Electrochemical hydride generation of thallium

An electrochemical hydride generation (ECHG) technique was developed to improve the determination of thallium by atomic spectrometry. The technique is based on the catholyte variation system for production of thallium hydride. Using Pb-Sn alloy as cathode, a transient peak shaped signal was achieved and its height, the maximum absorbance value, was taken as an analytical parameter. Parameters that might affect the hydride generation efficiency were investigated and the analytical performance of the method under the optimized experimental conditions was assessed. The linear range was 1-250 ng mL(-1) for thallium and the relative standard deviation of the method was 4.2% (RSD, n=7). The LOD for thallium was found to be 0.8 ng mL(-1), showing a significant improvement relative to conventional chemical hydride generation techniques. The proposed method was applied to the determination of thallium in unalloyed zinc standard reference material. This method offers high sensitivity, simplicity, rapidness, freeness from reagent and low acid consumption.

Mechanistic aspects of electrochemical hydride generation for cadmium

The mechanistic aspects of a novel methodology for the electrochemical hydride generation (EcHG) of cadmium, entitled as the catholyte variation, have been studied. The hydrogen overvoltage of different cathode materials was determined in dilute electrolyte. The lead-tin alloy used as the cathode material for the EcHG of Cd had the highest hydrogen overpotential. In this technique, both electrolyte medium and cathode surface would change during electrolysis. The catholyte variation EcHG coupled with a flame heated quartz tube atomizer (QTA) atomic absorption spectrometer (AAS) produced peak-shaped transient signal of Cd. The analytical signal was significantly enhanced at neutralization time. The simultaneous production of lead and tin hydrides as well as the hydrogen at that time may speed up the desorption of cadmium species from the surface of the cathode. Also the high hydrogen overvoltage and the neutral medium aided the formation and separation of cadmium hydride molecules. The generated CdH2 vapour was kinetically stable.