Abstract: An online preconcentration method, electrokinetic supercharging (EKS) was used for the enrichment of DNA fragments based on microchip electrophoresis （MCE）. EKS is a process that combines electrokinetic injection (EKI) with transient isotachophoresis (tITP). The results demonstrated that the large volume of low concentration sample could be introduced, preconcentrated, and eventually separated on a single channel microchip with the whole length of 40.5 mm. The limit of detection (S/N=3) of DNA fragments was around 0.07 mg/L, effectively improved 40-fold by EKS preconcentration with the normal UV detection at 260 nm. Some important parameters for enhancing preconcentration and qualitative analysis were examined.

Key words: DNA fragments , electrokinetic injection, electrokinetic supercharging, transient isotachophoresis, microchip electrophoresis