Determination of Nicotinic Acid by Square Wave Voltammetry on a Carbon Paste Electrode: the Crucial Effect of Electrode Composition and Analytical Conditions

The foregone studies have shown that nicotinic acid cannot produce noticeable reductive signal at carbon-based electrodes without appropriate modification of the electrode. This is an obvious reason that mercury is known as the main electrode material for electro-reduction of nicotinic acid. In this study, it has been shown that it is possible to create a remarkable reduction signal for NA at a carbon paste electrode (CPE) without any modification. This achieved by precisely adjustment of electroanalysis pH, appropriately choosing of binder kind, precisely controlling of the percentage of the binder in the electrode composition and utilizing of an effective voltammetric technique. A carbon paste electrode, containing 30% of n-eicosane (as binder) was shown to be the best electrode for NA determination. It was also shown that utilizing of square wave voltammetry in place of differential pulse voltammetry led to remarkably improvement in the analytical signal of NA. The pH value of the electroanalysis solution was shown to be a crucially effective factor for creating of NA signal and an optimum value of pH equal to 2.2 was chosen as the best pH condition. The optimized method exhibited a dynamic concentration linear range of 3.0×10−6-3.0×10−3 molL-1 with a detection limit of 5.63×10−7 molL-1. As an analytical application, the proposed sensor was successfully used for determination of nicotinic acid in the urine, serum and pharmaceutical samples.