COMPARATIVE-STUDIES OF SURFATRON AND MICROWAVE PLASMA TORCH SOURCES FOR DETERMINATION OF MERCURY BY ATOMIC-EMISSION SPECTROMETRY

Two cavities are compared for the determination of mercury with aqueous sample introduction by an ultrasonic nebulizer. The performances of the cavities, surfatron and microwave plasma torch (MPT), are compared, with particular emphasis on the characteristics of plasma features, the effects of operational conditions, tolerance to foreign material or the presence of other elements, and analytical figures of merit. The effect of potassium chloride and ammonium chloride on the analytical performance of MIP (surfatron)-AES and MPT-AES has been examined and a possible mechanism is discussed. An improvement of about 3-fold in detection limits was achieved by adding an appropriate amount of 0.05% m/v of ammonium chloride. The detection limits for mercury by surfatron AES and MPT-AES are 0.9 and 1.3 ng ml-1, respectively. The precision obtained in this work is below 2.0. Stable discharges were obtained in both cavities with use of a low-power microwave generator.