Fatty acids of cows' milk. B. Composition by gas-liquid chromatography aided by other methods of fractionation

A fresh sample of cows' milk was converted directly to the methyl esters by methanolysis and the esters were fractionated into eleven distilled fractions and an undistilled portion. The latter, which contained the bulk of the polyunsaturated and long chain esters, was further fractionated by adsorption chromatography on a silicic acid column. Each fraction from the distillation and adsorption chromatography was analyzed by gas-liquid chromatography on columns containing polyester stationary phases of different polarity. Twenty-seven minor components, including some not previously reported, were present each in less than 0.1%. The fatty acid distribution of the major components fell within the range generally reported. Presented at the 53rd Meeting of the American Oil Chemists' Society, October 17–19, 1960, New York. Eastern Utilization Research and Development Division, Agricultural Research Service, United States Department of Agriculture.     

Fatty acids of lard. A. Identification by gas-liquid chromatography

Abstrat A fresh commercially rendered lard was separated into its component fatty acids by subjecting the methyl esters to gas-liquid chromatography on nonpolar and polar columns. The lard methyl esters were first chromatographed on a silicone column. This column achieved separation of the component esters principally on the basis of chain length, and fractions which were represented by a single peak or series of peaks were collected. The collected fractions were then rechromatographed on an ethylene glycol succinate polyester column to separate and identify the saturated and the unsaturated esters. Qualitative evidence was obtained for the presence of 29 fatty acids ranging in chain length from 10 to 20 carbon atoms. Included were the esters of the following: Satrated acids (10,12,14,15,16,17,18,19,20, and 22 C-atoms), monounsaturated acids (14,16,17,18,19, 20, and 22 C-atoms), and polyunsturated acids (18∶2,20∶2,22∶2,18∶3,20∶3,22∶3,20∶4,22∶4,20∶5, and 22∶5).³. Peaks for several additional trace components were also observed. Presented in part at the AOCS meeting, St. Louis, Mo., 1961. Eastern Utiliz. Res. & Dev. Div. ARS, U.S.D.A.     

Determination of milk fat in chocolates by gas-liquid chromatography of triglycerides and fatty acids

The combination of two routine methods is proposed to determine the content of milk fat (MF) in chocolates, which is applicable even in the presence of lauric fats or others. The content of MF is obtained from the sum of C₄₀, C₄₂, and C₄₄ medium-chain triglycerides, determined by capillary gas-liquid chromatography (GLC). A new method, based on methyl esters of lauric acid and on minor acids situated between myristic and palmitic, is proposed. It enables detection and estimation of potential lauric fats, as well as the determination of the actual content of MF. The influence of other vegetable and animal fats is discussed. We analyzed 45 MF samples extracted from industrial milk powders and from pure or fractionated MF for chocolate manufacturing or pastry by GLC of triglycerides. We also analyzed by capillary GLC the methyl esters from 22 of those fats. Mixtures of these 22 MF samples with a cocoa butter also were used for chromatographic analyses of methyl esters and triglyceride. Results from the various analytical methods have been presented.     

Determination of cyclic fatty acids by gas-liquid chromatography

A method is described to determine cyclic fatty acids in cyclic monomers by gas-liquid chromatography (GLC), which separates saturated straight-chain esters from cyclic esters. The content of cyclic esters can be determined by integration of the area on the chromatograph under the cyclic peaks. GLC was applied to cyclic monomers made from linseed oil and from linolenic acid. Samples of both hydrogenated and nonhydrogenated cyclic monomers were analyzed; however, more reliable results were obtained on the hydrogenated samples. The results show a standard deviation of 0.25 for linseed oil and 0.36 for linolenic acid. Accuracy of the analysis was established by comparing data with that obtained by crystallization. The GLC method is approximately three times faster. Presented at the AOCS meeting, New Orleans, La., 1962. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, U.S.D.A.     

Characterization of unsaturated fatty acids by gas-liquid chromatography

The equivalent chain length (ECL) has been determined on 79 methyl esters of unsaturated fatty acids and on 7 ethyl esters by gas chromatography. Ethylene glycol succinate (EGS), diethylene glycol succinate, β-cyclodextrin acetate and Apiezon L were chosen as the liquid phases to be used. For methyl esters of mono- and polyenoic acids, the differences between ECL on EGS and ECL on Apiezon L approximate 0.84 per double bond. For positional isomers, the ECL on both EGS and Apiezon L are usually greater for the isomer having the longer proximal end of the molecule (smallest ω value). In these terms a triple bond is approximately equal to three double bonds. Esters of nonconjugated dienoic and trienoic acids of the same chain length are not separable on Apiezon L if their proximal structures are the same. This also applies to tetraenoic and pentaenoic acids of the same chain length and the same proximal structure. Conjugation of double bonds, either with the ester carbonyl group or with themselves, yields ECL values on Apiezon L greater than the number of carbon atoms in the acid. Monounsaturated and nonconjugated polyunsaturated esters have ECL values on Apiezon L lower than the number of carbon atoms of the acid. The ECL values of ethyl esters of 18 and 20 carbon acids are greater than the corresponding methyl esters on Apiezon L. Presented at the Chicago meeting of the American Oil Chemists’ Society, Oct. 13, 1964.     

Fatty acids of lard. B. Quantitative estimation by silicic acid and gas-liquid chromatography

A quantitative comparison was made of the fatty acid composition of a commercially rendered lard, a laboratory rendered lard, and a solvent extracted lard representing the same batch of pig tissue. The composition was determined by a preliminary separation of the methyl esters on a silicic acid column floowed by gasliquid chromatography of the fractions containing a known added amount of reference compound. This technique permitted estimation of the composition of each fraction and subsequent calculation of percentage of the minor as well as the major components in the original lard. It was concluded that the minor components were not artifacts produced in rendering. Presented in part at the AOCS meeting. St. Louis, Mo., 1961. Eastern Utiliz. Res. & Dev. Div, ARS, U.S.D.A.     

Gas-liquid chromatography of fatty derivatives. II. Analysis of fatty alcohol mixtures by gas-liquid chromatography

Conclusions Gas-liquid chromatography has been shown to be applicable to the analysis of fatty alcohols. Through the use of polyester columns these alcohols have been separated according to chain length and degree of unsaturation. A study has been made of the relationship between peak areas of the chromatograms and the actual weight percentages of the four C₁₈ alcohols found in the fatty alcohols derived from linseed oil. Fatty alcohols, prepared from soybean, linseed, and sperm oil have been prepared and analyzed by the proposed procedure. Craig and Murty (1) have recently reported that polyesters based on succinic acid are preferable for the liquid phase of the chromatographic column to those made from adipic in that they afford a better separation of methyl stearate from methyl oleate. Conversely adipic columns gave a more effective separation of the esters of linolenic and arachidic acids. The application of these polyesters to the analysis of fatty alcohol acetates is expected to improve their separation in a similar fashion, but further work is indicated in the search for a liquid phase that will permit both separations in the minimum time. ADM Technical Talk No. 166.     

Determination of trace amounts of fatty acids in edible oils by capillary gas-liquid chromatography

The effect of using different gas-liquid chromatography (GLC) hardware to quantify low concentrations of fatty acids was studies. A fused-silica capillary column was operated in two different chromatographs (A and B) that were interfaced to three different chromatographic data systems to process the flame-ionization detector signals (systems A, B1, and B2). A test routine was developed that allowed the proper selection of peak processing parameters for the automatic recognition and integration of fatty acids occurring at trace levels. However, agreement of analytical results between the three analytical systems was not satisfactory; components at concentrations <0.10 g/100 g could not be quantified with high reliability, although the same capillary column and identical sample solutions were used (quasi-repeatability conditions). Even for major fatty acids, deviations up to 1.0 g/100 g were noted, which could only be attributed to the use of different GLC hardware. Attention should be paid to these technical restrictions when formulating product specifications based on fatty acid profile parameters.     

Separation of the oxidation products of fatty acids by means of gas-liquid partition chromatography

Conclusions The oxidation of oleic, and particularly of linoleic and linolenic acids, indicated the presence of a considerable number of unexpected products in addition to those foreseen from a simple severance of the double bonds. The chromatograms of the oxidized pure C₁₈ acids, of Neo-Fat No. 140, and of a mixture of fatty acids from hydrolyzed soybean oil showed a striking similarity in many respects. It was not possible to identify all the peaks, especially those of trace amounts, in the chromatograms and to obtain a quantitative estimate of the oxidation products. Further work on this is in progress. The results indicate that gas-liquid partition chromatography is a sensitive method for the study of the oxidation of vegetable oils. Presented at the fall meeting, American Oil Chemists' Society, Chicago, Ill., September 24–26, 1956. One of the divisions of the Agricultural Research Service, U. S. Department of Agriculture.     

High-performance liquid chromatography of human milk triacylglycerols and gas chromatography of component fatty acids

Human milk triacylglycerols were separated by high-performance liquid chromatography. A 5-μ Supelcosil LC-18 column (Supelco, Inc., Bellefonte, PA) was used with acetone/acetonitrile (64∶36, vol/vol) as mobile phase. Triacylglycerols were tentatively identified based on theoretical carbon number and relative retention time. Despite changes resulting from dietary fat variation, the major component triacylglycerols were those composed of palmitic, oleic and linoleic acids. Triacylglycerols with palmitic, stearic and oleic acids were present as minor components. Fatty acids were quantified by gas chromatography relative to an internal standard. Ratios of n−6/n−3 fatty acids were found to be high than previously reported. Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

Detection of trace fatty acids in fats and oils by urea fractionation and gas-liquid chromatography

The detection of trace fatty acids (<0.1%) in a fat or oil by gas-liquid chromatography is possible when the methyl esters are fractionated with urea to provide a number of less complex fractions. Identification and estimation of trace fatty acids is simplified by quantitative removal of other fatty acids having similar gas chromatographic retention times. A detailed knowledge of the order in which inclusion compounds are formed was obtained by fractionating a complex mixture of marine and vegetable fatty acids. In addition, lanolin was fractionated to determine the preferential order in which saturated, branched chain (iso-, anteiso-) and hydroxy acids form inclusion compounds. Using urea fractionation and gas chromatography, 52 trace fatty acids were tentatively identified in butter, 30 in lard, and 26 in walnut oil. Presented at the AOCS Meeting in New Orleans, 1964.     

Fatty acids: XXIII. A rapid method for the preparation of C18 furanoid fatty ester involving dry-column chromatography

A rapid method for the synthesis of methyl 9,12-epoxyoctadeca-9,11-dienoate from methyl ricinoleate was developed. Methyl ricinoleate was oxidized to the corresponding keto ester, which was treated with mercury (II) acetate to give the required furanoid ester. Dry column silica gel chromatography was used for the purification process and was found to be reliable and efficient.     

Fatty acid composition of rice lipids by gas-liquid chromatography

Gas-liquid Chromatographic analysis of the methyl ester of lipids of four rice varieties showed that bran lipids had significantly higher mean contents of linoleic and linolenic acids, but lower contents of myristic, palmitic, palmitoleic, and stearic acids than milled rice lipids. Nine fatty acids were detected. The principal components were oleic, linoleic, and palmitic, which also was confirmed by thin-layer chromatography of the esters. Issued as I.R.R.I. Journal Series No. 12     

A study of octadecenoic acids by gas-liquid partition chromatography and infrared spectrophotometry

Summary The separation of methyl esters of octadecenoic acids by G.L.P.C. on a capillary column is shown for a sample of hydrogenated commercial vegetable oil. Comparisons are made with a regular packed column G.L.P.C., a capillary column G.L.P.C., and with infrared analysis. Good separation of methyl oleate and methyl elaidate was accomplished, using a capillary column. The amount of elaidate found by G.L.P.C. compared well with thetrans-acid found by infrared analysis. In addition, a small amount of a component was detected that is possibly another isomer of methyl oleate.     

Gas chromatography/tandem mass spectrometry as an analytical tool for the identification of fatty acids

Structures of fatty acids present at very low quantities in mycobacteria are difficult to determine. A commonly used strategy is to introduce heteroatoms into functional groups by chemical means before subjecting them to gas chromatography/tandem mass spectrometry (GC/MS/MS) analysis. Routinely used methods give very low abundance diagnostic ions leading to ambiguities in structural conclusions. GC/MS/MS associated with electron capture ionization of pentafluorobenzyl esters was used to study very complex mixtures of fatty acids fromMycobacterium fallax andM. aurum. The charge-remote fragmentation of fatty acid carboxylate anions was used for structure determination at the nanogram level of a large number of unsaturated, branched, and cyclopropane-containing fatty acids. Some of them have not been observed previously in these Mycobacteria. On the basis of these studies, biosynthetic pathways of unsaturated, branched, and cyclopropane-containing fatty acid are proposed.     

Quantitative fatty acid analysis of vegetable oils by gas-liquid chromatography

Summary The fatty acid composition of a number of vegetable oils and of two synthetic mixtures of methyl esters are compared by gas-liquid chromatography and by standard methods. The calculated iodine values from G.L.P.C. results are in good agreement with measured iodine values and are indicative of the reliability of the G.L.P.C. values. Standard methods gave lower values for linoleic acid and higher values for linolenic acid than did G.L.P.C. This deviation was particularly evident in oils with a high proportion of linolenic acid,e.g., linseed oil. The results of G.L.P.C. are considered to be accurate to within one unit percentage. Thermal stability of the polyester polymers can be improved by using 1,4-butanediol or ethylene glycol as the polyols instead of diethylene glycol. Issued as N.R.C. No. 5373. Presented at 32nd annual fall meeting, American Oil Chemists' Society, October 20–22, 1958, Chicago, Ill. National Research Council of Canada Postdoctorate Fellow, 1957     

trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist oftrans 20∶1 andtrans 22∶1 in addition to thetrans isomers of 18∶1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietarytrans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 dayspostpartum in sows. The dietary fats were PHFO (28%trans), or PHSBO (36%trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or “fully” hydrogenated fish oil (HFO) (19%trans), in comparison with coconut oil (CF) (0%trans), was fed with two levels of dietary linoleic acid, 1 and 2.7% from conception throughout the lactation period. Feedingtrans-containing fats led to secretion oftrans fatty acids in the milk lipids. Levels oftrans 18∶1 andtrans 20∶1 in milk lipids, as percentages of totalcis+trans 18∶1 andcis+trans 20∶1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively lesstrans 18∶1 andtrans 20∶1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels ofcis+trans 22∶1 were found in milk lipids. Feedingtrans-containing fat had no consistent effects on the level of polyenoic fatty acids but reduced the level of saturated fatty acids and increased the level ofcis+trans monoenoic fatty acids. Increasing the dietary level of linoleic acid had no effect on the secretion oftrans fatty acids but increased the level of linoleic acid in milk. The overall conclusion was that the effect of dietary fats containingtrans fatty acids on the fat content and the fatty acid composition of colostrum and milk in sows were moderate to minor.     

A method for the simultaneous analysis of unconjugated and glycine-conjugated bile acids by capillary gas-liquid chromatography

A method for the simultaneous analysis of unconjugated and glycine-conjugated bile acids by means of capillary gas-liquid chromatography without need for prior deconjugation is described. The method involves: i) the use of an aluminum-clad fused-silica capillary column coated with a very thin film (0.1 μm) of a highly thermostable bonded and crosslinked methyl polysiloxane, and ii) the analysis of the bile acids as their methyl ester-dimethylethylsilyl ether derivatives. This method, used to separate the major free and glycine-conjugated bile acids from human gall bladder bile, should be applicable for the analysis of other biological fluids.