Analysis for Cd, Cu, Ni, Zn, and Mn in estuarine water by inductively coupled plasma mass spectrometry coupled with an automated flow injection system

A flow injection inductively coupled plasma magnetic sector mass spectrometry (FI-ICP-MS) method was developed for the analysis of Cd, Cu, Ni, Zn, and Mn in estuarine waters. The method uses just greater than 3 ml sample, and employs an automated on-line preconcentration step using a metal chelating resin (Toyopearl AF-Chelate 650 M). Acidified samples for the analysis of Cd, Cu, Ni, and Zn were buffered on-line to pH of <F>5.6±0.2</F> with ammonia acetate just prior to loading onto the chelating resin, while samples for Mn analysis were adjusted to pH of <F>9.0±0.2</F> prior to concentration. Limits of detection were: <F>Cd=1.4</F> ng l−1 (0.013 nM), <F>Cu=17</F> ng l−1 (0.27 nM), <F>Ni=28</F> ng l−1 (0.48 nM), <F>Zn=46</F> ng l−1 (0.70 nM), and <F>Mn=86</F> ng l−1 (1.6 nM). The blank concentrations were less than 1.5% of the SLEW-2 concentrations for each element analyzed, except Ni, which had a significant, but very constant blank from the Ni cones used. The detection limits were less than 5% of the concentrations observed in the San Francisco Bay estuarine samples, with the exception of Zn where the detection limit was 10% of the concentration of lowest San Francisco Bay sample analyzed. Using the FI preconcentration technique, we conducted medium resolution scans of potential isobaric interferences (mass units 55–66) using a magnetic sector ICP-MS to identify a number of interferent complications with evaluating certain isotopes, especially, <F>59Co</F>, and <F>60Ni</F>. Investigations of potential interferents illustrate the importance of appropriate isotope selection and, in some instances, the need to perform blank corrections with both an instrumental and a matrix blank. The method was verified by the analysis of an estuarine water standard reference materials (SLEW-2), and San Francisco Bay samples with previously reported values. Six estuarine samples run in triplicate generated the following average precision (presented as % R.S.D.); <F>Cd=4.2</F>%, <F>Cu=3.2</F>%, <F>Ni=3.3</F>%, <F>Zn=4.4</F>%, and <F>Mn=2.2</F>%. [Copyright &y& Elsevier]