Silicic acid chromatography

Separation of aldehyde dinitrophenylhydrazines by TLC and column chromatography Excess dinitrophenylhydrazine reagent and the hydrazones of acetone, formaldehyde and acetaldehyde, which occur as contaminants, can be removed prior to preparative TLC by column chromatography. Silicic acid (Merck) columns (3x2.1 cm) may be used with chloroform to elute the aldehyde dinitrophenyl-hydrazones. 

Column chromatography (silicic acid partition, Sephadex, charcoal-celite etc.)... 

Figure 7. Infrared spectrum of pyrethrin I Isolated after dual partition chromatography First partition column. Celite-acetonitrile-hexane Second partition column. Silicic acid-nitromethane-hexane (with 5% acetone). Corresponds to peak 3 of gas chromatographic separation of pyrethrum mixture...

A method for determining the gamma isomer of benzene hexachloride by partition chromatography has been developed by Aepli et al. (1). Nitromethane and n-hexane are used as the partition solvents, and silicic acid is the supporting medium. The method appears to be useful for routine product analyses. An accuracy of about 2% of the actual gamma isomer present is claimed. 

The proton magnetic resonance spectrum of a C8De solution of the crude product exhibits benzylic CH doublets at <5 3.58 (J = 9.4 Hz., attributable to 90-96% of the threo aldol isomer) and at 8 3.42 (J = 5.3 Hz., attributable to 4-10% of the erthro aldol isomer) downfield from internal tetramethylsilane. This mixture may be separated by chromatography on acid-washed silicic acid to permit the isolation of both the threo and the erythro diastereoisomers. ... 

Procedures for determining fatty acids in sediments involved liquid-liquid extraction, liquid-solid adsorption chromatography followed by gas liquid chromatographic analysis [10-12], Liquid extractions have been performed with methanol-chloroform [13], methylene chloride [14] and benzene-methanol [15, 16]. Typical liquid-solid adsorbents are silicic acid. Standard gas chromatographic separations for complex mixtures employ non-polar columns packed with OV-1, OV-17, OV-101, SE-30, or glass capillary columns containing similar phases. 

Kirchner in 1950 was the first who used adsorption chromatography on impregnated glass-plate coated with silicic acid or alumina. It may be emphasized, however, that Egon Stahl s fundamental work stands as a landmark in the world-wide acceptance of this new technique in the laboratory. Later on, Stahl in 1958, introduced a standard equipment for preparing uniform thin-layers of known thickness, which eventually led to the ultimate acceptance of this new technique as an additional modem tool for analytical chemistry. 

Analysis of PCBs. PCB residues in extracts of egg samples were enriched by using a combination of gel permeation chromatography on BioBeads S-X3 and 1 1 (v/v) cyclohexane. methylene chloride. Adsorption column chromatography on silicic acid was used to separate PCBs from other co-extractives and contaminants (15). 

Column Chromatography of Crude Toxin. The WSAP obtained from culture 350F was retained in the crude state for assay. The 266.2 mg of WSAP obtained from 350G was treated on successive columns of silicic acid, DEAE cellulose, and Sephadex G-15 and yielded a single semipurified toxic product (GT-4) of 23.1 mg or 9% of the starting crude extract (Table I). 

Elemental composition Si 26.97%, F 73.03%. The gas is bubbled slowly through water to decompose into silicic acid and hydrofluoric acid. HE is analyzed for fluoride ion by fluoride-selective electrode or by ion chromatography. Silicon in the aqueous solution can be measured by AA or ICP. 

Phospholipids have usually been isolated from milk lipids by silicic acid column chromatography. This is a difficult separation because the phospholipids are only 1% of the total as compared to 98% TG. Gent-ner et al. (1981) have not only separated the phospholipids from the remainder by TLC but have also resolved the major types of phospholipids on one plate. 

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