Analysis of Central European Corydalis species by nonaqueous capillary electrophoresis–electrospray ion trap mass spectrometry

In the presented study, Central European Corydalis species, namely C. cava, C. intermedia, C. pumila, and C. solida were investigated by nonaqueous capillary electrophoresis–electrospray ion trap mass spectrometry (NACE–ESI-MS) utilizing an electrolyte consisting of 50 mM ammonium acetate, 1 M acetic acid and 10% methanol in acetonitrile, applying a separation voltage of 30 and 20 kV for 1 s for injection. Isopropanol-water (1:1) was used as sheath liquid at a flow-rate of 3 μl/min. Peak assignment was assisted by multistage-ESI-mass spectrometry (ESI-MSn). The optimized method was fully validated (RSD inter- and intraday <5%, LOD < 2.3 μg/ml, LOQ < 27.6 μg/ml, recovery rates >98.8%) and subsequently applied for the qualitative and quantitative determination of isoquinoline alkaloids in single plant tubers (sample size < 0.5 g) of the four Central European Corydalis species, each of them showing a characteristic and unique alkaloid pattern. Application of a principal component analysis (PCA) to the complete dataset of 39 analytes and 79 samples allowed the identification of 8 analytes responsible for lot discrimination. Hierarchical cluster analysis and descriptive statistical methods were used to confirm the findings of the explorative PCA.