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

The direct coupling of on-line continuous hydride generation methods t o low-pressure microwave-induced Ar and He plasmas, sustained in a sur fatron, was evaluated for the determination of trace amounts of arseni c, antimony and selenium by atomic emission spectrometry. The effect o f the hydrogen produced during the hydride generation step, the optimi zation of the operating conditions for He and Ar plasmas and the figur es 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, respec tively, using an Ar plasma at 50 Torr (1 Torr = 133.322 Pa) and a powe r 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 de tection limits were obtained for He than for Ar discharges (by about t wo to five times, depending on the emission line). Using an argon: dis charge, the method was applied successfully to the determination of As in sea-waters.