An application of a disposable electrode for the sensitive, selective, and cost-effective voltammetric determination of antiparkinsonism drug entacapone based on both its oxidation and reduction

Entacapone (ETC) is an important drug active ingredient frequently used together with levodopa (LD) and carbidopa (CD) in the treatment of Parkinson's disease. This study describes a simple, selective, sensitive, and cost-effective voltammetric determination of ETC based on both its oxidation and reduction at a disposable graphite pencil electrode (GPE). The electrochemical oxidation and reduction of ETC were investigated by recording cyclic voltammograms (CVs) of ETC based on the pH of the supporting electrolyte at a fixed scan rate and the scan rate at the supporting electrolyte of 0.10 M H2SO4. The analytical performance studies were carried out by recording differential pulse voltammograms (DPVs) under optimized conditions and by considering both the anodic and the irreversible cathodic peak at - 130 mV. DPV results show that the disposable and unmodified GPEs have linear ranges of 2.5-1500 and 2.5-1000 nM with detection limits of 0.79 and 0.69 nM for reduction and oxidation, respectively. The effects of some potential interferants were investigated, and no significant interference among the studied compounds, such as CD, LD, and dopamine (DA), was observed. The DP voltammetric procedure using disposable GPE was applied to determine ETC in pharmaceutical tablets using antiparkinsonism treatment including triple compounds (ETC, CD, and LD) and an artificial urine sample. Acceptable results for both samples show that ETC can be cost-effectively determined with high accuracy, sensitivity, and precision in real samples.