Simultaneous determination of naproxen and related compounds by HPLC using porous graphitic carbon column

A simple, selective and sensitive high performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of naproxen and its main degradation products such as 1-(6-methoxy-2-naphthyl) ethanol (MNE), 2-methoxy-6-ethyl naphthalene (MEN) and 2-acetyl-6-methoxy naphthalene (AMN). The separation of these compounds was achieved on porous graphitic carbon (PGC) column using tetrahydrofuran-methanol as the mobile phase, and the effluent from the column was monitored at 272 nm. At a flow rate of 1 ml min(-1), the retention time of the last eluting compound was less than 10 min. Correlation coefficient for calibration curves in the ranges 2-25 microg ml(-1) for all compounds studied were greater than 0.999. The sensitivity of detection is 0.05 microg l(-1) for naproxen, MNE and MEN and 0.20 microg ml(-1) for AMN. The reproducibility of the peak area of these compounds using isocratic elution were quite high, and the standard deviations (S.D.) were below 2% (n=5). The reproducibility of retention times of these compounds was within 1% (n=5). The proposed liquid chromatographic method was successfully applied to the analysis of commercially available naproxen sodium (NS) dosage forms with recoveries of 98.8-102%. A comparative study shows that the selectivity of these compounds on PGC column was different to that obtained with octadecyl silica (ODS) columns.