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Recentry, High-voltage VCBs up to 168kV have been developed using newly developed technologies such as electrode materials, insulation, and magnetic field analysis which optimizes VI configurations. In this short review, we describe these methods and a number of high-voltage VCBs 72/84kV Ceramic VI, 145kV Single-Break VCB,72/84kV SF6 gas-free VCB, 120kV tank-type VCB and 168kV tank-type VCB.

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Capillary electrophoresis (CE) is a powerful tool for the resolution of enantiomeric compounds owing to its high separation efficiency and its facility to use a wide variety of chiral separation media. [1][2][3][4] In addition to cyclodextrins, which are the cyclic a-1,4-linked oligosaccharides most frequently used as chiral selectors, some linear oligosaccharides have been recently utilized for the separation of optical isomers by CE. [5][6][7][8][9][10][11][12] Kano et al. 10 have reported that the chiral separation of some binaphthol derivatives is achieved by CE with linear a-1,4-linked oligosaccharides such as maltose and maltotriose as chiral selectors. However, no successful resolution of enantiomers by CE with monosaccharides has been achieved so far. In this study, therefore, we attempted the CE resolution of some racemic binaphthyl derivatives (Fig. 1) Boric acid (Kanto Chemical), tris(hydroxymethyl)-aminomethane (Tris) (Nacalai Tesque), tris(hydroxymethyl)methylglycine (Tricine), 2-hydroxy-N-tris-(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPSO) and N-cyclohexyl-3-aminopropanesulfonic acid (CAPS) (Dojin, Kumamoto, Japan) were used as buffer components. Monosaccharides were investigated as chiral selectors in capillary electrophoresis of binaphthyl compounds. Among monosaccharides tested, glucose, mannose and their derivatives, except for methyl-b-D-glucopyranoside, were found to be effective for direct separation of racemic mixture of 1,1¢-binaphthyl-2,2¢-diyl hydrogenphosphate (BNP). D-Forms of galactose, sorbose, fructose, ribose, arabinose and xylose failed chiral separation of BNP. We tentatively concluded that monosaccharides (in the case of D-forms) must satisfy the following structural requirements for successful chiral separation of BNP enantiomers: (1) oxygen atom at C-1 is in a-configuration, (2) -OH group at C-4 is downward configurated and (3) the presence of a -CH2OH or -CH3 group at C-5. Thus, in the case of D-glucose, the chiral separation of BNP is anticipated to be achieved predominantly through the hydrogen bonding between oxygen atom at C-1 and hydrogen atom of -OH group at C-4 on D-glucose and hydrogenphosphate moiety of BNP.

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