David Nurok
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Research
Planar Chromatography [also called Thin Layer Chromatography (TLC)] has a number of attractive features as compared to High Performance Liquid Chromatography (HPLC). These include the ability to separate multiple samples simultaneously on a single plate, the fact that there is no need to transport the separated components to a detector, the ease of performing post-separation visualization reactions, the large number of such reactions that are available, and the ability to perform true two-dimensional separations (as compared to the virtual two-dimensional separations obtained by HPLC). Sample clean-up is not required, because the plates are discarded after use, and long term build-up of impurities is not an issue. TLC is suitable for quantitative analysis, and good precision and accuracy is obtained with a modern densitometer.
The major reason why TLC is not widely used is that the flow rate of the mobile phase is inversely related to the distance migrated by the solvent front. This results in separations that are time consuming (specially in the reversed phase mode) and that are usually of low chromatographic efficiency. In order to improve the flow profile, forced-flow techniques have been introduced. The newest of these is Pressurized Planar Electrochromatography (PPEC), which has been developed in our laboratory. In PPEC an electric potential of several kilovolt is applied across the length of the TLC layer, and this results in the mobile phase being driven by the electroosmotic force. PPEC is substantially faster and more efficient than other forms of planar chromatography. This is illustrated below for the separation of a mixture of model compounds, using the same mobile and stationary phase for both separations.
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Publications
D. Nurok, J. M. Koers, and M. A. Carmichael The Role of Buffer Concentration and Applied Voltage in Obtaining a Good Separation in Planar Electrochromatography. J. Chromatography A. 983 (2003) 247 – 253.
D. Nurok, J. M. Koers, M. A. Carmichael, W. Liao and T.H. Dzido, “The Performance of Planar Electrochromatography in a Horizontal Chamber.” J. Planar Chromatogr. 15 (2002) 320-323.
D. Nurok, J. M. Koers, D. A. Nyman and W. Liao, “Variables that Affect Performance in Planar Electrochromatography with Electroosmotic Flow.” J. Planar Chromatogr., 14, 409-414 (2001).
D. Nurok, M.C. Frost and D. Chenoweth, “Separation Using Planar Chromatography with Electroosmotic Flow,” J. Chromatography A, 903 (2000) 211-217.
D. Nurok, “Forced Flow Techniques in Planar Chromatography,” Anal. Chem 72 (2000) 634A-641A.
