A simple and sensitive method of nonaqueous capillary electrophoresis with laser-induced native fluorescence detection for the analysis of chelerythrine and sanguinarine in Chinese herbal medicines

Laser-induced fluorescence (LIF) is a highly sensitive detection method for capillary electrophoresis (CE). However, it usually requires analyte to be derivatized, unless the wavelength of native fluorescence of analyte matches the laser's. That limits its application in drug analysis. In this work, we introduced a rapid, simple and sensitive method of nonaqueous capillary electrophoresis with laser-induced native fluorescence (NACE-LIF) detection for the analysis of chelerythrine and sanguinarine for the first time. As these two alkaloids have some native fluorescence, they were directly detected using a commercially available Ar⁺ laser without troublesome fluorescent derivatization. The fluorescence was enhanced by nonaqueous media. Compared with previously reported UV detection method, lower limit of detection (LOD) is achieved thanks to the high sensitivity of LIF detection (2.0 ng/mL for chelerythrine and 6.3 ng/mL for sanguinarine). Moreover, with NACE, the baseline separation of these alkaloids is finished within 3.5 min. This method is successfully applied to determine the contents of chelerythrine and sanguinarine in Macleaya cordata (Willd.) R. Br. and Chelidonium majus L.