Interference of copper and nickel on electrochemical hydride generation

Abstract

Interferences by copper and nickel on electrochemical hydride generation of stibine, arsine and hydrogen selenide were examined using flow injection sample introduction. Direct interference or memory interference by either metal was found to be severe when using lead, pyrolytic graphite or vitreous carbon as a cathode. With a lead cathode, corresponding signal recoveries (%) for AsH₃, SbH₃, and SeH₂ were, 20, 20 and 60 in the presence of 20, 10 and 40 µg ml^–1 of Ni^II, respectively, and 30 and 50 for AsH₃, and SbH₃ in the presence of 120 and 7.5 µg ml^–1 of Cu^II, respectively. Although nickel presented less interference on arsine production with a platinum cathode [no interference from 600 µg ml^–1 Ni^II], arsine production efficiency is too low to be analytically useful with this material (<8%). An increase in acidity of the catholyte solution and use of thiourea or L-cysteine resulted in no alleviation of interference from copper on stibine production [50% suppression due to 7.5 µg ml^–1 Cu^II]. A discussion is presented outlining the potential remedial action which can be undertaken to minimize or eliminate such interferences.