Development of a Raman Detector for Capillary Electrophoresis

Efficient detector optics incorporating a hyperhemispherical element have been developed to facilitate the coupling of capillary electrophoresis or microchromatography with Raman spectroscopy. The design has a high tolerance for alignment and focusing errors. A simple model has been developed to predict the behavior of the system as capillary diameter is varied. This approach was found to provide good qualitative agreement with experiment. Limits of detection in capillary electrophoresis experiments without preconcentration were found to be ∼ 5 mM for nitrate and perchlorate ions. Direct detection of several carbohydrates was also demonstrated; with the use of sample stacking, limits of detection were in the millimolar range. The analytes were distinguishable by their Raman spectra.