Despite environmental and geochemical interests, Cr and Fe have been left beyond the reach of determinations by ICP-MS due to severe interferences originating from Ar. The applicability of a dynamic reaction cell (DRC)-ICP-MS has been examined for determinations in environmental and geochemical samples. The reaction with NH
3 in the DRC system provides an eligible technique to determine Cr, because of a greater improvement in the signal/noise (
S/N) ratio due to an effective elimination of interferences arising from Ar (ArC, ArN and ArO), and makes it possible to analyze Cr even at sub-μg L
−1 levels. As compared to non-DRC mode analyses, the DRC technique using
m/z 56 appeared to be preferable for Fe determination in most terrestrial waters because of effective suppression of
40Ar
16O
+. In addition, the effects of cluster ions, such as
39K
14N
1H
3+ and
40Ca
14N
1H
2+, on Fe determination were also negligibly small. Measurements using
54Fe by the DRC mode are also advantageous for Ca-rich samples, such as limestone and dolomite.
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