Xin Liu

Date of Award

Spring 2019

Document Type

Open Access Thesis


Biomedical Engineering

First Advisor

Guiren Wang


Microchip electrophoresis (MCE) is a promising analytical tool started more than two decades. With the characteristics of short analysis time, trace level sample, high- throughput and easily integration, lots of efforts have been done with the transportation of the applications from capillary to microfabricated devices. However, with the complex designs on microchip rather than a single straight capillary channel, the strategies and approaches have to be figured out under the challenges of sample introduction, the improvement of separation conditions and the detection, for instance.

In miniaturized microchip, the separation channel is reduced to several centimeters or less, fast and quality separation is the priority in a very short effective distance. Compared with the results of incomplete separation of three fluorescent dyes in DC field, we modify the applied electric field by adding a short time of backward voltage to form a pulsed electric field which is inspired from the method of increasing the residence time of analytes by control the bulk flow velocity in a capillary (Kar & Dasgupta, 1999). The results show that the mixture is separated efficiently with three peaks in short distance. After the optimization of the condition of the pulsed field, the highest resolution can reach to 1.28 and 0.94 between two adjacent peaks. A longer traveling time in pulsed field is not caused the large decreasing of signal-to-noise ratio (SNR) in pulsed field as well.

Moreover, miniaturized analytical devices suffer from poor detection due to the small volume and low concentration sample. Therefore, an on-line sample pre-concentration through stacking anion species using electrophoretic method is also investigated. There are almost 4-fold increase on signal intensity in both DC and pulsed field with sample stacking over the cases without sample stacking. In the meanwhile, the comparison of sample stacking between DC and pulsed field is made. The results illustrate that the SNR in pulsed field is 25% higher than the one in DC field.