INDIRECT DETECTION OF AROMATIC-HYDROCARBONS BY SEMICONDUCTOR-LASER FLUOROMETRY IN MICELLAR ELECTROKINETIC CHROMATOGRAPHY

A semiconductor laser is used as an exciting light source in indirect fluorescence detection of neutral samples separated by micellar electrokinetic chromatography. A surfactant, tetradecyltrimethylammonium chloride, is used to form micelles, which act as a pseudostationary phase in the chromatographic separation. This surfactant has a positive charge, thus preventing adsorption of a visualizing agent, oxazine 750 (which contains a positive charge), to the capillary wall (which is negatively charged). The detection mechanism is based on the exclusion of the fluorophore, which is located in the hydrophilic part of the micelle, by a hydrophilic sample. The fluorescence intensity is reduced when the fluorophore is released into the aqueous solution. Separations of several aromatic compounds are demonstrated, and the parameters affecting the selectivity are discussed.