Gas-liquid chromatographic analysis of cyclopropenoid fatty acids

A method is described for the analysis of cyclopropenoid fatty acids in oils. The method consists of reacting the methyl esters of the cyclopropenoid fatty acids with silver nitrate in methanol to form ether and ketone derivatives. The derivatives formed from the cyclopropenoid fatty acids are separated from the methyl esters of the normal fatty acids by gas-liquid chromatography on a 15% diethylene glycol succinate column. The method is applicable to oils containing from 0.01% to 100% of cyclopropenoid fatty acids. The derivatives of oils containing lew levels of cyclopropenoids are separated from the normal methyl esters by alumina chromatography prior to gas-liquid chromatography. Studies on the quantitative aspects of the derivative formation, alumina chromatography, and gas-liquid chromatography are reported. Analyses for total cyclopropenoid fatty acid content of cottonseed oil andSterculia foetida oil by the gas-liquid chromatographic and hydrobromic acid titration procedures showed good agreement. Replicate analyses of a sample ofSterculia foetida oil for malvalic and sterculic acid gave coefficients of variation of 6.04% and 1.17%, respectively.     

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.     

一种聚酯污水中挥发性脂肪酸气相色谱法的建立

聚酯装置产生的废水含有大量的有机物,通过厌氧处理产生大量的挥发性脂肪酸,挥发性脂肪酸是污水系统运行的重要控制指标.公司采用传统蒸馏滴定法测定挥发性脂肪酸总量,检测时间长,存在安全隐患,且污水系统运行异常时,数据准确度不高,经改进,采用分析气相色谱法,检测时间缩短至0.5 h,且数据度高,提高分析效率,完全满足污水正常及异常情况的调整需要.     

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.     

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.     

Dimer acids: Gas chromatographic analysis

A gas chromatographic method is described for analyzing commercial polymerized fatty acids. The method determines unpolymerized acid, dimerized acid, and trimerized acid. Involved is an esterification to the methyl esters, followed by programed temperature gas liquid chromatography. Several years experience with this analysis has demonstrated its utility as a tool for quality control and research.     

Computer processing of gas chromatographic data: Quantitative analysis of fatty acid methyl esters using an off line magnetic tape system

This paper describes the off line processing of chromatographic data from fatty acid methyl ester mixtures by a large digital computer. The output of the gas chromatograph is recorded and stored on magnetic tape; the tape can then be processed at any convenient time. The system takes the analog signal from the electrometer and converts it to digital form, adds a time base and records the data using an incremental magnetic tape recorder. The data sampling rate can be varied from 0.05 to 5 times per second. The total number of samples per tape is limited only by the length of the tape. A 1200 ft reel can store up to 30 hr of gas chromatographic runs. The tape is processed by a CDC-6600 computer. The computer locates all peaks, determines the retention time and calculates the mass percentage of each peak. Along with the numerical output, a cathode ray tube plot of the data is also generated by the computer. The program has provisions for baseline corrections and peak overlap. The program also incorporates corrections for detector nonlinearity and variation in detector response to different molecular species. The accuracy of the system is within 5% based on analysis of fatty acid methyl ester samples of known composition. Computation time for a 1200 ft reel of tape is approximately 20 min. One of seven papers to be published from the Symposium ‘Computer Systems and Applications in the Oil and Fat Industry,’ presented at the ISF-AOCS Congress, Chicago, September 1970.     

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.     

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.     

Quantitative analysis of food fatty acids by capillary gas chromatography

The superior efficiency of capillary columns is desirable for the gas chromatographic analysis of complex mixtures of fatty acids, but there have been some reservations regarding quantitation and reproducibility. This paper discusses the use of wall-coated glass capillary columns in a semiautomated system for the determination of food fatty acids. Glass columns coated with SP2340 were used for extended periods at temperatures up to 200 C without appreciable deterioration. Up to 1900 samples were analyzed on a single column over an 11-month period, with only minor changes in retention ratios, response factors and column efficiency. Quantitative precision of results, calculated either as normalized weight percentage or as absolute amounts, based on the use of an internal standard, were typically within 2% relative deviation. Difficulties encountered in obtaining acceptable chromatograms and reproducible data are discussed, and typical analyses of the fatty acids from foods presented.     

Unusual gas chromatographic properties of fatty acid pyrrolidides

Fatty acid pyrrolidides have been found to have unusual gas chromatographic properties on a polar stationary phase of the Carbowax type. In particular, exceptional resolution of positional isomers was achieved, and in contrast to methyl esters, unsaturated isomers with double bonds in position 5 or earlier eluted before the corresponding saturated fatty acid derivative.     

Quantitative analysis of short chain fatty acids using gas liquid chromatography

The short-chain fatty acids, propionic to pelargonic, have been analyzed by gas liquid chromatography, as their butyl, phenacyl, and decyl esters to overcome losses due to their volatility. The three methods are compared and the decyl ester procedure offers the most advantages. Presented in part at the AOCS meeting in Los Angeles, Calif., 1959. Issued as N.R.C. No. 7261. National Research Council of Canada Postdoctorate Fellow 1957–1959.     

Gas liquid chromatographic analysis of hydroxy fatty acids,as their trimethylsilyl ether derivatives

A quantitative method is described for the rapid gas liquid chromatographic analysis of mono- and polyhydroxystearates as their trimethylsilyl (TMS) ether derivatives. The TMS derivatives of the hydroxy esters are formed rapidly and quantitatively at room temp. The retention times of ricinoleic acid as the methyl ester, acetylated derivative and the TMS derivative are compared. Purified diastereoisomers of di-, triand tetrahydroxystearates and their mixtures were analyzed on three different columns. Gas liquid chromatographic analysis of methyl mono-, di-, tri- and tetrahydroxysteartes were shown to give quantitative results as TMS derivatives. Analyses were carried out on a diethylene glycol succinate polyester (DEGS) packed column and on large-bore capillary columns of DEGS and Apiezon L. The elution order of the TMS derivatives of the hydroxy esters from the DEGS largebore capillary column was not the same as that obtained from the DEGS packed column. The unusual elution pattern of the large-bore capillary column is discussed. Presented at the AOCS Meeting in New Orleans, 1964.     

Phosphatidyl choline: Donor of 18-carbon unsaturated fatty acids for glycerolipid biosynthesis

Kinetics of radiocarbon inforporation into the phyosphatidyl choline of pumpkin leaf fed 1(-14)C-acetate at low light intensity were strongly suggestive of lipid bound fatty acids acting as substrates for desaturase enzymes. After pulse labeling in direct sunlight with the same precursor, phosphatidyl choline and phosphatidyl glycerol contained up to 90% of total glycerolipid radiocarbon at the shortest sampling times. Subsequent loss of radiocarbon from phyosphatidyl choline and a corresponding gain in other glycerolipids is taken to indicate a net flow of long chain fatty acids through phosphatidyl choline and into other lipids. It is proposed that there may be 2 separate synthetases in leaf tissue, one producing oleic and the other palmitic acids as their end products. Oleic acid is transferred almost exclusively to phosphatidyl choline where it is further desaturated to linoleic and linolenic acids before being made available for the biosynthesis of other lipids. Palmitic acid is transferred mainly to phosphatidyl glycerol, where it is desaturated to trans-delta3-hexadecenoic acid.     

Homogeneously catalyzed hydrogenation and gas-liquid chromatographic analysis of the methyl esters of cyclopropene fatty acids

Various concentrations of cyclopropene fatty acids have been determined down to 0.2% by the use of gas liquid chromatographic (GLC) analysis of the methyl esters of fatty acids that have been quantitatively hydrogenated using a homogeneous transition metal complex catalyst. The effectiveness of the use of bromotris(triphenylphosphine)-rhodium(I), Br(P(C₆H₅)₃)₃Rh, as a homogeneous hydrogenation catalyst to convert the cyclopropene ring to a cyclopropane ring has been evaluated and compared with the analogous chloro- and iodo-complexes. The hydrogenation/GLC method of analysis has been compared with the method of titration with hydrogen bromide in benzene and with the method involving the use of high resolution nuclear magnetic resonance (NMR).     

A capillary gas chromatographic method for the characterization of linear fatty alcohols

A capillary gas chromatography (GC) method for the analysis of fatty alcohols is described. The method can separate fatty alcohols, fatty acids, hydrocarbons and fatty acid methyl esters containing 6 to 22 carbons, as well as fatty-fatty esters to 40 or more carbons. The precision of the method is better than 2% (rsd); accuracy, based on analyses of a standard mixture and a spiking/recovery experiment, is better than 3% (relative difference between known and measured). A calculated hydroxyl value based upon the GC data agrees well with the titrimetric hydroxyl value.