Simultaneous determination of methylparaben, propylparaben, sodium diclofenac and its degradation product in a topical emulgel by reversed-phase liquid chromatography

A novel reversed-phase liquid chromatographic method with UV spectrophotometric detection was developed and validated for the determination of compounds in topical emulgel. The method describes determination of active component sodium diclofenac, its degradation product 1-(2,6-dichlorophenyl)-indolin-2-one (occurring in formulation after long-term stability tests) and two preservatives presented in the emulgel, methylparaben and propylparaben, using flurbiprofen as an internal standard. The chromatographic separation was performed on a SUPELCO Discovery C18 column; the mobile phase for separation of all the compounds was methanol/phosphate buffer, pH 2.5 (65:35, v/v). The analysis time was <17 min. The method was found to be applicable for routine analysis (stability tests) of active compound sodium diclofenac, preservatives and degradation product in a pharmaceutical product, topical diclofenac emulgel 1%. (C) 2002 Elsevier Science B.V. All rights reserved.