Application of capillary zone electrophoresis methods for the investigation of in vitro drug metabolism.

High performance liquid chromatography (HPLC) has for some time been the industry standard in pharmaceutical analysis. A diverse choice of column packing materials enables a wide range of analytical separations to be performed, including both normal and reversed phase as well as chiral chromatography. A variety of compatible detectors further increases the popularity of this instrument, allowing straight forward absorption/emission detection by ultraviolet light or fluorescence, in addition to the increased sensitivity of hyphenated technologies, with HPLC in conjunction with mass spectrometric detection and nuclear magnetic resonance spectroscopy. Capillary zone electrophoresis (CZE) offers an alternative analytical technique to a similarly broad range of analytes and mechanisms of detection. The advantages of CZE are the reduced run times, higher efficiency separations and savings on solvent usage and disposal. The pharmaceutical industry has increasingly employed CZE for dissolution analysis and impurity assessments as well as main-component assays.This thesis reports the potential of CZE as an analytical tool versus the more established technique of HPLC and their application to in vitro metabolism. In vitro metabolism looks at the metabolic fate of a drug, in this case by incubation with a suspension of the microsomal rat liver fraction. This method was chosen as it can generate a series of samples taken from a bulk incubation to provide a time profile over which the amount of parent compound present can be measured. In this way a series of compounds can be screened quickly and simply for their rate/extent of metabolism without the necessity for the more time consuming and expensive in vivo experimentation. Analytical methods were developed or modified from published work for both a series of basic analogues including propranolol and an acidic compound, chlorogenic acid. A novel approach to the CZE method development for the acid was a statistical analysis technique called Factorial Experimental Design (FED), which allowed the time-saving, simultaneous evaluation of the major influential parameters involved. Once these assays were established, they were investigated for reliability, accuracy, reproducibility and linearity. A comparison was made between two different CZE instruments, a Beckman P/ACE and a Hewlett Packard HP[3D], and also between CZE and HPLC. The final investigation was to apply these two analytical techniques in the field of in vitro drug metabolism, using propranolol as a model compound.