Fundamental studies of electrolyte-as-cathode glow discharge-atomic emission spectrometry for the determination of trace metals in flowing water

The fundamental characteristics and analytical performance were investigated of a new glow discharge emission source (GDES) for the determination of trace metals in flowing water. The application of an atmospheric glow discharge in argon gas between an electrolyte solution cathode and a platinum rod anode led to the development of a stable discharge. The intensity of the lines was found to depend strongly on the acidity of the water, the current and the discharge gap. The spectrum emitted from the tap water contained the basic atomic lines of the dissolved metals and OH band peaks, but no emission lines of argon from the discharge gas. The strong emission lines for an element and no emission lines from the discharge gas in the electrolyte-as-cathode glow discharge (ELCAD) were different from those in a solid-as-cathode discharge, suggesting a different excitation mechanism. Sub-parts-per-million detection limits of Al, Cd, Cr, Cu, Mn, Pb and Hg were obtained. The continuous-flow sample system demonstrates the possibility to develop a device for the continuous analysis of water and waste water solutions. (C) 1998 Elsevier Science B.V. All rights reserved