SIMULTANEOUS DETERMINATION OF ARSENIC, ANTIMONY AND SELENIUM BY GAS-PHASE DIODE-ARRAY MOLECULAR ABSORPTION SPECTROMETRY, AFTER PRECONCENTRATION IN A CRYOGENIC TRAP

This paper describes a method for the simultaneous determination of As (III), Sb(IV) and Se(IV) by combining hydride generation and gas phase molecular absorption spectrometry. A system for continuous hydride ge neration has been designed and developed, based an the use of a double process of gas-liquid separation, and optimal compromise operation co nditions for the three compounds have been found. After generation, th e hydrides are collected in a liquid nitrogen cryogenic trap, and then evaporated and driven to the flow cell of a diode array spectrophotom eter, in which the transient signals over the 190-250 nm wavelength in terval are measured. Under the recommended conditions (sample flow: 35 ml min(-1), 0.5 M HCl; reductor flow: 4 ml min(-1) of 4% NaBH4 soluti on) linear response ranges above 50 mu g l(-1) for As(III), 30 mu g l- 1 for Sb(III) and 200 mu g l(-1) for Se(IV) are obtained with detectio n limits of 22 mu g l(-1), 15 mu g l(-1) and 65 mu g l(-1), respective ly. Multiwavelength linear regression equations were used for the simu ltaneous determination of the three elements in different synthetic sa mples, with good precision and accuracy and to study simultaneously th e interference from different chemical species for the three compounds . Results were similar to those obtained by other techniques using hyd ride generation.