On-line synergistic stacking in capillary zone electrophoresis featuring field-amplified sample stacking and micelle to cyclodextrin stacking in determination of two alkaloids in complicated matrix samples.

A novel on-line synergistic proconcentration strategy coupling field-amplified sample stacking and micelle to cyclodextrin stacking for cationic analytes in capillary zone electrophoresis has been proposed and applied for the separation and determination of two alkaloids, matrine, and oxymatrine in complicated matrix samples. The approach was performed by the long injection of sample in a low-conductivity sodium dodecyl benzene sulfonate solution followed by the injection of hydroxypropyl-beta-cyclodextrin solution in higher conductivity. The stacking mechanism of this method has been expounded and parameters affecting stacking effect have been optimized in our study. Under the optimum experimental conditions, 169- and 218-fold sensitivity improvements were achieved for matrine and oxymatrine when compared with normal injection. Analytical indicators including linearity, limits of detection, and reproducibility (intra-and inter-day relative standard deviations) were evaluated. Moreover, sample matrix effect was studied using compound flavescent sophora and salicylic acid powder and spiked urine samples. The developed method is an attempt for the combination of micelle to cyclodextrin stacking with other stacking methods. It could be a good alternative choice for the determination of alkaloids in a complex sample matrix.