Class separations with Sephadex

Chemical fractionation of whole products and by-products from synthetic fuel production affords a logical first step in the evaluation of these materials for biological activity and the subsequent prediction of health hazards. Aliphatic and aromatic hydrocarbons, along with smaller amounts of heteroatomic species, constitute the bulk of all crude product materials and define a primary class separation need. Subfractionation of these fractions can lead to identification of bioactive components, Aliphatics are separated from the entire sample by a simple liquid chromatographic elution scheme. Aromatic compounds can be isolated by a cyclo-hexane-dimethylsulfoxide solvent partitioning scheme, A Sephadex LH-20 gel separation scheme appears feasible for the fractionation of crude liquids into aliphatic-aromatic, lipophilic-hydrophilic, polymeric, and hydrogen bonding classes of compounds. 

The biogenic components that interfere with the GC analysis of aromatic hydrocarbons are primarily long-chain components. Such compounds are much larger molecules than the compact aromatic hydrocarbons. Because of this major difference, gel permeation chromatography (GPC), which separates on the basis of molecular size, can be used very effectively to separate the two classes of compounds (9). The GPC materials that can be used for the separation include modified dextrans, for example, Sephadex LH-20, and styrene-divinylbenzene copolymers, for example, BioBeads, Styragel, or /x-Styragel. 

Single phospholipid classes were separated to identify the active components of lipid mixture. Non-lipid contaminants were removed on Sephadex 625 Lipids were the passed through a silicic acid column, washed with chloroform to eliminate neutral lipids and fatty acids, and phospholipids fractioned with various amount of methanol in chloroform. Single purified phospholipid classes were obtained from these enriched fractions by mean of one dimentional TLC on 20 x 20 cm Silica Gel G plates in chloroform-methanol-water (70 30 5), taken to dryness under nitrogen stream and dissolved in 50mM Tris-HCl pH 7.5. 

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