Thin-layer chromatography separation methods

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. 

Are there any other analytical protocols available from the analytical chemist The more information about a compound, the easier it will be to develop a purification procedure. For example, in addition to the reversed-phase method, are there thin-layer chromatography (TLC) methods available for this compound This could help in deciding whether a silica column may be the appropriate tool for this separation. 

Estimation of total lipids and phospholipids The total lipid content was estimated according to Tsuda et al.(23) and purified according to Bligh and Dyer(24). Phospholipids were separated by thin layer chromatography (TLC) method(25). The phospholipids were quantified by estimating the phosphorous content(26). 

Sometimes, the gas chromatographic retention times of two or more materials are so close that an identification is difficult, even if two different columns have been used. A thin layer chromatography separation (Chapter 22) then can be used, but this generally requires a lengthy cleanup and concentration because of the small (nanogram) samples involved. A much quicker method is the use of P-values. This method is based on the distribution of the pesticides between two immiscible phases. 

The biological activity of total, polar and neutral lipids, as well as purified fractions of each lipid class after thin layer chromatography separations (Nasopoulou et al., 2007) was studied against washed rabbit platelets according to the method of Demopoulos et al. (1979)... 

The thin-layer chromatography (TLC) method was used for purifying the intermediary products obtained from the synthesis of the oligonucleotide dendrimers. The separations were performed on silica gel plates using various solvent mixtures as mobile phases, e.g., methanol-methylene chloride (1 9, v/v), methanol-chloroform (1 30, 1 9, v/v), hex-ane-dichloromethane (1 3, v/v), hexane-ethyl acetate (3 1, 1 1,4 1, v/v). The separated compounds were visualized in an iodine atmosphere. 

The nitration of the 2-anilino-4-phenylselenazole (103) is much more complicated. Even careful nitration using the nitrate-sulfuric acid method leads to the formation of a mixture of variously nitrated compounds in an almost violent reaction. By the use of column chromatography as well as thin-layer chromatography a separation could be made, and the compounds could be partly identified by an independent synthesis. Scheme 33 shows a general view of the substances prepared. Ring fission was not obser ed under mild conditions. 

The successful separation of xanthate-related compounds by high performance Hquid chromatography (hplc) methods has been reported (91—93). The thin-layer chromatography procedure has been used to determine the nature of the alcohols in a xanthate mixture. A short mn of 3 cm at a development time of 25 min gives a complete separation of C —alkanol xanthates (94). 

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

Nonionic surfactants, including EO-PO block copolymers, may be readily separated from anionic surfactants by a simple batch ion exchange method [21] analytical separation of EO-PO copolymers from other nonionic surfactants is possible by thin-layer chromatography (TLC) [22,23] and paper chromatography [24], and EO-PO copolymers may themselves be separated into narrow molecular weight fractions on a preparative scale by gel permeation chromatography (GPC) [25]. 

Besides the calculation of the different sulfonated species, it is also possible to determine them directly by chromatographic methods. Separation of the ester sulfonate and the disodium salt is achieved by thin-layer chromatography on silica gel plates. With a solvent mixture of acetone and tetrahydrofuran (90 10 v/v) the disodium salt stays at the start whereas the ester sulfonate has an R value of 0.2. With the more polar solvent 0.1 N H2S04 + methanol + chloroform the ester sulfonate and the disalt have Rf values of 0.36 and 0.14. For visualization, the plate is sprayed with pinacryptol yellow. In UV light (254 and... 

This volume is the second of a series of practice-orientated TLC/HPTLC books published in excellent quality by VCH Publishers. As in the first volume, a series of reagents and detection methods have been reviewed with the intention of helping the practical analyst increase the detection specificity of routine samples separated by thin-layer chromatography. 

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