Microfluidics-based chromatography

H. Irth A microfluidic-based enzymatic assay for bioactivity screening combined with capillary liquid chromatography and mass spectrometry. Lab Chip 2005, 5,... 

Enantiomeric separation 261 Racemic mixtures of tryptophan and thiophenal investigated in microfluidic-based membrane chromatography... 

Wang PC, Gao J, and Lee CS. High-resolution chiral separation using microfluidics-based membrane chromatography. J. Chromatogr. A 2002 942 115-122. 

De Boer, A.R., Bruyneel, B., Krabbe, JG, Lingeman, H., Niessen, W.M.A., Irth, H., A microfluidic-based enzymatic assay for bioactivity screening combined with capillary liquid chromatography and mass spectrometry. Lab Chip, 5, 1286-1292, 2005. 

In microfluidic-based systems, material is transported within microstructures (of typical dimensions of 10-500 pm) where separations, reactions, and other processes occur. Focus has been on the realization of the traditional separation techniques (electrophoresis, chromatography, isoelectric focusing, etc.) and reactions in the microchip format. The principles of separation, as in the conventional formats, are based on differences in mass and charge (thus mobility) and partitioning between phases. However, advantages associated with the small dimensions provide superior performance. For example, the higher surface to volume ratio arising from the smaller dimensions results in lower heat and mass transfer resistances and thus an improved performance. 

When elution chromatography is used in both dimensions, the valve configurations are similar for the different column combinations. However, when CE is utilized as the second dimension, other types of interfaces not based on valves have been implemented with unique advantages. These and the microfluidic implementation of sampling systems for chip-based two-dimensional separations will be discussed below. 

Reoples, M. C., Rhillips, T. M., and Karnes, H. T., A capillary-based microfluidic instrument suitable for immunoaffinity chromatography. Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences 843(2), 240-246, 2006. 

Table 4 shows some applications that have been realized on the centrifugal microfluidic platform. At the top of the applications section, sample preparation modules (plasma separation, DNA extraction) are shown. This is followed by assays based on the detection of proteins, nucleic acids and small molecules (clinical chemistry). Two additional applications are presented at the end of the table, demonstrating chromatography and protein crystallization. Some instmctive examples are discussed in more detail below. 

The electrochemistry-based microfluidic amperometric sensor provides a powerful platform for the p-TAS for point of care diagnosis due to its natural properties like disposability, low cost, easy fabrication, etc. The applications relating to it have been extended to liquid chromatography, immunoassay, and determination of biomolecules like peroxide and nucleic acids. 

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