Studies On Continuous Sample Introduction Systems For Microfluidic Chip-based Capillary Electrophoresis

In recent years, microfluidic chip-based microanalytical systems have emerged as a main area of development in the field of micro total analysis systems (μTAS) or Labchips, the ultimate objective of which is to integrate all main analytical functions, including sample introduction, pretreatment, reaction, separation and detection operations on a single chip. Currently, particular interets are focused on achieving automated continuous introduction of a series of samples to meet the requirements for analysis of real world samples. Efficient interfacing between the microchip and the outside world is considered as a major challenge. The present work is focused on developing electrokinetic continuous sample introduction systems for microfluidic chip-based capillary electrophoresis.In Chapter 1, sample introduction techniques for microfluidic chip-based capillary electrophoresis are reviewed, including techniques involving on-chip fabricated reservoirs, flow-through sampling reservoirs and sampling probes.In Chapter 2, a continous sample introduction system developed for microfluidic chip-based capillary electrophoresis is described. The system employed a flow-through sampling reservoir featuring a guided overflow design on the basis of a commercial μTK microfluidic analytical device, that did not have continuous sample introduction functions by modifying high voltage supply output design. The operating conditions for sample introduction system were optimized and the performance of the system was demonstrated in the separation and determination of Cy5-labled amino acids.Chapter 3 describes an automated and continuous sample introduction system developed for chip-based CE systems, featuring, an efficient world-to-chip interface produced by horizontally connecting a Z-shaped fused silica capillary sampling probe to the samplie loading channel. A computer controlled autosampler platform with an array of bottom-slotted sample vials was adopted. Sub-microliter sample consumption was achieved without requirement of additional fluidic drivers for sample introduction. The sample composition is not changed during the analysis, and virtually all of the sample may be recovered for further use.Chapter 4 presents a simple technique for fabrication of on-chip sampling probes with a minimal tip diameter of 300 u.m for glass chips. Microfluidic chips with on-chip probes fabricated by this approach coupled,with the slotted vial array sample presentation system were applied to perform continuous sample introduction. This system was also usedsuccessfully to perform CE separations involving gradient variations of multi working electrolytes during each separation run. On-chip horizontal tubular reservoirs containing working electrolyte and wastes were used to maintain stable hydrostatic pressure in the chip channels during prolonged working periods. The sampling system consumed only about 30 nL for each sample.