Simultaneous HPLC determination of ketoprofen and its degradation products in the presence of preservatives in pharmaceuticals

A novel and quick high-performance liquid chromatography (HPLC) method with UV spectrophotometric detection was developed and validated for the determination of five compounds in topical gel. The described method is suitable for simultaneous determination of active component ketoprofen, two preservatives methylparaben and propylparaben and two degradation products of ketoprofen-3-acetylbenzophenone and 2-(3-carboxyphenyl) propionic acid-in a topical cream after long-term stability tests using ethylparaben as an internal standard. The chromatographic separation was performed on a 5 mum Supelco Discovery C 18 column (125 mm x 4 mm i.d., Sigma-Aldrich); the optimal mobile phase for separation of ketoprofen, methylparaben, propylparaben, degradation products 3-acetylbenzophenone and 2-(3-carboxyphenyl) propionic acid and ethylparaben as internal standard consists of a mixture of acetonitril, water and phosphate buffer pH 3.5 (40:58:2, v/v/v). At a flow rate of 1.0 ml min(-1) and detection at 233 nm, the total time of analysis was less than 10 min. The method was applied for routine analysis (batch analysis and stability tests) of these compounds in topical pharmaceutical product. (C) 2004 Elsevier B.V. All rights reserved.