EVALUATION OF A METHOD FOR ARSENIC(III) AND ANTIMONY(III) DETERMINATION BY VAPOR-PHASE MOLECULAR ABSORPTION SPECTROMETRY USING GRAPHITE-FURNACE VOLATILIZATION

This paper presents a procedure for determining As(III) and Sb(III) by vapour phase molecular absorption spectrometry (VPMAS). The chlorides of these elements are volatilized from aqueous solutions in a L'vov platform inside the graphite furnace of an atomic absorption spectrophotometer. Molecular absorption is measured at 205 nm for arsenic chloride and 220 nm for antimony chloride. Both species are formed in the sample drying stage. A study of the temperature program led to different results in each case. In the case of arsenic, a two-step program (one mixed drying and volatilization step, and another cleaning step) is found to be best, whereas in the case of antimony, three separate steps can be used (drying, volatilization and cleaning). In both cases, optimum volatilization was obtained with low HCl concentrations, and volatilization fell off sharply as HCl concentration increased. Under optimum generation and determination conditions, the linear response range is from 0.06 to 3.75 mug for As(III), and from 0.30 to 5.0 mug for Sb(III) with relative standard deviations of 2.1% for As(III) and 2.5% for Sb(III). The effect of other anions and cations on the arsenic analytical signal was studied, and other halides were found to interfere. The method was applied to arsenic determination in an arsenic ore.