Field-Amplified Sample Stacking for Rapid and Sensitive Determination of Aconitine Alkaloids by CE Using an Ionic Liquid Electrolyte System

A new capillary electrophoresis procedure with field-amplified sample stacking (FASS) concentration for analysis of three aconitine alkaloids has been established using 1-butyl-3-methylimidazolium-based ionic liquids as the electrolyte solution. The use of a short water plug at the column inlet is essential for improving the reproducibility of FASS with electrokinetic injection, and the water plug injection time affects the sensitivity significantly. With this stacking procedure, the concentration sensitivity was 5–142 fold higher than for pressure injection. After optimization of the separation and concentration conditions, the three alkaloids could be separated within 6 min and quantified with high sensitivity. The detection limits were 0.10 μg mL−1 for aconitine, 0.021 μg mL−1 for hypaconitine and 0.56 μg mL−1 for mesaconitine. The method was used for quantitative analysis of the three aconitine alkaloids in two Aconitum plants with recoveries of 95.8–105.4%.