Determination of naproxen in pharmaceuticals by differential pulse voltammetry at a platinum electrode

The anodic oxidation of naproxen has been carried out on a platinum electrode using cyclic, linear sweep and differential pulse voltammetry (DPV). Naproxen exhibited a single well-defined and irreversible peak in acetonitrile/0.1 M LiClO4 with a peak potential at 1146 mV versus Ag/AgCl. This allowed the development of a simple, selective and sensitive differential pulse voltammetric method for the determination of naproxen in pharmaceuticals. The calibration plot was linear (R-2 = 0.998) over the range 1-25 mug ml(-1). The limit of detection (3sigma/m) was 0.24 mug ml(-1) and the relative standard deviation of the measurements was 1.2% (n = 6). Well-defined peaks for two related compounds to naproxen (2-methoxy-6-ethylnaphthalene (MEN) and 2-acetyl-6-metho-xynaphthalene (AMN)) were detected, respectively, at 1096 and 1316 mV versus Ag/AgCl and no interference was measured during the determination of naproxen. The limits of detection of MEN and AMN were found to be respectively 0.28 and 0.21 mug ml(-1). The method was successfully applied to the determination of naproxen in commercial tablets and showed a good sensitivity and accuracy with mean recoveries between 99.8 and 101.2%. (C) 2003 Published by Elsevier B.V.