POLY(3,3'-DIAMINOBENZIDINE) FILM ON A GOLD ELECTRODE FOR SELECTIVE PRECONCENTRATION AND STRIPPING ANALYSIS OF SELENIUM(IV)

Electropolymerization of 3,3'-diaminobenzidine at solid substrate elec trodes (platinum, gold, and glassy carbon) gave stable and water-insol uble films under a wide range of pH. Under the conditions of this stud y, the polymer films were found to be electroactive in acidic solution s but not in neutral or basic solutions. The poly(3,3'diaminobenzidine )-modified gold electrode exhibited very high selectivity for the open circuit accumulation of Se(IV) through complexation with the aromatic o-diamine groups attached to the polymer backbone to form the piasele nole. This property was exploited for the preconcentration of Se(IV), followed by differential pulse anodic stripping voltammetry for its de termination. The differential pulse stripping analysis involved three steps: accumulation, electrochemical reduction to elemental selenium, and differential pulse anodic stripping. Factors affecting these steps were systematically investigated, and an optimized procedure was deve loped. Using this optimized procedure, a detection limit of 9.9 x 10(- 9) M Se(IV) (0.78 ppb Se(IV)) was realized for a 10 min accumulation. For 10 determinations of Se(IV) at concentrations of 1.00 x 10(-6) and 1.00 x 10(-7) M, relative standard deviations of 2.8% and 3.4% were o btained, respectively. The presence of selected ions and complexing ag ents gave no observable interferences. Finally, the developed method w as successfully applied to the analysis of selenium in a U.S. Environm ental Protection Agency water quality control sample and also in a com mercial health supplement sample.