High-sensitivity fluorescence detector for fluorescein isothiocyanate derivatives of amino acids separated by capillary zone electrophoresis

Abstract

A fluorescence detector has been developed for capillary zone electrophoresis that produces a ten-fold improvement in precision compared with the previous state-of-the-art in fluorescence detection. This instrument, which is based on a sheath-flow cuvette flow chamber and a 0.05-W argon ion laser beam, combines a high numerical aperture collection optic, N.A. = 0.65, with a high quantum yield photomultiplier tube, Φ ≈ 0.5 at the wavelength of maximum emission. Detection limits (3σ) range from injection of 1.7·10-12 M) of fluorescein isothiocyanate (FITC)-labeled arginine, the best case, to 6·10-21 mol (5.6·10-12 M) of FITC-cysteine, the worst case. Signal linearity extends for at least five orders of magnitude from the detection limit to greater than 10-16 mol (10-7 M) injected. © 1989.