This work is a contribution to the minimization of some of the selectivity and detection limitations in capillary electrophoresis. A more practical design of an electrochemical detector is introduced with simultaneous on-line UV detection¹, for the selective detection of a number of pungent and neurological compounds, the piperines and the capsacinoids. Commercially available microelectrodes together with large 25 μm id fused silica capillary columns are used for the first time in the presence of an auxiliary electrode. Minimum detectable quantities and efficiencies are sample dependent and were found to be comparable to the earlier more laborious electrochemical cell designs. To exploit the benefits of common additives that enhance the selectivity of electrolyte systems, various additives including α, β and γ Cyclodextrins, organic modifiers, as well as a series of cationic surfactants are explored for the separation of a number of industrially important isomeric aromatic carboXylic acids². The separation was found to depend largely on the analyte1s geometry, degree of ionization as well as on the buffer pH and composition. The resultant separations were compared for best efficiency, resolution and ruggedness. In addition, to add to the arsenal of CE selectors, a number of new micellar systems are investigated. Oligomeric sodium 10-undecylenate, a recently introduced oligomeric surfactant³ is structurally investigated through the separation of vitamins and the resultant selectivity and resolution is compared to the more commonly used surfactant sodium dodecyl sulfate⁴. Additionally, a number of phospholipids and Iysophospholipids, common constituents of cell membranes, are investigated not only as possible MECC surfactants but also as highly hydrophobic analytes needing themselves separation⁵. Finally, as a contribution to methods development, the effect of variations in systemparameter conditions is examined in a successful separation of a number of enzymes. / Ph. D.