The efficiency of the electrochemical generation of volatile hydrides studied by radiometry and atomic absorption spectrometry

Efficiencies of electrochemical generation (EcHG) of SeH2, AsH3 and SbH3 in a thin layer flow-through electrolytic cell with lead as wire as the cathode were studied by atomic absorption spectrometry (AAS) and, in the case of SeH2, by radiometry employing the radiotracer 75Se. The influence of relevant experimental parameters was investigated. The parameters studied were: electrolytic current; catholyte type (HCl, H2SO4), flow rate and concentration; the age of the lead cathode; analyte concentration and carrier gas flow rate. The influence of the most critical experimental parameters, i.e. electrolytic current and catholyte flow rate, on the fraction of analyte lost to the waste was determined by (wet chemical) hydride generation AAS and checked by graphite furnace AAS. These results indicate that EcHG efficiency for Se, As and Sb, respectively, in the electrolytic cell with the wire Pb cathode must be lower than 90%, 57% and 92%. The 75Se radiotracer was employed to determine SeH2 generation efficiency and to track ways in which analyte can be lost in the course of EcHG. The tracer experiments proved that the EcHG efficiency for selenium (72±2%) is lower than that estimated from analyte fraction lost to the waste – by the analyte fraction retained at all surfaces. Possible ways of improving the efficiency of EcHG are suggested.