Effect of molecular structure of tartrates on chiral recognition of tartrate-boric acid complex chiral selectors in chiral microemulsion electrokinetic chromatography.
Eight l-tartrates and a d-tartrate with different alcohol moieties were used as chiral oils to prepare chiral microemulsions, which were utilized in conjunction with borate buffer to separate the enantiomers of beta-blockers or structurally related compounds by the chiral microemulsion electrokinetic chromatography (MEEKC) method. Among them, six were found to have a relatively good chiral separation performance and their chiral recognition effect in terms of both enantioselectivity and resolution increases linearly with the number of carbon atoms in the alkyl group of alcohol moiety. The tartrates containing alkyl groups of different structures but the same number of carbon atoms, i.e. one of straight chain and one of branched chain, provide similar enantioseparations. The trend was elucidated according to the changes in the difference of the steric matching between the molecules of two enantiomers and chiral selector. Furthermore, it was demonstrated for the first time that a water insoluble solid compound, di-i-butyl l-tartrate (mp. 73.5 degrees C), can be used as an oil to prepare a stable microemulsion to be used in the chiral MEEKC successfully. And a critical effect of the microemulsion for chiral separation, which has never been reported before, was found in this experiment, namely providing a hydrophobic environment to strengthen the interactions between the chiral selector and enantiomers.
Hu
Shao-Qiang
SQ
National Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China.
Chen
Yong-Lei
YL
Zhu
Hua-Dong
HD
Shi
Hai-Jun
HJ
Yan
Na
N
Chen
Xing-Guo
XG
D001888:Boric Acids / Q000737:chemistry*; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004655:Emulsions / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D016014:Linear Models; D008968:Molecular Conformation; D011412:Propanolamines / Q000737:chemistry / Q000302:isolation & purification; D013237:Stereoisomerism; D013644:Tartrates / Q000737:chemistry*
D001888:Boric Acids; D004655:Emulsions; D011412:Propanolamines; D013644:Tartrates; C032688:boric acid