Design Of Switching Interface For Two-dimensional Microfluidic Chip And Corrosponding System Performance Testing

A powerful tool was presented for high efficiency separation of complex bio-chemical samples by two-dimensional separation system constructed on the micofluidic chip platform. Research work in two-dimensional microchip electrophoresis technique was summarized in this paper. Switching interface design is the bottleneck of two- dimensional microchip electrophoresis technique.Type of switching interface for two–dimensional electrophoresis microchip was classified and principle for separation mode combination was presented. This paper focused on switching interface design for the coupling of Micellar electrokinetic chromatography mode and capillary zone electrophoresis mode. Research on the design of switching interface for two-dimensional CE microchip and corresponding quantitative estimate of the testing results are of great significance for development of muti-dimensional separation technique. Meanwhile, it will supply theory basis and technique support for new miniaturized total analysis system.Firstly, electroosmotic flow (EOF) in glass micro-channel was measured by current monitoring method and voltage-current curves of the microchip were also measured. FITC-labeled mixed amino acid samples were separated by microchip MEKC and CZE modes, respectively. According to the optimized results in the one-dimensional separation experiments, MEKC mode was selected as the first dimension and CZE as the second dimension, the time based double T switching interface was proposed. Furthermore, the two-dimensional microchip CE separation system was constructed.And then, the performance and application of the two-dimensional microchip CE separation system were investigated. Two-dimensional microchip CE analysis of single FITC-labeled arginine sample was carried out. Arginine sample was successfully injected into the channel of the second dimension. Optimized startup time and injection time of the second dimension were 55s and 5s, respectively. Furthermore, MEKC on-line sweeping technique was introduced into the separation system, high efficiency enrichment of lysine and phenylalanine was realized in the first MEKC dimension. Corresponding enrichment multiple of lysine and phenylalanine were about 150 and 900, respectively. Each enriched sample was divided into 2-3 parts and introduced into the second dimension.Finally, two-dimensional analysis of 5 mixed amino acid samples were successfully realized on the constructed two-dimensional microchip CE system. Each sample was divided into 2-3 parts and introduced into the second dimension. Mathematical model was set up to evaluate orthogonality between MEKC and CZE, calculated value was 56.0%. Results showed designed switching interface could introduce sample band in the first dimension separation microchannel into the next one effectively and there was well orthogonality between the selecteded separation modes.Research showed two-dimensional separation of amino acid samples could be realized on the two-dimensional microchip electrophoresis system with time based double T switching interface. Final goal of two-dimensional microchip CE system development was to separate complex bio-chemical samples. And thus, application of the constructed system in protein separation is the key problem which should be settled in latter research work.