Chromatography multidimensional

CZE-APCI-MS [887] andCZE-CF-FAB-MSn [533] couplings have been described. CEC-MS coupling offers  

The combination of CE and MS enables high-efficiency separations of a wide range of solutes. As with any CE technique the running buffer determines the quality of the separation. In practice, therefore, most CE-MS separations have been performed in an acidic buffer. Unfortunately, these conditions severely constrain the range of samples that can be successfully analysed by CE-MS. CE-MS requires a small volume of a concentrated sample (ICC3 moleL-1). Sensitivity is reported as 1 pmol for SIM and lOpmol for full mass spectra. Very little quantitative work has been performed with CE-MS techniques. 

CE-MS and CEC-MS have raised a great deal of attention recently, because of their universality, specificity and sensitivity. CE-MS and CEC-MS are useful for adding an extra selectivity dimension to detect co-eluted molecules of different masses and obtaining information about molecular mass and structure. CE-MS has frequently been reviewed [433,434,440,873,876,890-896], 

The range of applications of CE-MS is still rather limited [899]. Few real unknown samples have been analysed by CE-MS. In particular, CE-MS activities for synthetic polymer additive analysis purposes are not abundant. On the other hand, ITP and ITP-CE separations of food additives on a chip have been reported [900]. 

Principles and Characteristics In some cases, analysis using an appropriate combination of a single separation and detection method is not satisfactory, and it becomes necessary to utilise a combination of separation methods and/or multidetector monitoring. This approach is termed multidimensional, or coupled chromatography and is meant to describe a specific sequential combination of chromatographic procedures. 

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H. J. Cortes, Multidimensional Chromatography Techniques and Applications, Marcel Dekker, New York, 1990. 

Multidimensional Chromatography Edited by Luigi Mondello, Alastair C. Lewis and Keith D. Bartle Copyright 2002 John Wiley Sons Ltd ISBNs 0-471-98869-3 (Hardback) 0-470-84577-5 (Electronic)... 

The main origin of multidimensional chromatography lies in planar chromatography. The development of paper chromatography, i.e. the partition between a liquid moving by capillary action across a strip of paper impregnated with a second liquid... 

Most developments in the past two decades, however, have involved coupled column systems which are much more amenable to automation and more readily permit quantitative measurements, and such systems form the subject of this present book. A review on two-dimensional GC was published (43) in 1978 (and recently updated (29)), and the development by Liu and Phillips in 1991 of comprehensive 2D GC marked a particular advance (33). The fundamentals of HPLC-GC coupling have been set out (37) with great thoroughness by Grob. Other work on a number of other aspects of multidimensional chromatography have also been extensively reviewed (44,45). 

W. Beitsch, Multidimensional gas chromatography , in Multidimensional Chromatography. Techniques and Applications, H. J. Cortes (Ed.), Marcel Dekker, New York, pp. 75-110 (1990). 

Sometimes, the resolving power attainable with a single chromatographic system is still insufficient for the analysis of complex matrices. An approach commonly used to obtain greater resolution is multidimensional chromatography. 

Multidimensional chromatography brings together separations often based on different selectivity mechanisms. Although the forms of the mobile phase are not required to be different in the individual steps of a multidimensional separation, we usually strive to achieve orthogonal selectivity of these individual separation steps (1). 

The point of all this is simply that we must not use the apparent plate height or the apparent plate number as performance criteria in the unified chromatography techniques on the justification that they already work well for LC and that they work well for GC when a pressure correction is applied. A considerable expansion of theory and an effective means for evaluating equations (7.4) or (7.5) are required first. Likewise, as we consider multidimensional chromatography involving techniques existing between the extremes of LC and GC, we must not build judgments of the multidimensional system on unsound measures of the individual techniques involved. 

Multidimensional Chromatography Foods, Flavours and Fragrances Applications... 

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