On-line enrichment of neutral solute in capillary electrochromatography

On-line enrichment of neutral solute in capillary electrochromatography (GEC) can be achieved by varying the concentration of organic modifier in sample solution and running buffer, together with extending the injection time. On-line enrichment is mainly controlled by two processes: self-enrichment and transfer enrichment. Based on the method of relaxation theory, an expression, which described the relationship between enrichment factor and running condition, was theoretically derived. Due to this expression, higher enrichment factor can be obtained by extending injection time, and the effect of the injection time on column efficiency depended on the concentration of organic modifier. If there were large difference of concentration of organic modifier in sample solution and naming buffer, proper extending of injection time would have a few effect on column efficiency. The theoretical results were experimentally proved with two drags: benzoin and mephenytoin. The enrichment factor of more than 100 folds was obtained.