Observations on the interference by copper(II), cobalt(II) and nickel(II) on the determination of arsenic by arsine generation atomic absorption spectrometry

Abstract

Previous reports on the interference of copper(II), cobalt(II) and nickel(II) on the determination of arsenic by arsine generation atomic absorption spectrometry have been reviewed and an attempt has been made to rationalise the differences between them by examining the influence of interferent concentration, hydrochloric acid concentration, the amount of sodium tetrahydroborate(III) and the oxidation state of arsenic on the interference pattern. The extent to which the interferents are precipitated during the arsine generation procedure has been examined by quenching the reaction at different time intervals and determining the extent of loss to the solution either by analysis or by visual observation. From the results, conclusions have been drawn on the association between the formation of metal-like precipitates and the degree of interference. These data suggest that the interference mechanism may involve formation of soluble species rather than adsorption of arsine on the precipitated metals. This view is supported by polarographic evidence and analysis of solid material formed during reaction with sodium tetrahydroborate(III). Arsine evolution rate studies showed that when intereference is removed arsine is evolved at the same rate as arsine from arsenic(III).