Determination of trace metals in sea-water by inductively coupled plasma mass spectrometry after off-line dithiocarbamate solvent extraction

An off-line solvent extraction procedure with inductively coupled plasma mass spectrometric (ICP-MS) determination was developed for the determination of heavy metals in sea-water at ultra-trace levels. The procedure was adapted from a dithiocarbamate-diisobutyl ketone solvent extraction system with Hg back-extraction, which was previously validated using electrothermal atomic absorption spectrometry. The simultaneous ICP-MS determination significantly reduced the analysis times and improved the detection limits (Cd 0.2, Co 0.3, Cu 3, Fe 21, Ni 2, Pb 0.5 and Zn 2 ppt). The rapid single extraction procedure was quantitative and external standards were used for ICP-MS calibration. The method gave good reproducibility with precisions at the 100 ppt level better than 5% (n=4), except for Fe (7%). The metbod was validated by accurate analysis of CASS-3 Nearshore Sea-water and NASS-4 Open Ocean Sea-water Standard Reference Materials.