Calcium phosphate

Calcium phosphate is the name given to a family of minerals containing calcium ions (Ca2+) together with orthophosphates (PO43-), metaphosphates or pyrophosphates (P2O74-) and occasionally hydrogen or hydroxide ions .

It is the principal form of calcium found in bovine milk. Seventy percent of bone is made up of hydroxyapatite, a calcium phosphate mineral (known as bone mineral). Tooth enamel is composed of almost ninety percent hydroxyapatite.

Contents

Chemical Properties

Unlike most other compounds calcium phosphate is increasingly insoluble at higher temperatures. Thus heating causes precipitation.

In milk it is found in higher concentrations than would be possible at the normal pH because it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc and citrate - collectively referred to as colloidal calcium phosphate (CCP) [1]

Uses

It is used in the production of phosphoric acid and fertilizers, for example in the Odda process. Overuse of certain forms of calcium phosphate can lead to nutrient-containing surface runoff and subsequent adverse effects upon receiving waters such as algal blooms and eutrophication.

Calcium phosphate is used in baking as a raising agent, with E number E341. It is also used in cheese products.

Tricalcium phosphate is also used as a nutritional supplement[2] and occurs naturally in cow milk, although the most common and economical forms for supplementation are calcium carbonate (which should be taken with food) and calcium citrate (which can be taken without food).[3] Hydroxyapatite (e.g. calcium hydrogen phosphate) as a food supplement has not been currently studied well, so its usage as a supplement is discouraged.[3]

It is used in a variety of dental products for remineralization and as a diluent in some medications where it will give the tablet a grey colour in the absence of additional colouring agents.[4]

Another practical application of the compound is its use in gene transfection of cells.[5] It is not too well understood, but the calcium phosphate precipitate DNA and form a complex that is thought to help the DNA enter the cell.

Calcium phosphates

In addition to the above, of the compounds occurring in the CaO-H2O-P4O10 phase diagram, Ca4P2O9 (probably Ca3(PO4)2.CaO) is notable.[6]

Compendial status

References

  1. ^ A. Y. Tamime, ed (2006). Brined cheeses - The Society of Dairy Technology (SDT). Wiley-Blackwell. ISBN 1405124601. 
  2. ^ Bonjour JP, Carrie AL, Ferrari S, Clavien H, Slosman D, Theintz G, Rizzoli R (March 1997). "Calcium-enriched foods and bone mass growth in prepubertal girls: a randomized, double-blind, placebo-controlled trial". J. Clin. Invest. 99 (6): 1287–94. doi:10.1172/JCI119287. PMC 507944. PMID 9077538. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=507944. 
  3. ^ a b Straub DA (June 2007). "Calcium supplementation in clinical practice: a review of forms, doses, and indications". Nutr Clin Pract 22 (3): 286–96. doi:10.1177/0115426507022003286. PMID 17507729. http://ncp.sagepub.com/cgi/pmidlookup?view=long&pmid=17507729. 
  4. ^ Weiner, Myra L.; Lois A. Kotkoskie (1999). Excipient Toxicity and Safety. pp. 81. ISBN 0824782100, 9780824782108. 
  5. ^ Kingston RE, Chen CA, Rose JK (August 2003). 9. "Calcium phosphate transfection". Curr Protoc Mol Biol. Chapter 9: Unit 9.1. doi:10.1002/0471142727.mb0901s63. ISBN 0471142727. PMID 18265332. 
  6. ^ N.N.Greenwood, A. Earnshaw, "Chemistry of Elements, 2nd Edition", Butterworth-Heinemann, 1997, p. 523.
  7. ^ British Pharmacopoeia Commission Secretariat (2009). "Index, BP 2009". http://www.pharmacopoeia.co.uk/pdf/2009_index.pdf. Retrieved 31 January 2010. 

See also