Minimization of Sample Discrimination Introduced by On-Column Fracture/Electrokinetic Injection in Capillary Electrophoresis

Abstract

Using on-column fracture/electrokinetic injection for sample introduction in capillary electrophoresis (CE) is thought to be a method of no-discrimination electrokinetic injection. However, in this study we found that significant discrimination was observed when injecting samples dissolved in deionized water with the above method. In addition, the discrimination is reverse to that in conventional electrokinetic injection, that is, the less mobile species are injected in larger quantities than the more mobile components. The reason for these phenomena and approaches to reduce the discrimination were studied. Equivalent circuits were established and used to analyze the discrimination under different conditions through computer simulation. The experimental results showed good agreement with the results of the computer simulations. Finally, an on-column fracture/electrokinetic injection method using ramped injection voltage was proposed and shown to be suitable for sample solutions with different conductivity. This method does not cause significant error for practical quantification, even without correcting for the discrimination, because its discrimination is very small.