Thin layer chromatography multiple development

M. T. Belay and C. E. Poole, Determination of vanillin and related flavor compounds in natural vanilla exti acts and vanilla-flavored foods by thin layer chromatography and automated multiple development , Chromatographia 37 365-373(1993). 

Fig. 2 The steps in the process of thin-layer chromatography that have been instrumentalized and automated to a large degree in the recent past. PMD = Programmed Multiple Development, AMD = Automated Multiple Development, DC-Mat or ADC = Automatic Development Chamber.

Mercadante A.Z. and Rodriguez-Amaya, D.B., Screening of carotenoids comparison of thin-layer chromatography with high-efficiency thin-layer chromatography, with multiple development, Cienc. Tecnol. Alim., 11, 200, 1991. 

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. 

Argentation thin-layer chromatography is an extemely useful procedure for the separation of methyl esters of fatty acids. Saturated fatty acids have the highest Rf values, which decrease with the increasing degree of unsaturation, and for a particular acid, the trans isomer usually travels ahead of its corresponding cis isomer. The solvents most commonly used contain hexane and diethyl ether (9 1) although a mixture of 4 6 is used to separate compounds with more than two double bonds. In order to separate positional isomers of the same acid, conditions must be carefully controlled and multiple development in toluene at low temperatures is often necessary. 

High performance thin-layer chromatography (HPTLC) has also been used for the determination of carbamate pesticides.Thus, TLC methods provide increased selectivity through silica derivatization, as well as higher analytical precision and sensitivity with high-performance plates. Butz and Stan reported an HPTLC system with automated multiple development (AMD-HPTLC) to screen water samples for pesticides. The method was applied to the determination of 265 pesticides in drinking water spiked with 100 ng/1 of each analyte. 

Butz, S. and Stan, H. J., Screening of 265 pesticides in water by thin-layer chromatography with automated multiple development. Anal. Chem., 67, 620-630, 1995. 

It is ommon practice in thin-layer chromatography, after application of a sample to a given plate, to develop the plate two or more times with drying of the plate between developments. This general technique will be referred to as multiple development. Three types of multiple development... 

Thin layer chromatography, normal, reverse phase, multiple development, analgesics. 

Equation (6.13) provides values that are about 25% smaller that those calculated by Eq. (6.12). Some typical results from theory or determined by experiment are summarized in Table 6.4. Results from theory are probably too high and represent an upper limit. Experiment indicates a zone capacity of about 12-14 for a single development with capillary flow. This rises to about 30 - 40 for forced flow. Automated multiple development with capillary flow provides a similar zone capacity to forced flow. Two-dimensional thin-layer chromatography employing different retention... 

Development in thin-layer chromatography is the process by which the mobile phase moves through the layer, thereby inducing differential migration of the sample components. The principal techniques are linear, circular and anticircular with the mobile phase velocity controlled by capillary forces or external pressure. The application of any of these techniques can be extended using continuous or multiple development. 

Gocan, S. Cimpan, G. Muresan, L. Automated multiple development thin layer chromatography of some plant extracts. J. Pharm. Biomed. Anal. 1995, 14, 1221-1227. 

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

Markowski, W. Computer-aided optimization of gradient multiple development thin-layer chromatography. Part n. Multistage development. J. Chromatogr. 1993, 653, 283-289. 

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