ISO is expressed as the fraction of a mass quantity and a charge quantity:

m/q = \frac{n\times Da}{z\times e} = n/z × Da/e

[edit] Graphs

According to ISO, graph axis should best be labled with name, symbol and unit. The numerical factor, however, is not in the label but is the axis itself. For example, a axis denoting a mass should be labeled with "m (kg)" or "m (Da)". The numerical factor n is what is read from the axis itself.

[edit] M/Z and ISO

Coming back to the M/Z, we try to identify the terms. Above we had:

\frac{M}{Z} = \frac{m}{q} \div \frac{Da}{e}

The term Da/e is straight foreward, it must be the unit. However, what is m/q? It is not a numerical factor. Regrouping brings more clarity:

\frac{m}{q} = \frac{M}{Z} \times \frac{Da}{e}

Now we can easily identify that m/q represents the symbol for the quantity, M/Z represents the numerical factor, and Da/e represents the unit.

m/q = {m/q} × [m/q]

resolves to

m/q = M/Z × Da/e

this is very close to the situation when just dividing the mass quantity and the charge quantity:

m/q = n/z × Da/e

[edit] Conclusion

We found that the dimensionless M/Z that mass spectrometrists so much like to use, is in fact just the numerical factor of the quantity mass-to-charge ratio m/q. This means that according to all conventions, mass spectra x-axis should not be labeled with the symbol of this numerical factor, but with the quantity symbol (which is m/q), and units in brackets. For example: "m/q (Da/e)", and not "M/Z".

[edit] Proposed entries for the IUPAC gold book

mass-to-charge ratio
the physical quantity of ions measured by mass spectrometers. The mass-to-charge ratio of an ion is defined as its mass m divided by its charge Q. Use the composed symbol m/q or m/Q to denote this quantity and use the units Da/e or Th for this quantity.
m/Q
m/Q is the ISO symbol for the quantity mass-to-charge ratio of ions in the same way as m is the symbol for a mass quantity and Q is the symbol of a charge quantity. m/Q can have any unit with dimension mass/charge, however, for mass spectra the units Da/e == Th are recommended.
m/q
m/q is the old symbol for the quantity mass-to-charge ratio of ions. Its use is no longer recomended. Use the ISO compatible symbol m/Q instead.
m/z
the dimensionless m/z has long been misunderstood as a quantity. However, it is only a symbol for the numerical factor belonging to m/q.
mass number
no longer used in mass spectrometry
charge number z
no longer used in mass spectrometry

[edit] Do not remove deputed tags

Those who read this article be careful. Some editors here are deleting tags labeling it as disputed when it continues to be disputed on content and bias.--Nick Y. 19:04, 18 May 2006 (UTC)

[edit] Accuracy Dispute

Rockwood and Cooks are misquoted: see Talk:Mass_spectrum. If NPOV is going back on, then accuracy should be tagged until fixed. Also, the article should be in Category:Mass_spectrometry. Note the link in Mass_spectrometry#Mass_analyzer.

--Kmurray 16:37, 27 April 2006 (UTC)

There is no misquotation, Rockwood and Cooks [12] clearly state 1 Th = 1 u/atomic charge and not 1 Th = 1 u/atomic charge number. Please stop with your NPOV. Therefore tag was removed.

Kehrli 17:40, 4 May 2006 (UTC)

Kehrli - The source that you give quotes Rockwood and Cooks as saying "This [mass-to-charge] unit would be defined as the quotient of mass in units of u and the number of charges, z." Seems to be exactly contradictory to what you are saying. I will not argue with you but the accuracy dispute tag is not to be removed until there is consensus. Unilateral removal is very uncool. Please don't do it.--Nick Y. 19:48, 5 May 2006 (UTC)

Nick, I have seen that. Unfortunately even Cooks seems not able to come up with a coherent definition. However, in this case, I think it is fair to say that the formula is what counts. For three reasons:

1) Cooks formula leaves no doubt: 1 Th = 1 u/atomic charge.
2) According your interpretation, 1 Th = 1 u/atomic charge number, the unit Th would be the same as the unit Da. There would be no need to introduce a new unit in the first place.
3) According to your interpretation, the Th would not be a mass-to-charge unit but only a mass unit. Cooks explicitly explained that the Th should be a mass-to-charge unit.

Therefore there is no doubt what Cooks and Rockwood actually meant. Look, the two of us had a valid agreement on the article. I am sorry that we are back in the fighting mode, but it is really not my fault. Kmurray restarted it. He would better get his act together and improve the IUPAC definition instead of enforcing misconcepted mass spec terminology onto the wider scientific community at Wikipedia.

Kehrli 10:26, 6 May 2006 (UTC)


[edit] Cooks and Rockwood Definition of Thomson

It is clear that Cooks and Rockwood mean u/z, not u/e as you indicate in the article. For reference, here it is: Cooks & Rockwood Rapid Commun. Mass Spectrom. 1991, 5, 93.

--Kmurray 13:09, 6 May 2006 (UTC)

Kamurray, no - this is not clear at all for the following reasons:

1) they explicitly write 1 Th = 1 u/atomic charge (which is u/e) and not atomic charge number z.
2) nowhere did they write u/z, as you suggest.
3) u/z is a mixture of a unit (u) and a quantity (z) and therefore dos not make any sense. Cooks would never be so stupid to make this absolutely foolish mistake. It is the equivalent of writing miles/t instead of miles/h.
4) further down they write: " ... the benzoate anion, mass 121 u and and charge -1 atomic units, is -121 Thomson ..." which once more states that they divide by a charge measured in atomic units e (not by a charge number z, what you promote).

The only (rather unimportant) error they make is they use z as a symbol for the quantity charge, instead of the symbol q or Q. This usage, however, is rather common in mass spectrometry. You find it in many reviewed articles.

Thanks for posting the copy, it clearly shows that I was right. Unfortunately Cooks used confusing wording, but at second sight it is very evident what he meant. Please, please, do your job and get the IUPAC to abandon the "dimensionless" m/z and have them accept the thomson in a way that complies to the ISO 31 standard. The current mess is really pitiful.

83.77.124.27 17:46, 7 May 2006 (UTC)
Sorry, the statement "[The thomson] would be defined as the quotient of the mass in units of u and the number of charges z" sounds a lot like u/z to me. The elementary charge e is 1.602 176 53(14) × 10-19 and isn't what you want to divide u by. I'm afraid I am missing your argument here. Kmurray 01:13, 8 May 2006 (UTC)
Kmurray, I agree that (unfortunately) Cooks writing is not completely coherent. However, there are 3 or 4 passages that hint in my direction and only one passage that hints in your direction. And if we assume that he used z as a symbol for charge (e.g. did not realize that z is supposed to be dimensionless, as many people do not realize) then the passage that hints in your direction is no longer hinting in your direction.
It seems that you are confused by the elementary charge e. You write e is 1.602 176 53(14) × 10-19. That is completely wrong. The numerical factor of e depends on the units you use. If you use atomic charge units (as Cooks does) then e = 1. Only if you use coulomb (which nobody uses in this discussion) then e is 1.602 176 53(14) × 10-19 C. This is because e is a physical constant, not a numerical constant. Now we are back on a fundamental ISO discussion: physical quantities (and hence physical constants) need units - period. The way mass spectrometrists turn m/z into a "dimensionless" quantity is against all ISO rules and very confusing. It is confusing everyone, including you. The same situation would appear if some people suddenly would turn all length quantities into dimensionless quantities. The world would become a mess instantly. In order to avoid this mess, units were invented. Therefore we should use them. And especially the IUPAC should use them and recomend them to its members. And that is where you come in. Please, please make the IUPAC to clean up this mess.
Thanks, Kehrli 15:43, 8 May 2006 (UTC)

[edit] Nominate for Deletion

The mass-to-charge ratio article is a primary source for mass spectrometry nomenclature and should be deleted based on No original research standards. Those portions that are not primary research should be merged with the mass spectrum article. The article arose from m/z misconception (deleted: Wikipedia:Articles for deletion/M/z misconception) and in edits of the mass spectrometry page (see Talk:Mass_spectrometry#Could_the_m.2Fq_vandal_please_stop). Mediation Wikipedia:Mediation Cabal/Cases/2006-04-10 mass-to-charge ratio resulted in a POV fork between mass-to-charge ratio and mass spectrum. The part of mass-to-charge ratio that did not relate to mass spectrometry was supposed to go in mass-to-charge ratio and the mass spectrometry part was supposed to go in the mass spectrum article. Unfortunately, all but one sentence of the mass-to-charge ratio article relates to mass spectrometry. The remainder either duplicates existing information in the mass spectrometry entry or constitutes original research that is a primary source for mass spectrometry nomenclature (it is referenced five times in the mass spectrometry article and the article's novel proposal to replace the accepted m/z with the new m/q notation makes this Wikipedia entry the top Google hit for 'm/q "mass spectrometer"). This notation is in conflict with the definitions that exist in the peer-reviewed literature (e.g. American Society for Mass Spectrometry [13] and IUPAC [14] - for an simplified overview see Ken Busch's Spectroscopy Magazine article: [15]), books (e.g. McLafferty ISBN 0935702253, Dass ISBN 0471330531, Siuzdak ISBN 0126474710, Sparkman ISBN 0966081323, Grayson ISBN 0941901319, etc.) and on-line glossaries (e.g. The Little Encyclopedia of Mass Spectrometry [16], Pharmaceutical Mass spectrometry glossary [17], Base Peak Mass Spectrometry Glossary of Terms [18], Spectroscopy Magazine Glossary [19], Shimadzu Mass Spectrometry Glossary [20]). The POV and accuracy of the article have been repeatedly flagged and the author has each time removed these flags. The article makes many valid points and contains some novel suggestions on how to improve the existing nomenclature. However, advocating this non-standard point of view in a Wikipedia entry is counterproductive and will only serve to cloud the issue and make consensus building within the mass spectrometry community more difficult. -- Kmurray 03:07, 9 May 2006 (UTC) --


[edit] Kmurray is not telling the truth

He is telling the story from the perspective of a small part of the scientific community which has established its own nomenclature which is not used by the rest of the scientific community, nor is it compatible with the international standards issued about exactly this topics, the ISO 31. Here are the facts:

1) mass-to-charge ratio is a quantity that is used by a wide field of sciences, not only the mass spectrometry part. Therefore mass spectrometrists should stop hijacking this term on Wikipedia
2) even within the mass spectrometry community many people realize that the Kermit's IUPAC definitions are boguous, incoherrent and not in line with ISO 31 and therefore should be abandoned.
3) Kmurray as the chairman of the IUPAC group [21] that should prepare a revised set of definitions is unfortunately not qualified for this job. He does not understand the basics of metrology, he continuously mixes up quantities with units, he does not know the ISO 31 document whith which his work should comply. He is a total failure in his job of bringing mass spectrometry terminology on a modern standard.
4) In order to cover up his dismal track record he tries to hijack and delete the mass-to-charge ratio page, as it includes definitions that are according to the wider and more basic ISO 31 standards instead of the boguous, incoherent and outdated IUPAC standards.
5) Since Kmurray is running out of arguments he is now trying to have this page deleted. He is trying to censure the internet from facts he doesn't like.
6) Everyone willing to invest the (unfortunately huge amount of) time to read the relevant documents documents will see that the page is correct and should not be deleted.
7) The reason why he wants to delete this page is because he thinks the definition 1 Th == 1 u/e is not in line with what Cooks and Rockwood wrote in their article. They wrote: 1 Th = 1 u/atomic charge. e is the internationally accepted symbol for the elementary charge which is equivalent to the atomic charge unit. Now, you be the judge.
Conclusion: he is looking for a straw-man reason to delete the article. The real reason is that he does not want to comply to the international standards which are reenforced by the article.
Kmurray should be expelled from Wikipedia because he is doing advocacy for his own boguous terminology, against the internationally accepted standards of ISO 31.

The truth shall make you free, but first it shall make you angry. (Anon)

relevant documents:

  • ISO 31-0 introductory part of international standard ISO 31 on quantities and units. This is the document with which all scientific communities should comply, and to which Kmurray's IUPAC unfortunately does not comply.
  • BIPM SI brochure
  • Quantities, Units and Symbols in Physical Chemistry (IUPAC green book). This excellent ducument explains nomenclaure to be used by chemsists. Unfortunately Kmurray's group is not complying to this document.
  • Chapter 12: Mass Spectrometry in the IUPAC orange book is supposed to define nomenclature for mass spectrometry. Unfortunately it is not in line with the more basic documents above. Unfortunately, some terms are ill defined and confusing. Kmurray is heading the group that should improve this document. Instead, he decides to delete articles on Wikipedia.
  • Mass
  • Charge
  • Mass spectrometry and m/z
  • Cooks, R. G. and A. L. Rockwood (1991). "The 'Thomson'. A suggested unit for mass spectroscopists." Rapid Communications in Mass Spectrometry 5(2): 93.
  • NIST on units and manuscript check list
  • Physics Today's instructions on quantities and units
  • International Vocabulary of Basic Terms in Metrology (Second edition 1993: ISBN 92-67-01075-1); a guide whith contributions of the following organizations: IUPAP, IUPAC, ISO, OIML, IEC, IFCC.
  • IUPAP Red Book SUNAMCO 87-1 "Symbols, Units, Nomenclature and Fundamental Constants in Physics" (unfortunately does not have an online version).
  • Symbols Units and Nomenclature in Physics IUPAP-25 IUPAP-25, E.R. Cohen & P. Giacomo, Physics 146A (1987) 1-68.
  • AIP style manual

[edit] Don't be misled

The facts about this article are:

  • There is an ongoing content dispute
  • Most of the content dispute has been about what the standard should be (original research)
  • There was mediation
  • Mediation resulted in an agreement that mass spec related material would be removed from this article and placed in mass spectrum so as to give Kerhli the space to cover the non-mass spec usage of mass-to-charge ratio in other fields
  • Aside from a single sentence mentioning other fields this article has remained redundant.

This article is redundant and not needed unless it is expanded to include material not covered in other articles (mass spectrum, mass spectrometry etc.)

--Nick Y. 16:59, 9 May 2006 (UTC)

The facts about this article are:

  • The only ongoing content dispute is how the Th is defined in the Cooks article. I have three arguments for my interpretation, whereas Kmurray and Nick have one false argument for their interpretation.
  • this article strictly keeps to ISO 31 standards and has no original content
  • the mass spectra article mainly discusses mass spectrometry nomenclature that does not comply to ISO standards and that is advocated by Kmurray and his group.
  • Nick and Kmurray don't like this article because it is not in line with their POV
  • Mediation has resulted in the agreement that the ISO 31 compatible definitions stay in the mass-to-charge ratio article adressed to the larger scientific community whereas the minor opinion of the mass spec community is moved into the mass spectrum article
  • For this reason, the mass spectrum article contains many redundant content that could be removed and refered to this article instead. Most of this content adresses mass-to-chare ratio nomenclature and not mass spectra. Most of this content was copied from this page into the mass spectrum page. Most of this content was written by myself.
  • therefore, if anything needs to be deleted, it is the [mass spectrum]] article (which I do not recomend).
  • the root of the problem comes from the fact that the IUPAC comitee (especially Kmurray, its chairman) is not capable or not willing to come up with nomenclature that comply with ISO 31, nor with the IUPAC green book standards. On top of this they are arrogant enough to try to impose their non-compliant nomenclature onto the larger scientific community.
Kehrli 07:35, 10 May 2006 (UTC)

[edit] Unbiased Improvement

I am looking for someone with a physics background to help me improve this article, sort of as a counter balance to my mass spectrometry bias. There has been disagreement about this article before so I would like the input and consensus of another reasonable editor with a different background. I am still not certain that this article is totally necessary. --Nick Y. 16:30, 10 July 2006 (UTC)

Here is an unbiased opinion from a physicist and mass spectrometrist: it does not need any degree in physics to understand that m/z is against all internatinal conventions established by ISO 31, the IUPAP red book as well as the IUPAC green book. According to those three organizations m/Q must be used instead of m/z. If anything m/z should be deleted.

I'm sorry, but that sort of childish unsigned response and behavior (removing the disputed tag in response to a dispute) is not productive. You are not who I am looking to work with. I guess I failed to mention that the individual must be mature. Grow up. That has to be about the most disingenuous response I have ever had to a well intentioned, open-minded request to collaborate with someone of a different perspective.--Nick Y. 22:33, 20 July 2006 (UTC)

Look, Nick, the only person that behaves childish is you. You are not even willing to think about the issue. You are just looking for backup for your misguided predjudice. Otherwise you would just read the IUPAC green book. What you are looking for is all in there. Can you read? If you can, please read the document carefully and you will see that m/z is against all rules. But what am I talking - you are not ready to question your own predjudices and therefore there is no chance that you will ever understand the issue.

“Few people are capable of expressing with equanimity opinions which differ from the prejudices of their social environment”
Albert Einstein

And please - keep the flag removed as long as you don't have an argument what fact should be wrong. Okay?

That is not the way this works. You must verify that Cooks and Rockwood suggested the use of m/q in combination with Th outside the area of mass spectrometry. I assume that this anonamous person is Kerhli? I know you have the article and you know m/q does not appear in the "article". As I have said hundreds of times I believe in your cause. Your statements, however, are false. Cooks and Rockwood did not suggest using m/q, that convention was used elsewhere before their article but they specifically did not use it. You also know from searching the literature that the few cases in which Th is used it is often in conjunction with m/z. Furthermore it is rare for this to appear outside areas very closely related to mass spectrometry. These are the facts. It does not mean that I like the facts or that I do not get your point. I understand that there are inconsistencies in nomenclature and standards that seem to be irreconsilable within the current definitions and standards. Your contentions simply are not verifiable and constitute original research.--Nick Y. 21:18, 21 July 2006 (UTC)

Nick, you are mixing two things up.

Topic 1) what is the correct symbol for the physical quantity mass/charge
The answer is given in the IUPAC green book: it is m/Q, not m/z. Cooks does not address this issue at all and it is not relevant.
Topic 2) what is the correct unit of mass/charge
This is the question that Cooks addressed. Because he thinks that there is no good unit, he proposed the thomson. This of course means that the thomson can be used independent of the symbol that m/Q or m/z that one uses.

Comparison: The same problem consists with many other physical properties. Lets take electrical potential: some people use U (the correct SI term) and some people use the incorrect V as a symbol. Both parties, however, use V (volt) as the unit.

Conclusion: The thomson is independent wether it is useed with m/z or m/q. Unfortunately, since you don't even understand the difference between a physical quantity and a unit, you won't understand the argument. And one more thing: mass spectrometry is a part of physics. Therefore, whenever Th is used in MS it is also used in physics.

Response Your novel suggestions are a good idea and consistent with the greater scientific unit system. I agree that there is nothing stopping someone from following your suggestion as long as the journal in question accepts its use. Please provide sources demonstrating common use of this within the peer reviewed scientific literature. The onus is on you to demonstrate current common usage.--Nick Y. 17:11, 24 July 2006 (UTC)
This is not "my novel suggestion". It is what has been written by Cooks and Rockwood a long time ago. I just try to explain you their writing since you seem not to be able to read.
Please give specific citations using your notation system in use in a peer reviewed journal.--Nick Y. 19:57, 26 July 2006 (UTC)
I have given you these citations many times already
(1) the fact that the correct symbol for mass-to-charge ratio is m/Q is written in the IUPAC green book. THIS IS COMPLETELY INDEPENDENT OF THE UNITS ISED. Please understand that m/Q is the only acceptable symbol for mass-to-charge ratio that complies with the rules of ISO 31 and IUPAC green book, no matter wether u/e, kg/C, or Th units are used.
(2) the fact that the thomson has been proposed as a new unit for the mass-to-charge ratio is written in Cooks & Redwood article. They write about the thomson : ... that a unit of MASS-TO-CHARGE RATIO be adopted."
Combine the two sources and figure out yourself.
Nope that is original research. You are combining sources to reach a conclusion. Please provide sources that actually use your novel notation. I understand what you are saying and I agree that you have a good point but without sources it can not be verified as actually used within the scientific literature. If it is actually used then it is verifiable. If it is not used then it has no place here. If it is used a large proportion of the time then it should be given significant space. Please provide sources, otherwise the content must be removed.--Nick Y. 17:12, 27 July 2006 (UTC)
I am not combining anything - you are combining what should NOT BE COMBINED. As I said before: THE TWO THINGS ARE COMPLETELY INDEPENDENT. m/Q does not imply the unit that is used. Read the IUPAC green book, it is in there. Nick, you should slowly start to use your brain and accept that your opinion may be widely used among a small group of scientists, but it is against all international conventions that you find in the IUPAC green book and ISO 31 established by the wider scientific community. Your opinion is therefore original research (of a small group). Please stop your vandalizm.
I recognize that there is nothing to stop someone from using such a combination. Please provide a source demonstrating use of this combination in the scientific literature to at least indicate its prevalance and thus notability..--Nick Y. 18:22, 31 July 2006 (UTC)
There is no need to show such a combination because these two things are completely independent. When will you ever get this? --Kehrli 07:41, 2 August 2006 (UTC)

[edit] Discussion with Bduke

The constant addition and removal of the disputed tag is quite unhelpfull. Most of us no longer see what the issue is. I have removed reference to units in the introduction as that may be seen as slightly POV. The section on units is more balanced. So if anyone still thinks this article is disputed would they please clearly state below here what exactly is disputed. It seems OK to me. --Bduke 23:54, 7 August 2006 (UTC)

Clarification of dispute for Bduke

The dispute is over the section:

"Cooks and Rockwood proposed the unit thomson (Th) for the mass-to-charge ratio:

   1 Th == 1 u/e == 1 Da/e.

For example, for the ion C7H72+, m / q = 45.5 Th or m / q = 45.5 Da/e"

My issues with it are:

1) It is disproportionate and non-representative being that there are some 20+ papers that use the units Th ever written compared to thousands using m/z. I am very willing to be flexible on this since I think that the proposal to change units is notable. I have personally given it significant space in my own writing of the mass spectrum article and think it should be included appropriately.

Since the Th is out there, it deserves a Wikipedia article.

2) It is false that Cooks and Rockwood proposed the use of this unit in the manner used. They specifically suggested its use with the m/z notation.

The unit is completely independent of the symbols in use. Ref: IUPAC green book Therefore, this is not a viable argument.

3) The suggestion was mass spectrometry specific and should be stated as such. Every single paper using m/z (Th) was a mass spec paper. It simply is not used outside of this small field at all and only ~20 times within this small field over how many years?

The unit is completely independent of the symbols in use. Ref: IUPAC green book Therefore, this is not a viable argument.

4) There are zero, zip, ziltch papers that use the notation/units "m/q (Th)" in this combination. Not that there is a rule against it. Should we really be the first?

The unit is completely independent of the symbols in use. Ref: IUPAC green book Therefore, this is not a viable argument.

5) Overall the unit Thomson is a notable suggestion that was never adopted by any governing body (and specifically rejected) and used only a few dozen times in history.

There are also several important points left out of this article:

1) In the field of mass spectrometry m/z is near universally used as the abcissa of a mass spectrum and is required by most journals. The use of m/q within this field specifically in electrodynamics problems in standard units (see below) are normal.

The IUPAC green book recommends m and Q as symbold for mass and charge. Therefore m and Q are the symbols currently in use by the scientific community.

2) In electrodynamics mks or cgs SI based units are near universally used along with some use of atomic units. Never, ever, ever Th.

In theoretical electrodynamics no units are used, only the quantities m and Q.

To summarize, I strongly object to the representation of m/q (Th) being disproportionately and erroneously represented at the expense of the units and notation currently in use by the scientific community (SI units, atomic units and m/z).

Nick, show me a verifiable reference that explicitly states that m/q (Th) is wrong. Otherwise your strong objection is pure NPOV !!!. The IUPAC green book recommends m and Q as symbold for mass and charge. Therefore m and Q are the symbols currently in use by the scientific community.
--Nick Y. 17:26, 8 August 2006 (UTC)

I am afraid you have both added more noise and heat than light to the situation. Also by both of you playing tag with the dispute tag, neither of you are showing good faith in trying to resolve this problem. Nick, you do seem to be not covering the difference between dimensions and units. To the anon user, I say this. If you going to get into a dispute like this, then get a user name, do not insert your comments in the middle of someone else's comments and sign your comments. OK, lets us look at the dispute:-

  1. Now the intro has nothing about units, it seems to be entirely about the one section headed "Symbols & Units". Is this right?
  2. The first para is "The official symbol for mass is m. The official symbol for electric charge is Q. However, q is also very common. Therefore the official symbol for the mass-to-charge ratio is m / Q or m / q.". This gives dimensions and official symbols. Is this disputed? It does not seem so.
  3. The next para is "The SI unit of the physical quantity m / q is kilogram/coulomb. [m / q] = kg/C". Is this disputed? It is the SI unit, is'nt it?
  4. The next para is "In most fields dealing with particles it is much more common to use the atomic mass unit u (the former amu) or its synonym dalton, Da, and the elementary charge unit e, whereby the unit of the mass-to-charge ratio becomes u/e or Da/e.". This describes the wide useage of atomic mass units and atomic units of charge. [m / q] = u/e = Da/e. Is this disputed? If so, is it the [m / q] bit?
  5. The next para is "Cooks and Rockwood proposed the unit thomson (Th) for the mass-to-charge ratio: 1 Th == 1 u/e == 1 Da/e.". Is this disputed? They did propose it, did'nt they? If it is disputed, would you both accept adding something like "but it is not in wide useage, particularly in the mass spectroscopy community", although that of course needs a cite as does the Cook and Rockwood paper.
  6. The next para is "For example, for the ion C7H72+, m / q = 45.5 Th or m / q = 45.5 Da/e". Nick seems to be objecting to the use of m/q here. Could the last bit be rewitten as ",the mass-to charge ratio is 45.5 Th or 45.5 Da/e"?
  7. The final para is "In mass spectrometry besides m/q the notation m/z is also commonly used. (see Mass spectrum)". Is this disputed. I think not.

It seems to me that the dispute is about a very small part of this article and that reasonable people should be able to resolve it.

A final point. Could the article actually say what the IUPAC Green book and the ISO standard actually says about the "mass-to-charge" ratio, not about mass and charge separately. I think this would be helpfull. If there is a dispute in IUPAC about this it should be documented in the article in a NPOV way.

--Bduke 23:27, 9 August 2006 (UTC)
Hi Bduke,
thanks for your comments, they are very helpful. The anon user was me and I will start not inserting comments and signing everything.
  • I agree with everything you said.
  • I do not know what problem Nick has with this article. I think he would favor "m/z (Th)" instead of "m/Q (Th)". However, according to the latest rules established by a IUPAC work group the m/z is no longer considered a mass-to-charge ratio, therefore m/z cannot be used here. Find the final draft definition of m/z of this group here: [22].
  • Here (m/z) I collected the many different (incompatible) definitions of m/z. You will also find the definition referenced in the previous paragraph.
  • You will find that this latest definition is inconsistent (a mass divided by a number is not dimensionless) and uses a illegal symbol (m/z).
  • The IUPAC green book gives rules on how to handle quanties and units in general. There are 9 base quantities and all other quantities are derived from these base quantities. Mass-to-charge ratio is also a derived quantity and unfortunately does not have its own symbol. (Some authors, however, use a capital M = m/Q). Below you find section 1.5 about products and quotients of quantities. In most books about ion optics the mass-to-charge ratio is reverenced as m/Q or m/q. The notation m/z is not compatible with those general rules in the IUPAC green book. The details are explained in m/z.
1.5 PRODUCTS AND QUOTIENTS OF PHYSICAL QUANTITIES AND UNITS
Products of physical quantities may be written in any of the ways a b or ab or a• b or a x b and similarly quotients may be written a/b or or ab^-1 Examples F = ma, p = nRT/V
--Kehrli 15:00, 10 August 2006 (UTC)
Bduke, yes you are very correct, this should be something easily solved by reasonable people. I should make you aware that there is an arbitration request in process at Wikipedia:Requests_for_arbitration regarding Kehrli's behavior. It is essentially about his unwillingness to engage in constructive dialog and his generally disruptive behavior which is inconsistent with the goals of wikipedia. I understand your frustrations and yes there are minor points that are in dispute however there is a long history of this which I think you have been partially aware of. I agree that we are much closer to reality and concensus than previously however this is due almost entirely to my efforts to educate Kehrli and escalation of adminstrative action to where it currently is now. I am absolutely certain that you are exactly the type of person we need here at wikipedia and am equally certain that you could, given sufficient authority solve this problem. I would suggest you read the arb request; however I will respond to your suggestions to let you understand my position. Your suggestions are pretty much right on the money. The issue of units and dimensions is a very hairy issue and I have avoided it to avoid contraversy. This largely comes about through the sloppiness and convenience of many in the field (not to deprecate mass spectrometrist). There are two important points that need to be included/excluded from the article to be accurate: 1) The unit Th is not and never has been widely accepted or used nor is it accepted by any governing body and has been specifically rejected by such bodies. 2) The unit Th has never been used with m/q and has never been used in the purely physics sense. It has only been used very few times in conjuction with m/z as the independent variable of teh abcissa of a mass spectrum. Regarding proportionality these facts should be reflected in how much space it is given. I would suggest a mention only and only in the specific context of mass spectrometry. I think there should be a page dedicated to the unit Thomson, however it should also reflect these facts. Remember however that there are other pages such as M/z which are in much worse shape and need to be fixed.--Nick Y. 16:55, 10 August 2006 (UTC)
Haha, Nick, I like your wiesel words, this very much sounds like a confession of yours that you actually placed your tags for no real reasons. "very hairy issue", "sloppiness and convenience", nice excuses, I have to say. Fact is: m/z is no longer a mass-to-charge ratio and therefore cannot be used with the unit Th. Just because you ignored this basic fact you placed hundreds of unjustified tags. This is not what Wikipedia is about, Nick. --Kehrli 01:22, 12 August 2006 (UTC)

It is indeed clear that you are not too far apart, but I wish you would use more good faith. Nick, it is not helpfull to talk of Kehrli's disruptive behaviour, and Kehrli, you are perhaps pushing your point too hard. Units do cause a lot of dispute, but they are not the real science. Let us put them in perspective. I'm terribly busy prior to leaving for 6 weeks in UK, so I will have to be brief.

  1. Nick does not like the Thomson and Kehrli's links say it is deprecated by IUPAC, so can any mention of it be deleted or can we add after the line about it being proposed "but is now deprecated"?
  2. I had forgotten the article M/z. That surely needs to be cleaned up, made more NPOV and merged into this article. This article does need the appropriate IUPAC statements in a balanced way.
  3. Neither of you responded to the changes I suggested. Are they acceptable? Do they go someway to solve the problem? In fact, in would be good if you both went though my 7 points and clearly indicated whether you have a problem with each paragraph that I talk about. Let us get down to detail. For each paragraph state clearly whether you are happy with the current wording or not. If not tell us what you think the wording should be.
  4. I'll look at the arbitration request, but I would have thought that reasonable scientists could sort this out without it.
  5. BTW, I have never been involved with IUPAC matters but early in my career I was at Reading and knew Ian Mills and Max McGlashan, so I got a flavour of the debates that went on about units. I knew Max better than Ian because I was actually employed to do Ian's teaching while he was on sabbatical at MIT for a year. --Bduke 23:14, 10 August 2006 (UTC)
Point by Point reply on your points on your points:
1. Agreed
2. This statement amounts to synthesis. No where does IUPAC say that m/Q is the official symbol for mass-to-charge ratio. I agree that m/Q is indeed symbolic of a mass to charge ratio since m is mass and Q is charge. I would suggest the more neutral wording of "The official symbol for mass is m. The official symbol for electric charge is Q. However, q is also very common. Therefore the mass-to-charge ratio may be expressed as m / Q or m / q.".
3. No big problems but there is some foundations of argument sneaking in.
4. Yes I dispute this. SI units are more common in electrodynamics in my experience primarily because physical constants are found in SI. However once again I have no big issue with it but there is some foundations of argument sneaking in.
5. Agreed, howevr there are issues of proportionality as you hint.
6. The only way that Th has ever been used is with m/z; however again I object to it being used as the primary example given that is has been used in about 20 or so papers ever in history.
7. Agreed.
In summary your suggestions are great and in the right direction however the solution is not some half way point. Th deserves a mention and direction to the main article which should be corrected extensively. I would note to you that the M/z article was a redirect until August 5th (just a few days ago) and is 100% kehrli and is pure POV. It is impossible to make a better article with constant interjection of kehrli's agenda. If you and I disappeared you would get that sort of writing in all of these articles. I think in reality we are very far from a solution except with drastic intervention by administrators when you look a tthe bigger picture. It's just this article that is somewhat reasonable.--Nick Y. 00:48, 11 August 2006 (UTC)
Bduke, here are my comments to your recent suggestions. As I mentioned before, all your 7 former suggestions are ok with me. As to Nick's argument about those points:
2) m/Q is not "the symbol for mass-to-charge ratio", it is not a single symbol but a perfectly legal Quotient of two symbols, as adviced by the green book. There is (unfortunately) no single symbol that complies with the IUPAC green book. There used to be the symbol m/z but first it does not comply with the IUPAC rules and second it is now redefined and no longer is a mass-to-charge ratio. So I would suggest. "There is no single symbol for the mass-to-charge ratio, therefore the symbols m/Q should be used" - but this seems a bit too clumsy and obvious to me. Therefore we can do what Bduke proposes and just leave it as it is.
3) I agree with Bduke
4) I agree with Bduke but not with Nick. If anything then Plank units are most often used. However, it is of no importance here because according to the IUPAC green book rules the symbols (here m and Q) do not imply any unit. You can use quantities for calculations and worry about the units later. Therefore, in most books the units are not even mentioned. I guess as a theoretical chemist you often make calculations without worrying about the units. Unfortunately Nick seems not to understand this point and constantly insist on combining quantity symbols with some special units (which is illegal according to IUPAC). As you can see in almost every argument I tried to explain this to him a million times but he is prone to this argument, never responds to it but alway brings it back as a reason for placing a tag.
5) I agree with Bduke
6) I agree with Bduke, not with Nick: Thomson has been used with m/z because at that time m/z was still defined as a mass-to-charge ratio (see m/z yellow book definition). Since recently m/z is defined as a mass per charge number and therefore no longer is a mass-to-charge ratio. Therefore it obviously cannot be used anymore with the Th. This is the very point that Nick has problems to understand since he has big difficulties to make the difference between units, and quantities and the symbols of both. This is basically where the communication broke down and I hope you can explain him that m/z no longer can be used with the unit Th since m/z was recently redefined by the IUPAC and no longer is a mass-to-charge ratio.
7) Now that I think about it, this paragraph needs to be changed slightly since m/z no longer is a mass-to-charge ratio. It is also possible to drop the paragraph completely.
Notes:
  • I insist that there is mentioning of the Th since it is out there and it is being used. Otherwise people cannot look it up when they find it in a paper. I also think it is a good idea to have an own unit for the mass-to-charge ratio as in the unit Da/e the e is not an official unit. The Th was basically deprecated for use with m/z becuase m/z no longer is a mass-to-charge ratio. In my opinion there is no IUPAC regulation that speaks against the use of the thomson as a unit of mass-to-charge ratio except that IUPAC strongly favors SI units.
  • M/z should not be merged into this article because m/z is depricated for use as mass-to-charge ratio. m/z is since very recently a "mass per charge number" which is something very different and needs a unit like dalton or kg.
--Kehrli 06:52, 11 August 2006 (UTC)

Thanks for both your responses. I am going to think about this for a while, certainly overnight. Tomorrow I am running a Science Week activity at the Melbourne Museum all day so it may be the day after tomorrow that I respond. --Bduke 07:39, 11 August 2006 (UTC)

[edit] Concern about non-Mass SPec usage

I am still concerned about the common usage of this term and the prefered units in the electron optics and related (i.e. non-mass spec) fields. In my limited experience in pure electrodynamics (non-MS) I remember solving problems involving m/q but do not remember using Da/e. I think this needs to be validated. I can't find it in the literature with a quick search but then it is a hard search term. Additionally, although I know that m/q enters into the physics of many of the fields listed (other than mass spectrometry) I have yet to see evidence that there is use of the term "mass-to-charge ratio" in these fields or that it is somehow notable. In fields that involve electron optics I see no advantage to using Daltons, and no point in stopping at the m/q relationship since the mass and the charge are known. Why not just solve the problem and be done. Accelerator physics and ion optics I get stopping at m/q. I still would think that for the most part SI units would be more handy, except where these fields morph into mass spectrometry or are used as a component thereof.--Nick Y. 17:51, 2 October 2006 (UTC)

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