Mixed mode chromatography

Reversed-phase chromatography and reversed-phase ion-pair chromatography Mixed mode chromatography Size-exclusion chromatography Practical Considerations Apparatus Colunrn Eluants... 

Mixed-mode chromatographies and mixed-functionality resins... 

Spikmans, V., Lane, S. J., Tjaden, U. R., and van der Greef, J., Automated capillary electrochromatography tandem mass spectrometry using mixed mode reversed phase ion-exchange chromatography columns, Rapid. Com-mun. Mass Spectrom., 13, 141, 1999. 

Separation by size can occur even on a nonporous material, as the flow in the center of a flow channel is faster than that near the walls. Since large molecules are excluded from the wall regions, they tend to travel in the faster flow down the flow channel center, a phenomenon known as hydrodynamic chromatography (HDC).5658 As discussed in Chapter 1, a mixed-mode form of HDC called "slalom chromatography" has found application in DNA analysis. HDC, however, is far less efficient as a separation process than GPC. 

A mixed-mode method called liquid chromatography under limited conditions of adsorption has been described and applied to analyzing co-polymer composition of poly(styrene)-co-(methylmethacrylate).41 The polymer, dissolved in a good solvent, was injected onto a GPC column and eluted with a poor solvent. The polymer partially adsorbed to the column, allowing the plug of injection solvent to catch up with the adsorbed polymer and desorb it. 

Ferguson PL, Iden CR, Brownawell BJ (2001) Analysis of nonylphenol and nonylphenol ethoxylates in environmental samples by mixed-mode high performance liquid chromatography-electrospray mass spectrometry. J Chromatogr A 938 79-91... 

This section deals briefly with classical methods based on conventional mixing of the sample and reagents such as the batch mode and low-pressure flow mixing methods, as well as the use of CL detection in continuous separation techniques such as liquid chromatography and capillary electrophoresis for comparison with the unconventional mixing mode. 

Nogueira, R., Lubda, D., Leitner, A., Bicker, W, Maier, N.M., Lammerhofer, M., and Lindner, W, Silica-based monohthic columns with mixed-mode reversed-phase/weak anion-exchange selectivity principle for high-performance liquid chromatography, J. Sep. ScL, 29, 966, 2006. 

MA systems can easily add a module to increase membrane capacity or resolution. Alternatively, the series addition of a traditional chromatography column for improvement of capacity or resolution is seldom practiced. Thus, membrane chromatography offers the chromatographer a new flexibility of easy expansion of inadequate systems. Alternatively, the easy connectibility also enables a simple way to couple multiple units of different chemistries for a mixed-mode separation.43 The next section describes these configurations in greater details. 

Freitag, R., Splitt, H., and Reif, O.-W. (1996). Controlled mixed-mode interaction chromatography on membrane adsorbers. ]. Chromatogr. A 728, 129-137. 

Burton, S. C., and Harding, D. R. K. (1997). High-density ligand attachment to brominated allyl matrices and application to mixed mode chromatography of chymosyn. J. Chromatogr. 775, 39-50. 

Vergara, C. Mardones, C. Hermosin-Gutierrez, 1. von Baer, D. 2010. Comparison of high-performance liquid chromatography separation of red wine anthocyanins on a mixed-mode ion-exchange reversed-phase and on a reversed-phase column. J. Chromatogr. A. 1217 5710-5717. 

For small neutral organic compounds, reversed-phase chromatography usually provides much better efficiency than lEC. However, a mixed-mode separation mechanism on ion-exchange columns can offer a unique selectivity for the separation of some biopolymers such as peptides or proteins [73). 

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