Silica Gel Layers

It was used 200x200 mm plates of Silufol UV 254 as a fixed layer. Unfixed layer Silica gel LC 5/40 p. was spread on the 200x200 mm glass plates. 

Fig. 60 Chromatogram of a 6 dyestuff mixture made up (according to falling Rf values) of Sudan red 7B, Sudan orange G, Sudan black B, Sudan yellow, Artisil blue 2RP and Sudan black B (2 components) under different humidity conditions. From left to right 72, 65, 47, 42, 32,18, 14 and 9% relative humidity layer silica gel 60 mobile phase toluene.

Note System layer silica gel 60 F254 (0.25 mm, Merck Art. 5716) developing solvent ethyl acetate-formic acid-acetic acid-water (100 11 11 27). 

Thick-layer silica gel chromatography can also be employed [7], although most separations are now accomplished by high-performance liquid chromatography. Resolution of complex mixtures often requires both normal and reverse phase modes [19]. A further dimension is added, when bioactivity is correlated with spectroscopically-monitored chromatographic profiles. 

In fact, it is extremely important to eliminate as completely as possible the solvent imbedded into the thin layer of coated adsorbent. It is achieved conveniently first by air-drying the TLC plates for a duration of 30 minutes and then in a hot-air oven maintained at 110 °C for another 30 minutes and subsequently cooling them in a dessicator. This drying process helps a great extent in rendering the adsorbent layer active. In order to achieve very active layers, silica gel and alumina coated plates may be heated upto 150 °C for a duration of 4 hours and colling them in a dessicator. 

Figure 3-5 Photograph of a two-dimensional thin layer (silica gel) chromatogram of a mixture of flavins formed by irradiation of 10 pg of the vitamin riboflavin. The photograph was made by the fluorescence of the compounds under ultraviolet light. Some riboflavin (RF) remains. The arrows indicate the location of the sample spot before chromatography. Chromatography solvents a mixture of acetic acid, 2-hutanone, methanol, and benzene in one direction and M-butanol, acetic acid, and water in the other. See Treadwell et al.H)2...

Saito, K., Takekuma, M., Ogawa, M., Kobayashi, S., Sugawara, Y., Ishizuka, M., Nakazawa, H. and Matsuki, Y. (2003) Extraction and cleanup methods of dioxins in house dust from two cities in Japan using accelerated solvent extraction and a disposable multi-layer silica-gel cartridge. Che.mosphe.re, 53,... 

Methyl pseudomonate was separated from methyl pseudomonate-A by preparative layer silica gel (GF245) chromatography on development with chloroform/isopropanol (9 1). 50% of methyl pseudomonate was recovered from the impure residue by crystallization from benzene/petroleum ether to give colorless needles of m.p. 76.5-78°C. 

Essentially three approaches can be used in the isolation of phosphatidylserine from a total lipid sample. These include thin-layer silica gel chromatography, aluminum oxide chromatography, and high-performance (high-pressure) liquid chromatography. The merits of these techniques are discussed as follows. 

A mixture of 6-chloro-9-(2,3,5-tri-0-acetyI-)3-D-ribofuranosyl)purin-2-amine (0.293 g, 0.685 mmol), anhyd, distilled pentyl nitrite (1.53 mL, 11.4 mmol), and dry CCL (30 niL) was heated at reflux temperature under Nj for 24 h. The solvent was then removed and the resulting residue taken Up in CH,Cl2 (3 mL) and chromatographed (preparative layer silica gel plates, developed twice with i-PrOH/CH CL, 1 50). Elution of the only significant band Rf = 0.29) with MeOH/CH CIj gives, after crystallization (EtOH), colorless needles yield 0.2 g (66%) rap 139 -t4t°C. 

Carefully add petroleum ether to the column, open the valve and elute the two compounds. The first to be eluted, ferrocene, will be seen as a yellow band. Collect this in a tared 50-mL flask. Any crystalline material seen at the tip of the valve should be washed into the flask with a drop or two of ether. Without allowing the column to run dry, add a 50 50 mixture of petroleum ether and diethyl ether and elute the acetylferrocene, which will be seen as an orange band. Collect it in a tared 50-mL flask. Spot a thin-layer silica gel chromatography plate with these two solutions. Evaporate the solvents from the two flasks and determine the weights of the residues. 

Three modifications of TLC are in use in Upid analysis (a) separation on unmodified silica gel layer, silica gel TLC (b) separation on a layer impregnated with silver ions, silver-ion TLC (Ag TLC), and (c) separation on a layer modified with silanes or long-chain hydrocarbons to give a nonpolar stationary phase, reverse-phase TLC (RP-TLC). 

Analytical Procedures. Glyceride fractions from purification of reaction mixtures were analyzed by thin layer silica gel chromatography (TLC) and HPLC. In addition, several preparative TLC s were performed on the isolated triglycerides. The purified triglycerides were esterified directly to methyl esters by a modification of the method of Morrison and Smith (19), and the fatty acid profile determined by gas chromatography using conventional techniques described elsewhere (10). 

Figure 3 Thin layer silica gel chromatogram of the feed and fractions obtained in the fractionation of the tri-EPA reaction mixture using SC-CO2. MG monoglyceride, DG - diglyceride,...

A solution of 77 mg. of (-)-cis-l-hydroxy-3-(l,l-dimethylheptyl)-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[b,d]pyran-9-one in 5 mL. of dicblorometbane containing 77 mg. of aluminum chloride was stirred at 25° C. for four hours. The reaction mixture then was diluted with 20 g. of ice, and the resulting aqueous mixture was extracted with diethyl ether. The ethereal extracts were combined, washed with 2N hydrochloric acid and with ten percent aqueous sodium bicarbonate solution, and then washed with water, dried, and the solvent was removed by evaporation under reduced pressure to provide 75 mg. of the product as an oil. The oil so formed was chromatographed over a thick layer silica gel coated plate. Elution of the principle band with a twenty percent solution of ethyl acetate in benzene, and evaporation of the solvent therefrom, afforded 54 mg. of (-)-trans-l-hydroxy-3-(l,l-dimethylheptyl)-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[b,d]pyran-9-one. [a]20D - 53.8° (c = 1.0, CHCB). 

The partially purified biologically active extract from rape pollen will be referred to as "brassins" in this Chapter. The extract was partially purified via a thin layer silica gel chromatographic procedure. Biologically active fractions were detected and monitored via the "bean 2nd internode bioassay" (6). Fractions from the... 

When paper chromatographic techniques designed for work on adult urine, such as those of Bush and Mahesh (B41), were applied to infant urine, considerable modifications were required mainly to deal with the increased amount of material which interfered both with chromatography and the specificity of color reactions (B18). Thin-layer silica-gel chromatography was found to be less susceptible to this interference, and with its use little preliminary purification is necessary (S9, SIO). 

Fig. 5. Thin-layer silica-gel chromatography of an extract of umbilical cord plasma after enzyme hydrolysis and a further extract obtained after solvolysis. The chromatogram was developed once in the system benzene-ethyl alcohol (95 5 v/v) and twice in the system cyclohexane-ethyl acetate (50 50 v/v). Color development was by spraying with antimony trichloride with subsequent heating.

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