Investigation of the electrochemical behavior of tenofovir disoproxil fumarate on glassy carbon and poly(p-aminobenzenesulfonic acid)-modified glassy carbon electrodes

Tenofovir disoproxil fumarate (TDF) is an antiretroviral drug used to control the effects of the HIV virus. In this study, cyclic voltammetry (CV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) techniques were used to analyse active pharmaceutical ingredients. Due to the limitations of the working electrode used in voltammetry, the electrode surface was modified with semiconducting polymers to increase both selectivity and sensitivity. In the study, a glassy carbon electrode (GCE) was coated with a thin film layer using the electropolymerisation technique in a 0.1 M phosphate buffer (pH 7.0) containing 2x10-3 M p-aminobenzenesulfonic acid (p-ABSA) at a scan rate of 100 mVs-1 over a potential range of -1.5 V to +2.5 V for 5 cycles. Then, the modification process was carried out by taking 3 cycles with cyclic voltammetry technique in the range of -1.0 V and +1.0 V in phosphate buffer (pH 7.0). Acetate buffer, phosphate buffer, and Britton-Robinson (BR) buffer were selected as supporting electrolytes to determine the electrochemical behaviour of TDF. Prior to the study, nitrogen gas was passed through the medium for 300 seconds. The absence of an anodic peak in the reverse scan in the studies indicated that the reaction was irreversible. The changes of peak currents and peak potentials with pH were compared on GCE and modified GCE using CV, SWV and DPV techniques. Based on the obtained data, the analytical conditions were determined to be around pH 4 in acetate buffer. It was observed that on the modified GCE, peak potentials shifted to positive values, while peak currents increased. Considering all evaluations, it was concluded that the use of poly(p-ABSA)-modified glassy carbon electrode is suitable for the analysis of the active drug substance tenofovir disoproxil fumarate.