Abstract
A capillary electrophoresis method using carboxymethyl‐β‐cyclodextrin as the chiral selector and mixture of methanol and ethanol as the organic additive was successfully developed for the simultaneous enantioseparation and determination of six β‐blockers, namely, carteolol, atenolol, sotalol, metoprolol, esmolol and propranolol in this paper. The most suitable running buffer for enantioseparation was found to be the solution of 20 mmol/L NaH~2~PO~4~–Na~2~HOP~4~ (pH 5.5) containing 1.5% w/v carboxymethyl‐β‐cyclodextrin, 5% v/v methanol and 5% v/v ethanol. Furthermore, field‐amplified sample injection as an on‐line sample stacking method was developed in order to increase the detection sensitivity. The experimental conditions for both simultaneous enantioseparation and the field‐amplified sample injection method had been investigated in detail. Under the optimum conditions, the detection limits (defined as S/N=3) of this method were 0.01, 0.05, 0.05, 0.05, 0.05 and 0.5 μg/mL for (±) carteolol, (±) atenolol, (±) sotalol, (±) metoprolol, (±) esmolol and (±) propranolol, respectively, which were much lower than those of the conventional methods. The enhancement factors were greatly improved by 25‐fold for the enantiomers of the β‐blockers except five‐fold for (±) propranolol. Eventually, the proposed method has been applied for the analysis of human serum sample.