Determination of Mn, Fe, Ni, Cu, Zn, Cd and Pb in seawater using offline extraction and triple quadrupole ICP-MS/MS

Highly resolved temporal and spatial distributions of trace elements in ocean water can provide insight into ocean processes but carry a significant analytical demand which requires methods that combine accuracy and precision with high sample throughput. Here a multi-element method is presented which combines the commercially-available seaFAST preconcentration system with ICP-MS/MS for the analysis of Mn, Fe, Ni, Cu, Zn, Cd and Pb in seawater. Samples (20 mL or 40 mL) are loaded on to a chelation resin column and trace metals eluted into 2.5 mL of 1.6 N HNO3. Analysis of the eluate was carried out by ICP-MS/MS, which combines two mass-selecting quadrupoles separated by an octopole collision/reaction cell. The collision/reaction cell was pressurized with O2 gas for the analysis of Mn, Ni, Cu, Cd and Pb and H2 gas for the analysis of Fe and Zn, which removed common interferences (e.g. ArO+ on 56Fe and MoO+ on Cd) yet maintained the highest instrument sensitivity across the entire mass range. Measured blanks and detection limits were ≤0.050 nmol L−1 levels, except for the Fe (blank 0.14 nmol L−1) and were suitable for open-ocean seawater analysis. We report results for the certified reference material NASS-6, consensus reference standards SAFe S and SAFe D and depth profiles of trace metals from the Arctic Ocean, collected as part of the Canadian GEOTRACES program.

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