Determination of Cd and Pb in seawater by graphite furnace atomic absorption spectrometry with the use of hydrofluoric acid as a chemical modifier

High concentration of added hydrogen fluoride converted the seawater chloride to the corresponding fluoride matrix, and the liberated hydrochloric acid could be removed during the drying step. The atomization of cadmium and lead could be performed at a relatively low temperature (similar to 1300 degreesC) at which the vaporization of the fluoride matrix was relatively slow, and the corresponding weak background signals could be separated from the analytical signals in time. Experimental conditions for the determination of Cd and Pb in seawater in the presence of HF were optimized with the use of the a priori calculation of the limit of detection. The experimental limit of detection obtained for Cd and Pb were, respectively. 0.007 and 0.25 mug l(-1) for a 15-mul seawater sample (3sigma, 20 replicates). The concentrations of Cd determined in a SLEW-1 estuarine water and a CASS-2 seawater were 0.020 +/- 0.002 and 0.016 +/- 0.002 mug l(-1) Cd, respectively, in good agreement with the 0.018 +/- 0.003 and 0.019 +/- 0.004 mug l(-1) Cd certified values (At the 95% confident level, 10 replicates). (C) 2002 Elsevier Science B.V. All rights reserved.