Affinity capillary electrophoresis coupling with partial filling technique and field-amplified sample injection for enantioseparation and determination of DL-tetrahydropalmatine.

A novel, simple and sensitive method for the enantioseparation and determination of DL-tetrahydropalmatine (DL-THP) was developed using ACE in combination with partial filling technique and field-amplified sample injection. A chiral selector, i.e. BSA, was used for the enantioseparation of DL-THP in ACE. Effects of BSA concentration, pH and separation voltage on the effectiveness of the enantiomer separation were evaluated. In an optimal condition, D- and L-THP were completely enantio-separated in less than 9 min by partially filling an electrophoretic capillary with 50 micromol/L BSA (50 mbar, 100 s) and carrying out an electrophoresis with 20 mmol/L phosphate buffer (pH 7.4) at 15 kV. The sensitivity was further improved by making use of field-amplified sample injection to lower the LOD (defined as S/N=3) down to 6 ng/mL. Real samples were also tested and promising results for the determination of DL-THP enantiomers were obtained.