Determination of local anaesthetics and their impurities in pharmaceutical preparations using HPLC method with amperometric detection

A method for the determination of local anaesthetics and their impurities - 2,6-dimethylaniline and o-toluidine - by high-performance liquid chromatographic method with amperometric detection has been developed. The analysis was performed in an isocratic mode on a reversed phase Luna column 5 μm C-18 (100 mm × 4.6 mm). A mobile phase [0.01 mol l−1 Tris buffer of pH 7.9:acetonitrile (45:55)] was selected for the separation and determination of studied anaesthetics and their impurities. Chromatograms were recorded for 500 s by means of an amperometric detector at a potential of +1.0 V 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 pharmaceutical preparations. The limit of the detection for 2,6-dimethylaniline and o-toluidine was 0.8 ng ml−1. The limit of qantitation, considering a signal to noise ratio was 1.5 ng ml−1. The method developed in this study is sensitive and selective and can be applied to routine studies of pharmaceuticals in the form of cream and injection.