Evaporation thin layer chromatography

Stewart, G. H., and Wendel, C. T. (1975). Evaporative thin layer chromatography, solvent flow, and zone migration. J. Chromatogr. Sci. 13 105-109. 

Diaminoanthraquinone [128-95-0] M 238.3, m 268°. Purified by thin-layer chromatography on silica gel using toluene/acetone (9 1) as eluent. The main band was scraped off and extracted with MeOH. The solvent was evaporated and the quinone was dried in a drying pistol [Land, McAlpine, Sinclair and Truscott J Chem Soc, Faraday Trans 1 72 2091 1976]. Crystd from EtOH in dark violet crystals. 

In the case of thin-layer chromatography there is frequently no wait to establish complete equilibrium in the chamber before starting the development. The chamber is usually lined with a U-shaped piece of filter paper and tipped to each side after adding the mobile phase so that the filter paper is soaked with mobile phase and adheres to the wall of the chamber. As time goes on the mobile phase evaporates from the paper and would eventually saturate the inside of the chamber. 

A solution of 0.2 g of cholestenone and 0.47 g of (< 3P)3RhCl in 150 ml of acetone is stirred under a hydrogen atmosphere for 3 days. The solvent is evaporated and the residue separated by thin layer chromatography to afford 5a-cholestan-3-one in 25-35% yield. ... 

The bacteriochlorin 10 (65 mg, 0.11 mmol) was dissolved in coned H2S04 (18 mL) and allowed lo react at 20 C for 5 min. The mixture was poured into ice, diluted with H20 and NaOAc (7.5 g, 91 mmol) was added. The mixture was extracted several times with CHC13, the organic extractions were washed with H20 (2 x), dried (Na2S04) and evaporated. Preparative thin-layer chromatography (silica gel) gave 11 and 12 yields 10.7 mg (17%) and 44 mg (70%), respectively. 

Removal of solvent from the extracts leaves a residue that is purified by dry-column chromatography.2 The residue is dissolved in 40 ml. of acetone in a 300-ml., round-bottomed flask, 30 g. of silica gel (Note 8) is added, and the acetone is removed with a rotary evaporator. The resulting solid mixture is placed on top of 360 g. of dry silica gel (Note 8) packed in flexible nylon tubing (Note 9), and the column is developed with 420 ml. of 10 1 (vjv) benzene-acetone. Approximately 150 ml. of solvent drips from the bottom of the column toward the end of development, and this eluent is collected in 25-ml. fractions and checked for product by thin layer chromatography (Note 10). The column itself is then cut into 2-cm. sections, the silica gel in each section is eluted with three 25-ml. portions of ethyl acetate, and the eluent from each section is analyzed by thin-layer chromatography (Note 10). Combination of all the product-containing fractions yields 1.2-1.5g. (40-47%) of the benzylated compound as an oil, n 1.6083 (Notes 11 and 12). 

Thin-layer chromatography (TLC) is used both for characterization of alcohol sulfates and alcohol ether sulfates and for their analysis in mixtures. This technique, combined with the use of scanning densitometers, is a quantitative analytical method. TLC is preferred to HPLC in this case as anionic surfactants do not contain strong chromophores and the refractive index detector is of low sensitivity and not suitable for gradient elution. A recent development in HPLC detector technology, the evaporative light-scattering detector, will probably overcome these sensitivity problems. 

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). 

Spengler and Jumar [90] used a spectrophotometric method and thin layer chromatography to determine carbamate and urea herbicide residues in sediments. The sample is extracted with acetone, the extract is evaporated in vacuo at 40°C and the residue is hydrolysed with sulphuric acid. The solution is made alkaline with 15% aqueous sodium hydroxide and the liberated aniline (or substituted aniline) is steam distilled and collected in hydrochloric acid. The amine is diazotized and coupled with thymol, the solution is cleaned up on a column of MN 2100 cellulose power and the azo-dye is determined spectrophotometrically at 440nm (465nm for the dye derived from 3-chloro- or 3.4-dichloroaniline) with correction for the extinction of a reagent blank. 

Merck 60 F254 thin-layer chromatography (TLC) plates rotary evaporator... 

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