Indirect laser-induced fluorescence detection of diuretics separated by capillary electrophoresis

Indirect LIF detection was applied to the detection of four acidic diuretics separated by CZE. Semiconductor laser was employed to provide the stable excitation of 473 nm. With an optimized electrophoretic buffer system which contained 5 mM of triethylamine, 0.1 microM of fluorescein, and 5% of n-butanol, fast separation of four diuretics (ethacrynic acid, chlorthalidone, bendroflumethiazide, and bumetanide) can be performed within 3 min with the detection limits of 0.2-2 microg/mL. The impacts of buffer components including the concentrations of the electrolytes, fluorescence probe, and the organic additives were demonstrated. The method was applied for the detection of diuretics in urine. As an alternative way for the fast analysis of diuretics, this indirect detection method provided the technical support for future microchip performances, in which diuretics may be detected in the microchip by the common LIF detector without derivatization.