Dry-column chromatography

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). 

Silica gel Woelm for dry-column chromatography, activity III/30 mm. [according to Brockmann and Schodder, Ber., 74B, 73 (1941)], was supplied by M. Woelm, Eschwege, Germany. 

Dry column chromatography 494 Dry packing, columns (LC) 349 Dry test meter 843 Dual oven (GC) 62 Durapak phases (GC) 125 Dwell time, gradient elution, (LC) 489, 563... 

Dry column chromatography [528] provides several improvements over traditional column chromatography, such as better resolution and high speed. Another important characteristic is the near-quantitative applicability of TLC results in dry column analysis. Knowledge of the TLC characteristics of a sample is useful before column chromatography is employed. Careful control of the moisture content of the adsorbent is crucial to the dry column as well as other types of chromatography. 

Dry-column chromatography is another approach to the separation of large quantities of a mixture of products. I think it s easier than wet-column chromatography, though more limited. 

The manufacturers of dry-column chromatography adsorbants suggest piercing the bottom of the column with a few pin holes. They would know. 

Once the sample is in the column, there s not much difference between what happens here and what happens in paper, thin-layer, vapor-phase (gas), wet-column, or dry-column chromatography. The components in the mixture will stay on the stationary phase, or move in the mobik phase for different times and end up at different places when you stop the experiment. 

Modifications of the method (dry-column chromatography, vacuum liquid chromatography, VLC, for example) are also of practical use for the rapid fractionation of plant extracts. VLC with a polyamide support has been reported for the separation of flavonol glycosides. ... 

The free base 5,10,15,20-tetraphenyl-21 A/,23//-porphine (H2tpp) may be prepared from pyrrole and benzaldehyde4 or purchased from Strem Chemicals, P.O. Box 108, Newbury Port, MA 01950 or Aldrich Chemical Co., 940 St. Paul Ave., Milwaukee, WI 53233. The material should be chlorin free, which can be effected either by dry column chromatography using alumina and chloroform or by oxidation of the chlorin to porphyrin using 2,3-dichloro-5,6-dicyano-... 

Scientific Adsorbents, Inc. DCC adsorbents, which are commercially available from Scientific Adsorbents, Inc. (Atlanta, GA, U.S.A.) are adjusted to meet the physical-chemical properties of TLC as closely as possible. These adjustments are made during the manufacturing cycle, and the material is packaged ready to use. With similar physical-chemical properties, the Rf values obtained for the substances under investigation from TLC are practically identical to those obtained with dry-column chromatography. 

Chromatography is perhaps the most useful means of separating compounds to purify and identify them. Indeed, separations of colored compounds on paper strips gave the technique its colorful name. Although there are many different types of chromatography, all the forms bear tremendously striking similarities. Thin-layer, wet-column, and dry-column chromatography are common techniques you ll run across. 

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