Thin-layer and Paper Chromatography

The infrared spectra of a set of 2-thiazolylthioureas are reported in Ref. 486. The ultraviolet spectra of l-aryl-3-(2-thiazolyl)thioureas are characterized by two bands of approximate equal intensity around 282 and 332 nm (492). For l-alkyl-3-(2-thiazolyl)thioureas these bands are shifted to 255 and 291 nm, respectively (492). The shape of the spectrum is modified further when l.l -dialkyl-3-(2-thiazolyl)thioureas are considered (491). Fragmentation patterns of various 2-thiazolylthioureas have been investigated (100, 493), some of which are shown in Scheme 158. Paper and thin-layer chromatography provide an effective tool for the analysis of these heterocyclic thioureas (494. 495). 

Finally, the techniques of nmr, infrared spectroscopy, and thin-layer chromatography also can be used to assay maleic anhydride (172). The individual anhydrides may be analyzed by gas chromatography (173,174). The isomeric acids can be determined by polarography (175), thermal analysis (176), paper and thin-layer chromatographies (177), and nonaqueous titrations with an alkaU (178). Maleic and fumaric acids may be separated by both gel filtration (179) and ion-exchange techniques (180). 

Gas-flow counting is a method for detecting and quantitating radioisotopes on paper chromatography strips and thin-layer plates. Emissions are measured by interaction with an electrified wire in an inert gas atmosphere. AH isotopes are detectable however, tritium is detected at very low (- 1%) efficiency. 

Paper and Thin-Layer Chromatography. Both of these techniques aie separation methods useful for dye identification. The dyes are... 

W E Court, Quantitative thin-layer chromatography using elution techniques. In Quantitative Paper and Thin-Layer Chromatography E J Shellard (Ed) Academic Press, New York, 1968, p 29... 

Because of the instability of many of the compounds involved, it is necessary to determine the chemical recoveries in all cases. This requires the use of macro quantities (10 mg up to several hundred mg) of carriers and target compounds. This, in turn, makes it impractical to use the various thin-layer methods, such as paper and thin-layer chromatography and paper electrophoresis, although such methods have proved useful in identifying products and in checking the purity of fractions. The separation methods now most commonly used are column chromatography and sublimation. 

Paper chromatography (PC) and thin layer chromatography (TLC) have been used since the 1940s. Preparative PC on Whatman 3 paper, analytical PC on Whatman 1 paper, and analytical TLC on microcrystalline cellulose, silica gel, or polyamide have been applied with a variety of solvents and the behaviors of anthocyanins have been similar in all media. Two-dimensional TLC allows the separation of several compounds and has been nsed to clarify the anthocyanin compositions of different commodities. ... 

Stahl, E., Ed., Thin-Ixiyer Chromatography, 2nd ed.. Springer-Verlag, Berlin, 1969. Barret, G.C., Nondestructive detection methods in paper and thin layer chromatography, in Advances in Chromatography, Vol. 11, Marcel Dekker, New York, 1974, pp. 145-179. 

Connors, K.A. (1974). Use of multiple Rf values for identification by paper and thin-layer chromatography. Anal. Chem. 46, 53-58. 

In paper and thin-layer chromatography, the separation process is halted at a stage which leaves the separated components in situ on the surface in the form of spots. The rate at which a solute has moved is then determined by its retardation factor, R, which is defined as... 

The examination of neomycin by paper and thin-layer chromatography has been for two main purposes -... 

Paper and Thin Layer Chromatography Radiochemical Methods... 

Table 10.7 Solvents for both paper and thin-layer chromatography...

Experimental and theoretical studies of the behavior of 2,2 -, 2,3 -, 3,3 -, and 4,4 -bipyridines in paper and thin-layer chromato-graphy and of 2,2 - and 4,4 -bipyridines in linear-elution adsorp-tion, - gas, and gas-liquid chromatography have been de-... 

Dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid were shown to form after the red pigment stage that occurred during the conversion of DOPA into a melanin, by Raper, who isolated these compounds as their dimethyl ethers.72 The presence of 5,6-dihydroxyindoles in solutions of DOPA, dopamine, and noradrenaline which are undergoing oxidation has subsequently been confirmed by paper and thin-layer chromatography.118,120,222 5,6-Dihydroxyin-dole and 5,6-dihydroxyindole-2-carboxylic acid have recently been isolated from the alkali fusion products of sepiomelanin, indicating... 

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