Approaches to Eliminating Interferences

There are three primary instrumental approaches to eliminating or reducing interferences in atomic mass spectrometry (1) use of high mass resolution ICP-MS (HR-ICP-MS) (2) use of a collision cell to break apart polyatomic interferences (3) use of gas phase chemical reactions in a reaction cell to eliminate polyatomic interferences. The approach of changing the instrument operating conditions to form a cool or cold plasma has been discussed. 

A collision cell is often a small hexapole or quadrupole inserted between the ion optics and the mass analyzer of the instmment. As the ions, including polyatomic ions, pass through the cell, they are bombarded with gas molecules, usually helium or hydrogen. The collisions break apart the polyatomic ions, greatly reducing their numbers. A simple hexapole collision cell can reduce the interference on Fe by the polyatomic ArO ion by 10.  

The Dynamic Reaction CelF (DRC) from PerkinElmer uses specific gas phase chemical reactions to greatly reduce polyatomic interferences. The DRC is a quadrupole 

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The determination of an inorganic analyte in an inorganic matrix, e.g. aluminium in rocks, requires the use of classical methods of separation, possibly complexation and a final determination which is designed to remove the effect of interferents by use of a specific chemical reaction(s) or spectrophotometric measurement at a wavelength which is specific to the analyte to be determined. Even so, the ability of this approach to eliminate interference from other elements (or compounds) must be established. 

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