Electrochemical analysis of some drug substances in complex matrices

This thesis describes the development of several analytical methods, based on electrochemical techniques, for the determination of various drug substances in formulations, biological fluids and environmental samples. The work included a study of the voltammetric behaviour of both sumatriptan succinate and salbutamol sulphate at a glassy carbon electrode. Based on these studies, simple, rapid and sensitive voltammetric methods were developed for the determination of these drugs in tablet dosage forms without any interferences from the excipients. Using differential pulse voltammetry, the dissolution profile of salbutamol tablets was also investigated. The principal criteria for designing electrochemical flow detectors, and the great advantages of carbon fibre electrodes, have been utilized in the development of a versatile electrochemical detector for HPLC that is based on a carbon fibre (14 pm diameter) placed in a polyethylene tube connected directly to the end of the chromatographic column. The analysis of salbutamol in human plasma was then developed based on extracting the drug from the plasma into an organic solvent and separation of the drug on a reversed-phase Cjg column, followed by detection using the carbon fibre flow electrode. Several advantages of the carbon-fiber flow electrodes over conventional electrodes have also been demonstrated. The cell was then used for monitoring of terbutaline concentrations in human plasma in the range of 1-35 ngml'l using columnswitching LC. The method involved direct injection of the plasma sample into a Ci 8 extraction column for sample clean-up. This method was also applied for the simultaneous determination of both salbutamol and terbutaline at overdose levels in human plasma. A method was then developed to determine the suspected carcinogen gentian violet in human urine and in poultry feed. Liquid chromatography with electrochemical detection was also applied in environmental studies for the analysis of malachite gree