毛细管电泳柠檬酸-Zn2+体系对异亮氨酸对映体的手性分离

摘要

应用毛细管电泳/电容耦合非接触式电导(CE-C4D)分离检测技术,研究了柠檬酸-Zn2+体系对异亮氨酸对映体的手性识别行为.结果表明,采用未涂层石英毛细管(45 cm×50 μm,Leff=40 cm),以2.8 mmol/L NaOH+0.8 mmol/L柠檬酸+2.0 mmol/L乙酸锌为非手性介质电泳运行液,分离电压+13 kV,D,L-异亮氨酸对映体得到了良好的手性识别,对映体分离度达到2.0.线性检测范围为1.0~20 mg/L,检出限(S/N=3)为0.40 mg/L.对影响分离度的因素(Zn2+的浓度、电泳运行液的组成、分离电压以及其他氨基酸的干扰情况等)进行了详细的讨论,并对手性识别机理作了初步探讨.%The enantiomeric separation of unmodified D,L-isoleucine was achieved in citric acid-zinc(Ⅱ)medium by capillary electrophoresis(CE)with contactless conductivity detector (C4D). In the conventional chiral separation methods of amino acid,a chiral complex used as the chiral selector was added into the eluent in order to yield a chiral environment. However,in this study a non-chiral solution,i. e. 2.8 mmol/L NaOH+0.8 mmol/L citric acid+2.0 mmol/L zinc acetate was used as the running buffer,and the citric acid-zinc(Ⅱ)acted the role of a chiral selector. Under the optimum experimental conditions:uncoated fused-silica capillary(45 cm×50 μm,Leff=40 cm),separation voltage of +13 kV,electrokinetic injection of 11 kV×8 s, the enantiomers of D,L-isoleucine were baseline separated within 8 min with the resolutions (Rs)of 2.0. The calibration curve of each enantiomer showed good linearity in the range from 1.0 mg/L to 20 mg/L,with the limits of detection of 0.40 mg/L. The intra- and inter-day preci-sions were examined. The RSDs of peak area and migration time were found to be below 5.0%and 2.5%(n=6),respectively,indicating good repeatability(intra-day)and reproducibility (inter-day)of the method. Interference experiment was also tested. As a result,other common amino acids did not interfere with the detection. The proposed method provided a potential new way to further investigate the enantioseparation of unmodified or native amino acids.