A countercurrent chromatography protocol for support-free preparative enantiomer separation of the herbicidal agent 2-(2,4-dichlorphenoxy)propionic acid (dichlorprop) was developed utilizing a purposefully designed, highly enantioselective chiral stationary-phase additive (CSPA) derived from bis-1,4-(dihydroquinidinyl)phthalazine. Guided by liquid−liquid extraction experiments, a solvent system consisting of 10 mM CSPA in methyl tert-butyl ether and 100 mM sodium phosphate buffer (pH 8.0) was identified as a suitable stationary/mobile-phase combination. This solvent system provided an ideal compromise among stationary-phase retention, enantioselectivity, and well-balanced analyte distribution behavior. Using a commercial centrifugal partition chromatography instrument, complete enantiomer separations of up to 366 mg of racemic dichlorprop could be achieved, corresponding to a sample load being equivalent to the molar amount of CSPA employed. Comparison of the preparative performance characteristics of the CPC protocol with that of a HPLC separation using a silica-supported bis-1,4-(dihydroquinidinyl)phthalazine chiral stationary phase CSP revealed comparable loading capacities for both techniques but a significantly lower solvent consumption for CPC. With respect to productivity, HPLC was found to be superior, mainly due to inherent flow rate restrictions of the CPC instrument. Given that further progress in instrumental design and engineering of dedicated, highly enantioselective CSPAs can be achieved, CPC may offer a viable alternative to CSP-based HPLC for preparative-scale enantiomer separation.
开发了一种用于无支撑制备性对映体分离的反向流动色谱协议,针对
除草剂2-(
2,4-二
氯苯氧)
丙酸(dichlorprop),该协议采用了一种经过专门设计的高选择性手性固定相
添加剂(C
SPA),其来源于双-1,4-(二
氢喹啉基)
苯二
甲酸。通过液-液萃取实验的指导,确定了由10 mM C
SPA在
甲基叔丁基醚中和100 mM
磷酸钠缓冲液(pH 8.0)组成的溶剂体系,作为适合的固定相/流动相组合。该溶剂体系在固定相保留、对映选择性和良好的分析物分布行为之间提供了理想的折中。使用商业离心分配色谱仪,能够实现对多达366 mg的外消旋dichlorprop的完全对映体分离,其样品负载量等同于所用C
SPA的摩尔量。将
CPC协议的制备性能特征与使用
硅胶支撑的双-1,4-(二
氢喹啉基)
苯二
甲酸手性固定相C
SP的高效
液相色谱分离进行比较,显示两种技术的负载能力相当,但
CPC的溶剂消耗显著较低。就生产力而言,HPLC被发现优于
CPC,这主要是由于
CPC仪器固有的流速限制。考虑到在专用、高选择性C
SPA的仪器设计和工程方面可以取得进一步进展,
CPC可能为基于C
SP的HPLC在制备规模的对映体分离中提供一个可行的替代方案。