Electrochemical Sensors for the Stripping Voltammetric Determination of Antimony(III)

The conditions of the modification of a glassy-carbon electrode with various polyphenols were studied by multicyclic voltammetry over a wide range of pH. The state of the electrode surface was additionally monitored by measuring cyclic voltammograms of ferrocyanide ions in the presence of a phosphate buffer solution (pH 7.0). It was found that the electrooxidation of all the studied polyphenols at the electrode surface resulted in the formation of a water-insoluble film which is capable of accumulating antimony(III) from aqueous solutions. The surface concentration of chemically active cites was of the order n × 10^–9 M/cm². The electrochemical sensors thus prepared were found to be suitable for the selective determination of antimony(III) by adsorption stripping voltammetry. The maximum signals of antimony(III) were obtained at electrodes modified with pyrocatechol and pyrogallol upon metal deposition from acetate buffer solutions (pH 4.5). The detected peak areas S (A · s) were directly proportional to the deposition time t _d (min) and the concentration of antimony(III). The analytical range was 10–250 g/L at t _d = 5.0 min, and the detection limit was 6 g/L. It was found that a sensor based on a pyrogallol film can selectively determine antimony(III) in the presence of Sb(V), Cu(II), and Pb(II), and can be used for the analysis of natural water.