1. As you know by now, the ICP when coupled with atomic emission spectrometer or

Question

1. As you know by now, the ICP when coupled with atomic emission spectrometer or mass spectrometer will result in very powerful analytical techniques called ICP-OES and ICP-MS that are very useful for elemental analysis. Both single element and multi-element analyses can be readily performed. However ICP-MS using argon plasma will NOT easily allow the determination of two important elements namely potassium and calcium. Provide the answer to following questions:

a) Why CAN’T potassium and calcium be easily determined using argon ICP-MS?

b) Suggest a way to solve the problem in 1(a), i.e. how to determine Ca and K using ICP.

[ Recommended: Answer should be no longer than ONE page ]

2. Compare the result of a separation and detection processes of a urine sample involving GCMS and HPLC-MS assuming compounds to be determined are capable of withstanding the high temperature associated with GC. The sample was analysed to determine the presence of banned substances in performance sports.

[ Recommended: Answer should be no longer than TWO pages including figures, if any ]

Explanation / Answer

Ans 1: High background from the Ar plasma is the major cause which prevent the use of ICP-MS for the measurement of K and Ca isotopes. Difficulty in the determination of K and Ca by ICP-MS roots from intense background peaks at masses 39, 40, 41 and 42 from 38Ar1H+, 40Ar+, 40Ar1H+ and 40Ar1H2+. Various means have been used to reduce the magnitude of these interferences in an ICP-MS, including high resolution, desolvation, dynamic reaction and multipole collision cells, etc.

Use of reduced forward power and a metal shield inserted between torch and load coil overcome this interference. This is known as cold plasma conditions which bring down the background induced by argon species and the interfered analytes can be easily detected.

thanks

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