The versatility and exceptional efficiencies afforded by modern liquid chromatography (LC) have made it indispensable for separations and quantitative analysis in virtually every discipline within the physical and biological sciences. Despite rapid advances in column technology, the development and applications of LC have been slowed by the absence of truly universal and highly sensitive detectors. On the other hand, the recent explosive growth of capillary electrophoresis (CE) applications has created challenges in developing highly efficient detectors. This dissertation presents the development and improvements of instrumental techniques for detection in LC and CE. The first chapter reviews the current status of the various detection methods for LC and CE;Section I presents the first universal detector based on magneto-optical rotation (MOR) for high performance liquid chromatography (HPLC). The experimental results confirm the linear dependance of the MOR signal on the analyte concentration. The feasibility of this method is demonstrated in the detection of polynuclear aromatic hydrocarbons, where the limit of detection is in the sub-microgram range;For the first time, a novel axial-beam on-column absorption detector for open tubular capillary liquid chromatography is described in Section II. The axial coupling of source light with the capillary columns and the use of optical waveguide capillary columns made it possible to utilize the full length of the sample bands inside the capillary columns as the path length for absorbance measurements. For a typical 10 [mu]m i.d. capillary column, the axial-beam detection provides an increase of up to 1000 times in path length and a 192-fold associated improvement on the limit of detection;The project described in the third section is the optimization of detectability in the laser-based polarimetric detector for HPLC. A mathematical simulation is performed in order to optimize the detectability of the detector. The designing parameters of the detector are systematically chosen for optimum performance. The experimental verification of the optimized parameters provides the performance approaching the shot-noise limit;Finally, Section IV demonstrated the feasibility of axial-beam absorption detection for capillary electrophoresis using a conventional light source. The cross-beam and axial-beam detection schemes can be easily switched. The high stability of light intensity, variable wavelength and UV ability make this detector attractive. The improved limit of detection in the axial-beam arrangement should make CE with absorption detection feasible to a wider range of applications.