Determination of 4-aminophenol impurities in multicomponent analgesic preparations by HPLC with amperometric detection

A method for the determination of 4-aminophenol, the main impurity of paracetamol, by high-performance liquid chromatographic (HPLC) method with amperometric detection has been developed. The analysis was performed in an isocratic mode on a reversed phase Luna column 5 mum C- 18 (100 x 4.6 mm). A mobile phase (0.05 mol l(-1) LiCl solution containing 18% methanol adjusted to pH 4.0 with orthophosphoric acid) was suitable for the separation and determination of 4-APh. Chromatograms were recorded for 250 s by means of an amperometric detector at a potential of +325 mV of the glassy carbon electrode versus the reference electrode Ag/AgCl. The proposed liquid chromatographic method was successfully applied to the analysis of commercially available multicomponent dosage forms. The sensitivity of the detection for 4-aminophenol was 1 ng ml(-1) for substance and 4 ng ml(-1) for tablets or capsules. The method developed in this study is sensitive and selective and can be applied for routine studies of pharmaceuticals in the form of tablets or capsules. (C) 2003 Elsevier Science B.V. All rights reserved.