Chromatographic systems thin-layer chromatography

Residues are determined in the purified extracts by chromatographic or immunochemical techniques. In the chromatographic systems, thin-layer chromatography (TEC), liquid chromatography (LC), and GC, the analytes are separated on plates or columns and determined by colorimetry, by spectrophotometry (ultraviolet (UV), infrared (IR, Fourier transform infrared (FTIR)), by fluorescence, by selective detectors (in GC analysis ECD, flame photometric (FPD), nitrogen/phosphorus (NPD, TSD), etc.), or by MS. Separations may also be achieved by... 

Aromatic amines can sometimes be chromatographed successfuly after their conversion to derivatives. For example, isomeric toluidines and aniline, which are poorly separated as salts, can be clearly separated after their conversion to bromo derivatives (105) a series of primary amines can be separated after conversion to arylazo-2-naphthole (p. 342), and for the separation of isomers the products of the reaction of amines with diazonium salts (p. 324) can also be employed. They can be chromatographed in a formamide/hexane system. Thin-layer chromatography of free bases can be carried out on nonadhering layers of alumina (106, 107), or on silica gel G layers using the mobile phase cyclohexane — carbon tetrachloride-ethyl ecetate (10 70 20) ... 

Fig. 1. Classification of chromatographic systems where gsc is gas—soHd chromatography glc, gas—Hquid chromatography sec, size-exclusion chromatography Isc, Hquid—soHd chromatography Uc, Hquid—Hquid chromatography iec, ion-exchange chromatography tic, thin-layer chromatography ...

A modification of the thin-layer chromatography (TLC) technique with external control over the chromatographic system is proposed. 

There is no other facet where thin-layer chromatography reveals its paper-chromatographic ancestry more clearly than in the question of development chambers (Fig. 56). Scaled-down paper-chromatographic chambers are still used for development to this day. From the beginning these possessed a vapor space, to allow an equilibration of the whole system for partition-chromatographic separations. The organic mobile phase was placed in the upper trough after the internal space of the chamber and, hence, the paper had been saturated, via the vapor phase, with the hydrophilic lower phase on the base of the chamber. 

Chromatographic characterisation of hydrolysis products Hydrolysis products from sodium polypectate were analysed by thin-layer chromatography on silica gel G-60, using ethyl acetate / acetic acid / formic acid / water (9 3 1 4, by volume) as the mobile phase system. Sugars were detected with 0,2% orcinol in sulphuric add-methanol (10 90ml) [14]. 

The theoretical work that exploited the advantages of the multidimensional separation format appears to have been developed much later than the original experimental work. One of the earliest studies was conducted by Connors (1974), who assumed that the distribution of spots on a two-dimensional thin-layer chromatography (2DTLC) plate could be modeled using a Poisson distribution of data on each retention axis. He then constructed equations that related the number of chromatographic systems needed to resolve a specific number of compounds. One... 

G. Matysik, E. Soczewinski, M. Wojciak-Kosior and E. Wojtasik, Optimization of chromatographic systems for the high-performance thin-layer chromatography of flavonoids. Chromatographia 52 (2000) 357-362. 

In view of its rapidity we found thin layer chromatography convenient for identification of the amino acids liberated by the first 20—30 degradation cycles. For identification of PTH-derivatives from additional degradation steps we prefer gas-liquid chromatography because of its merits mentioned above, particularly its greater sensitivity. Several colorimetric reactions and chromatographic systems are available for the identification of those PTH-amino acids which remain in the aqueous phase when the PTH-derivatives are extracted with ethyl acetate 23.24,25,13) our hands, thin layer electrophoresis was found to be satisfactory 26,27)... 

After 1 hour, the reaction is complete as monitored by gas chromatographic analysis on an Hewlett-Packard F M 5751 research chromatograph (1.85 m. x 0.313 cm. stainless-steel column of 10% Apiezon L on Chromosorb W AW/DMCS column temperature 250°). Thin-layer chromatography was found to be of little use in monitoring the reaction, as the Rf values for benzyl disulfide and benzyl sulfide are virtually identical for a variety of solvent systems tried. Proton magnetic resonance (benzene) shows that these two compounds have coincidental chemical shifts for the benzylic protons 8 3.4 (singlet). 

An analagous process for isolating and concentrating portions of a sample is the use of thin layer chromatography. Here, however, it is common practice, in the treatment of an unknown sample, to place a known standard on the same plate and to run the two systems parallel so that differences in performance of an adsorbing system from one laboratory to another are accounted for by basing isolation of the desired components from the plate on the determined position of the known standard, run on the same plate. The normally limited capacity of thin layer chromatographic systems tends to exclude their wide use for the combined isolation-concentration steps of trace analysis, but circumstances in which this technique may be useful should not be overlooked. ... 

Knappe, E. and Rohdewald, I., Thin-layer chromatography of dicarboxylic acids. IV. Combination of thin-layer chromatographic systems for the identification of individual components in dicarboxylic acid mixtures, Z. Anal. Chem., 210, 183, 1965 Chem. Abs., 63, 3600f, 1965. 

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