Simultaneous determination of arsenic, antimony and selenium by gas phase diode array molecular absorption spectrometry, after preconcentration in a cryogenic trap

Resumo

This paper describes a method for the simultaneous determination of As(III), Sb(III) and Se(IV) by combining hydride generation and gas phase molecular absorption spectrometry. A system for continuous hydride generation has been designed and developed, based on the use of a double process of gas-liquid separation, and optimal compromise operation conditions for the three compounds have been found. After generation, the hydrides are collected in a liquid nitrogen cryogenic trap, and then evaporated and driven to the flow cell of a diode array spectrophotometer, in which the transient signals over the 190-250 nm wavelength interval are measured. Under the recommended conditions (sample flow: 35 ml min -1, 0.5 M HCl; reductor flow: 4 ml min -1 of 4% NaBH 4 solution) linear response ranges above 50 μg l -1 for As(III), 30 μg l -1 for Sb(III) and 200 μg l -1 for Se(IV) are obtained with detection limits of 22 μg l -1, 15 μg l -1 and 65 μg l -1, respectively. Multiwavelength linear regression equations were used for the simultaneous determination of the three elements in different synthetic samples, with good precision and accuracy and to study simultaneously the interference from different chemical species for the three compounds. Results were similar to those obtained by other techniques using hydride generation.