Electrochemical behaviour and electroanalytical methods for the determination of arsenic compounds

Abstract

The electrochemical behaviour of inorganic and organic arsenic compounds is subject of investigations presented here. Macro scale electrolysis at mercury, carbon and noble metal electrodes in aqueous or non-aqueous solutions allows the synthesis of compounds usually difficult to prepare by traditional chemical methods. A new technique for the electrochemical generation of arsine with subsequent determination by atomic spectroscopy is proposed as an alternative to chemical reduction. A variety of different toxic inorganic and organic arsenic compounds are found in the environment. Living organisms are capable of transforming arsenic compounds, some alkyl and aryl compounds are transferred to the environment by industrial activities, e.g. warfare agents, pharmaceutical products and herbicides. Electrochemical methods offer simple and accurate procedures for the determination of arsenic compounds, however, often restricted to relatively pure solutions. In most cases reductions are carried out at dropping mercury electrodes and allow the determination of inorganic arsenic at low ppb levels. Electrochemical determinations of organic arsenic compounds in real samples offer the possibility to differentiate between arsenic(III) and arsenic(IV) compounds. For all types of compounds, the electrode reactions and reduction pathways are extensively investigated. A new field in the electrochemistry of arsenic compounds has been made available by the introduction of sensors for the determination of gaseous arsines with or without gas chromatographic separation as well as the new possibility of capillary electrophoretic separations of anionic and cationic arsenic compounds.