Gradient multiple development

Figure 10.16 Densitograms obtained for four subsequent developments of the extract from Radix rhev. (a) first development, 10% (vol/vol) ethyl acetate/chloroform, distance 9 cm (b) second development, 50% (vol/vol) ethyl acetate/chloroform, distance 9 cm (c) tliird development, 100% ethyl acetate, distance 8 cm (d) fourth development, 15% (vol/vol) methanol/ethyl acetate, distance 5 cm. Reprinted from Chromatographia, 43, G. Matysik, Modified programmed multiple gradient development (MGD) in the analysis of complex plant exti acts , pp. 39-43, 1996, with permission from Vieweg Publishing.

G. Matysik, Modified programmed multiple gradient development (MGD), in the analysis of complex plant exti acts , Chromatographia 43 39-43 (1996). 

Simultaneous evolution of chromatography, as a method of analysis and separation, enables the confirmation and development of chemotaxonomic investigations of new plant species, as well as the accomplishment of quality and quantitative determinations. Thin-layer chromatography (TLC) especially proved to be very useful for analysis and isolation of small amounts of some compounds. The most significant and advantageous points of the TLC technique are its speed, cheapness, and capacity to carry out the analysis of several solutes simultaneously its continuous development under equilibrated conditions its gradient and multiple development and its ability to scale up the separation process. 

The possibility of determining trace phenolic pollutants in water by TLC was investigated. The analytes were preconcentrated by SPE and subjected to both classical and multiple gradient development TLC. In situ quantation was performed by UV absorption or by visible light absorption after treatment with Wuster s reagent (115). LOD was... 

Common methods for constructing solvent strength gradients in multiple development are summarized in Table 6.9. Gradients of increasing solvent strength are used to fractionate complex mixtures by separating just a few components in each... 

With the program and derived mathematics, the scientist can calculate the retention times and peak widths for any set of solutes, run under any conditions ranging from Isocratlc to complex gradients with multiple columns. Given this mathematical tool, the problem of determining which chromatographic conditions will achieve the desired separation, within any constraints, becomes the next problem to be approached. The solution to such an "optimization" problem Is not easy, however, the necessary universal mathematical tools are now available for researchers In this area to develop approaches to optimization strategies. 

Matysik, G. Separation of DABS derivatives of amino acids by multiple gradient development (MGD) in thin-layer chromatography. Chromatographia 1996, 43, 301-303. 

A wide range of mobile and stationary phases combined with capillary flow and forced flow one- and two-dimensional and multiple and gradient development modes lead to high separation selectivity. 

The horizontal DS chamber has been described for use in isocratic, gradient, and multiple development, as well as simultaneous development using different mobile phases under different conditions (Waksmundzka-Hajnos and Wawrzynowicz, 1994 Matysik, 1994 Matysik and Wojtasik, 1994 Matysik et al., 1994 Golkiewicz, 1996 Matysik and Toczolowski, 1997). A modified version of the DS chamber allows the solvent entry position to be changed by movement of the plate, increasing efficiency in single and multiple development (Dzido et al., 1995). 

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