The focus of this research was to develop improved methods for the analysis of drug metabolism by capillary electrophoresis Coumann was initially chosen as the model for the study, which then broadened in its scope to include the analysis of ammo acids Chapter one is a literature survey, which includes capillary electrophoresis techniques, with particular emphasis on sensitivity enhancement methods, in vitro models for drug metabolism, and coumann analysis. Chapter two details the application of a sample enhancement strategy, pH-mediated sample stacking, to the analysis of three of the metabolites of coumann 7- hydroxycoumarm, 4-hydroxycoumann and o-hydroxyphenylacetic acid. A suitable separation method for the three analytes was developed and, once optimised, was applied to the analysis of microsomal incubations of coumann using Cynomologus monkey microsomes 7-hydroxycoumann was identified m the incubation mixture by spiking of the mcubation mix with a standard, and then formation of this metabolite was momtored over time. Chapter three deals with the development of an automated system for the analysis of microsomal incubation reactions A separation method, capable of separating seven of the potential metabolites of coumann was initially developed and was then applied to the on-system technique The system allowed the metabolism of coumann to be momtored over time with minimal sample handling. Chapter four is a detailed study of pH-mediated sample stacking with investigations carried out into the influence of injection type, injection length and sample base injection ratio Conclusions are drawn on the mode of action of this form of sample stacking under each of the injection conditions studied In addition, the use of an alternative sample matrix to the previously employed Ringer’s solution is investigated. Chapter five details the application of pH-mediated sample stacking, with mdirect detection, to the analysis of eight ammo acids. The developed method showed that pH-mediated sample stacking was compatible with indirect UV detection and the eight amino acids could be detected sensitively with a run time of less than 13 minutes. Finally, chapter six summarizes the research carried out in each chapter and describes the future role of CE, as applied to the analysis of microsomal samples.