Sequential determination of Pb, Cd and Hg by flow injection-chemical vapour generation-inductively coupled plasma mass spectrometry

Abstract

An inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the sequential determination of Pb, Cd and Hg in natural waters, including sea-water, using an on-line preconcentration flow injection chemical vapour generation (FI-CVG) system. The system is based on the use of two minicolumns packed with a chelating resin which were placed in two injection valves of a simple flow manifold to be loaded simultaneously. A third valve was arranged to select the reagent for the selective vapour generation of the analytes and, thus make possible the sequential determination of the three metals. By using this device, diverse advantages are attained: increase of the sensitivity and reduction of the interferences by the preconcentration and the vapour generation. The detection limits achieved (3 min sample loading time) were: 9, 17 and 12 ngL⁻¹ for Pb, Cd and Hg, respectively, with a sample throughput of about 10.4 h⁻¹. The accuracy of the proposed method was checked with three certified reference materials (CRMs): TMDA-54.4 fortified lake water, LGC6016 estuarine water and CASS-5 oceanic water, and the results obtained were in good agreement with the certified values. The method was also applied to the determination of Pb, Cd and Hg in different sea-water samples from Málaga Bay.