MINIMIZATION OF SAMPLE DISCRIMINATION INTRODUCED BY ON-COLUMN FRACTURE ELECTROKINETIC INJECTION IN CAPILLARY ELECTROPHORESIS

Using on-column fracture/electrokinetic injection for sample introduct ion in capillary electrophoresis (CE) is thought to be a method of no- discrimination electrokinetic injection. However, in this study we fou nd 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 injec tion, that is, the less mobile species are injected in larger quantiti es than the more mobile components. The reason for these phenomena and approaches to reduce the discrimination were studied. Equivalent circ uits were established and used to analyze the discrimination under dif ferent conditions through computer simulation. The experimental result s showed good agreement with the results of the computer simulations. Finally, an on-column fracture/electrokinetic injection method using r amped injection voltage was proposed and shown to be suitable for samp le solutions with different conductivity. This method does not cause s ignificant error for practical quantification, even without correcting for the discrimination, because its discrimination is very small.