Fatty Acid Composition of Cod Liver Oil Determined by Urea Fractionation and Modified Programmed Temperature Gas Chromatography

Esters of fatty acids in marine oils, with similar GLC retention times, are concentrated in separate fractions by this proposed urea fractionation procedure. Esters which are present at the ppm level and are normally hidden under major peaks can then be detected. By modified programmed temperature gas chromatographic techniques, it is possible to detect trace amounts of the short and long chain fatty acids. Accurate identifications are assured by the correlation of fatty acid structure with the preferential order in which they form complexes and retention times before and after hydrogenation. Cod liver oil was found to contain 130 fatty acids. Most of the esters present in trace amounts are predominately C20 to C34 acids which have not been previously reported.

Fatty Acid Composition of Crude and Refined Cottonseed Oils

The fatty acid composition of 20 cottonseed oils was determined by isothermal GLC analysis of the total esters. A urea fractionation procedure, combined with modified programmed temperature GLC, was used to detect esters present in trace amounts (0.001–0.1%) in four refined and three crude oils. The odd a n d even chain length saturated acids from C8 to C26 were present. Mono-unsaturated acids from C15 to C20 were also detected. The crude and refined oils did not differ markedly in their fatty acid composition. The presence of malvalic and sterculic acids and the possible presence of shorter and longer chain length cyclopropenoid acids with their interfering GLC peaks make it impossible to detect and quantitatively estimate the branched and multiple branched acids.

Fatty Acid Composition of Cocoa Butter Oil by Urea Fractionation and Programmed Temperature Gas Chromatography

This proposed urea fractionation procedure concentrates esters with similar GLC retention times in separate fractions. GLC peaks of esters present in cocoa butter oil in trace amounts (0.001–0.1%), which are normally hidden under major peaks, can then be detected. By modified programmed temperature GLC techniques, it is possible to detect the short and long chain length fatty acids present in cocoa butter oil. The odd and even chain length saturated acids from C10 to C28, mono-unsaturates C16 to C24, branched acids C16 to C24, and linoleic and linolenic acids were detected.

Fatty Acid Composition of Palm Kernel, Illipe, and Shea Nut Oils by Urea Fractionation and Programmed Temperature Gas Chromatography

The detection of C6 to C28 fatty acids is possible when their methyl esters are concentrated by urea fractionation so that esters with similar gas chromatographic retention times are in different fractions. By modified programmed temperature gas chromatographic techniques, it is possible to detect and estimate fatty acids present in trace amounts (0.1 to 0.001%) in palm kernel, shea nut, and illipe oils. The odd and even chain length saturated fatty acids from C6 to C28 were detected. The odd and even chain length mono-unsaturates from C14 to C24 and the even chain length dienes from C14 to C24 were detected

Fatty Acid Composition of White Mustard Seed Oil by Urea Fractionation and Gas-Liquid Chromatography

The detection of C20 to C26 polyunsaturated fatty acids in a Cruciferae seed oil (white mustard) is possible when these methyl esters are concentrated by urea fractionation. The detection and estimation of fatty acids present in trace amounts (< 0.1%) was simplified by quantitative removal of other fatty acids with similar gas chromatographic retention times. Odd and even chain length di- and tri-unsaturated fatty acids were tentatively identified in white mustard seed oil. A tetraenoic acid, presumably arachidonic acid, was tentatively identified for the first time in a plant lipid of the highest evolutionary level, i.e., angiospermae. More easily extracted “free” lipids have a significantly different fatty acid composition than the more difficult to extract “bound” lipids.

Preparation of β-casein by a modified urea fractionation method

It has been shown by Hipp, Groves, Custer & McMeekin (1952) that the differential solubility in urea of the casein components of cow's milk can be utilized for preparative purposes. Fractionation is achieved by step-wise dilution of a solution of all the casein components in strong (6·6 molar) urea. In connexion with the work on the three genetically distinct β-caseins discussed in the preceding paper, the need arose to prepare the variants A, B and C from the milk of appropriate homozygotes. This led to the development of the modified procedure described in this note, a procedure more sparing in urea and more effective in the initial isolation of the β-casein fraction than the original method of Hipp et al.