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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2025 · Mains Paper III

Q4(b). Interferences in ICP–MS and their elimination

Question

What are the interferences in inductively coupled plasma mass spectrometry? How are they eliminated?

Answer in brief

Spectroscopic overlaps (isobaric, polyatomic, doubly charged, oxide ions) and matrix effects. Cures: collision/reaction cell, another isotope, internal standard.

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The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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Topic notes: X-ray methods and ICP (Bragg's law, powder XRD, XRF, ICP torch, ICP-MS interferences), with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversICP-MS interferencespolyatomic interferenceisobaric interferencecollision cellkinetic energy discriminationinternal standard

All parts of Question 4