Ketones, detection thin layer chromatography

Plasticizers include the esters of a few aliphatic and aromatic mono and dicarboxylic acids, aliphatic and aromatic phosphorus acid esters, ethers, alcohols, ketones, amines, amides, and non-polar and chlorinated hydrocarbons. These additives are used in various mixtures. For their separation and qualitative detection, thin-layer chromatography (TLC) is preferred. Usually Kieselgur plates, 0.25 mm thick, activated at 110°C for 30 min, in the saturated vapor are used. Methylene chloride and mixtures of diisopropyl ether/petether at temperatures between 40 to 60°C have been successfully used as the mobile phase. Refer to Table 1. 

Many impurities are present in commercial caprolactam which pass into the liquid wastes from PCA manufacture from which caprolactam monomer may be recovered. Also, the products of die thermal degradation of PCA, dyes, lubricants, and other PCA fillers may be contained in the regenerated CL. Identification of die contaminants by IR spectroscopy has led to the detection of lower carboxylic acids, secondary amines, ketones, and esters. Aldehydes and hydroperoxides have been identified by polarography and thin-layer chromatography. 

Diphenylacetyl-l,3-indandione-l-hydrazone, first prepared by Braun and Mosher [143], reacts readily with carbonyl compounds such as aldehydes and ketones in weakly acidic media. The derivatives are separated by paper or thin-layer chromatography [144]. The derivatives are excited at 400-415 nm and emit at ca. 525 nm. The limit of detection is 2 ng per spot. 

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. 

Radiochemical Purity. Tc-DMSA complex is described in the Ph. Eur. (Council of Europe 2005). Thin-layer chromatography (TLC) on silica gel (SG) fiberglass sheets in two different solvents is recommended for the detection of free Tc-pertechnetate and reduced, hydrolized Tc activity. Free Tc-pertechnetate is measured in methyl ethyl ketone (MEK) at the solvent front, reduced, hydrolized Tc activity is identified in saline at the start. The radiochemical purity of Tc-DMSA should not be less than 95%. The amount of free Tc-pertechnetate should not exceed 2% of the measured radioactivity (Ph. Eur.). 

Application of this sequence to alicyclic four-, five-, and six-membered ketones results in ring expansion, as illustrated for the case of cyclopentanone (4). An intermediate in the conversion of (5) to (6) was detected by thin layer chromatography and was eventually isolated in the case of the adduct (7) from (1)... 

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