Determination of bismuth in aluminium and in steels by electrothermal atomic absorption spectrometry after on-line separation using a minicolumn of activated carbon

Abstract

A simple on-line separation and preconcentration flow injection system for the determination of Bi in steels and aluminium solutions by electrothermal atomic absorption spectrometry is proposed. The system requires only a manual injector–commutator and a peristaltic pump. Bismuth is separated after complexation with the ammonium salt of dithiophosphoric acid O,O-diethyl ester and sorption in a minicolumn filled with activated carbon, using ethanol as eluent, which is received in the autosampler cup of the electrothermal atomic absorption spectrometer. A L’vov platform covered with 500 µg of Ir allows a pyrolysis temperature of 900 °C. The preconcentration, pre-elution and elution flow rates were optimized. The column was cleaned with 2 mL of ethanol followed by 5 mL of water. For 10 mL of sample solution, an enrichment factor of about 14 was obtained for Bi in Al or Fe matrices. The detection limit, in the sample solution, was 0.048 µg L–1. The linear regression coefficients of the calibration curves were better than 0.997. For the certified steel samples, the results were in agreement with the reference values. For the non-certified aluminium sample, the recoveries of spiked samples were in the range 87–105%. The fact that the complexing agent does not complex Al and Fe(II) allows the separation of more than 99.5% of the major components.