Localized Stacking At Micro-nano Interface Of Polycarbonate Membrane And Capillary For Microchip Electrophoresis

In chip electrophoresis, detection of low concentration sample is difficult due to limit of injection volume. Enrichment based on ion concentration polarization is important to increase the concentration of the analyte and thus the detection power could be enhanced. The combination of online preconcentration of trace sample based on ion concentration polarization and chip electrophoresis is significant for improving the analysis performance of micro-nanofluidic chip.In the first chapter, principle of ion concentration polarization, devices and applications of micro-nanofluidic concentrator are presented, and the main sampling methods of capillary electrophoresis are introduced. And the current situation and existing problems of the combination of electrophoresis separation on chip and enrichment based on the principle of concentration polarization are discussed.In the second chapter, a new micro-nano interface was prepared by itegration of molding of Polycarbonate nanoporous membrane (PCTETM). The number of nanopores on the micro-nano interface was measured by electrochemical workstation with the aide of a cylindrical pore shape model. The factors of buffer solution concentration and voltage on enrichment were investigated. It was found that below 150 V, the enrichment effect decreased with ionic strength. When voltage was increased, fluorescence value was increased in high ion strength due to electric field strength and it was almost same to the value in low ion strength buffer. In the end, we realized 103 enrichment for 1×10-6 mol/L fluorescein sodium in 1×TBE under 250 V bias.In the third chapter, a fracture on capillary was used as sample introduction channel, and located concentration of probe molecules was carried out on the micro-nano interface formed by Nafion porous membrane and capillary, and interfaced to capillary electrophoresis. The relation between injection fracture width and sample injection was explored. It was noticed that the peak height fistly increases with the fracture width and decreases. The optimum injection fracture width of 70-140 nm was defined according to the peak height and width at half height. Eenrichment and separation of DNA Marker by independent injection and concentration was improved under follwing conditions:injection voltage 300 V, injection time 9 s, enrichment voltage 300 V, accumulation time 180 s. Field strength and effective separation length on resolution of the peak were also investigated.In this paper, we introduced a new nanopore interface in PDMS-PCTETM chip by simple preparation method. The micro-nano interface demonstrated good reproducibility. The capillary microchip is characterized in fracture sampling, located enrichment and non-gel sieving capillary electrophoresis, and the performance of the chip electrophoresis could be greatly enhanced with the established method.