Chapter Chiral Separations in Nonaqueous Media
In CE, nonaqueous separation can be used as a complement to aqueous separation since it facilitates the use of chiral selectors with a low solubility in water [4,6,14]. Furthermore, it may improve the enantioseparation for selectors with a lack of or low enantioselectivity in aqueous buffers . Another advantage of NACE is that the use of organic solvents enables poorly water-soluble substances to be analyzed . The enhanced solubility of nonpolar substances is advantageous when injection of high concentrations is necessary to lower the limit of detection (LOD), e.g., for chiral
impurity analysis [17-20]. Another way of improving the detection sensitivity in CE is the use of hyphenation with mass spectrometry (MS) [21,22]. Since the nonaqueous solvents are generally more volatile than water, they are preferable in these systems, because a higher volatility would facilitate ionization in the MS interface. An additional advantage of NACE is that some of the organic solvents used in the background electrolyte (BGE), e.g., formamide (FA), might also reduce the adsorption of the analytes to the capillary wall below the level found for aqueous BGEs [23,24].