Methanol thin layer chromatography

An important publication by Kost et al. (63JGU525) on thin-layer chromatography (TLC) of pyrazoles contains a large collection of Rf values for 1 1 mixtures of petroleum ether-chloroform or benzene-chloroform as eluents and alumina as stationary phase. 1,3- and 1,5-disubstituted pyrazoles can be separated and identified by TLC (Rf l,3>i y 1,5). For another publication by the same authors on the chromatographic separation of the aminopyrazoles, see (63JGU2519). A-Unsubstituted pyrazoles move with difficulty and it is necessary to add acetone or methanol to the eluent mixture. Other convenient conditions for AH pyrazoles utilize silica gel and ethyl acetate saturated with water (a pentacyanoamine ferroate ammonium disodium salt solution can be used to visualize the pyrazoles). 

Thin layer chromatography of (-)-DAG on Silica Gel G using the solvent system, benzene methanol acetone acetic acid (70 20 5 5), shows one spot with Rf 0.7. 

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... 

A more concentrated (1000 ppm) solution of dibenzo-p-dioxin in methanol was irradiated for 1.5 hours under a 450-watt lamp fitted with a borosilicate glass filter while nitrogen was bubbled continuously through, the solution. Unchanged starting material was recovered to the extent of 85%. The principal photolysis product again was a dark brown insoluble gum similar to that described above. Its mobility on thin layer chromatography (TLC) was very low in the benzene/ethyl acetate (4 1) solvent used to separate the other products. 

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]. 

In reversed-phase thin-layer chromatography (RP-TLC), the choice of solvents for the mobile phase is carried out in a reversed order of strength, comparing with the classical TLC, which determines a reversed order of values of compounds. The reversed order of separation assumes that water is the main component of the mobile phase. Aqueous mixmres of some organic solvents (diethyl ether, methanol, acetone, acetonitrile, dioxane, i-propanol, etc.) are used with good results. 

Most often the sterols have been collected by liquid-liquid extraction using petroleum ether and ethyl acetate [408], chloroform and methanol [409], -hexane [410,411] or chloroform [412,413]. After concentration, gas chromatography was generally used for the final separation and determination, although thin-layer chromatography has also been employed. The extra sensitivity of the electron capture detector could be used by reacting the concentrated sterols with bromomethyldimethylchlorosilane (BMDS) before separation and measurement [414],... 

It was preferred to first separate the impurities from bromocriptine by thin layer chromatography and then to isolate the substance by elution from the silica gel of the plate with methanol. The intact active ingredient is measured in 0.01 M methanolic methanesulphonic acid (26). 

The identification of bromocriptine mesilate in the dosage form can be carried out by thin layer chromatography using Merck plates with dichloromethane/methanol/formic acid 78 20 2 (v/v/v) and subsequent uv-visualization at 254 and 360 nm. Using this method, it is important to only air-dry the spot after application to the plate, since more vigorous evaporation of the solvent will give rise to artifacts (32). 

The consumption of the oxime can be checked by thin-layer chromatography on silica gel G with the solvent system chloro-form/methanol (95/5 v/v) and a spray reagent consisting of 5% potassium dichromate in 40% sulfuric acid. The oxime appears as an immediate dark spot and the aziridine as a yellow spot. The checkers observed identical mobilities (Rf 0.8) for both compounds. 

The question as to the potential availability of the requisite amphiphilic precursors in the prebiotic environment has been addressed experimentally by Deamer and coworkers, [143,145] who looked into the uncontaminated Murchison chondrite for the presence of such amphiphilic constituents. Samples of the meteorite were extracted with chloroform-methanol and the extracts were fractionated by thin-layer chromatography, with the finding that some of the fractions afforded components that formed monomolecular films at air-water interfaces, and that were also able to self-assemble into membranous vesicles able to encapsulate polar solutes. These observations dearly demonstrated that amphiphiles plausibly available on the primitive Earth by meteoritic infall have the ability to self-assemble into the membranous vesides of minimum protocells. ... 

A drin and Dieldrin Metabolism.— The in vivo metabolism of the chlorinated alicyclic insecticides, aldrin and dieldrin, has been measured. Fish were exposed to l c-labelled aldrin or dieldrin for 6 hours. The metabolism of each compound was monitored by thin layer chromatography of hexane and chloroform-methanol extracts of liver homogenates, followed by liquid scintillation counting of the spots (5,15,16). 

The nature of the radioactivity in the water, soil and fish from the carbon-14 DDT experiment was examined by thin-layer chromatography as shown in Figure 5. The radioactivity in the water was very polar in nature and did not migrate appreciably from the origin. About 78% of the radioactivity in the soil was extracted with methanol. The major metabolite in the extractable fraction was DDD which represented 33% of the total radioactivity. The reductive dechlorination of DDT to DDD is a known pathway under anaerobic conditions and has been shown to be due to microbial metabolism (5). Since carbon-14 DDT was incor-... 

The soluble metabolites excreted from animals dosed by injection were collected on AmberliteR XAD-4 resin, the resin eluted sequentially with diethyl ether, acetone, and methanol, and the solutes separated by thin-layer chromatography on silica gel and quantitated by liquid scintillation counting. 

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