Studies on the hydrolysis and utilization of long chain acyl CoA thioesters by liver microsomes

Acyl CoA thioester “hydrolase” activity exhibited by liver microsomal preparations using a spectrophotometric assay for released CoA has been shown to be a composite of several enzymatic reactions. Pig liver microsomes form a considerable amount of triacylglycerol from endogenous precursors, with essentially all acyl groups being incorporated into the 1,3 positions. Rat and rabbit liver microsomes form very little triacylglycerol under the same conditions. The true acyl CoA hydrolase activity of pig liver microsomes is relatively insensitive to diisopropylfluorophosphate (DFP), whereas this compound strongly inhibits the rat and rabbit enzymes. The hydrolase remaining in the liver microsomes after DFP treatment is rapidly inactivated when incubated in the presence of substrate.     

Pyrolysis gas chromatographic analysis of polyacrylonitrile

Pyrolysis gas chromatographic analysis of polyacrylonitrile under an inert atmosphere was made in a temperature region of 500–900°C. It was confirmed that the main degradation products are various kinds of lower nitriles that include CH₂CHCN, CH₃CN, and HCN. In addition, lower hydrocarbons such as CH₄ and C₂H₄, which are related to secondary decomposition, were detected. Various thermo‐analytical data were obtained, including those concerning the relation between retention time and the polarity of nitriles, and the dependence of the products' limiting yield on pyrolysis temperature. Based on the above results, specific applications of the pyrolysis gas chromatographic analysis and the utility of this procedure in the study of thermal degradation of polyacrylonitrile are described. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 473–478, 2001     

直接法合成甲基氯硅烷及其气相色谱分析

采用简单混合法和超声分散法2种催化剂触体制备方法,将自制铜粉与适量的氧化锌助催化剂混合,由直接法合成甲基氯硅烷,并建立了毛细管气相色谱法定量分析甲基氯硅烷的方法。结果表明:超声分散法比简单混合法制备的催化剂触体活性高,其合成的二甲基二氯硅烷选择性和反应中硅粉转化率均较高;以苯为内标物,采用OV-210为固定液的毛细管色谱柱和火焰离子化检测器,对合成产物进行气相色谱法定量分析,分析方法的准确度及精确度均较高。     

Automated gas chromatographic system for volatile profile analysis of fats and oils

A system is described for automating the direct gas chromatographic method for examining volatile profiles of vegetable oils. The system couples an external inlet device to a microprocessor-based gas chromatograph for providing automatic control of the analysis cycle. Automation of the analysis cycle permits consistent control over sampling and analysis to obtain rapid and reproducible volatile profiles. Manual control is completely eliminated and the analyst is freed for other tasks. Volatile Profile Analysis (VPA) is employed to monitor “protected oil” quality of oils being processed, as well as in the finished product, in an objective manner, thus eliminating the subjectivity found in many flavor panels. Automated VPA is also a useful tool in modifying operating parameters when handling various oil types. Presented at the AOCS annual meeting, Toronto, 1982.     

A simplified gas chromatographic procedure for analysis of lipoxygenase reaction products

A simple and very sensitive technique was devised to analyze lipoxygenase reaction products by direct gas chromatography. Results showed that peanut lipoxygenase oxidizes linoleic acid at the C-13 position exclusively. S. Reg. Res. Div., ARS, USDA.     

Quantitative gas liquid chromatographic analysis of butterfat triglycerides

Gas liquid chromatographic triglyceride separation by carbon number, and integration of the area response obtained in the hydrogen flame ionization detector, has permitted the calculation of the following molar proportions for the various triglyceride types in a blended butterfat sample: C₂₄ 0.5, C₂₅ 0.08, C₂₆ 0.57, C₂₇ 0.18, C₂₈ 0.81, C₂₉ 0.17, C₃₀ 1.15, C₃₁ 0.2, C₃₂ 3.1, C₃₃ 0.34, C₃₄ 5.41, C₃₅ 1.0, C₃₆ 10.6, C₃₇ 1.2, C₃₈ 12.8, C₃₉ 1.15, C₄₀ 10.7, C₄₁ 1.0, C₄₂ 6.1, C₄₃ 0.58, C₄₄ 5.15, C₄₅ 0.6, C₄₆ 5.8, C₄₇ 1.0, C₄₈ 6.45, C₄₉ 1.47, C₅₀ 8.5, C₅₁ 1.43, C₅₂ 6.95, C₅₃ 1.05, C₅₄ 4.0. The validity of these estimates was verified by similar determinations performed on molecular distillates of butterfat and on butterfats with known amounts of added saturated and unsaturated long chain triglycerides. The fatty acid carbon recoveries estimated on the basis of the observed triglyceride peak proportions were of the order of 95% or better. A comparison of the experimentally determined triglyceride type distributions with those calculated on the basis of a completely random fatty acid arrangement for the blended and the molecularly distilled samples showed considerable differences, the most apparent of which was the greater proportion of both short and long chain triglycerides consistently predicted for the random population. On the basis of these studies, it is suggested that butterfat possesses a non-random fatty acid distribution which is reflected in its triglyceride type distribution. Presented at the AOCS meeting in Toronto, Canada, 1962     

A preconcentration and subsequent gas liquid chromatographic analysis method for trace volatiles

A glass column containing a porous polymer was used to concen-trate headspace volatiles from enzymatically mediated reactions and inserted directly into the injection port of a gas liquid chromatog-raphy (GLC) for elution and separation of adsorbed volatiles. The polymer column was placed in an entrainment system attached to a water aspirator at 30 psi to collect volatiles produced by the en-zymatic reaction. A useful chromatogram was obtained from 1 g of raw material by this method. Volatiles collected in this manner could be stored on the polymer matrix at ambient temperatures without deleterious effects for subsequent GLC analysis. Multiple columns of the same or different trapping material could also be used in the entrainment system. Paper Number 5523 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27650.     

氨气法制备氢氧化镁工艺研究

以水氯镁石和氨气为原料,在不加入任何添加剂的条件下,利用直接沉淀法,制备具有高料浆质量分数的氢氧化镁阻燃剂。研究了搅拌强度、氨镁摩尔比、氨气加入流量、陈化时间、反应温度、氯化镁浓度对制备氢氧化镁粒度分布以及料浆浓度的影响,确定了最佳工艺条件:搅拌强度350 r/min、氨镁摩尔比2∶1、氨气加入流量320 mL/min、陈化时间90 min、反应温度60℃、氯化镁浓度4.30 mol/L。用扫描电子显微镜、X射线衍射仪和激光粒度分布仪表征产品的形貌、结构及粒度。在最佳工艺条件下制备得到的氢氧化镁D501.43μm,D902.40μm,料浆质量分数12.26%,Mg收率69.41%,氢氧化镁纯度99.60%,白度99.34。     

衍生化气相色谱法测定水中的氯酚类

本文建立了水中3种氯酚类的痕量检测方法。使用衍生化气相色谱法,内标定量,同时对《生活饮用水卫生规范》中的3种氯酚类：2,4-二氯酚（2,4-DCP）、2,4,6-三氯酚（2,4,6-TCP）和五氯酚（PCP）进行分析。在0～100μg·L^-1范围内,三支标准曲线的线性相关系数分别为0．9992,0．9994和0．9998;方法检出限分别为：0．32,0．04和0．02μg·L^-1;平均加标回收率范围分别为：96．8％～120％,97．1％～117％,97．8％～115．7％;相对标准偏差均小于5．6％;表明该方法能满足饮用水和废水的痕量分析要求。     

毛细管气相色谱法测定甲基丙烯酸二甲氨基乙酯的含量

采用50mOV 1毛细管柱,FID检测器,正二十二烷做内标,测定甲基丙烯酸二甲氨基乙酯的含量,其变异系数为0.92%,结果准确、可靠。     

Formation of N- and O-methyl derivatives of lipids containing amino,amide or hydroxy groups by the pyrolytic reaction with trimethylsulfonium hydroxide

Base-catalyzed transesterification of acyl lipids with methanol in the presence of trimethylsulfonium hydroxide (TMSH) is an easy and convenient method for the preparation of fatty acid methyl esters for GC analyses. However, lipids containing functional groups such as amino, amide and hydroxy groups are converted in varying degrees to the corresponding N- and O-methyl derivatives by the pyrolytic reaction of TMSH occurring in the injector of the gas chromatograph. For example, lipids containing amino or amide groups are converted into the corresponding N-methyl and N,N-dimethyl derivatives, fatty acid ethanolamides to the corresponding N-methyl, O-methyl and N,O-dimethyl derivatives, whereas alkyl methyl ethers are formed from long-chain alcohols. Furthermore, 2-O- and 3-O-monomethyl ethers as well as 2,3-di-O-methyl ethers are formed from 1-O-alkylglycerols, methoxy fatty acid methyl esters from hydroxy fatty acids as well as steryl 3β-O-methyl ethers from cholesterol and other sterols. Since some of the mentioned artefacts may interfere with fatty acid methyl esters in GC separations the TMSH derivatization method is recommended only with caution for lipids containing amino, amide and hydroxy groups. The methylation reactions, which finally lead to the corresponding N-methyl, O-methyl, N,N-dimethyl or N,O-dimethyl derivatives of fatty acids and lipids may, however, be of some diagnostic value for the structural analysis of such lipids by GC/MS.     

Identification of soapstocks by gas chromatographic techniques

The stock of a given soap may be estimated when the ratios of the fatty acids present are known. A new gas chromatographic procedure utilizing a novel automatic attenuator is presented. The samples are prepared by refluxing the soap with a methanolic solution of boron trifluoride and separating the esters so formed by standard gas-liquid chromatographic procedures. Soapstock compositions are determined by comparison with reference curves.     

聚氨酯涂料中TDI游离单体的气相色谱分析法

叙述用气相色谱仪 ,氢火焰检测器 ,经过 10 %SE - 30 /chromosorb W AW DMCS色谱柱将涂料中残留的甲苯二异氰酸酯单体 (TDI)分离后 ,以正十四烷作内标物 ,进行定量的分析方法。     

Preliminary gas chromatographic analysis of flavor compounds in mayonnaise

The flavor compounds in fresh, 3- and 6-month-old mayonnaise at room temperature have been analyzed by a gas chromatographic method. The results indicate that as the storage time of mayonnaise increased, the flavor compounds formed from oil in mayonnaise increased. However, the concentrations of allyl isothiocyanate which is the major flavor compound of mustard, and acetic acid and ethyl acetate which are the major compounds in vinegar did not change during the 6 months’ storage at room temperature. The analytical method described has shown good reproducibility in the analysis of mayonnaise flavor compounds and can be used as an instrumental analytical method to evaluate the mayonnaise flavor quality and to complement the sensory evaluation of mayonnaise. Ohio Agricultural Research and Development Center Journal Series Article 46–82.     

Gas chromatographic analysis of ester-type surfactants by using mixed anhydride reagent

Polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene fatty acid ester-type surfactants have been analyzed by gas chromatography after chemical decomposition by using the mixed anhydride of acetic and p-toluene-sulfonic acids. In this way, the hydrophobic groups of the polyoxyethylene alkyl ether sulfates and polyoxyethylene alkyl ether phosphates can be identified in the form of alkyl acetates, and the alkyl compositions can be determined easily. On the other hand, the hydrophobic groups of the polyoxyethylene fatty acid ester-type surfactants, such as polyoxyethylene fatty acid ester, polyoxyethylene glycerol fatty acid ester, and polyoxyethylene sorbitan fatty acid ester, have been identified after conversion into their corresponding fatty acids. At the same time, the base compounds of the hydrophilic groups have been converted into ethylene glycol diacetate, glycerol triacetate, and isosorbide diacetate, respectively, so these surfactants may be distinguished easily.     

毛细管气相色谱法测定2-硝基对苯二甲酸二甲酯含量

研究了2 硝基对苯二甲酸二甲酯的气相色谱测定方法。在选定的试验条件下,线性关系良好,标准曲线的相关系数为0.9998,测定的相对偏差为1.05%,样品加标准品回收率为99.0%～100.3%。该方法操作简便,灵敏度高,定量准确。     

Direct gas chromatographic analysis of volatiles from raw and roasted peanuts

Ground samples of raw and roasted peanuts were packed in glass liners and introduced into the heated injection port of a gas chromatograph where the volatiles were vaporized in situ. Chromatograms from ground peanuts are qualitatively similar to those from expressed oil samples. Fourteen compounds were tentatively identified. National Research Council Postdoctoral Research Associate 1969–1971. So. Mark. and Nutr. Div., ARS, USDA.     

Dynamic headspace capillary gas chromatographic analysis of soybean oil volatiles

To develop new knowledge on preventing or eliminating the formation of undesirable flavors in soybean oil, we analyzed quantitatively the major volatile products in samples that were oxidized during storage in the dark at ambient conditions. The volatiles formed were recovered and separated by dynamic headspace capillary gas chromatography. The effect of sampling temperatures was investigated by heating the sample, sweeping the volatiles with helium and trapping and desorbing them from a porous polymer Tenax trap. The volatiles were flushed from the trap onto a fused silica capillary column with a bonded mixed dimethyldiphenyl siloxane phase. At peroxide values between 2 and 13, the major volatile products found were acrolein, pentene, pentane, 1-penten-3-ol, pentanal, hexanal, 2-hexenal, 2-heptenal, 2,4-heptadienal, 2-octenal and 2,4-decadienal. The profile of volatiles was significantly affected by the sampling temperature used and by the presence or absence of citric acid in the oils before storage. The relative amounts of volatile thermal decomposition products of linolenate and linoleate hydroperoxides, such as 2,4-heptadienal and 2,4-decadienal, increased significantly when samples were heated above 90 C. Dynamic headspace gas chromatography made it possible to analyze the volatiles in samples heated to 60 and 90 C. These volatiles may be representative of those present in oils at time of tasting.