Rapid determination of free fatty acids in vegetable oils by gas liquid chromatography

Determination of the free fatty acids in small quantities of vegetable oil is accomplished by gas liquid chromatography. The free fatty acids are isolated from a hexane solution of the vegetable oil into an aqueous solution of trimethylphenylammonium hydroxide (TMPH). Due to the alkalinity of TMPH, the free fatty acids readily partition into this aqueous phase. Injection of the free fatty acid-TMPH salts into a gas chromatograph results in pyrolytic methylation of the free fatty acid salts—yielding the methyl esters. Excellent results were obtained when this new procedure was used on neutral lipid oils containing known amounts of free fatty acids and compared with the results obtained by a modified BF₃/MeOH esterification procedure. When compared to the AOCS titration procedure, this new procedure gave comparable results. This new procedure has advantages over the AOCS procedure: it is more sensitive and gives quantitative results for individual free fatty acids. This new procedure also has several advantages over the modified BF₃/MeOH esterification procedure: it is easily and more rapidly performed, there is no deposition of glyceride on the column when the sample is injected, and because there is quantitative recovery, the new procedure is more sensitive and can be used on oils with a low weight percentage of free fatty acids.     

气相色谱串接质谱快速检测植物油中邻苯二甲酸酯

建立了气相色谱-串接质谱联用检测植物油中16种邻苯二甲酸酯类塑化剂的方法。采用乙腈直接萃取,固相萃取柱净化、洗脱,洗脱液经浓缩后,直接用气相色谱-串接质谱仪测定,内标法定量。结果显示,16种邻苯二甲酸酯类塑化剂的线性关系较好,方法检测限范围在0.004～0.01 mg/kg。在高、中、低3个水平下进行植物油加标实验,平均回收率为67.5%～117%,相对标准偏差小于15%(n=6)。方法简便快速,整个分析流程可在1 h之内完成,溶剂消耗量小,且应用串接质谱更好地消除了基质效应的干扰,灵敏度高,定性更为准确。     

Analyses of flavor qualities of vegetable oils by gas chromatography

Soybean oil, hydrogenated soybean oil, and corn oil were exposed to fluorescent light for different periods of time to obtain a wide range of flavor qualities. The flavor qualities of these oils were evaluated by sensory and gas Chromatographic methods. Sensory evaluation was conducted using a 10-point hedonic scale to rate overall flavor quality. The sensory panel was made up of 94 members from 8 different laboratories. The correlation coefficients (r) of the flavor scores between sensory evaluation and instrumental analysis for soybean oil, hydrogenated soybean oil, and corn oil were 0.95, 0.97 and 0.97, respectively. These results were very close to the correlation coefficients (r) 0.99, 0.98 and 0.95 obtained from 10 sensory panel members from one specific laboratory.     

Elution and analysis of volatiles in vegetable oils by gas chromatography

A simple and very sensitive technique was devised to analyze volatiles in vegetable oils by direct gas chromatography. A large sample of oil is diffused on glass wool in an injection port liner. After the liner is inserted in the injection port, the volatiles are rapidly swept into the column of the gas chromatograph for analysis. Southern Marketing and Nutrition Research Division, ARS, USDA.     

Determination of mixtures in vegetable oils and milk fat by analysis of sterol fraction by gas chromatography

A rapid gas-chromatographic (GC) procedure was developed for the analysis of the total sterol fraction of vegetable oils, milk fat or mixtures, to detect possible admixtures of sunflower with olive oil and the addition of vegetable oils to milk fat. The method, which employs alkali-catalyzed transesterification with KOH/methanol, was compared with saponification procedures with and without transformation of sterols into silyl derivatives prior to analysis. Repeatability of the method was assessed, and the coefficient of variation was 6.0 and 8.0% for β-sitosterol in olive and sunflower oils, respectively. Recovery of β-sitosterol ranged from 92.6 to 95.8 for both oils. The GC method assayed in this work requires little analysis time and eliminates the need for saponification, extraction, and derivatization steps. It offers good repeatability and recovery and is thus well suited to routine use.     

Analysis of vegetable oils for flavor quality by direct gas chromatography

Recently, a direct gas Chromatographic method for examining volatiles in vegetable oils was reported [Dupuy et al., JAOCS 50:340 (1973); and Dupuy et al., Ibid. 53:628 (1976)]. The procedure stimulated the development of instrumental techniques for determining odor and flavor characteristics of vegetable oils. This symposium paper describes modifications of the original direct gas Chromatographie procedure that substantially enhance its sensitivity and applicability. Profiles of volatiles for several experimental oils obtained by the modified system are presented, together with mass spectral data characterizing significant flavor-related peaks. Regression analysis of the instrumental data, with oil flavor scores, indicates that reliable flavor characteristics of high- and low-quality vegetable oils may be obtained rapidly and efficiently by instrumentation. Presented at the AOCS Meeting, New Orleans, April 1976.     

Pancreatic lipolysis of some brominated vegetable oils

Pancreatic lipolysis of several commercially used brominated vegetable oils has shown that although hydrolysis proceeds more slowly, these oils are degraded in a similar way to the common vegetable oils.     

Direct sampling capillary gas chromatography of volatiles in vegetable oils

Direct sampling gas chromatography used for determining volatiles and, indirectly, the flavor of vegetable oils, has been improved by a capillary column in place of the usual packed columns. Data on two good vegetable oils from a supermarket, and on one of these samples after intentional deterioration, are presented. Use of the capillary column provides a more efficient technique to differentiate between the better oils than did the previously used packed columns.     

Determination of citric acid and its decomposed products in edible oils by gas liquid chromatography

A quantitative gas liquid chromatographic (GLC) method for four organic acids-citric, aconitic, itaconic, and citraconic acids-in refined oils and fats was developed. After the organic acids are extracted with water from soybean oils, the extract is esterified with n-butanol and an aliquot of the ester is subjected to GLC on a temperature-programmed 10% DEGS column equipped with a flame ionization detector. At 20 and 30 ppm levels, recoveries of the acids from the oil varied from 95 to 100% except for itaconic acid. Citric acid content in commercial edible oils in Japan was from trace to 16 ppm. However, aconitic, itaconic, and citraconic acids were not detected.     

Determination of triacylglycerol composition in vegetable oils using high-performance liquid chromatography: a collaborative study

Triacylglycerol (TAG) composition in vegetable oils was collaboratively analyzed in 9 laboratories using high-performance liquid chromatography (HPLC) equipped with a refractive index detector. Dococyl (C22) and triacontyl (C30) silica columns were used for analysis. The TAG molecular species in soybean, rapeseed, and palm oils were individually separated on the chromatogram. The collaborative study demonstrated that TAG composition in vegetable oils could be analyzed based on partition numbers (PN) between 38 and 50. In conclusion, the HPLC method using C22 and C30 silica columns would be useful for determining the TAG composition (%) in vegetable oils.     

A simple technique for determining the gas liquid chromatography profile of volatile compounds in vegetable oils

A simple procedure has been developed for the isolation, concentration and gas liquid chromatographic detection of the volatile compounds in vegetable oils. The volatile compounds are isolated by bubbling purified helium through a measured quantity of vegetable oil heated in an oil bath having a temperature of 350 F. These compounds are collected on activated charcoal and then extracted from the charcoal with carbon disulfide containing an internal standard. The distribution of the volatile compounds is determined with a flame ionization detector. A 400-fold concentration of the volatile compounds is achieved with this procedure. The technique provides good reproducibility (94.3% to 105.5%) and has been successfully used for measuring the increase of volatile compounds in vegetable oils during storage and food production.     

Fatty acid composition of capsicum oils by gas liquid chromatography

The fatty acid composition of oils extracted from various parts (pericarp, seeds and stem) of the fruit ofCapsicum and from samples of Greek red pepper itself were obtained by gas liquid chromatography. Samples from three different varieties ofCapsicum annuum, cultivated in the region of Almopia, Greece, were taken from two crops (1967, 1968) and examined. The results are discussed. No characteristic differences in fatty acid composition of the corresponding samples of the parts ofCapsicum fruit of the three Greek varieties were noticed and there was no difference between the two crops. However, considerable differences in fatty acid composition between Greek and American varieties were observed, probably due to climatic conditions. Presented at the Association of Greek Chemists Meeting, Athens, 1970.     

Toxicological effects induced by the chronic intake of brominated vegetable oils

Several biochemical parameters of male Wistar rats fed during 15 weeks with standard laboratory chow, supplemented with 0.1 g of brominated vegetable oil (olive, sunflower) per 100 g of diet, were compared to those of a control group fed a normal diet during the same period of time. The former group showed a significant increase of triglyceride content in both heart and soleus muscle, as well as of total and sterified cholesterol in heart muscle. This increase was accompanied by decreased plasma levels of total and HDL-cholesterol. Some of these abnormalities were similar to those observed in rats fed the same standard laboratory chow, supplemented with 0.5 g of brominated oil per 100 g of diet. The hepatic levels of triglycerides, total proteins and glycogen, as well as the weight gain and caloric intake of the animals which were fed 0.1 g of brominated oil per 100 g diet, were similar to those of the control group. In summary, the toxicologic effects observed during the chronic intake of diets supplemented with relatively low doses of brominated oils, suggest the need to undertake wider and deeper biochemical studies. The authors consider that these are necessary in order to ascertain the maximum tolerance levels for the use of these compounds, to minimize the risk of inducing important biological alterations.     

Determination of plasma tocopherols by gas liquid chromatography

A method is described for the separation and determination of plasma tocopherols by gas liquid chromatography (GLC). Proteins in 0.1 g samples of plasma were precipitated with ethanol containing a known amount of 5,7-dimethyltocol which served as an internal standard. Tocopherols were extracted into petroleum ether, purified by thin layer chromatography and analyzed as trimethylsilyl ethers by gas liquid chromatography (GLC) on 0.5% Apiezon L. Recoveries of α- and γ-tocopherols averaged 100% and 93%, respectively. The mean total tocopherol content of eight human plasma samples was 8.5 μg/g by GLC and 9.9 μg/g by a ferric chloride-α,α′-dipyridyl method. The α- and γ-tocopherol contents of 16 human plasma samples ranged from 4.0 to 12.3 μg/g and 0.6 to 2.1 μg/g, respectively.     

Effect of brominated vegetable oils on heart lipid metabolism

Normal rats fed for 105 days on an experimental diet made up of standard laboratory chow supplemented with 0.5% of a mixture of brominated sunflower-olive oil (BVO) developed a significant increase in the triacylglycerol content of the heart, liver and soleus muscle compared to controls. In addition, BVO-treated rats had a decrease in plasma levels of triacylglycerol and total and HDL cholesterol. Plasma fatty acid levels and plasma post-heparin lipolytic activities, such as H-TGL, LPL, T-TGL and MGH were similar to those of control animals fed the standard chow alone. Heart PDH_a (active portion of pyruvate dehydrogenase) was dramatically decreased in the BVO-fed rats. A faster rate of spontaneous lipolysis was recorded in the isolated perfused preparation of hearts from the experimental animals. The addition of 10⁻⁷ M of glucagon to the perfusate, however, revealed a lipolytic effect comparable to the one observed in the control rats. In summary, our findings of normal fatty acids and low triacylglycerol plasma levels associated with normal activities of the various PHLA (post-heparin lipolytic activity) enzymes suggest that accumulation of triacylglycerol in heart muscle may not be explained essentially in terms of an elevated uptake and/or increased delivery of plasma fatty acids or plasma triacylglycerol. A decreased in situ catabolism of tissue triacylglycerol also appears unlikely because the spontaneous as well as the glucagon induced lipolysis in the heart both were found to be unimpaired. Our results suggest that the mechanisms involved in the toxicologic effects of a BVO diet on heart lipid metabolism could be exerted mainly at the level of triacylglycerol biosynthesis rather than a derangement in some known step of their catabolic pathway. Additional studies are necessary to clarify this matter. An abstract pertaining to this work was presented in November 1984 at the IV Congress of the Pan American Association of Biochemical Societies (PAABS), Buenos Aires, Argentina.     

A rapid method for analysis of refined vegetable oils for TBHQ by gas chromatography

A simple and rapid extraction technique using acetonitrile solvent has been used to extract TBHQ antioxidant from refined soybean and cottonseed oils. The extracts have been analyzed by a gas Chromatographic technique, using silyl derivatization, to quantitate the TBHQ content of the oil. The method has been calibrated using 14 data points for linear regression, showing a coefficient of deter-mination of 0.9587. Average recoveries over a 14-day period range from 102 to 106.6% at the 50-150 ppm levels. The overall test standard deviation, which includes the effects of time, is 5.9. Presented at the JOCS/AOCS Annual Meeting, 1979, San Francisco.     

气相色谱法分析重质油中的饱和烃加环烷烃馏分

重质油用经典柱分离得到的饱和烃加环烷烃组分，可用SE-30石英毛细管柱，在300℃的汽化室温度下，以3℃／min的升温速率分离并进行定性和定量分析。方法简便快速，具有较高的精密度和准确度，适合于生产控制分析。     

气相色谱法测定氯乙酸母液

通过对氯乙酸母液生成氯乙酸乙酯的酯化条件和色谱分析条件的研究,确定了以浓 硫酸为催化剂,以三氯甲烷为萃取剂的酯化条件,并采用热导检测器,面积归一化法进行定量。     

Characterization of soapstock and deodorizer distillates of vegetable oils using gas chromatography

Soapstock and deodorizer distillates are complex lipid mixtures that are produced in significant amounts by the vegetable oil refining process. These mixtures contain components such as fatty acids, sterols, squalene and tocopherols that have important commercial value and therefore their characterization and quantification are of interest. We describe here the development of a simple gas chromatography (GC) method based on a silylation derivatization technique coupled with the use of a medium polar column to separate the different classes of fatty compounds in these waste streams. This method is suitable for GC coupled with either a flame ionization detector or a mass spectrometer.     

Analysis of the monoenoic fatty acid distribution in hydrogenated vegetable oils by silver-ion high-performance liquid chromatography

A silver-ion high-performance liquid chromatography column (hexane/acetonitrile as solvent, ultraviolet detection) was used to analyze the fatty acid distribution (as fatty acid methyl esters) of a representative sample of hydrogenated oil. Fractions containingcis- andtrans-18:1 isomers were readily separated. The positional fatty acid isomers were separated by rechromatographing these fractions. The elution order and percent compositions were compared with results obtained by gas chromatography. Of the Δ8 to Δ14trans-18:1 isomers, only the Δ8 and Δ9 pair could not be separated. The Δ8 and Δ9cis-18:1 pair also could not be separated, and the Δ10 isomer was poorly separated from this pair. Area percents were comparable to results obtained by gas chromatography.