Capillary electrochromatography in anion-exchange and normal-phase mode using monolithic stationary phases

Hydrophilic macroporous weak and strong anion-exchange stationary phases ha ve been prepared in a monolithic format within untreated fused-silica capil laries by the simple thermally or UV-initiated polymerization of 2-dimethyl aminoethyl methacrylate, 2-hydroxyethyl methacrylate and ethylene dimethacr ylate in the presence of a binary porogenic mixture of dodecanol and cycloh exanol. The tertiary amino functionalities were then alkylated in situ to a fford strong anion-exchangers. These new monolithic stationary phases with optimized porous properties were used for the CEC separation of various org anic anions. Thus, a mixture of 2-substituted propionic acid drugs (profens ) was separated in 13 min and high column efficiencies of up to 231 000 pla tes/m were achieved. The separation of substituted benzoic acids indicates that the selectivity results primarily from the anion-exchange interactions , while electrophoretic migration contributes only slightly. In addition, t hese hydrophilic anion-exchangers are also able to separate weakly acidic, neutral and basic compounds such as phenols, xanthines and aromatic amines in normal-phase electrochromatographic mode. (C) 2001 Elsevier Science B.V. All rights reserved.