Multielement Determination of Trace Metals in Seawater by Inductively Coupled Plasma Mass Spectrometry after Tandem Preconcentration Using a Chelating Resin

Abstract

Abstract A tandem preconcentration method using a chelating resin was exploited for simultaneous multielement determination of trace metals in seawater by inductively coupled plasma mass spectrometry (ICP-MS). In the first preconcentration step, 500 mL of seawater sample was adjusted to pH 6.0, and the adsorption of trace metals on 0.4 g of Chelex-100 resin in dry weight was carried out at 55 °C. After equilibrium, the resin was collected on a glass filter and rinsed with 30 mL of ammonium acetate solution (pH 6.0) to reduce major elements such as Na, K, Mg, and Ca that had been partly adsorbed on the resin. Then, trace metals on the resin were eluted with 7.5 mL of 2 M nitric acid and collected in a 30 mL polypropylene bottle. In the second preconcentration step, the mixture of the filtrate and the rinsing solution obtained in the first step was adjusted to pH 4.0, and metal adsorption on another 0.4 g of Chelex-100 resin was carried out at 20 °C. In a similar manner to the first step, the resin collected on a glass filter was rinsed with 10 mL of ammonium acetate solution (pH 4.0), and trace metals adsorbed on the resin were eluted with 6 mL of 2 M nitric acid. This eluate was taken into the same polypropylene bottle as used in the first step. The final sample volume thus obtained was 15 mL including 1.5 mL of internal standard solution. Then a 33-fold preconcentration factor was achieved, where the recoveries for 33 elements were larger than 80%. The analytical results for trace metals in coastal seawater reference material (CASS-4) were in fairly good agreement with the certified or information values after correction with the recovery values. The coastal seawater samples from the Ise Bay and the Take Island were also analyzed by the present method. The concentrations for 20 trace metals in the Ise Bay coastal seawater were found to be more than 2-fold larger than those in the Take Island coastal seawater, indicating considerable anthropogenic pollution in the Ise Bay area.