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Chromatography multimodal methods

Coupled systems include multidimensional and multimodal systems. Multidimensional chromatography involves two columns in series preferably two capillary columns, with different selectivity or sample capacity, to optimize the selectivity of some compounds of interest in complex profiles or to provide an enrichment of relevant fractions. In multimodal systems, two chromatographic methods or eventually a sample preparation unit and a chromatographic method are coupled in series. Coupled systems that received much interest in recent years are multidimensional CGC (MDCGC), the combination of high-performance liquid chromatography with CGC (HPLC-CGC) and the on- or off-line combination of supercritical fluid extraction with CGC (SFE-CGC). Multidimensional and multimodal techniques in chromatography arc described in detail in [65],... [Pg.244]

The term multimodal has been used in two ways in TLC, to designate layers such as bonded cyano sorbents that can operate with two or more mechanisms (see Section IV.C) or, in the context of this section, to specify multidimensional separations that are performed by coupling TLC, HPTLC, or OPLC (223) with another technique, such as gas chromatography, supercritical fluid chromatography (224), countercurrent chromatography (225), and, most commonly, HPLC (145, 226-228), in order to improve the separation capacity available from either of the individual methods. For example, the combination of adsorption AMD-HPTLC and partition HPLC for water analysis produced as many as 700 individual densitometric peaks (49). Multimodal TLC separations have been reviewed (229-231). [Pg.41]

There are many classes of CSPs applicable in different mobile-phase modes. In particular, CSPs based on derivatized polysaccharides, native and derivatized cyclodextrins, macrocyclic glycopeptides, and Pirkle-type chiral selectors operate quite well in four separation modes, i.e RP, polar organic phase, NP, and super- or subcritical fluid chromatography (SFC) conditions. It is common that a chiral compound can be separated on the same CSP in more than one separation mode [58, 160, 166, 170-176]. For example, Nutlin-3, a small molecule antagonist of MDM2, has been baseline resolved from its enantiomer in all four mobile-phase conditions (Fig. 16) [170]. Multimodal enantioseparation on the same CSP would be greatly beneflcial for chiral method development in pharmaceutical industry. [Pg.182]


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