ULTRASENSITIVE DETECTION FOR CAPILLARY ZONE ELECTROPHORESIS USING LASER-INDUCED CAPILLARY VIBRATION

The laser-induced capillary vibration method (CVL), a novel photothermal method, has been applied to on-column ultrasensitive detection of nonlabeled analytes separated by capillary zone electrophoresis (CZE). The feasibility and performance of the combined CZE/CVL were confirmed by using visible excitation with riboflavin as a sample. The lower detection limit of absorbance was 1.8 x 10(-7) for a 30-mu-m capillary, and the corresponding absolute amount was 80 amol, when the 476-nm, 40-mW lasing line of an argon laser was the visible excitation beam. These results were at least 3 orders superior to conventional absorption detectors and are of the same order as laser-induced fluorometry for riboflavin. Next, UV excitation was applied to the detection of nonlabeled amino acids separated by CZE. The second harmonic of the argon laser (257.2 nm, 5 mW) was used for excitation, and 15 fmol of tryptophan and 110 fmol of phenylalanine were detected without derivatization.