The osmium-catalyzed asymmetric dihydroxylation (AD) of olefins is one of the most widely used methods for the synthesis of chiral vicinal diols, which are the synthetic intermediates of chiral drugs, natural products and fine chemicals. [1][2][3] For this reason, considerable and continuous efforts have been made to improve the optical purity of the resulting diols with the desired absolute configuration. 2,3 Similarly, the enantioselectivity estimation of a increasing number of chiral catalysts demands convenient, fast and sensitive methods to measure enantiomeric excesses and impurities of the chiral vicinal diol products. Besides the major HPLC method, cyclodextrin-modified capillary zone electrophoresis (CZE) is enjoying increasing popularity. 4,5 In contrast to HPLC, in which chiral selectors are immobilized to the solid support, CZE shows many advantages by dissolving chiral selector in separation buffer, such as simplification, high efficiency, reduced analysis time, and smaller sample volumes. In CZE, borate buffers were widely used for the separation of carbohydrates, glycoproteins, nucleosides, and other compounds of biological interest. [6][7][8][9][10][11][12][13] The phenomenon of borate complexation has been extensively studied and the principle of mixed borate-cyclodextrin complexation has been found to be a useful approach for the chiral separation of neutral compounds with diol structures. [6][7][8][9] For neutral analytes in the CZE separation mode, enantioseparation is not achievable with neutral CDs unless the electrophoretic system is modified with the use of a buffer system containing CD which can form charged complexes with analytes or with the addition of charged CDs in a buffer system. In those studies, to the best of our knowledge, so far only two articles on the enantioseparation of vicinal diols by the neutral cyclodextrin-modified capillary electrophoresis have been reported. 14,15 Moreover, the enantioseparation of hydrobenzoin, which is a 1,2-diol compound, and structurally related benzoin compounds have been achieved using charged CDs alone or mixed with neutral CDs as chiral selectors. 16,17 Unfortunately, no detailed information on the enantioseparation of typical vicinal diol compounds was provided. Thus, enantioseparation and migration behavior of typical vicinal diol compounds in the presence of borate complexation need to be explored further.In this study, the optimum conditions for the separation of six 1,2-diols synthesized in our laboratory according to literature methods 18,19 using native β-CD by CZE were described. Especially, the enantioseparation and migration behavior of several 1,2-diols, such as 1-(3-chlorophenyl)-1,2-ethanediol, 1-methyl-1-phenyl-1,2-ethanediol, 2-methyl-1-phenyl-1,2-ethanediol and 1-naphthyl-1,2-ethanediol, were firstly explored with neutral β-CD as a chiral selector in a borate buffer at an alkaline pH. For our studies, the influences of the concentration of β-CD, the pH of borate buffer and the buffer concentration on the chiral separation we...