Thin-layer chromatography separation techniques

Due to the small beam diameter ( 1 mm to 1 /xm) of the laser excitation source, only small samples are required (<1 /xg). This allows the technique to be easily coupled to gas, liquid, and thin-layer chromatography separation techniques. Moreover, this allows for high spatial resolution of samples. 

The 2-D TLC was successfully applied to the separation of amino acids as early as the beginning of thin-layer chromatography. Separation efficiency is, by far, best with chloroform-methanol-17% ammonium hydroxide (40 40 20, v/v), n-butanol-glacial acetic acid-water (80 20 20, v/v) in combination with phenol-water (75 25, g/g). A novel 2-D TLC method has been elaborated and found suitable for the chromatographic identification of 52 amino acids. This method is based on three 2-D TLC developments on cellulose (CMN 300 50 p) using the same solvent system 1 for the first dimension and three different systems (11-IV) of suitable properties for the second dimension. System 1 n-butanol-acetone -diethylamine-water (10 10 2 5, v/v) system 11 2-propanol-formic acid-water (40 2 10, v/v) system 111 iec-butanol-methyl ethyl ketone-dicyclohexylamine-water (10 10 2 5, v/v) and system IV phenol-water (75 25, g/g) (h- 7.5 mg Na-cyanide) with 3% ammonia. With this technique, all amino acids can be differentiated and characterized by their fixed positions and also by some color reactions. Moreover, the relative merits of cellulose and silica gel are discussed in relation to separation efficiency, reproducibility, and detection sensitivity. Two-dimensional TLC separation of a performic acid oxidized mixture of 20 protein amino acids plus p-alanine and y-amino-n-butyric acid was performed in the first direction with chloroform-methanol-ammonia (17%) (40 40 20, v/v) and in the second direction with phenol-water (75 25, g/g). Detection was performed via ninhydrin reagent spray. 

Thin layer chromatography. This technique is particularly effective at separating triacyclycerol, free fatty acid, and phospholipids from lens (Fleschner, 1995) and... 

The most popular thin layer chromatography (TLC) techniques for separation of enantiomers are described here 1) use of non-chiral phases for indirect resolution of optical isomers after derivatization to obtain the corresponding diastereoisomers and 2) direct resolution of enantiomers using chiral stationary phases or chiral mobile phases. Advantages and limits of all reported techniques are discussed. 

A review of all sorbents used as stationary phases in thin-layer chromatography (TLC) is reported. The specific apphcation field of aU sorbents is described according to tbeir relative chemical physical properties. New materials have been developed for the high-performance thin-layer chromatography (HPTLC) technique to offer both high-efficiency separations and high-sensibility analysis. In particular, sUanized sihca gel bas been extensively used as stationary phase in reversed-phase (RP) chromatography for its hydrophobic properties. 

Nearly all forms of conventional chromatography have been used for the separation of the various members of the retinoid family. These techniques include alumina, silicic acid, Sephadex LH-20, and thin-layer chromatography. Other techniques that have been employed, such as ion-exchange chromatogra-... 

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). 

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

THIN-LAYER CHROMATOGRAPHY — THE RECOVERY OF SEPARATED SURSTANCES RY ELUTION TECHNIQUES 8.9... 

The purpose of the experiment is to illustrate the elution technique for the recovery of pure substances after their separation by thin-layer chromatography. The experiment can be readily extended to include the quantitative determination of the recovered substances. 

Figures 2 through 9 are infrared spectra of fractions collected from partition columns, gas chromatography, thin-layer chromatography, or a combination of these separation techniques. Figure 10 is the infrared spectrum of a compound isolated by gas chromatography after hydrolysis of a pyrethrum concentrate. In this case the compound is a long-chain ester. All the infrared spectra were made with a Perkin-Elmer Model 221 instrument. The following operating parameters were used. A liquid demountable cell with a 0.01-mm path length was employed.

The first part of the book consists of a detailed treatment of the fundamentals of thin-layer chromatography, and of measurement techniques and apparatus for the qualitative and quantitative evaluation of thin-layer chromatograms. In situ prechromatographic derivatization techniques used to improve the selectivity of the separation, to increase the sensitivity of detection, and to enhance the precision of the subsequent quantitative analysis are summarized in numerous tables. 

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