Determination of selenium(IV) by a photooxidized 3,3′-diaminobenzidine/perfluorinated polymer mercury film electrode

A new, and easily fabricated, chemically modified electrode for the determination of selenium(IV) was examined by cathodic square-wave stripping voltammetry. This new electrode consisted of an anion-exchange perfluorinated polymer (Tosflex) coated thin mercury film electrode containing photooxidized 3,3′-diaminobenzidine (ODAB). The coating solution of Tosflex and ODAB was spin-coated on a glassy carbon electrode followed by electroplating of a thin film of mercury. During the preconcentration, ODAB was reduced electrochemically and selenium was accumulated simultaneously onto the electrode by interacting with the reduced ODAB. After a 5-min preconcentration period, linear response was observed from 0.5 to 50 ppb selenium, and the detection limit was 0.1 ppb. The proposed method does not require a darkened room, which was required in many of the previous methods involving 3,3′-diaminobenzidine. In addition, the resistance to interference from surface-active compounds was improved by incorporating Tosflex in the film.