Simultaneous determination of naproxen and related compounds by HPLC using porous graphitic carbon column Lotfi Monser a, *, Frida Darghouth b a Chemistry Department, Institut National des Sciences Applique ´es et de Technologie, Centre Urbain Nord, B.P.No. 676, 1080 Tunis Cedex, Tunis, Tunisia b S.I.P. Ibn Albaytar, 11 Rue 8610, Z.I. Charguia, 2035 Tunis-Carthage, Tunis, Tunisia Received 24 April 2002; received in revised form 5 November 2002; accepted 7 November 2002 Abstract 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 mg ml 1 for all compounds studied were greater than 0.999. The sensitivity of detection is 0.05 mgl 1 for naproxen, MNE and MEN and 0.20 mg 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. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Naproxen; Degradation products; Isocratic elution; Porous graphitic carbon 1. Introduction Naproxen [(S)-6-methoxy-a-methyl-2-naphtha- lene acetic acid] is a non-steroidal anti-inflamma- tory drug widely used as mild to moderate pain relief and in the treatment of osteo- and rheuma- toid arthritis [1]. Naproxen action is due to the inhibition of the cyclooxygenase enzyme, which in turn, presents the biosynthesis of certain prosta- glandines [2]. The stability of naproxen in the raw materiel or in the final product could be altered under abnormal conditions such as: temperature, light, humidity and pH, which could yield different kinds of degradation products such as 1-(6-meth- * Corresponding author. Tel.:  /216-71-70-3829; fax:  /216- 71-70-4329. E-mail address: lotfi.monser@insat.rnu.tn (L. Monser). Journal of Pharmaceutical and Biomedical Analysis 32 (2003) 1087  /1092 www.elsevier.com/locate/jpba 0731-7085/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0731-7085(03)00213-9