Jojoba oil analysis by high pressure liquid chromatography and gas chromatography/mass spectrometry

Two analytical procedures for determining com-positions of jojoba liquid wax esters are described and compared. One, the more tedious, involves separation of wax ester homologs by high pressure liquid chro-matography followed by determination of the acid and alcohol moieties from each homolog. The second allows rapid determination of wax ester composition by gas Chromatographic separation of hydrogenated jojoba wax esters according to chain length, followed immediately by ancillary mass spectrometric identifi-cation of the acid and alcohol moieties. Double bonds in the alkyl chains in jojoba liquid waxes were almost exclusively (98%) ω-9, when examined by gas chro-matography/mass spectrometry (GC/MS) and ozonolysis/GC/MS. Presented in part at the 2nd International Conference on Jojoba and Its Uses, Ensenada, Mexico, February, 1976.     

Sperm whale oil analysis by gas chromatography and mass spectrometry

Gas liquid chromatography of winterized sperm oil showed that its wax esters with even carbon numbers range from C₂₄ to C₄₂ and are present in quantities resembling a normal distribution curve with C₃₄ as the mean. Between these even-numbered wax esters, ones with odd chain lengths were eluted. Triglycerides, similarly present in a normal distribution pattern, ranged from C₄₂ to C₅₈ and also included traces of odd chain species. The component acids and alcohols were analyzed by gas chromatography-mass spectrometry, and double bond positions in the monoenoid components were established. Branched chain and odd chain constituents, both saturated and unsaturated, were detected among both alcohols and acids. These moieties, when combined with those having even chains, are responsible for the wax esters and triglycerides with odd carbon numbers. ARS, USDA.     

Double-bond localization in heneicosapentaenoic acid by a gas chromatography/mass spectrometry (GC/MS) method

Double-bond locations in heneicosapentaenoic acid from eel lipids were determined by a method involving gas chromatography/mass spectrometry (GC/MS). The methyl esters of the pentaenoate fraction were first partially reduced with hydrazine. The resultingcis-monoenoates were then methylthiolated, and the resultant adducts were analyzed by GC/MS. The key fragmentation ions generated by the cleavage between the methylthio-substituted carbons were used to ascertain the original double-bond positions in the native fatty acid esters. Based on mass spectral evidence, the acid was identified as all-cis-6,9,12,15,18-heneicosapentaenoic acid.     

Fatty acid composition of oil in snow crab (Chionoecetes opilio) by gas chromatography/mass spectrometry

The hepatopancreatic fatty acid extract of the snow crab contains a high percentage (26%) of odd-carbon-numbered fatty acids and a substantial quantity (29%) of methyl-branched fatty acids, as indicated by gas chromatography/mass spectrometry (GC/MS) and gas liquid chromatography (GLC). A wide distribution in chain length of the fatty acids (C₁₀ to C₂₆) and in positional isomers of the linear monoenes are also indicated by GC/MS.     

Primary study of volatiles composition of Rhodiola sachalinensis by using gas chromatography and mass spectrometry (GC/MS)

To determine the volatile compounds in Rhodiola sachalinensis, hydro-distillation (HD) and headspace liquid-phase micro-extraction (HS-LPME) were used to extract 75 and 68 volatiles, respectively. Geraniol (24.73%), n-octanol (15.56%), and linalool (14.51%) were the most abundant essential oils detected in the HD samples, while geraniol (24.17%) and n-octanol (15.81%) were also detected at high levels in the HS-LPME samples. The main chemical classes of the essential oils were monoterpene alcohols in both the HD and HS-LPME samples at 59.02% and 37.64%, respectively. The O-heterocyclic (8.52%) and aromatic (5.92%) compounds were more abundant in the HS-LPME samples than in the HD samples.     

Comparison of some commercial waxes by gas liquid chromatography

Volatile components (hydrocarbons, monoesters, free acids as methyl esters and free alcohols as acetates) of seven unhydrolyzed commercial waxes-ouricury, carnauba, Chinese insect, lac, esparto, candelilla and Japan wax—have been analyzed and compared by gas liquid chromatography. Though appreciable portions of the waxes were nonvolatile, the results were sufficient to distinguish the seven waxes completely. Methanolysis products were analyzed directly by gas liquid chromatography, and the results agreed with those previously obtained for hydrolysis products of these waxes. Ouricury wax gave 18% C₂₄−C₃₄ αω-diols and 4% C₂₄−C₃₂ ω-hydroxy acids, in addition to 28% C₂₀−C₃₂ aciods and 17% C₂₂−C₃₄ alcohols, on methanolysis. NRCC No. 13387.     

Molecular heterogeneity of platelet-activating factor (PAF) in rat glandular stomach determined by gas chromatography/mass spectrometry. PAF molecular species changes upon water-immersion stress

The molecular heterogeneity of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (alkylacetyl-GPC) and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (acylacetyl-GPC) in normal rat glandular stomach was studied by gas chromatography/mass spectrometry (GC/MS) and tandem mass spectrometry. The percentage compositions of the molecular species of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC in the antrum were, respectively. 1-alkyl [16∶0 (34%) and 18∶0 (66%)]-2-acetyl-GPC and 1-acyl [16∶0 (60%), 18∶0 (14%) and 18∶1 (26%)]-2-acetyl-GPC. The alkyl chain composition of 1-alkyl-2-acyl-GPC was quite different from that of 1-alkyl-2-acyl-GPC in both the antrum and corpus, demonstrating a high degree of selectivity of alkyl chain utilization in PAF biosynthesis. The amount of 1-acyl-2-acetyl-GPC was much greater than that of 1-alkyl-2-acetyl-GPC. The molecular heterogeneity of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC in the corpus was similar to that in the antrum. Water-immersion stress affected not only the amount of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC, but also their molecular heterogeneity in the antrum and corpus. Whereas the amounts of 1-hexadecyl-2-acetyl-GPC and 1-acyl [16∶0, 18∶0 and 18∶1]-2-acetyl-GPC decreased markedly (to less than one-fifth) in the antrum after such stress for 1 hr, the amount of 1-octadecyl-2-acetyl-GPC increased markedly (up to 4-fold) in the corpus and severe lesions were observed after stress for 7 hr. The changes may be associated with the pathogenicity of gastric ulcers. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Measurement of the metabolic interconversion of deuterium-labeled fatty acids by gas chromatography/mass spectrometry

An analytical method that was developed to analyze deuterium-labeled fatty acids in human blood has been extended to identify labeled fatty acids from C₁₄ to C₂₄ chain length which are formed by metabolic processes such as desaturation, elongation, or shortening of the labeled fatty acids fed. A new computer and a hard-wave adder have been utilized to assure reliable data acquisition. Relative standard derivations for the analysis of labeled fatty acids were measured at 0.02, 0.03, and 0.04 at the 5%, 1%, and 0.2% levels of the labeled fatty acid methyl esters, respectively. The method makes extensive use of standards and computer processing for accuracy and high productivity. Data from a chylomicron triacylglycerol fraction are included to demonstrate the sensitivity of detection of metabolites formed by desaturation and elongation. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Headspace gas analysis of salad oils by mass spectrometry

A mass spectrometer was used to analyze the content of hydrogen, nitrogen, oxygen, carbon dioxide and argon in headspace gas of commercially packaged soybean, cottonseed and corn salad oils. A leakproof sampling system was designed to avoid air contamination and obtain a representative headspace gas sample. Some edible oils are packaged under pure nitrogen, whereas other samples contained various amounts of oxygen in the headspace gas. The presence or absence of argon in the headspace gas indicates that some oils are packaged with pure nitrogen and others with nitrogen obtained by controlled burning of hydrocarbons to remove all the oxygen in air. The presence of hydrogen in some samples where argon was also present suggested that catalytic purifiers were used to remove the last traces of oxygen and to ensure pure nitrogen for packaging oils. The decrease in oxygen of oils bottled in air was followed during storage at room and at elevated temperatures. No. Market. and Nutr. Res. Div., ARS, USDA.     

Pyrolysis/gas chromatography/mass spectrometry of glycidyl methacrylate—alkyl acrylate copolymers

Thermal degradation pattern of copolymers of glycidyl methacrylate with alkyl acrylates have been studied by pyrolysis/gas chromatography/mass spectrometry method. Various degradation products have been identified and based on the products obtained, the mechanisms of polymer degradation have been elucidated.     

Analysis of α-branched fatty acids by gas chromatography and mass spectrometry

Gas liquid chromatography and mass spectrometry were utilized in combination to identify isomeric α-branched chain fatty acid methyl esters. In a given isomeric series equivalent chain length, values decreased with increase in the number and size of α-alkyl substituents. Mass spectra of the α-monoalkyl derivatives are characterized by prominent McLafferty rearrangement ion peaks, whereas those of the α,α-dialkyl isomers contain the former ions plus an α-cleavage ion. Presented at the AOCS Meeting, Chicago, September 1973.     

Applied analysis and identification of ancient lacquer based on pyrolysis‐gas chromatography/mass spectrometry

Three lacquer samples taken from a “four‐eared” pottery container, which was designated an important National Cultural Property of Japan excavated in 16–17th century ruins of Kyoto City, were analyzed by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) and infrared (IR) spectroscopy to determine the source of the lacquer. It is an unexpected result that the lacquer in this pottery container is actually used by Melanorrhoea usitata. Alkylbenzene and alkenylbenzene as cleavage pieces of undecylbenzene (MW = 232 g/mol) and undecenylbenzene (MW = 230 g/mol), which are products of the pyrolysis of thitsiol, were detected in all three samples. Moreover, ω‐phenylalkylcatechols and ω‐phenylalkylphenols, which are the specific components of M. usitata, were also detected by Py‐GC/MS, suggesting that lacquer sap of M. usitata was used by the Japanese people in the 16–17th centuries. In addition, Japanese lacquer culture and the advantages of the Py‐GC/MS method for lacquer analysis are discussed in detail. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Analysis of neutral volatiles of mayonnaise by direct gas chromatography and mass spectrometry

Simple procedures have been developed for analyzing neutral volatiles from mayonnaise by direct gas chromatography and combined direct gas chromatography-mass spectrometry. For gas Chromatographic analysis, a glass liner containing glass wool coated with alkali in the lower quarter and plain glass wool in the remaining space is placed in the heated inlet of a gas Chromatograph, and mayonnaise and water are injected onto the plain packing. Neutral volatiles eluted from the mayonnaise by the combined action of water, carrier gas, and heat collect on the cool column of the gas Chromatograph, but acetic acid is trapped by the alkaline glass wool and thus does not interfere with the analysis. After removal of the liner with the spent sample, the temperature of the column oven is programmed to resolve the volatiles. For mass spectrometric analysis, neutral volatiles are passed directly from a Chromatograph inlet to a second inlet liner containing a porous polymer that traps most organic compounds but has low affinity for water. These neutral organic volatiles are desorbed from the porous polymer in the inlet of a Chromatograph interfaced with a mass spectrometer for analysis. This procedure allows components resolved by the gas Chromatograph to be identified by mass spectrometry without interference from either water or acetic acid. A total of 21 neutral volatile compounds was identified in mayonnaise. Presented at the AOCS Meeting, Chicago, September 1976.     

气质联用法鉴别ESBR和SSBR

本文介绍了一种通过气质联用法（GC/MS）测定提取液中的松香酸类物质以区分溶液聚合丁苯橡胶（SSBR）和以松香酸皂或混合酸皂为乳化剂的乳液聚合丁苯橡胶（ESBR）的方法,适用于生橡胶、混炼橡胶、硫化橡胶和橡胶制成品。对多个SBR进行GC/MS实验,谱图分析显示ESBR均含有松香酸类物质和脂肪酸类物质,而SSBR则未发现这两类物质。在此基础上开展已知配方硫化橡胶的实验。结果表明：对于生橡胶而言,无论ESBR使用何种乳化剂,均可以通过松香酸类物质和/或脂肪酸类物质完全区分ESBR和SSBR;混炼橡胶、硫化橡胶和橡胶制成品样品在确定含有丁苯橡胶的基础上,通过松香酸类物质的存在即可确认ESBR。     

大体积顶空-气相色谱/质谱联用测试人造革中的氯乙烯单体含量

建立了大体积顶空-气相色谱/质谱联用测定人造革中氯乙烯单体的方法。采用正交试验优化了影响氯乙烯检测的大体积顶空仪参数(如吹扫时间、吹扫温度、载气流速、解吸温度和解吸时间),并对影响氯乙烯检测的色谱条件进行了优化。在最佳条件下,氯乙烯在66.1～6610mg/L范围内呈较好的线性关系,检测限低至0.07 mg/kg(以S/N≥13计算);重现性试验(N=6)相对标准偏差为6.17%,平均回收率高于98.13%。指出该方法操作简单、实用性强。     

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。     

Surface characterization of intact fibers by inverse gas chromatography

Inverse gas chromatography (IGC) was used to determine adsorption isotherms and isosteric heats of adsorption for several normal alkanes on a number of intact textile fibers and to determine the specific surface areas of these fibers. Surface areas obtained by IGC were in excellent agreement (except for cotton) with those calculated from the geometric dimensions of circular cross-section fibers and with those obtained by the adsorption of krypton. Heats of adsorption were found to be only slightly higher than the corresponding heats of liquefaction of the probes. The effect of fiber surface purity on adsorption behavior as well as computerized data reduction are briefly discussed.     

Selected ion monitoring gas chromatography/mass spectrometry of 1,2-diacylglyceroltert-butyldimethylsilyl ethers derived from glycerophospholipids

Selected ion monitoring was used in conjunction with gas chromatography/mass spectrometry to analyzetert-butyldimethylsilyl ethers (tert-BDMS) of 1,2-diacyl-sn-glycerols derived from naturally occurring glycerophospholipids, including those ofEscherichia coli, soybean, egg yolks and porcine liver. First, the fatty acid composition of the unknown glycerophospholipid was determined by gasliquid chromatography (GLC) and, based on that, the fatty acids (mostly >0.5 wt%) were selected for monitoring the characteristic fragmentation ions produced from the fatty acid residues of the correspondingtert-BDMS derivatives of 1,2-diacyl-sn-glycerols. Next, thetert-BDMS derivatives were separated by GLC on a 65% methylphenylsilicone gum wall-coated open-tubular (WCOT) column according to the degree of unsaturation and the chain length of the fatty acid residues, and then directly introduced into the ion source of the mass spectrometer. The selected fragmentation ions, [RCO+74]⁺ representative of the fatty acid residues, and [M-57]⁺ indicative of the molecular weight of the derivatives, were monitored simultaneously. It thus became possible to determine the molecular species of thetert-BDMS derivatives by measuring a specific combination of two [RCO+74]⁺ and an [M-57]⁺ ion with the same retention time on the selected ion monitoring (SIM) profile. High background noise caused by volatilization of stationary phase at high temperature was largely overcome by selected ion monitoring. However, the fragmentation ion peaks produced fromtert-BDMS derivatives of highly unsaturated glycerophospholipids showed a distorted SIM profile, which was attributed to interaction between thetert-BDMS derivatives and the methylphenylsilicone phase of the column. Use of a WCOT column with a more polar liquid phase is therefore recommended for the analysis of highly unsaturated molecular species.     

Selective analysis of lipids by thin-layer chromatography blot matrix-assisted laser desorption/ionization imaging mass spectrometry

Thin-layer chromatography (TLC) is an essential method for food composition analyses such as lipid nutrition analysis. TLC can be used to obtain information about the lipid composition of foods; however, it cannot be used for analyses at the molecular level. Recently we developed a new method that combines matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) with TLC-blotting (TLC-Blot-MALDI-IMS). The combination of MALDI-IMS and TLC blotting enabled detailed and sensitive analyses of lipids. In this study, we applied TLC-Blot-MALDI-IMS for analysis of major phospholipids extracted from bluefin tuna. We showed that TLC-Blot-MALDI-IMS analysis could visualize and identify major phospholipids such as phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin.