Lipids and surfactants

Simple lipids, or fatty acids, are n-alkyl carboxylic acids typically derived from the hydrolysis of the triglycerides of fats or of the phospholipids found in the cell wall. Many naturally occurring fatty acids contain one or more sites of unsaturation. Fatty acids are found in nature conjugated to such sugars as glycolipids or lipopolysaccharides, to amino acid residues of pep-tides and proteins, to glycerol to form the acylglycerols of fats, and to glyc-erophosphocholate and glycerophosphatidylethanolamine residues of phos-pholipids. Because of their amphipathic character, lipids have some tendency to form micelles, which chromatograph quite differently than the unaggre-gated compound. A class fractionation of plant-derived extracts into the component waxes (e.g., cetiolate), hydrocarbons, fatty acids (e.g., linoleic acid), fatty acid methyl esters (e.g., methylpalmitate), sterols (e.g., stigmas-terol), sterol esters (e.g., cholesteryl linoleate), glycerylethers (e.g., chimyl alcohol), fatty alcohols (e.g., behenyl alcohol), vitamin E, and mono-, di-, and triglycerides was performed with stepped gradient elution on a 7-^, 250 x 4-mm i.d. Nucleosil™-300 C18 column.91 Coumarin-derivatized 1-O-alkyl-2-sn-lysoglyceryl-3-phosphoryl choline, a fluorescent-labeled phospholipid platelet activating factor, was separated on a 4-^ particle size

Nova-Pak® C18 column in a methanol:water:chloroform gradient.92 Choline chloride was added to the mobile phase. One review of techniques used in the analysis of triacylglycerols lists over 300 references on separations of the triglyceride fraction of fats using nonaqueous RPLC, aqueous RPLC, argen-tation chromatography, and other chromatographic methods.93

Surfactants, like lipids, tend to be amphipathic. One of the simplest surfactants is sodium dodecyl sulfate. Linear alkylbenzene sulfonates were separated on a Supelcosil™ C8-DB (deactivated base) column in metha-nol:water containing sodium perchlorate.94 Ethoxylated alkylamines, used as surfactants in pesticide formulations, were analyzed on Polygosil 60 D-10 CN using methanol:water:dioxane.95 Mono- and dialanine surfactants such as alkylaminoethylcarboxylates, laurylamino(diethylcarboxylate), and alkylaminodi(ethylcarboxylates) were separated in acetonitrile:water containing sodium perchlorate.96

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