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 electr okinetic chromatography. A surfactant, tetradecyltrimethylammonium chl oride, is used to form micelles, which act as a pseudostationary phase in the chromatographic separation. This surfactant has a positive cha rge, thus preventing adsorption of a visualizing agent, oxazine 750 (w hich contains a positive charge), to the capillary wall (which is nega tively charged). The detection mechanism is based on the exclusion of the fluorophore, which is located in the hydrophilic part of the micel le, by a hydrophilic sample. The fluorescence intensity is reduced whe n the fluorophore is released into the aqueous solution. Separations o f several aromatic compounds are demonstrated, and the parameters affe cting the selectivity are discussed.