Application of a Dynamic Reaction Cell (DRC) ICP-MS in Chromium and Iron Determinations in Rock, Soil and Terrestrial Water Samples

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 NH3 in the DRC system provides an eligible technique to determine Cr, because of a greater improvement in the signal/noise (SIN) 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-mu g 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 (ArO+)-Ar-40-O-16. In addition, the effects of cluster ions, such as (KNH3+)-K-39-N-14-H-1 and (CaNH2+)-Ca-40-N-14-H-1, on Fe determination were also negligibly small. Measurements using Fe-54 by the DRC mode are also advantageous for Ca-rich samples, such as limestone and dolomite.