Methanol solvent thin layer chromatography

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. 

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. 

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. 

Also thin-layer chromatography is applied to the separation of both elements . Pertechnetate and molybdate can be separated on silica gel or alumina with mixtures of 1 M HCl methanol or 1 M HCl ethanol (1 5) as solvent and also on cellulose MN 300 with butanol saturated with 1 M HCl . 

Thin layer chromatography. Thin layer chromatography (TLC) was carried out on precoated Silica gel 60 plates (Merck) with the solvent system benzene-acetone-methanol-6N acetic acid (150 80 19 1). Toxins were detected by heating the plates after spraying 50% sulfuric acid. 

Thin-layer chromatography was carried out on DC-Fertigplatte Merck Kieselgel F254 supplied by Firma Merck AG, 61 Darmstadt, Germany. For the solvent system methylene chloride/methanol (97/3) the product has an Rf value of 0.45. 

By appropriate choice of the type (or combination) of the organic solvent(s), selective polar dipole-dipole, proton-donor, or proton-acceptor interactions can be either enhanced or suppressed and the selectivity of separation adjusted [42]. Over a limited concentration range of methanol-water and acetonitrile-water mobile phases useful for gradient elution, semiempirical retention equation (Equation 5.7), originally introduced in thin-layer chromatography by Soczewinski and Wachtmeister [43], is used most frequently as the basis for calculations of gradient-elution data [4-11,29,30] ... 

Figure 9.29 Membrane formation by meteoritic amphiphilic compounds (courtesy of David Deamer). A sample of the Murchison meteorite was extracted with the chloroform-methanol-water solvent described by Deamer and Pashley, 1989. Amphiphilic compounds were isolated chromatographically on thin-layer chromatography plates (fraction 1), and a small aliquot ( 1 p,g) was dried on a glass microscope slide. Alkaline carbonate buffer (15 p,l, 10 mM, pH 9.0) was added to the dried sample, followed by a cover slip, and the interaction of the aqueous phase with the sample was followed by phase-contrast and fluorescence microscopy, (a) The sample-buffer interface was 1 min. The aqueous phase penetrated the viscous sample, causing spherical structures to appear at the interface and fall away into the medium, (b) After 30 min, large numbers of vesicular structures are produced as the buffer further penetrates the sample, (c) The vesicular nature of the structures in (b) is clearly demonstrated by fluorescence microscopy. Original magnification in (a) is x 160 in (b) and (c) x 400.

Lipids can be identified and quantified using thin-layer chromatography (TEC) and gas chromatography (GC) (Galliard, 1968). Extraction of lipids is achieved by homogenizing potato tubers with isopropanol in a blender, followed by a series of filtrations and extractions with chloroform-methanol (2 1). Chloroform is removed by rotary evaporation and the residue is redissolved in benzene-ethanol (4 1). This extract is passed through a DEAE-cellulose column, and the fractions collected are subjected to TEC on 250 p,m layers of silica gel G, using three solvent systems. Fatty acid methyl esters for GC analysis are prepared by transmethylation of the parent lipids, or by diazomethane treatment of the free fatty acids released by acid... 

Ortega extracted dried and milled leaves with hot chloroform. He isolated salvinorin from the green residue left over after evaporating the solvent with column chromatography. He used thin layer chromatography to test for salvinorin in the fractions, and found it in the sixth and seventh of thirteen. The TLC plates were developed with 10 per cent phosphomolybdic acid in isopropanol (ethyl acetate/hexane, 45 55, Rf=0.7). Crystallize from methanol, melting point 238-240°C. 

V-(9-Fluorenylmethoxycarbonyl)-0-(2,3,4-tri-0-benzoyl- 3-D-xylopyranosyl)-L-serine 15. The Fmoc O-xylosyl serine benzyl ester 13 (1.0 g, 1.2 mmol) is stirred in methanol (40 mL) at room temperature and subjected to hydrogenolysis for 18 h under atmospheric pressure using palladium-charcoal (0.2 g, 5%) as the catalyst. The educt 13 dissolves slowly. The catalyst is filtered off, and the solvent evaporated in vacuo. If the residue is not pure according to thin-layer chromatography (TLC), it is dissolved in 2 mL of ethyl acetate and purified by chromatography on a short column of silia gel 60. The byproducts are eluted with petroleum ether-ethyl acetate the product 15 with methanol yield 0.85 (92%) mp 109°C, [cr]D -12.6° (c 0.3, CH3OH) Rf 0.64 (toluene-ethanol, 1 2). 

Figure 4-20 Separation of a mixture of O-methylated glucoses by ascending thin-layer chromatography. Whatman K6 TLC plates were used with two ascents of the solvent acetonitrile/chloroform/methanol in the ratio 3/9/2, V/...

Thin-layer chromatography of dansyl-amino acids on a polyamide plate. A After solvents 1 (1.5% formic acid) and 2 (toluene-acetic acid). B After solvents 1,2, and 3 (ethyl acetate-methanol-acetic acid). See text for further details. 

B. Lactones. The crude mixture of rac-3 and rac-4 is dissolved in 300 mL of dry methanol (distilled from sodium) containing 10 drops of coned hydrochloric acid and heated under reflux for about 8 hr until the reactants can no longer be detected by thin layer chromatography (Note 6). The solvent is removed on a rotary evaporator at 25°C and the remaining residue, which consists of an 8 1 mixture of lactone rac-5 and dimethyl ester rac-6 is dissolved in dry dichloromethane (50 mL). The solution is acidified with trifluoroacetic acid (10 mL) and stirred at room temperature for about 48 hr, until the thin layer chromatogram does not show any dimethyl ester rac-6 (Note 6). The organic layer is washed with water (50 mL), saturated sodium bicarbonate solution (2 x 50 mL), water (50 mL), and brine (50 mL), dried over sodium sulfate,... 

Figure 1 shows the scheme for the preparation of purified lipid A from endotoxin. S. typhimurium G30/C21 was extracted by the method of Galanos t aK (24) and submitted to one of two different conditions of hydrolysis (a) 0.1 N HC1 [in methanol-water (1 1, v/v)], 100 °C, 45 min, to yield the crude monophosphoryl lipid A (nontoxic), and (b) 0.02 M sodium acetate, pH 4.5, 100 °C for 30 min (two cycles) to yield the crude diphosphoryl lipid A (toxic). The 0.1 N HC1 hydrolysis product was fractionated on a Sephadex LH-20 column (23). Each of these fractions was then separated by preparative thin layer chromatography (TLC) on silica gel H (500 ym), with the solvent system chloroform-methanol-waterconcentrated ammonium hydroxide (50 25 4 2, v/v) as previously described (23) to yield TLC fractions 1-7 and 1-9 respectively. 

---