Evaluation of open-air type electrolyte-as-cathode glow discharge-atomic emission spectrometry for determination of trace heavy metals in liquid samples

Electrolyte-as-cathode glow discharge-atomic emission spectrometry (ELCAD-AES) has been used for on-line determination of trace heavy metals in tap and drinking waters and fresh milk. The fundamental characteristics are: pH of electrolytes; discharge current; discharge gap shown influenced the plasma stability; and the intensity of emission lines emitted from different elements of solution. A stable discharge plasma which significantly improved the sensitivity was achieved when approximately 1.6 kV, several tens of milli-amperes current and a few millimeters discharge gap between the Pt rod anode and acidified electrolyte cathode in atmospheric air pressure were applied. Although the OH band dominates the solution spectra between wavelengths of 300 and 700 nm, nine elements including Pb and Cu have been determined from freshly collected unspiked tap and drinking waters and fresh milk. The limits of detection (LOD) of Hg, Pb, Cd, Cu, Na and K were obtained as 0.001-0.08 mg/l. The open-air ELCAD has used for the first time for Hg, Cd, Na and K detection and an improved LOD of Pb was found compared to reported values. The LOD values of Hg, Pb, Cd and Cu improved by more than one order of magnitude compared to closed-type ECLAD.