Dynamic Reaction Cell
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[edit] DRC
Introduced by Perkin-Elmer on their Elan DRC (followed by Elan DRC II and Elan DRC-e) instrument, the Dynamic Reaction Cell is a room placed before the traditional quadrupole room of an ICP-MS device, for elminating isobaric interferences. The room has a quadrupole (do not confuse this quadrupole with the main one, placed after DRC and before the detector, which has longer rods and is, in generally, bigger) and can be filled-up with so-called reaction (or collision) gases (amonia, methane, oxygen or hydrogen), with one gas type at a time or a mixture of two of them, which reacts with the introduced sample, eliminating some of the interference. The DRC is characterized by the following paramters, that can be modified: RPq (the corresponding q parameter from the Mathieu equation), RPa (the corresponding a parameter from the Mathieu equation), which refer to the voltage applied to the quadrupole rods and the gas flow of the reaction gas. Amonia gas is the best solution for the majority of interferences, but it is far for being the perfect gas. Sometimes, for specific isotopes, other gas must be used for better results or even mathematical correction, if no gas offers a satisfactory advantage.
[edit] AFT
Axial Field Technology (AFT) is a patented improvement of DRC made by Perkin-Elmer, which consists in two suplimentary rods placed in the DRC room, smaller than normal quadrupole's rods, with the purpose of "pushing" the ions faster to the exit by generating a suplimentary electric potential, minimizing the time needed for the gas to be in the DRC and improving analysis speed. The suplimetary potential of the AFT rods does not contribute significantly to the global energy, but drastically improve ion pasage time.
[edit] Other implementations
Other implementation of this interference removal is an octopole room (instead of a quadrupole), implemented by Agilent's 7500 series. The ORS (Octopole Reaction System) uses only collision gases (helium or hydrogen) and the volume of the room is smaller that a DRC. The small molecules of helium and hydorgen collide with bigger unwanted polinucleic molecules formed in plasma and brakes them into more useful ions, that can be separated in the quadrupole region. However, the OCR system is based only in collision reactions and not chemical reactions, like DRC.
[edit] References
A dynamic reaction cell for ICP-MS. Part 1: The rf-field energy contribution in thermodynamics of ion-molecule reactions V. Baranov, S. Tanner J. Anal. At. Spectrom., 1999, 14, 1133-1142 [1]
A dynamic reaction cell for ICP-MS. Part 2: Reduction of interferences produced within the cell S. Tanner, V. Baranov J. Am. Soc. Mass Spectrom, 1999, 10, 1083-1094 [2]
A beginner’s Guide to ICP-MS R. Thomas [3]
Reaction cells and collision cells for ICP-MS: a tutorial review S. Tanner, V. Baranov, D. Bandura Spectrochimica Acta B 57, 2002, 1361-1452 [4]
