Automated flow injection system for the preconcentration of bismuth and lead from acid solutions of alloys and determination by electrothermal atomic absorption spectrometry

An automated flow injection system for the preconcentration of Bi and Pb from acid solutions of alloys is proposed. The system uses three-way solenoid valves, a peristaltic pump, a mixing coil and a minicolumn filled with activated carbon. The valves are time-based controlled by a microcomputer using a program written in Turbo Pascal 4.0. Bismuth(III) and Pb(II) are preconcentrated on activated carbon after complexation with the ammonium salt of dithiophosphoric acid O,O-diethyl ester. Ethanol is used as the eluent in a reverse-flow mode, and is delivered into the autosampler cup of the electrothermal atomic absorption spectrometer. Four certified steel samples and a non-certified aluminum foil, spiked with the analytes, were analyzed after microwave-assisted dissolution with acids. For the steel samples, ascorbic acid was added to the sample solution to reduce Fe(III) to Fe(II). Iron(II) and Al(III) do not react with the complexing agent and are separated in the preconcentration step. The obtained analyte concentrations were in agreement with the certified or recommended values. The recoveries for the spiked aluminum sample were between 88 and 110%. The relative standards deviations were reasonable for a non-commercial flow system, ranging from 4 to 19%. (C) 2000 Elsevier Science B.V. All rights reserved.