Use of flow injection cold vapour generation and preconcentration on coated graphite tubes for the determination of cadmium in sea-water by electrothermal atomic absorption spectrometry

Abstract

Methods were developed for the determination of ultratrace amounts of cadmium in sea-water by cold vapour/trapping and atomization in a graphite furnace. Iridium-, tungsten-and zirconium-coated graphite tubes were investigated for the in situ preconcentration of cadmium cold vapour. Hydrochloric acid (0.25 mol l^–1) and sodium tetrahydroborate (2%) were used as carrier and reducing solutions, respectively. Cobalt, gallium and silicon were used as catalysts for cadmium species generation. By using iridium-coated graphite tubes and gallium as a catalyst, a characteristic mass of 3 pg and a detection limit of 4 ng l^–1 were obtained for a 500 µl sample volume. The precision was between 0.2 (for unspiked sea-water) and 1.3%(for sea-water spiked with 0.5 µg l^–1 of cadmium). The proposed method was applied to the determination of cadmium in several certified water reference materials and sea-water samples.