An analytical method for alkaloids of Coptis chinensis based on mixed-mode surface electrostatic exclusion/reversed-phase chromatography

A mixed-mode chromatographic method based on surface electrostatic exclusion and reversed-phase chromatography was established for the determination of alkaloids present in Coptis chinensis. The effects of two mobile phase additives, formic acid and acetic acid, on retention, peak shape and selectivity of the alkaloids in Coptis chinensis were investigated using the self-made C18HCE column. Acetic acid (0.1%, v/v) used as the additive was found to be optimum for effective separation of the main alkaloids present in Coptis chinensis. The main chromatographic peaks of Coptis chinensis were recognized by the established method and references, which were coptisine, epiberberine, columbamine, jatrorrhizine, berberine and palmatine, respectively. With reference to the content determination method of Coptis chinensis in the 2015 edition of pharmacopoeia, the linear relationship of berberine in the range of 0.5-100 mg/L was good, the correlation coefficient was 0.9996, and the average recovery was 93.74%. The contents of alkaloids in Coptis chinensis in different batches of Hubei and Chongqing were determined. The method is simple, reliable and accurate, and can be used as reference for separation and analysis of other basic compounds.