FLUORESCENCE DETECTION IN CAPILLARY ELECTROPHORESIS USING A VARIABLE WAVELENGTH EPI-FLUORESCENCE MICROSCOPE

A capillary electrophoresis fluorescence detector is described. A high -pressure mercury lamp with a filter block allowed the selection of a particular excitation waveband. Detection was performed on-column, the fluorescence emission was monitored and measured with a silicon photo diode detector with a built-in amplifier. The concentration limit of d etection (CLOD) of 0.4 ng/mL was obtained for rhodamine B, a fluoresce nt indicator. Based on an estimated injection volume of 2.5 nL, the ma ss limit of detection (MLOD) was 2.1 x 10(-18) mol. The separation of three fluorescent indicators: thionine, eosin yellowish and rhodamine B, was achieved in less than 6 min. The separation of nine porphyrin-f ree acids using the system developed was also demonstrated. The advant ages and potential of using an epi-illumination microscope as a versat ile and sensitive fluorescence detection system for capillary electrop horesis are described.