Competition studies in voltammetric measurements based on extractive accumulation into carbon paste electrodes

Abstract The selectivity of voltammetric measurements following extractive and adsorptive accumulation at carbon paste electrode is evaluated. Various situations where more than one electroactive species accumulate at the electrode are considered. It is shown that extractable species can be measured in the presence of adsorbable species if the outer layer of the surface is removed following the accumulation step and the voltammetric measurement is performed in a blank solution. As the extractive accumulation process can be treated on the basis of solvent extraction principles, the voltammetric measurement, performed on the electrode interior, provides the desired quantitative information. Due to differences in acid-base properties of various extractable organic compounds, it is possible to design an accumulation scheme specific for a given analyte. New information on the nature of the extractive accumulation step is reported. Chlorpromazine, uric acid, N,N -dimethylaniline and butylated hydroxyanisole are used as test systems. The implications of the method on the development of selective voltammetric sensors are discussed.