Research On Transfer Characteristics Of Solutes In Capillary Electrochromatography

Capillary electrochromatography (CEC) combines the advantages of high column efficiency of capillary electrophoresis (CE) and excellent selectivity of high performance liquid chromatography (HPLC). It also has advantages of high speed, low consumption of samples and so forth. Accordingly, it has been applied into different fields.Based on relaxation theory, with the consideration of the transfer process of solutes in CEC column, the theoretical expression to describe the relationship between the characteristics of eluting curves and separation conditions could be obtained. It demonstrated the effects of retention behavior and electrophoresis mobility of solutes on their peak shapes, which were further proved by the continuous on-column detection of solutes. Both theoretical and experimental results approved that tailing peaks, symmetry peaks and leading peaks might appear simultaneously for the separation of solutes with obvious difference in charges.By reforming high voltage power supply, CEC experiments with separation voltage as high as 70 kV were carried out. In addition, a column with effective length of 100 cm was prepared by electrokinetic packing. The highest absolute column efficiency (16 x 104 theoretic plates/m) in HPLC and CEC were obtained. A pCEC instrument to study the separation behavior of solutes on 320 um CEC column was established, and the separation of neutral solutes with low concentration organic salt as the mobile phase was realized. Furthermore, nine compounds with similar structure were separated in a saltless system.Retention of solutes on CEC columns packed with cyano stationary phase was investigated. It was found that polarization of the double layer on the surfaces of both stationary phase and neutral solutes might be changed with the composition of theinvestigated. It was found that polarization of the double layer on the surfaces of both stationary phase and neutral solutes might be changed with the composition of the mobile phase, leading to the change of retention mechanism from normal to reversed phase. In addition, it was found that in pCEC, the retention of solutes were governed by electrophoresis mobility, elctroosmatic flow and flow dynamics. For charged solutes, both pressure and voltage could be used to adjust the separation selectivity, which broadened the application scope of pCEC.