Rapid gas-liquid chromatographic procedure for the analysis of methyl esters of long chain fatty acids

A gas-liquid chromatographic procedure permitting rapid analysis of the major fatty acids commonly found in vegetable oils was evaluated with standards of known composition and found to be both accurate and precise. A standard containing 20% by weight of each of the methyl esters of palmitic, stearic, oleic, linoleic, and linolenic acid was analyzed in 2.7 min with errors of 1.6, 0.7, 3.3, 0.8, and 3.1%, respectively. Six procedures, requiring from 2.7 to 25 min for the eluation of the effects of the operational parameters, carrier gas flow rate and column temperature, on the precision and accuracy of gasliquid chromatographic analysis of fatty acid methyl esters. The most rapid procedure, obtained with a column temperature of 235C and a helium flow rate of 110 ml/min was found to be comparable in accuracy and precision to the other procedures and gave quantitative results with National Heart Institute type fatty acid standards KA, KB, and KD, that agreed with stated composition with a relative error of less than 2% for major components (10% or more of total mixture) and less than 6% for minor components (less than 10% of total mixture). Approved as Journal Series Paper No. 535, Georgia Experiment Station. This research was supported in part by Corn Industries Research Foundation and by Corn Products Company.     

Gas-liquid chromatographic analysis of cyclopropene fatty acids

A gas-liquid chromatographic method is described for the quantitative estimation of cyclopropene fatty acids as their methyl mercaptan derivatives. This method estimates individual cyclopropene acids as well as normal and cyclopropane acids. Nine seed oils were analyzed for their cyclopropene fatty acid content. Evidence was obtained for the presence of a cyclopropene fatty acid of shorter chain length than malvalic inAlthaea rosea cav and one with a higher chain length than sterculic inBombacopsis glabra seed oil. This method is less accurate for cottonseed oil than for the other oils tested because of the appearance of some unsymmetrical peaks of unknown origin. The mercaptan derivatives of the cyclopropene acids may be isolated by silver ion thin-layer chromatography. Small amounts of cyclopropane fatty acids were found in a number of the oils analyzed for cyclopropene fatty acids. Presented at the AOCS meeting, Chicago, October 1964.     

Two-step homogeneous conjugation and hydrogenation of methyl esters of unsaturated fatty acids

A new approach to the selective hydrogenation of unsaturated fatty acids is suggested. It consists of a two step process. The first is a selective conjugation of the double bonds, while the second consists of the hydrogenation reaction using a catalyst which is specific to conjugated systems. Potassiumt-butoxide was used as a conjugation catalyst and its activity and selectivity were tested at various concentrations, different molar ratios of catalyst to oil, and in various solvents. Phenanthrene chromium tricarbonyl was used as the hydrogenation catalyst and its activity tested at various concentrations, temperatures and in various solvents. UN Expert, Physical Organic Chemist.     

Homogeneously catalysed hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols

The use of copper and cadmium oxides or soaps as catalysts for the hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols has been investigated. It is shown that copper soaps homogeneously activate hydrogen. When copper and cadmium oxides are used as catalysts, they react with the acid under formation of a homogeneous soap solution. A continuous reaction system for the preparation of unsaturated fatty alcohols by hydrogenation under the influence of copper and cadmium soaps is described.     

Hydrazine reduction in the gas liquid chromatographic analysis of the methyl esters of cyclopropenoic fatty acids

Hydrazine was used to hydrogenate the double bond of cyclopropenoic fatty acids (CPEFA) without cleaving the cyclic system. Using gas liquid chromatography (GLC), quantitation studies showed that it was possible to accurately determine CPEFA at concentrations as low as 0.1%. Studies with kapok seed oil methyl esters illustrated the potential application of such a technique to selectively hydrogenate the CPEFA to cyclopropanoic fatty acids (CPAFA), rendering them stable on the column, with a minimum effect on the degree of unsaturation of the remaining double bonds. Hydrazine reduction was found to be a simple and accurate method of measuring CPEFA in seed oils. Decomposition of pure methyl sterculate (methyl 9,10-methylene-9-octadecenoate) on GLC columns of various polarities also was examined.     

Selective hydrogenation of fatty acids and methyl esters of fatty acids to obtain fatty alcohols–a review

In this paper, a review is presented of the evolution of different catalytic systems and operating conditions used in the selective hydrogenation of acids and esters of fatty acids to obtain fatty alcohols, which have broad industrial applications in the oleochemical industry. In addition, the current status of the different technologies used industrially (Lurgi, Davy and Henkel) for obtaining fatty alcohols, as well as major global sources of raw materials for the oleochemical industry are put forward. Finally, the reaction mechanisms of the selective hydrogenation process of oleic acid and methyl oleate to obtain the corresponding unsaturated alcohol as well as the new catalysts proposed by researchers are described. © 2016 Society of Chemical Industry     

Reaction of cyclopropene esters with hydrogenation catalysts

Methyl esters of stereulic and malvalic acids were heated under nitrogen in the presence of various hydrogenation catalysts, and the effect on the cyclopropene moiety was established. Similar tests were conducted with cottonseed oil, which contains glycerides of sterculic and malvalic acids. Palladium catalysts, and some palladium compounds which were tested, readily gave cyclopropene-free products, while nickel and platinum catalysts did not. Palladium catalysts freshly activated with hydrogen were not as active as those freed of adsorbed hydrogen. The catalysts could be reused. Heating cottonseed oil (0.73% cyclopropenes, calculated as trimalvalin) with 0.02% palladium, as a 10% palladium-on-carbon catalyst, gave a cyclopropene-free oil after 2 hr at 150 C. The treated oil was unaltered in appearance, and the noncyclopropene components were unaffected. Heating methyl sterculate with palladium catalyst produced a mixture of unsaturated condensation products and a number of unsaturated monoesters of practically unchanged molecular weight. The palladium treatment was shown to cleave the cyclopropene ring and produce methyl and methylene substituted fatty acid groups. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968.     

Comprehensive two dimensional gas chromatographic separation of fatty acids methyl esters with online reduction

The accurate analysis of complex fats and oils often requires combining data from multiple GC separations, fractionation by LC prior to GC analysis, and identifying fatty acids or confirming their identities by mass spectrometry and synthetic reference materials. Comprehensive two dimensional gas chromatography markedly increases the number of resolved fatty acid methyl esters (FAME) in a single separation experiment by combining the separations of two capillary columns. The addition of a capillary reducer in front of the second capillary column provides unique separation patterns and structural information for fatty acids based on simple elution rules.     

Synthesis of deuterated cyclopropene fatty esters structurally related to palmitic and myristic acids

To develop a synthesis of tritiated cyclopropene fatty acids (CPFA), compounds that should prove useful for affinity labeling of desaturases in insect pheromone biosynthetic studies, a series of novel, selectively deuterated CPFA analogues was prepared and characterized. In methyl [16-²H]12,13-methylene-12-hexadecenoate, the incorporation of deuterium was achieved by treatment of the corresponding ω-chloro derivative with sodium borodeuteride in dimethylsulfoxide at 70°C for 24 h (67% yield) following conventional procedures. Alkylation of the tetrahydropyranyl derivative of 13-tridecynol in the presence of lithium diisopropylamide in tetrahydrofuran at −20°C with 1-chloro-3-iodopropane in hexamethylphosphoramide, followed by Jones oxidation of the crude product, yielded 16-chloro-12-hexadecynoic acid (54%), which was esterified to the corresponding methyl ester by treatment with potassium carbonate and methyl iodide in dimethylformamide. Treatment of this acetylenic ester with ethyldiazoacetate in the presence of activated copper-bronze as catalyst followed by hydrolysis in KOH solution at room temperature yielded 16-chloro-12,13-(carboxymethylene)-12-hexadecenoic acid. This diacid was treated with excess oxalyl chloride to give the corresponding diacyl chloride, which was decarbonylated in a diethyl ether solution with zinc chloride, and the cyclopropenium ions thus formed were added at −40°C to a methanolic sodium hydroxide solution of sodium borohydride to give methyl 16-chloro-12,13-methylene-12-hexadecenoate. Analogous procedures were followed to prepare methyl [17-²H]10,11-methylene-10-hexadecenoate, methyl [17-²H]11,12-methylene-11-hexadecenoate and methyl [17-²H]12,13-methylene-12-hexadecenoate from the corresponding diacids using sodium borodeuteride in the reduction of the cyclopropenium ions. Alternatively, methyl [2,2,3,3-²H₄]hexadecynoate, prepared by reaction of methyl 2,11-hexadecadiynoate with magnesium in deuterated methanol at room temperature, was submitted to the above cyclopropenylation and reductive decarbonylation sequence to give methyl [2,2,3,3,17-²H₅]-11,12-methylene-11-hexadecenoate. In summary, complementary methods for the selective incorporation of one to five deuterium atoms into cyclopropene fatty acids, at different sites, in moderate to high yields have been developed. The methods should easily be applicable to the preparation of the corresponding tritiated analogues.     

Fatty acids of Thespesia populnea: Mass spectrometry of picolinyl esters of cyclopropene fatty acids

Thespesia populnea belongs to the plant family of Malvaceae which contain cyclopropane and cyclopropene fatty acids. However, previous literature reports vary regarding the content of these compounds in Thespesia populnea seed oil. In this work, the content of malvalic acid (8,9‐methylene‐9‐heptadecenoic acid) in the fatty acid profile of Thespesia populnea seed oil was approximately 7% by GC. Two cyclopropane fatty acids were identified, including dihydrosterculic acid. The methyl and picolinyl esters of Thespesia populnea seed oil were also prepared. The mass spectrum of picolinyl malvalate was more closely investigated, especially an ion at m/e 279, which does not fit the typical series of ions observed in picolinyl esters. It is shown that this ion is caused by cleavage at the picolinyl moiety and contains the fatty acid chain without the picolinyl moiety. This type of cleavage has previously not been observed prominently in picolinyl esters and may therefore be diagnostic for picolinyl esters of cyclopropene fatty acids. The NMR spectra of Thespesia populnea methyl esters are also discussed. Practical applications: The work reports the fatty acid composition of Thespesia seed oil whose derivatives have not yet been extensively utilized for industrial purposes, for example, biodiesel. Knowing this composition is essential for understanding potential uses and, for example, in case of biodiesel the fuel properties. Besides this issue, some data (mass spectrometry and NMR) crucial for obtaining the composition information are analyzed in detail. The biodiesel properties of methyl esters of Thespesia populnea will be reported separately.     

Application of specific response factors in the gas chromatographic analysis of methyl esters of fatty acids with flame ionization detectors

The relative responses for flame ionization detectors in the analysis of the longer chain fatty acid methyl esters are shown to correlate with the theoretical responses based on weight percent content of “active” carbon. While particularly affecting estimation of the shorter chain length saturated fatty acids, these corrections have a less marked effect on the estimation of unsaturated fatty acids.     

Autoxidation of methyl esters of cyclopentenyl fatty acids

The early stages of the autoxidation of methyl hydnocarpate, chaulmoograte and gorlate in air have been examined at 40, 60 and 80 C, and the initial products have been compared by several methods with those derived from methyl oleate and linoleate autoxidized at 60 C. To supplement information about oxygen absorption and peroxide development in relation to time, other information about the early products, and some information about the reduced products, have been obtained by ultraviolet (UV) and infrared (IR) spectrophotometry, and by thin layer chromatography (TLC). The kinetic and other data presented in this study strongly support the conclusion that the methyl esters of cyclopentenyl fatty acids yield initial autoxidation products that, although they are primarily peroxides, differ in some ways (as expected) in the kinetics of their formation and their chemical nature, compared to those of oleate and linoleate. Nevertheless, all the data obtained strongly support the surmise that the peroxides are formed autocatalytically by a chain mechanism, and that secondary products not derived from peroxide decomposition, are formed pari passu in lesser, but increasing amounts with increasing temperature, probably from free radical intermediates. The autoxidation of esters of cyclopentenyl fatty acids has potential importance in several ways, 3 of which are mentioned briefly.     

Partial hydrogenation of fatty acid methyl esters at supercritical conditions

Under supercritical or near-critical conditions propane is a very good solvent for both lipids and hydrogen. Thus, it is possible to generate an essentially homogeneous phase, in which the transport resistances for the hydrogen are eliminated. Therefore, the hydrogen concentration at the catalyst surface can be greatly increased, resulting in extremely high reaction rates and products having low trans fatty acid contents. In this study we present results from hydrogenation of rapeseed fatty acid methyl esters under near-critical and supercritical conditions. Temperature, residence time, hydrogen pressure, and catalyst life were varied systematically, using a statistical experimental design, in order to elucidate reaction rate and trans fatty acid formation as functions of the above variables. The experiments were carried out in a microscale fixed-bed reactor, using a 3% Pd-on-aminopolysiloxane catalyst. At 92 °C, a hydrogen pressure of 4 bar, and a residence time of 40 ms we obtained a trans content of 3.8 ± 1.7% at a iodine value of 70. Our results support the findings from traditional processes that at a constant iodine value (IV) the trans content decreases with decreasing temperature, increasing pH₂, and increasing residence time. The reaction rate at our best conditions was roughly 500 times higher than in traditional batch hydrogenation.     

The amplified distillation of methyl esters of fatty acids

Summary Amplified distillation is a useful technique for the quantitative analysis of mixtures of fatty acid esters, especially for the detection and estimation of minor components and for the analysis of small samples. The amplified distillation of free fatty acids is largely limited to qualitative work on account of the formation of azeotropes with mineral oils. Presented before the 1945 Fall Meeting of the American Oil Chemists' Society, Chicago, Ill.     

亚临界相脂肪酸甲酯加氢制备脂肪醇

以Cu - Zn为催化剂,在正己烷亚临界状态下以脂肪酸甲酯为原料加氢制备脂肪醇.考察了正己烷用量、温度、氢气与原料油体积比对反应的影响,并对Cu - Zn催化剂和Cu - Cr催化剂的催化活性进行了比较.结果表明,在系统压力6.0 MPa,反应温度250℃,空速0.8h-1,正己烷与脂肪酸甲酯体积比7∶1,氢气与原料油体积比250∶1的条件下脂肪酸甲脂转化率为99.5％,脂肪醇选择性为99.6％,Cu - Zn催化剂的催化活性和选择性均优于Cu - Cr催化剂.     

Efficient synthesis of fatty monoglyceride sulfates from fatty acids and fatty acid methyl esters

An efficient high yield synthesis of fatty monoglyceride sulfates from fatty acids or fatty acid methyl esters, glycerine and chlorosulfuric acid in chloroform using stoichiometric amounts of reagents was developed. Sodium coco monoglyceride sulfate was prepared in 79% yield with 93% purity from coco fatty acids. Similarly, sodium palm kernel monoglyceride sulfate in 57% yield and sodium palm monoglyceride sulfate in 71% yield were obtained from palm kernel fatty acid methyl esters and palm fatty acids, respectively. This new synthetic method produced better quality products with higher active ingredients and improved yields without having to use such cost prohibitive, high purity, fatty acid monoglycerides, and it reduced the undesirable aqueous sodium sulfate by-product by 60% over a current commercial process. The product’s composition and purity were confirmed by cationic titration, infrared and C-13 NMR spectroscopy.     

Displacement of the double bonds during hydrogenation of unsaturated fatty acid methyl esters

Summary The displacement of the double bond of several unsaturated fatty acid methyl esters during hydrogenation with a nickel-kieselguhr catalyst at 180°C. was investigated. The analysis of the dicarboxylic acids (obtained by oxidation of the reaction products with KMnO₄ in acetic acid solution) by means of partition chromatography enabled a reliable semiquantitative determination of the position isomers formed. During hydrogenation of methyl esters of oleic, elaidic, petroselinic, and linoleic acid formation of large amounts of position isomers was proved to occur. Migration of the double bonds in both directions took place but was in all cases strongly pronounced in a direction opposite the ester group. The place and configuration (cis or trans) of the double bonds in the starting material apparently were of little importance in this respect. It follows that hydrogenation of fatty acid esters leads to products which are far more complicated, as is generally known. This is especially of importance with respect to the application of hydrogenated fatty oils in the food industries.