Recent Advances in the Gas Chromatographic Separation of Methyl Esters of Fatty Acids

Abstract

The first reported use of gas chromatography in the separation of fatty acids was by James and Martin' at the Oxford Congress of Analytical Chemistry in 1952. They described the separation of acids from formic through dodecanoic on silicone-stearic acid columns, and detected the eluted acids by titration.In 1953, Cropper and Heywood2 extended the gas chromatographic separation to the methyl esters of the even-numbered fatty acids from Clz to Czz. They used Dow Corning high vacuum silicone grease on Celite columns and employed a platinum-wire thermal conductivity cell as the detector. The efficiency of their columns allowed only a separation based on differences in chain length, and methyl oleate and methyl stearate were not separated.A major contribution to the field of fatty ester separation and to gas chromatography in general was made with the invention of the gas density balance detector by Martin and James3 in 1953. The high sensitivity of this ingenious device was largely responsible for improvements in the separation of the methyl esters of the fatty acids containing from 8 to 26 carbon atoms by James and Martin,4e6 James and Wheatley," and Beerthuis and Keppler? The high sensitivity allowed the use of extremely small samples that, in turn, reduced the band spreading that results from overloaded columns. These. workers found Apiezon M or Apiezon L vacuum greases on Celite to be the preferred partition medium and reported the successful separation of saturated and monounsaturated methyl esters of the same carbon chain length, as well as some branched chain fatty esters prepared from natural lipid sources. However, methyl linoleate and methyl linolenate were not separated. ' and Lipskylo have reported further refinements in the separation of high molecular weight fatty esters using Apiezon greases. These refinements resulted from improved technique in the preparation of the coated Celite and in the packing of columns. Lipskylo found that improvements could be made in the separation by precise control of the temperature of the detector, in this case a high-sensitivity thermal conductivity cell, through use of proportional controllers. Using Apiezon L and temperatures in the range of 200 to 250' C., Lipsky and Insull and James obtained excellent separations of methyl stearate, methyl oleate, and methyl linoleate. In no case, however, was it possible to resolve methyl linoleate and methyl linolenate on Apiezon L. TABLE 1 summarizes data taken from the best curves published by the above authors and gives the efficiencies of the separations obtained. Theoretical plate calculations are based on the methyl stearate peak and the percentage impurities were calculated using the method of Glueckauf," with a separation factor of 1.15 for methyl stearate relative to metbyl oleate. The factor R is 649 More recently Insull and Jamess#

The Fatty Acids of Bacteria

“…This technique, first introduced by James and Martin (78), has been widely and enthusiastically adopted by lipid chemists as the most nearly ideal analytical method now available for fatty acids. A number of reviews have appeared discussing the principles of this technique and in particular its application to fatty acid analysis (10,54,77,94,115).…”

The Fatty Acid Composition of Human Thoracic Duct Lymph Lipids *

“…As stationary phase, a polar polyester (LHC-1 R-296, obtained from Cambridge, Mass.) was used in the ratio celite: stationary phase, 4: 1 (13). This column had a retention time of 10 minutes for methyl stearate.…”

Dimethoxypropane Induced Transesterification of Fats and Oils in Preparation of Methyl Esters for Gas Chromatographic Analysis.

“…at 11°p er IV) were obtained with EGS columns operating isothermally at 187°C . More reproducible results were obtained using EGS columns because of the lack of prominent "ghosting" (6) that occurred when Lac columns w7ere used. NOMENCLATURE Abbreviated nomenclature for fatty acids: CIS = oleic; Gis = linoleic; CÜ = linolenic; Cle = palmitoleic.…”