Metal speciation by coupled in situ graphite furnace electrodeposition and electrothermal atomic absorption spectrometry

The technique of coupled in situ electrodeposition-electrothermal atomic absorption spectrometry (ED-ETAAS) is applied to the analytes Bi, Pb, Ni and Cu. Bi, Pb,Ni and Cu are deposited quantitatively from their EDTA complexes at E-cell = 1.75, 2.0, 3.0 and 2.5 V, respectively (E-cell = E-anode -E-cathode + iR). By varying the cell potential, selective reduction of free metal ions could be achieved in the presence of the EDTA complexes. For Bi3+ and Pb2+ this utilised the voltage windows E-cell = 0.6-1.0 and 1.8-2.0 V, respectively. For Ni, deposition at. E-cell = 1.7-2.0 V achieved substantial, but not complete, differentiation between Ni2+ (ca. 90-100% deposition) and Ni(EDTA)(2-) (ca. 12-20% deposition). An adequate voltage window was not obtained for Cu. The ability of ED-ETAAS to differentiate between electrochemically labile and inert species was demonstrated by application of both ED-ETAAS and anodic stripping voltammetry to the time-dependent speciation of Pb in freshly mixed Pb2+ -NaCl media, Application to natural water samples is complicated by adsorption of natural organic matter to the graphite cathode. (C) 2000 Elsevier Science B.V. All rights reserved.