同时裂解甲基化气相色谱法鉴别合成胶粘剂

 应用同时裂解甲基化气相色谱法 (Py Me GC)对合成胶粘剂进行了鉴别。采用热丝型裂解器、氢火焰离子化气相色谱仪、FFAP毛细管柱、程序升温方式及季铵盐甲基化试剂 ,对刑事案件中常见的丙烯酸酯类及其改性体、醋酸乙烯酯、聚乙烯醇等合成胶粘剂进行了测定 ,并对样品裂解各主要组分峰进行了GC/MS定性分析 ,同时比较了相同样本用常规裂解气相色谱法 (Py GC)测定的结果。结果表明 :Py Me GC法比Py GC法可获得更多的物质组分信息 ,是一种适用于法庭科学鉴定的方法。     

有机硅烷KH—550的气相色谱／质谱分析

对硅-550交联剂的组分进行了研究报道。通过GC对样品进行了研究分析,得到了七个分离很好的色谱峰以及样品中各组分的含量,再利用GC/MS联用技术和质谱裂解规律鉴定出样品各组分的分子结构。     

93号汽油样品组分的GC-MS分析

采用气相色谱-质谱法(GC—MS)在DB-5石英毛细管柱上对93号汽油样品进行了分析，检出94种组分；用归一化法进行定量，分析了其中的烯烃化合物，对于汽油生产中控制和降低汽油中烯烃含量有较好的实际意义。     

水体中有机污染物的分析

采用大孔径树脂吸附法对地表水和地下水中微量有机污染物进行富集，再用GC—MS法进行分析，其中地表水样品中共检出有机污染物42种，两处地下水样品中分别检出有机污染物9种和10种。对地表水与地下水之间相关性的研究表明，地下水样品中捡出的有机污染物都包括在地表水所含有机污染物的范围之内，地下水中含有有机污染物与地表水受到污染存在支接联系。     

傅里叶变换红外光谱和气相色谱-质谱法快速检测鼠药

用傅里叶变换红外光谱(FT-IR)差谱技术和气相色谱．质谱(GC/MS)全扫描法及特征离子监测技术，建立了毒鼠强和氟乙酰胺的标准质谱图库。利用有机溶剂直接萃取与FT-IR和GC/MS的结合，建立了混合组分原形物中毒鼠强和氟乙酰胺的快速检测方法。对7份实际样品的鉴定获得满意的结果。建立的方法为侦破案件提供了快速、灵敏、准确、有效的分析手段。     

分级净化结合气相色谱-质谱联用法测定豆芽中10种植物生长调节剂

建立了豆芽10种植物生长调节剂的分级净化体系,采用气相色谱质谱法(GC/MS)对该体系的效果进行了评价。豆芽先用酸性乙腈提取,浓缩后用甲醇复溶,部分经QuECHERS试剂盒净化后用GC/MS分析2,4-D-乙酯2,4-D-丁酯。另一部分经MCS固相萃取柱净化,先用5 mL甲醇洗脱得组分1,再用5%氨化甲醇洗脱得组分2;组分1浓缩后用10%三氟化硼甲醇溶液甲酯化,提取后GC/MS测定4-氯苯氧乙酸、α-萘乙酸、2,4-二氯苯氧乙酸、吲哚乙酸、吲哚丁酸,组分2浓缩后用GC/MS测定多效唑、激动素、6-苄基腺嘌呤。采用此净化体系对可以对不同性质的植物生长调节剂进行有效净化。结果表明,本方法完全可以用于豆芽中10种植物生长调节剂残留的检测,在豆芽中的添加0.01~0.1 mg/kg,10种植物生长调节剂平均回收率范围为70.5%~93.2%,RSD为5.2%~12.3%,本方法对10种植物生长调节剂的定量限(S/N≥10)为0.01~0.025 mg/kg,检出限(S/N≥3)为0.003~0.008 mg/kg。此净化体系简便、快速、准确,结合GC/MS可以满足豆芽中植物生长调节剂多残留检测要求。     

甲基化辅助实时直接分析电离的机理研究

实时直接分析电离源(DART)已经广泛应用于固体、液体和气体样品的快速检测. 在使用DART对低挥发性化合物进行分析时, 样品衍生化是十分重要的. 四甲基氢氧化铵(TMAH)是强的瞬时甲基化试剂, 常用于GC-MS的分析中. 以人参皂苷及人参寡糖为例, 研究了它们在TMAH的辅助下在DART中发生甲基化及电离的过程, 并从凝聚相和气相的角度对电离过程中的甲基化机理进行了研究. 人参皂苷主要发生不完全和全甲基化, 人参寡糖的甲基化则随着糖链的增长以及羟基的增多由全甲基化主导转变为过甲基化主导. 结果表明, 凝聚相和气相的共同作用是质谱检测到甲基化及过甲基化样品分子的根本原因.     

吹扫/捕集-热脱附气质联用法对荷叶挥发油成分的对比分析

采用同时蒸馏萃取提取得到荷叶挥发油, 通过吹扫/捕集-热脱附法(P&T-TD)对上述提取物中挥发性成分进行富集, 以气质联用(GC/MS)进行定性检测, 同时与直接进样GC/MS法分析的成分进行比较. 两种方法成功分离分析出有机酸、酯、醛、醇、酚、烷烃、芳香烃、烯烃以及含氮、硫、氧杂原子的化合物等共计84种成分, 其中P&T-TD GC/MS鉴定出63种有机化合物, GC/MS鉴定出41种有机化合物, 有20种成分共同检出. 对比分析表明: P&T-TD GC/MS的吹扫/捕集-热脱附过程能富集各种组分, 相比GC/MS分析, 可以鉴定出微量成分及更多挥发性和半挥发性成分, 在精油等挥发性成分的分析检测中使用优势明显.     

全二维气相色谱/飞行时间质谱用于莪术挥发油分离分析特性的研究

用全二维气相色谱 /飞行时间质谱 (GC×GC/TOFMS)研究莪术挥发油。对GC×GC与GC的分离特性和GC×GC/TOFMS与GC/MS的定性能力进行了比较。在相同条件下 ,GC分离出 87个峰 ,GC×GC分出约 5 0 0个峰 ,GC/MS和GC×GC/TOFMS鉴定出匹配度大于 80 0的组分分别为 4 6种和 2 2 7种。除此之外 ,GC×GC/TOFMS对每一个组分可给出三维定性信息 ,定性可靠性大大提高。研究结果显示与传统的分析技术相比 ,GC×GC/TOFMS在中药挥发油成分分析领域有很大的优势     

酱香型珍酒香气成分的GC/MS分析

对酱香型珍酒进行了化学处理,分类收集组分,将各组分用GC—MS联用法进行分离与定性定量测定。分离出200多个色谱峰,鉴定出了4个化合物。并平行地进行了与茅台酒的对比分析。结果表明此两种酒的主要组分一致,含量接近。     

Dimethyl carbonate as a novel methylating reagent for fatty acids in analytical pyrolysis

Dimethyl carbonate (DMC) was investigated as a mild, harmless and odorless reagent for pyrolytic methylation of fatty acids. Soybean oil was selected as test material for its high content of (poly)unsaturated fatty acids. Pyrolyses were performed at 500, 700 and 900 degrees C by means of a heated platinum filament pyrolyser on-line and off-line to the GC-MS apparatus. Methyl esters of palmitic, linoleic, oleic and stearic acid were formed as prominent products from off-line pyrolysis of soybean oil in the presence of DMC and zeolite 13X. Fatty acid methyl esters (FAMEs) were not observed at important levels in the absence of zeolite, while on-line Py-GC-MS experiments resulted principally in the formation of free fatty acids and hydrocarbons. The FAME profiles obtained from the DMC/zeolite off-line pyrolysis were compared to those resulting from tetramethylammonium hydroxide (TMAH) thermochemolysis and BF3-methanol procedure. The observed differences between pyrolysis and methanolysis methods were principally attributed to the thermal degradation of unsaturated fatty acids. The effectiveness of the DMC/zeolite pyrolytic methylation was further demonstrated by the analysis of tripalmitine and soybean seeds.     

Reaction efficiency of organic alkalis with various classes of lipids during thermally assisted hydrolysis and methylation

Reaction efficiencies of two organic alkalis, tetramethylammonium hydroxide (TMAH) and trimethylsulfonium hydroxide (TMSH), with lipids during thermally assisted hydrolysis and methylation (THM) were examined focusing on (1) the types of lipids and (2) degree of unsaturation of fatty acid moieties. Different types of lipids such as triglycerides, phospholipids, free fatty acids and cholesteryl esters containing saturated, monounsaturated or polyunsaturated fatty acid (PUFA) residues were subjected to THM-gas chromatography (GC) in the presence of TMAH or TMSH. The obtained results revealed that the THM reaction using TMAH allowed almost quantitative methylation of saturated and monounsaturated fatty acid components independently of the classes of lipids. However, strong alkalinity of TMAH brought about isomerization and/or degradation of PUFA components. In contrast, the use of TMSH was effective to highly sensitive detection of PUFA as well as saturated and monounsaturated fatty acid components contained in triglycerides, phospholipids (phosphatidylcholines) and free fatty acids. On the other hand, TMSH was proved to react hardly with any kind of fatty acid residues in cholesteryl esters due to their steric hindrance.     

Composition of the black crusts from the Saint Denis Basilica, France, as revealed by gas chromatography-mass spectrometry

The organic fraction of black crusts from Saint Denis Basilica, France, is composed of a complex mixture of aliphatic and aromatic compounds. These compounds were studied by two different analytical approaches: tetramethyl ammonium hydroxide (TMAH) thermochemolysis in combination with gas chromatography-mass spectrometry (GC-MS), and solvent extraction, fractionation by silica column, and identification of the fraction components by GC-MS. The first approach, feasible at the microscale level, is able to supply fairly general information on a wide range of compounds. Using the second approach, we were able to separate the complex mixture of compounds into four fractions, enabling a better identification of the extractable compounds. These compounds belong to different classes: aliphatic hydrocarbons (nalkanes, n-alkenes), aliphatic and aromatic carboxylic acids (n-fatty acids, alpha,omega-dicarboxylic acids, and benzenecarboxylic acids), polycyclic aromatic hydrocarbons (PAH), and molecular biomarkers (isoprenoid hydrocarbons, diterpenoids, and triterpenoids). With each approach, similar classes of compounds were identified, although TMAH thermochemolysis failed to identify compounds present at low concentrations in black crusts. The two proposed methodological approaches are complementary, particularly in the study of polar fractions.     

Characterisation of varnishes used in violins by pyrolysis-gas chromatography/mass spectrometry

The correct characterisation and a detailed knowledge of the materials originally used in violin varnishes, like natural resins, is crucial for the conservation in museums and for a suitable restoration technique. The study presented here reports on the potential of pyrolysis (Py) coupled with gas chromatography (GC) and mass spectrometry (MS) for the identification of chemical markers of each resin; this technique is very sensitive and selective, it needs a small quantity of sample and does not require chemical treatments. To improve the chromatographic behaviour of polar compounds the derivatising agent tetramethylammonium hydroxide (TMAH) in combination with pyrolysis has been used, in the so-called TMAH thermochemolysis or thermally assisted hydrolysis and methylation (THM), or more simply pyrolysis-methylation. The natural resins studied were colophony, sandarac, manila copal, elemi, amber and benzoin, mainly composed of terpenic compounds, with the exception of the latter, composed of aromatic compounds. Many compounds were identified; in particular, methyl esters of resinous acids that, individually or in a group, can be used as chemical markers. However, through this technique it was not possible to distinguish between the sandarac and manila copal resins because their chromatographic behaviour is very similar. Finally, the procedure applied has been employed in the characterisation of original varnish samples.     

Use of an injection port for thermochemolysis–gas chromatography/mass spectrometry: Rapid profiling of biomaterials

A simple and direct approach was developed for thermochemolytic analysis of a wide range of biomolecules present in plant materials using an injection port of a gas chromatograph/mass spectrometer (GC/MS) and a novel solids injector consisting of a coiled stainless steel wire placed inside a modified needle syringe. Optimum thermochemolysis (or Thermally Assisted Hydrolysis/Methylation) was achieved by using a suitable methanolic solution of trimethylsulfonium hydroxide (TMSH) or tetramethylammonium hydroxide (TMAH) with an injection port temperature of 350 °C. Intact, methylated flavonoids, saccharides, phenolic and fatty acids, lignin dimers and diterpene resin acids were identified. Samples include tea leaves, hemicelluloses, lignin isolates and herbal medicines. Unexpected chromatographic results using TMAH reagent revealed the presence of intact methylated trisaccharides (658 Da) and structurally informative dimer lignin markers.     

四甲基氢氧化铵降解苯酐固化双酚A型环氧树脂的研究

将四甲基氢氧化铵(TMAH)降解聚酯的方法移植用于降解苯酐(PA)固化双酚A型环氧树脂(DGEBA),降解生成的邻苯二甲酸二甲酯(DMP)可被气相色谱―质谱(GC-MS)快速检测到,同时通过内标法考察了TMAH用量对降解率的影响,结果表明TMAH降解苯酐固化环氧树脂效率较高,甲酯化率在95%以上。此项研究为剖析毫克级酸酐固化环氧树脂中的固化剂提供了一种快速且有效的方法。     

Measurement of oleic acid in human plasma by isotope dilution mass spectrometry

Summary A method for the quantitative determination of oleic acid in human plasma by isotope-dilution mass spectrometric technique is described. For the measurement of the fatty acid concentration (1-¹³C) oleic acid is added to the plasma sample. The fatty acids are extracted with n-hexane. Portions of the extract are esterified by the boron trifluoridemethanol method or stable isotope methylation. The methyl ester derivatives of the fatty acids are separated and detected by GC-MS with the mass spectrometer set to m/z 296 and 297. For the measurement of oleic acid after stable isotope methylation the m/z 299 and m/z 300 are monitored. The amounts of oleic acid in the plasma are calculated from the isotope ratios measured by selected ion monitoring. The recovery of the methylation step and the precision and accuracy of the GC-MS method are presented and discussed.     

Compositional analysis of copoly (DL-lactic/glycolic acid) (PLGA) by pyrolysis-gas chromatography/mass spectrometry combined with one-step thermally assisted hydrolysis and methylation in the presence of tetramethylammonium hydroxide

Rapid and precise compositional analysis of copoly (DL-lactic/glycolic acid) (PLGA) was performed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) combined with one-step hydrolysis and methylation in the presence of tetramethylammonium hydroxide (TMAH). Pyrolysis of PLGA with TMAH gave two characteristic products, derivatives of DL-lactic acid and glycolic acid, which directly reflect the average molar composition of PLGA. The analytical results for PLGA samples with various compositional ratios were in good agreement with those obtained by 1H-NMR spectrometry, and the precision was satisfactory.     

热辅助下的在线甲基衍生化-气相色谱法分析银杏叶中的银杏酸

采用热辅助下的在线甲基衍生化-气相色谱法测定银杏叶中的银杏酸。银杏叶样品与衍生化试剂四甲基氢氧化铵(TMAH, 25%甲醇溶液)同时进样,在300 ℃的进样口瞬间生成了银杏酸甲基衍生物,银杏叶中6种银杏酸得到很好的分离。在一定的质量浓度范围内银杏酸的线性关系良好,回归系数均大于0.9966,最低检出限范围为0.8～2.8 mg/kg。银杏叶中主要的烷基酚类物质为银杏酸C13∶0,C15∶1和C17∶1,它们的含量(用质量分数表示)分别为11.0%,36.7%和42.8%,3次平行测定的相对标准偏差(RSD)均小于3.4%(n=3)。银杏叶样品中总银杏酸的含量为4.0～10.9 mg/g。该方法无需繁琐费时的衍生化和纯化等前处理步骤,不失为银杏叶中银杏酸测定的一种快速、简便、准确的方法。