气相色谱/质谱法分析孔石莼中的脂肪酸

建立了孔石莼脂肪酸的气相色谱/质谱(GC/MS)测定方法。使用Folch法提取了孔石莼中的总脂,经过2 mol/L HCl-甲醇溶液的甲酯化处理后,采用GC/MS法对其脂肪酸组成进行了分离分析,同时结合有机质谱学规律,分别对饱和脂肪酸甲酯、单不饱和脂肪酸甲酯和多不饱和脂肪酸甲酯的裂解规律和质谱特征进行了分析归纳。通过质谱数据库检索和标准品对照,鉴定出孔石莼中的24种脂肪酸,其中9,12,15-十八碳三烯酸、4,7,10,13-十六碳四烯酸和6,9,2,15-十八碳四烯酸3种主要多不饱和脂肪酸占总脂肪酸含量的45.14%。通过对孔石莼中脂肪酸的分析,表明特征离子在脂肪酸甲酯尤其是多不饱和脂肪酸甲酯的定性方面具有很好的应用价值。     

Identification of triacylglycerols by high-performance liquid chromatography-gas-liquid chromatography and liquid chromatography-mass spectrometry

Triacylglycerols from rat adipose tissue were chromatographed by high-performance liquid chromatography (HPLC), with a gradient of propan-2-ol in acetonitrile as the mobile phase. Fractions of the material eluting from the column were collected and analysed by automated gas - liquid chromatography of the fatty acid methyl esters obtained after transmethylation. Triacylglycerols were identified by using a combination of their fatty acid content and elution time from the HPLC column. Fractions corresponding to whole peaks or groups of peaks were also collected and re-chromatographed on a liquid chromatography - mass spectrometry system equipped with a belt interface. For most triacylglycerols, good agreement was obtained between the two methods, although mass spectrometric identification of the early eluting peaks was complicated by poor resolution of the triacylglycerols on the HPLC system.     

Determination of phospholipid fatty acid and triacylglycerol composition of rat caecal mucosa.

The lipid composition of rat caecal mucosa, including the fatty acid composition of phospholipids and triacylglycerols, has been examined by capillary gas chromatography. Thirty-seven peaks were resolved, ranging in chain length from 12 to 24 carbon atoms. Preliminary identification of fatty acids by comparison with authentic standards was confirmed by gas chromatography-mass spectrometry using electron-impact ionization. The neutral and polar components were examined. Fatty acid methyl esters were quantified in absolute amounts with respect to the percentage of total phospholipid and triacylglycerols. The results show significantly higher levels of 16:0, 18:0, 18:1(n-9), 18:1(n-7), 18:2(n-6) and 20:4(n-6) in phospholipids, and higher levels of 16:0, 18:1(n-9) and 18:2(n-6) in triacylglycerols. On the other hand, analysis of caecal triacylglycerols revealed sn-glycerol-palmitate-oleate-palmitate, sn-glycerol-palmitate-linoleate-palmitate and sn-glycerol-palmitate-linoleate-oleate as major components.     

Quantitative analysis of fatty-acid-based biofuels produced by wild-type and genetically engineered cyanobacteria by gas chromatography-mass spectrometry

Simple and rapid quantitative determination of fatty-acid-based biofuels is greatly important for the study of genetic engineering progress for biofuels production by microalgae. Ideal biofuels produced from biological systems should be chemically similar to petroleum, like fatty-acid-based molecules including free fatty acids, fatty acid methyl esters, fatty acid ethyl esters, fatty alcohols and fatty alkanes. This study founded a gas chromatography-mass spectrometry (GC-MS) method for simultaneous quantification of seven free fatty acids, nine fatty acid methyl esters, five fatty acid ethyl esters, five fatty alcohols and three fatty alkanes produced by wild-type Synechocystis PCC 6803 and its genetically engineered strain. Data obtained from GC-MS analyses were quantified using internal standard peak area comparisons. The linearity, limit of detection (LOD) and precision (RSD) of the method were evaluated. The results demonstrated that fatty-acid-based biofuels can be directly determined by GC-MS without derivation. Therefore, rapid and reliable quantitative analysis of fatty-acid-based biofuels produced by wild-type and genetically engineered cyanobacteria can be achieved using the GC-MS method founded in this work.     

Technology for the identification of unusual cis, cis octadecadienoic fatty acids.

In this article methods are presented for the separation and identification of unusual cis, cis dienoic and polygnoic long chain fatty acids. Special emphasis has been laid on the identification of cis, cis octadecadienoic acids. The steps followed are: after transesterification the fatty acid methyl esters are separated by preparative gas chromatography according to chain length followed by argentation chromatography on thin-layer plates. After hydroxylation of the double bonds with osmium tetroxide the polyhydroxy compounds are derivatized to the per-O-trimethylsilyl-ethers. Separation and identification of individual compounds are achieved by combined gas chromatography-mass spectrometry using SCOT columns and low ionization energy.     

气相色谱质谱法测定植物油中脂肪酸

建立了气相色谱质谱法测定食用植物性油中脂肪酸检测的方法。植物油中的脂肪酸甘油酯在碱性条件下被水解为游离脂肪酸,随后采用三氟化硼将其转化为脂肪酸甲酯。采用同位素标记脂肪酸进行加标回收试验,回收率在94%以上。通过质谱的选择离子检测模式对硬脂酸、油酸、亚油酸等10种目标脂肪酸进行了检测,结果显示,该方法可用于油品的质量检测和日常分析。     

Simple thin-layer chromatographic purification procedure for the determination of cholesterol ester fatty acid compositions

A mild procedure for the purification of methyl esters of the fatty acid components of cholesterol esters, from interfering free cholesterol and other contaminating residues, is described. Methyl esters and free cholesterol are formed during the methylation of cholesterol esters. When co-extracted, cholesterol and other contaminating residues interfere with the methyl esters because minute proportions of these residues tend to elute at the same retention times as palmitoleic and stearic acids, to yield unreliable but significantly higher values for palmitoleic (p less than 0.001) and stearic acids (p less than 0.0001), and correspondingly lower values for oleic acid (p less than 0.0001). Purification of methyl esters by thin-layer chromatography eliminates this problem and yields reliable analysis of cholesterol ester fatty acids, without measurable oxidation of unsaturated fatty acids.     

Gas chromatography-mass spectrometry coupled with pseudo-Sadtler retention indices, for the identification of components in the essential oil of Curcuma longa L.

Gas chromatography-mass spectrometry was applied to the cyclohexane extract of Curcuma longa L. The chromatographic conditions generated retention indices very close i.e., greater than 99.9%, to those reported for structures in the Sadtler Standard Gas Chromatography Retention Index Library. In addition to the extensively reported sesquiterpene ketones, this essential oil extract contained a series of saturated and unsaturated fatty acids. Wiley mass spectra library matching for the free fatty acids, their trimethylsilyl esters and methyl esters narrowed their identity down to a few candidates. Combining this information with the retention indices of the fatty acid methyl esters in the Sadtler library allowed the identification of some of the double bond positions.     

大鼠肝过氧化物酶体中脂肪酸的分析

 用双 (2 乙基己基 )酚酞酸酯 (DEHP)诱导大鼠肝过氧化物酶体增殖 ,再用蔗糖密度梯度离心法分离大鼠肝细胞过氧化物酶体 ,并用十七烷酸作内标 ,以毛细管气相色谱法在非极性SPB 1石英毛细管柱上对其中的 11种脂肪酸进行分离测定。正常组和诱导组的大鼠肝过氧化物酶体中的不饱和脂肪酸和长链脂肪酸所占总脂肪酸的比例及总脂肪酸的统计结果是 :诱导组的不饱和脂肪酸的含量高于正常组的 (P <0 0 5 ) ,而两个组的脂肪酸总量及长链脂肪酸的含量无明显差别。结果提示 :诱导组的大鼠肝过氧化物酶体的脂肪酸成分发生了变化 ,其膜结构与正常组的不相同。     

Determination of very-long-chain fatty acids in plasma by a simplified gas chromatographic-mass spectrometric procedure

The concentration of very-long-chain fatty acids (VLCFA) (straight chain, more than 22 carbon atoms) in plasma or in cultured fibroblasts is one of the most important diagnostic criteria for the diagnosis of the peroxisomal disorders. A sensitive method for VLCFA assay in plasma, using small sample volume and a simplified procedure, is described. After adequate extraction and derivatization, methyl esters of VLCFA are separated, identificated and quantified by gas chromatography-mass spectrometry (GC-MS). The method is sensitive, reproducible, accurate and relatively simple. GC-MS equipment used for routine organic acid analysis can be used.     

Non‐polar lipids characterization of Quinoa (Chenopodium quinoa) seed by comprehensive two‐dimensional gas chromatography with flame ionization/mass spectrometry detection and non‐aqueous reversed‐phase liquid chromatography with atmospheric pressure chemical ionization mass spectrometry detection

A chemical characterization of major lipid components, namely, triacylglycerols, fatty acids and the unsaponifiable fraction, in a Quinoa seed lipids sample is reported. To tackle such a task, non‐aqueous reversed‐phase high‐performance liquid chromatography with mass spectrometry detection was employed. The latter was interfaced with atmospheric pressure chemical ionization for the analysis of triacylglycerols. The main triacylglycerols (>10%) were represented by OLP, OOL and OLL (P = palmitoyl, O = oleoyl, L = linoleoyl); the latter was present in the oil sample at the highest percentage (18.1%). Furthermore, fatty acid methyl esters were evaluated by gas chromatography with flame ionization detection. 89% of the total fatty acids was represented by unsaturated fatty acid methyl esters with the greatest percentage represented by linoleic and oleic acids accounting for approximately 48 and 28%, respectively. An extensive characterization of the unsaponifiable fraction of Quinoa seed lipids was performed for the first time, by using comprehensive two‐dimensional gas chromatography with dual mass spectrometry/flame ionization detection. Overall, 66 compounds of the unsaponifiable fraction were tentatively identified, many constituents of which (particularly sterols) were confirmed by using gas chromatography with high‐resolution time‐of‐flight mass spectrometry.     

Transesterification of fatty acid ethoxylates in supercritical methanol, then gas chromatography-mass spectrometric determination of the derived methyl esters, for identification of the initiators

Unknown fatty acid ethoxylate samples have been transesterified in supercritical methanol, using a loop made of a stainless-steel tubing as the reactor vessel. The initiator acids, now present as the corresponding methyl esters, were determined by gas chromatography-mass spectrometry (GC-MS). Quantitative transesterification is achieved by heating a solution of the ethoxylate sample in methanol at 280 degrees C for 10 min under pressure. The influence of reaction time, temperature, and presence of a Lewis acid catalyst has been investigated. The method of transesterification was optimized in respect of low cost, short reaction time, and availability to laboratories with standard analytical equipment.     

Examination of the esterified fatty acids from mouse erythrocyte and synaptosomal membrane phospholipids and their distribution between the various phospholipid types

Esterified fatty acids from mouse erythrocyte and synaptosomal membranes were characterised by fused-silica capillary gas-liquid chromatography and gas chromatography-mass spectrometry. Structural information was obtained from the mass spectra of a number of derivatives including trimethylsilyl (TMS), methyl and picolinyl esters together with the TMS ethers of glycols derived from the unsaturated acids. In addition to previously characterised acids, small concentrations of several acids previously unreported from these membranes were identified. These included branched chain acids and several unsaturated acids.     

N-Methylation and N,N-dimethylation of amino acids. An artifact production in the analysis of organic acids using diazomethane as derivatizing agent

In the fractions of the methyl esters of urinary organic acids seventeen N-methylated or N,N-dimethylated amino acid methyl esters are identified by gas chromatography-mass spectrometry. It is shown for twelve amino acids that their amino group reacts with diazomethane to form these derivatives. Using deuterated reagents, in particular deuterated diazomethane, in the sample preparation procedure during the organic acid analysis, it is shown that the N-methylated and N,N-dimethylated amino acids are artifacts from diazomethane and are not biochemical N-methylation products.     

Characterization and purification of polyunsaturated fatty acids from microalgae by gas chromatography-mass spectrometry and countercurrent chromatography

Summary The present study was undertaken in order to characterize then to purify fatty acids from marine phytoplankton. From a crude mixture of fatty acid methyl esters it was possible to isolate by countercurrent chromatography a mixture of four polyunsaturated fatty acid methyl ester identified as being hexadecatrienoic acid methyl ester, octadecatetraenoic acid methyl ester, eicosapentaenoic acid methyl ester and docosahexaenoic acid methyl ester by gas chromatography coupled with mass spectrometry in electron impact and in positive-ion chemical ionization mode. The four polyunsaturated fatty acids are in different ratios in mixtures from the two microorganisms:Skeletonema costatum andIsochrysis galbana.     

Basic profiles of organic acids in urine

Altogether 143 of the organic acids regularly occurring in urine of healthy individuals are identified as methyl esters by gas chromatography-mass spectrometry with respect to their complete chemical structures. They are classified as dicarboxylic acids, oxocarboxylic acids, hydroxycarboxylic acids, aromatic acids, furancarboxylic acids, nitrogen-containing acids and acid conjugates. By pre-fractionating the complex mixture of the total organic acids, peak overlap is minimized, and substances in low concentrations can also be detected and identified. The qualitative patterns of the urinary organic acids in the fractions are constant and reproducible, and in many cases a reliable identification of organic acids is possible by gas chromatography alone, using methylene units and separation on OV-1701 capillary columns.     

Evaluation of ionic liquid stationary phases for one dimensional gas chromatography-mass spectrometry and comprehensive two dimensional gas chromatographic analyses of fatty acids in marine biota

Ionic liquid stationary phases were tested for one dimensional gas chromatography-mass spectrometry (GC-MS) and comprehensive two dimensional gas chromatography (GC×GC) of fatty acid methyl esters from algae. In comparison with polyethylene glycol and cyanopropyl substituted polar stationary phases, ionic liquid stationary phases SLB-IL 82 and SLB-IL 100 showed comparable resolution, but lower column bleeding with MS detection, resulting in better sensitivity. The selectivity and polarity of the ionic liquid phases are similar to a highly polar biscyanopropyl-silicone phase (e.g. HP-88). In GC×GC, using an apolar polydimethyl siloxane×polar ionic liquid column combination, an excellent group-type separation of fatty acids with different carbon numbers and number of unsaturations was obtained, providing information that is complementary to GC-MS identification.     

Cinnamyl alcohols and methyl esters of fatty acids from Wedelia prostrata callus cultures

Two methyl esters of fatty acids, namely octadecanoic acid methyl ester (methyl stearate) and hexadecanoic acid methyl ester (methyl palmitate), in addition to four cinnamyl alcohol derivatives, sinapyl alcohol, coniferyl alcohol, p-coumaryl alcohol and coniferyl alcohol 4-O-glucoside (coniferin), were isolated from callus cultures of Wedelia prostrata. The structure of coniferin was established by spectroscopic and chemical methods, while the other compounds were identified by gas chromatography-mass spectrometry and thin layer chromatography in comparison with standards.     

Identification by combined gas chromatography-mass spectrometry of constituent long-chain fatty acids and alcohols from the meibomian glands of the rat and a comparison with human meibomian lipids

Constituent long-chain fatty acids and alcohols from the meibomian secretions of the rat were examined as trimethylsilyl (TMS) and methyl ester-TMS derivatives by capillary gas chromatography and by combined gas chromatography-mass spectrometry. The positions of double bonds and methyl branch points were determined by the mass spectra of picolinyl esters and nicotinates for long-chain fatty acids and alcohols, respectively. Fatty acids had chain lengths from C12 to C34 and were of the straight-chain iso, anteiso and monounsaturated types. The unsaturated acids had double bonds in the omega-7 and omega-9 positions. The alcohols had corresponding structures. In common with the constituent acids and alcohols of other meibomian secretions, the chain lengths of the constituents showed a biphasic distribution with maxima around C16-C18 and C25-C27. The profile was qualitatively similar to that obtained from human meibomian secretion but with some differences in the relative proportions of certain acids and alcohols.     

Analysis of methyl and ethyl esters of hydroxybenzoic and hydroxycinnamic acids in plant material

A method is described for the extraction and purification of methyl and ethyl esters of hydroxybenzoic and hydroxycinnamic acids from plant material. The esters were analyzed as trimethylsilyl derivatives by glass capillary gas chromatography (OV-1, OV-73, Dexsil 300) and gas chromatography-mass spectrometry. The method has been applied to analysis of methyl and ethyl esters of hydroxybenzoic and hydroxycinnamic acids in vegetables and potato peels.