Both ICP-MS (Inductively Coupled Plasma – Mass Spectrometry) and ICP-OES (Optical Emission Spectrometry) are workhorses of modern geochemical analysis. They are not interchangeable tools — each has defined strengths, limitations, and appropriate applications.
ICP-OES:
– Detection range: typically, mg/kg (ppm) to per cent levels.
– Best suited for major and minor elements: Fe, Al, Ca, Mg, Na, K, Ti, Mn, Cr, Ni, Cu, Zn, Pb.
– Robust against high matrix loads (concentrated acid digestions, brines).
– Spectral interferences are manageable with careful wavelength selection.
ICP-MS:
– Detection range: µg/kg (ppb) to low mg/kg — typically 100–1000× lower than ICP-OES.
– Essential for trace and ultra-trace work: REE, PGE, Tl, Bi, In, Cd, and pathfinder elements at exploration-level concentrations.
– Mass-based detection means isobaric and polyatomic interferences must be managed (e.g., Arc on 75As, MoO on Cd isotopes).
– More sensitive to total dissolved solids (TDS); solution preparation must control the matrix.
Method selection should follow analyte concentration, matrix type, and required uncertainty — not instrument availability alone.
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