Enantioselective analysis in complex matrices using capillary electrophoresis-mass spectrometry: A case study of the botanical drug Corydalis Rhizoma

Enantioselective analysis is critically important in the pharmaceutical and agricultural industries. However, most of the methods reported were developed for the analysis of pure racemates acquired from chemical synthesis or purification. Direct analysis of chiral enantiomers in complex matrices has rarely been reported. This work demonstrated capillary electrophoresis-mass spectrometry (CE-MS) for the enantioselective analysis of botanical drugs for the first time, using a widely used botanical drug, Corydalis Rhizoma, as an example. The method was used for the simultaneous enantioselective analysis of dl-tetrahydropalmatine and (RS)-tetrahydroberberine (canadine) in Corydalis Rhizoma extract. Using (2-hydroxypropyl)-β-cyclodextrin as the chiral selector, a partial filling technique was used to avoid signal suppression and contamination of the MS detector. Post column organic modifier was used to assist with ionization in the flow through microvial CE-MS interface, therefore, organic solvents was not used in the background electrolyte. The completely aqueous background electrolyte contributed to better chiral separations. The CE-MS method established here can directly determine the analytes in their complex matrix without any pre-purification steps, while also offering high sensitivity and low operational costs (including sample, chiral selector and solvent). In the method validation process, good linearity (r > 0.993), sensitivity and accuracy (recoveries within 89.1-110.0%) were demonstrated. The CE-MS technique was shown to be able to provide good selectivity for the simultaneous chiral separation of multiple pairs of enantiomers in complex matrices.