Capillary electrophoresis separation of enantiomeric thymopentin analogs substituted by D-amino acids

The separation and resolution of thymopentin analogs substituted by D-amino acids were carried out by capillary electrophoresis with dimethyl-β- cyclodextrin (DM-β-CD) as a chiral selector. The optimum experimental conditions were 20 mmol/L DM-β-CD, 40 mmol/L phosphate buffers (I : pH 6. 03; II : pH 5. 05) with an effective voltage of 20 kV at 25°C (I), 15°C (II) separately. The influence of buffer pH, temperature on the selectivity and voltage was investigated. Two pairs of samples were separated successfully. It was shown that samples substituted by D-amino acid resulted in an increase of migration speed. It suggested that the stability of samples substituted by D-amino acid binding with DM-β-CD was less than samples substituted by L-amino acid.