DIRECT-DETECTION OF VACUUM-ULTRAVIOLET RADIATION FOR NONMETAL DETERMINATIONS WITH A HELIUM MICROWAVE-INDUCED PLASMA

A study of the determination of metals, nonmetals, and metalloids (F, Cl, Br, I, S, P, Se, As, Sb, and Pb) in the vacuum-ultraviolet spectra l region with a kilowatt-plus helium microwave-induced plasma is prese nted. A spectrometer system similar to that used for far-ultraviolet o ptical sampling with an inductively coupled plasma was designed and im plemented. This arrangement was produced by using an optical sampler t o couple the plasma discharge with a helium-purged monochromator. Moni toring was performed at wavelengths less than 200 nm with no N2 or O2 in the optical path. Helium was chosen as the purge gas because it is transparent in the wavelength region of interest (>58 nm). Sample intr oduction was accomplished with ultrasonic nebulization. Limits of dete ction, linear ranges, and matrix effects caused by group IA and IIA el ements were studied. Analytical calibration plots were linear over a r ange of 2-3 orders of magnitude. Detection limits ranged from 0.06 mug /mL for sulfur to 5 mug/mL for selenium.