Properties and applications of mixed packing capillary electrochromatography

Mixed packing capillary electrochromatography (MP CEC) with the stationary phase comprising a physical mixture of strong cation exchange (SCX) phase a nd octadecpilyl (ODS) phase was developed. With the existence of a sulfonic acid group on the surface of SCX, not only could the electroosmotic flow ( EOF) remain high at low pH, but also the hydrophilicity of the stationary p hase was increased greatly, leading to broad adaptable ranges of both pH an d organic modifier concentration in the mobile phase. At the same time, wit h the coexistence of C-18 on the surface of ODS, both the retention and the resolution of samples vr ere improved. Accordingly, MP CEC combined the ad vantages of both SCS and ODS columns. Effects of operation parameters on EO F and the capacity factors of solutes as well as the retention mechanism of such a column were studied systematically. In addition, MP CEC columns wer e used in the analysis of strong polar solutes as well as for the high spee d separation of acidic, basic, and neutral compounds in a single fun.