An innovative approach to the analysis of 3-[4-(2-methylpropyl)phenyl]propanoic acid as an impurity of ibuprofen on a carbon-coated zirconia stationary phase

3-[4-(2-Methylpropyl)phenyl]propanoic acid has been introduced as impurity F to the European Pharmacopoeia in its Supplement 4.2. In contrast to other impurities, which are evaluated by HPLC, the content of impurity F is determined by gas chromatography after previous derivatization. Thus a novel reversed-phase HPLC method was developed to simplify the evaluation of pharmacopoeial impurity F of ibuprofen. Favourable properties of zirconia stationary phases were employed for this purpose. The HPLC separation was achieved on a Zr-CARB column (150 mm × 4.6 mm i.d., 5 μm) using the mobile phase acetonitrile-phosphate buffer (pH 3.5, 25 mM) (38:62, v/v), temperature 80 °C and the flow rate 1.2 ml min−1. The fluorescence detection was employed to enhance the sensitivity of the method. Optimal detection parameters were chosen on the basis of fluorescence spectra of the analytes. The excitation and emission wavelengths were 220 nm and 285 nm, respectively. The analysis was completed within 25 min. The subsequent validation of the method confirmed the applicability of method for the analytical assay of impurity F.