CONTINUOUS HYDRIDE GENERATION LOW-PRESSURE MICROWAVE-INDUCED PLASMA-ATOMIC EMISSION-SPECTROMETRY FOR THE DETERMINATION OF ARSENIC, ANTIMONY AND SELENIUM

The direct coupling of on-line continuous hydride generation methods to low-pressure microwave-induced Ar and He plasmas, sustained in a surfatron, was evaluated for the determination of trace amounts of arsenic, antimony and selenium by atomic emission spectrometry. The effect of the hydrogen produced during the hydride generation step, the optimization of the operating conditions for He and Ar plasmas and the figures of merit of the analytical systems are given. Detection limits (3s) of 0.7, 0.9 and 4.1 ng ml(-1) were obtained for As, Sb and Se, respectively, using an Ar plasma at 50 Torr (1 Torr = 133.322 Pa) and a power of 115 W. The relative standard deviations, calculated at the 50 ng ml(-1) level, were in the range 3-4% for the three elements. Poorer detection limits were obtained for He than for Ar discharges (by about two to five times, depending on the emission line). Using an argon: discharge, the method was applied successfully to the determination of As in sea-waters.