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 invest igated of a new glow discharge emission source (GDES) for the determin ation of trace metals in flowing water. The application of an atmosphe ric glow discharge in argon gas between an electrolyte solution cathod e and a platinum rod anode led to the development of a stable discharg e. The intensity of the lines was found to depend strongly on the acid ity of the water, the current and the discharge gap. The spectrum emit ted from the tap water contained the basic atomic lines of the dissolv ed metals and OH band peaks, but no emission lines of argon from the d ischarge gas. The strong emission lines for an element and no emission lines from the discharge gas in the electrolyte-as-cathode glow disch arge (ELCAD) were different from those in a solid-as-cathode discharge , suggesting a different excitation mechanism. Sub-parts-per-million d etection limits of Al, Cd, Cr, Cu, Mn, Pb and Hg were obtained. The co ntinuous-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