Comparison of on-line concentration methods in capillary zone electrophoresis for analysis of water-soluble vitamins

The separation of water-soluble vitamins by capillary zone electrophoresis was developed, in which on-line concentration methods, namely field-enhanced sample stacking and dynamic pH junction, were utilized to improve the detection sensitivity. The effects of some critical parameters, including pH and concentration of background electrolyte, sample matrix pH and concentration, and injection volume were examined. The effects of field-enhanced sample stacking and dynamic pH junction on the separation resolution and concentration efficiency were compared. The limits of detection of the vitamins were from 6 to 119 ng ml(-1) (2.7 x 10(-8) to 53.4 x 10(-8) M) based on the signal-to-noise ratio of 3 and the relative standard deviations of migration time and peak area for each vitamin (1 mu g ml(-1)) were less than 3.5% using the field-enhanced sample stacking as an on-line concentration method. The developed method was applied to the analysis of water-soluble vitamins in corns.