Nonaqueous capillary electrophoresis using a zirconia-coated capillary

A zirconia-coated capillary was prepared by sol–gel technique. Its electroosmotic flow (EOF) properties were investigated in a variety of nonaqueous media (methanol and mixtures of methanol and acetonitrile). The zirconia-coated capillary exhibited the switchable EOF whose direction and magnitude were strongly dependent on the properties of nonaqueous solvent composition, their apparent pHs (pH*), and the electrolytes (tris(hydroxymethyl) aminomethane and ammonium acetate). It was found that the isoelectric point (pI) of the zirconia-coated capillary moved to higher pH* with increasing acetonitrile content from 0 to 75% (v/v) when tris(hydroxymethyl) aminomethane was used as the electrolyte. The nonaqueous capillary electrophoresis (NACE) with the positively charged zirconiacoated capillary was investigated for separations of several alkaloids. The effect of changing the binary solvent composition on the separation was also studied. Finally, the separation between coated and uncoated capillaries in nonaqueous media was compared.