Saturday, March 30, 2013

shallow region on microchannel for better separation

CZE technique, introduced in the 1960s, is used to separate charged analytes under the influence of an electric field. Charged analytes are separated on the basis of their size to charge ratio. Some of the applications of CZE include separation of DNA (e.g, in DNA fingerprinting), separation of proteins, analysis of basic drugs and related substances in pharmaceutical analysis etc.
Researchers from University of Wyoming have demonstrated that "shallow region" in a microfluidic separation duct enhances the resolving power of capillary zone electrophoresis (CZE). They have shown a 8 fold increase in resolving power while separating a mixture of amino acids utilizing this technique. 

Abstract Image
Simple microfluidic device to have better separation in CZE
as described by Xia and dutta (copied from Anal Chem)
In their recent article published in Analytical Chemistry, Prof Dutta and his student Ling used pressure driven back flow (counter flow to electroosmotic flow in the microchannel) to achieve their goal of high resolution CZE. This back flow was produced by a ~0.5 um deep shallow region. When electric field is applied on the separation channel, a mismatch in electroosmotic flow generates pressure driven back flow. Even though this back flow introduces some band broadening, overall increase in resolving power was better than a device without shallow region.

Authors claim to have following advantages in their device:
1. This device omits the use of an external pump for pressure generation simplifying its fabrication and operation;
2. It can readily be integrated into any detection and/or downstream analysis method; and 
3. It is suitable for further miniaturization of the CZE technique to the submicrometer length scale.

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