Determination of pharmaceuticals and related impurities by capillary electrophoresis

In the first part of this work, the use of capillary electrophoresis (CE) for the separation of two groups of pharmaceuticals, namely a metabolite of tamoxifen and a basic drug substance, DS1 was investigated. The effects of pH and types of modifiers, e.g. surfactant, bile salt, gamma-cyclodextrin and hydroxypropyl-beta-cyclodextrin on selectivity, separation and peak shape were studied. Besides achieving complete separation of the compounds, the CE system was capable of providing separation with significant improvements in overall peak shape of the compounds compared with HPLC. In the case of the basic drug substance DS1, validation of the CE system developed in terms of linearity, selectivity, sensitivity and reproducibility was satisfactorily performed. At the same time, a study of the sample solvent matrix effects on the separation of this group of compounds was examined. The system was successfully applied to the analysis of laboratory-synthesized samples. Good correlation was observed between CE and HPLC, although higher efficiency and faster speed of separation were obtained using the CE system developed. For the tamoxifen metabolite, special emphasis was placed on the use of CE for the separation of the pair of isomers. This was readily achieved through the introduction of gamma-cyclodextrin in the electrolyte. Resolution of at least 1.5 was obtained for the isomers using the CE method.