Voltammetric determination of diazepam using a bismuth modified pencil graphite electrode

Abstract

In this study, a bismuth modified pretreated pencil graphite electrode (BiPPGE) was employed for the determination of diazepam (DZ). First, the pencil graphite electrode (PGE) was electrochemically pretreated and then a bismuth film was prepared by ex situ plating of bismuth on the pretreated PGE. The modified electrode displayed enhanced electroactivity toward the reduction of DZ compared to the simple bare PGE. The electrochemical reduction of DZ on the BiPPGE was totally irreversible and controlled by diffusion. The transfer coefficient, i.e. α, for diazepam at the BiPPGE was determined. Under optimum conditions, differential pulse voltammetry was used for the determination of DZ, which showed a linear calibration graph of i_pversus DZ concentration in the range of 1.4 to 16.7 μM with a correlation coefficient of 0.9956. The determined detection limit for S/N = 3 was 1.1 μM. By using the BiPPGE, high concentrations of uric acid and ascorbic acid existing in human urine did not show any interference with the determination of DZ. Finally, the BiPPGE was used for the determination of DZ in tablets and biological samples such as human urine using the standard addition method.