Simultaneous determination of the two non-steroidal anti-inflammatory drugs ; diflunisal and naproxen in their tablets by chemometric spectrophotometry and HPLC.

Chemometric spectrophotometry and HPLC were applied to the simultaneous determination of the two non-steroidal anti-inflammatory drugs; diflunisal (I) and naproxen (II). The applied chemometric techniques are multivariate methods including classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS); and the second derivative of the ratio spectra ((2)D(r)) method. To develop the multivariate methods, the UV absorption spectra of the standard solutions of the training and validation sets in methanol were recorded in the range of 242-274 nm at 2 nm intervals. The specificity of the studied multivariate methods has been tested. In the (2)D(r) method, analytical signals at 235 and 259 nm were selected for the determination of (I) and (II), respectively. The HPLC method depends on reversed-phase separation using C18 column. The mobile phase consists of a mixture of acetonitrile - acetate buffer (pH 4.2; 50 mM) (60:40, v/v). The UV detector was set at 255 nm. The developed methods were validated and successfully applied to the simultaneous determination of (I) and (II) in their tablets. The assay results obtained using the chemometric methods were statistically compared to those of the HPLC method and good agreement was observed.