Identification of lipoxygenase-linoleate decomposition products by direct gas chromatography-mass spectrometry

Lipoxygenase, prepared from Virginia-type peanuts, was used to catalyze the oxidation of linoleic acid and methyl linoleate to form the C−9 and C−13 hydroperoxides. These reactions were monitored by rapid unconventional direct gas chromatography-mass spectroscopy. An aliquot of the enzymatic reaction mixture, without prior extraction or chemical modification, was secured directly into the heated (40–70 C) or nonheated (room temperature) injection system. When the reaction mixture was analyzed at room temperature, only hexanal was found. At elevated temperatures, five major and several minor components were identified. The predominant compounds identified were pentane, hexanal, 2-pentylfuran,trans-2,cis-4-decadienal, andtrans-2,trans-4-decadienal. These products originate from decomposition of either the C−9 or C−13 hydroperoxides generated by peanut lipoxygenase. Use of a company of product name by the Department does not imply approval or recommendation of the product to the exclusion of others, which may also be suitable.     

气相色谱-质谱联用法测定儿童产品中残留的甲酰胺

采用甲醇作萃取溶剂,超声萃取样品中残留的甲酰胺,选用DB-VRX色谱柱进行目标物分离,质谱定量检测。建立了气相色谱-质谱（GC-MS）联用法快速测定儿童产品中残留的甲酰胺分析方法。考察了萃取方法、萃取溶剂、极性色谱柱对甲酰胺分离检测的影响。结果表明,在1~30 mg/kg内,线性关系良好（R2〉0.999 5）,重现性良好。在1~10 mg/kg甲酰胺添加水平内,平均回收率为86.7%~93.2%,相对标准偏差为4.4%~6.4%。甲酰胺的方法检出限为1 mg/kg。该方法快速简捷,易于操作,适用于进出口儿童产品的甲酰胺残留量的日常检测工作。     

Combination gas chromatography-mass spectrometry

The direct combination of gas-liquid chromatography with mass spectrometry represents one of the most powerful techniques available for the analysis of complex mixtures of lipids. Principal advantages are the extremely small amounts of material required, the relative speed of analysis, and the wealth of molecular structural information available. The ability to record rapidly several mass spectra of one emerging chromatographic peak may also frequently be of use in detecting impurities, unresolved mixtures, or thermal decomposition of the sample. In the development of new gas chromatographic analytical procedures, the combination instrument may frequently prove highly useful for following chemical reactions in the preparation of new types of derivatives for GLC.     

Investigation of the reaction products of unsymmetrical dimethylhydrazine with potassium permanganate by gas chromatography-mass spectrometry

The gas chromatography-mass spectrometry technique was used to investigate the composition of the reaction products of unsymmetrical dimethylhydrazine with a potassium permanganate and potassium permanganate-hydrogen peroxide mixture. If the water contamination level is within 50 threshold limit values (TLV) (1 mg/ml), the proposed detoxication method utilizing potassium permanganate in combination with hydrogen peroxide allows for the reduction of the UDMH concentration to a safe level without the accumulation of transformation products. The detoxication of aqueous solutions with significant UDMH concentrations (up to 50000 TLV) (1 g/l) with potassium permanganate alone or in combination with hydrogen peroxide reduces the UDMH concentration to a safe level, but UDMH transformation products, including the extremely toxic nitrozodimethylamine, are accumulated in the solution.     

绿奇楠沉香成分GC/MS分析研究

采用乙醇浸泡提取绿奇楠沉香成分,并采用气相色谱质谱对绿奇楠化学成分进行分离鉴定,共鉴定出52种化合物,占成分总质量分数的85.052％,其中色酮类成分24种,主要成分为2-(2-苯乙基)色酮(质量分数为27.521％)、2-[2-(4-甲氧基)苯乙基]色酮(质量分数为24.224％)和2-[2-(3-羟基-4-甲氧基)...     

超声萃取气相色谱-质谱联用法快速测定儿童产品中2种有机磷阻燃剂

建立了气相色谱-质谱(GC-MS)联用法快速测定儿童产品中2种有机磷阻燃剂,磷酸苯基(二叔丁基苯基)酯(DBPP)和2,2-双氯甲基-三亚甲基-双[双(2-氯乙基)磷酸脂(V6)的分析方法。考察了不同萃取方法,不同萃取溶液,不同极性色谱柱对DBPP和V6分离检测的影响。采用丙酮作为萃取溶剂,超声萃取样品中DBPP和V6,选用DB-5MS色谱柱进行目标物分离,质谱定量检测。结果显示,DBPP在0.01~10 mg/kg内,线性关系良好(R20.999 1),重现性良好。V6在1~30 mg/kg内,线性关系良好(R20.999 3),重现性良好。在0.01~10 mg/kg添加水平内DBPP的平均回收率为89.3%~94.2%,相对标准偏差3.8%~4.3%。在1~30 mg/kg V6添加水平内的平均回收率为87.2%~95.7%,相对标准偏差4.8%~6.5%。DBPP和V6的方法检出限(S/N10)分别为0.01,1 mg/kg。该方法快速简捷,灵敏度高,定性准确,易于操作,适用于进出口儿童产品中的DBPP和V6日常检测工作。     

气相色谱-质谱联用法直接测定痕量十二烷基吗啉的方法研究

针对目前钾肥生产中反浮选药剂测定难度大,建立了一种气相色谱-质谱联用法直接测定痕量十二烷基吗啉的方法。样品溶解后经正己烷3次萃取待测,仪器条件：色谱柱TG-5MS,长度为30 m,内径为1.9 μm,膜厚度为0.25 μm;质谱参数：EI源,离子源温度为240 ℃,毛细管温度为250 ℃,进样量为1 μL,流速为1 mL/min,气相色谱分流比为40:1,色谱柱柱温选择程序升温。该方法标准工作曲线线性较好,精密度、回收率均满足分析的要求,相对标准偏差≤2%,方法的检测限为0.15 μg/mL,定量限为0.5 μg/mL。     

利用气相色谱-质谱联用技术测定微藻油脂的组成

采用超临界CO2萃取技术从微藻粉中提取油脂,微藻油脂经预处理后,采用气相色谱-质谱联用技术分析微藻油脂的组成成分.测定结果显示微藻油脂中主要有20种组分,主要是C12到C24的化合物,其中酯类化合物较多,以邻苯二甲酸二异辛酯居多,质量分数占70％以上,其次分别为反式角鲨烯、软脂酸等.     

Characterization of sterols by gas chromatography-mass spectrometry of the trimethylsilyl ethers

The utility of combined gas chromatography-mass spectrometry in the analysis and characterization of sterols has been explored. Methylene unit (MU) values and principal mass spectrometric data are presented for trimethylsilyl ethers of 28 sterols, including the major natural sterols. The diagnostic value of the fragmentation of trimethylsilyl ethers of Δ⁵-3 β-hydroxysteroids has been confirmed. Characteristic fragmentations of Δ⁴-3 β-trimethylsilyloxysteroids, and of Δ^5,7-3 β-trimethylsilyloxysteroids were also found. Location of side-chain hydroxyl groups is facilitated by the α-cleavages typical of the trimethylsilyl ethers. Fragmentations of saturated sterols, and of Δ⁷, Δ⁸⁽⁹⁾ and Δ⁽¹⁴⁾ stenols, are less influenced by trimethylsilyl ether formation, but the derivatives still afford satisfactory mass spectra. The combination of gas chromatographic and mass spectrometric information allows positive identification of any of the sterols examined, whereas application of either technique alone may give inconclusive results.     

Identification of sterols and bile acids by computerized gas chromatography-mass spectrometry

In mass spectrometry, sterols and bile acids form fragment ions characteristic of certain steroid structures. After separation of derivatized sterols or bile acids by the gas chromatograph and fragmentation in the mass spectrometer, data collected by the computer can be collated to provide a reconstructed gas chromatogram and a series of fragment ion current chromatograms in which the relative abundances of characteristic fragment ions are plotted vs time or scan number. Intensities of these fragment ions will be greatest and hence coincide with peak elution of unidentified sterols or bile acids. The use of known amounts of labeled appropriate sterols or bile acids permits quantitation of the identified sterol or bile acid.     

气相色谱-质谱联用法测定丁二烯中对叔丁基邻苯二酚含量

采用气相色谱一质谱联用(GC-MS)法测定丁二烯中阻聚剂对叔丁基邻苯二酚(TBC)含量,并与分光光度法和液相色谱法进行了比较.结果表明,用甲苯作为TBc的溶剂,其在被测组分的出峰区域不会形成干扰;采用选择离子模式检测可提高灵敏度.TBC质量分数为1×10-6～50×10-6时,外标法测定TBC含量的线性回归系数为0.999 5,加标回收率为98.60%～102.73%,相对偏差为2.42%～3.87%;GC-MS法与分光光度法、液相色谱法测得丁二烯中TBC含量相近,但GC-MS法更简便和快捷.     

Analysis of autoxidized fats by gas chromatography-mass spectrometry: X. Volatile thermal decomposition products of methyl linolenate dimers

The online version of the original article can be found at     

Analysis of autoxidized fats by gas chromatography-mass spectrometry: X. Volatile thermal decomposition products of methyl linolenate dimers

High-molecular weight compounds previously were found to be important secondary products from autoxidation of polyunsaturated fatty esters. The contribution of dimers to oxidative deterioration was investigated by analyzing their volatile thermal decomposition products by capillary gas chromatography-mass spectrometry. Dimers were isolated by gel permeation chromatography from autoxidized linolenate and from the corresponding monohydroperoxides, cyclic peroxides and dihydroperoxides. Major volatile decomposition products identified from these oxidative dimers were similar to those formed from the corresponding monomeric hydroperoxides. However, dimers from linolenate hydroperoxides produced more propanal and methyl 9-oxononanoate than the corresponding monomers but less methyl octanoate and much less or no 2,4-heptadienal and 2,4,7-decatrienal. Significant differences in minor volatile products also were observed between dimeric and monomeric products of methyl linolenate oxidation compounds. Mechanisms are suggested for the formation of volatile decomposition products from different dimeric structures. These dimers are believed to be important sources of volatile compounds contributing to flavor and oxidative deterioration of fats.     

Analysis of autoxidized fats by gas chromatography-mass spectrometry: VIII. Volatile thermal decomposition products of hydroperoxy cyclic peroxides

Secondary oxidation products are important sources of volatiles because of their susceptibility to further decomposition. Volatiles from the thermal decomposition of hydroperoxy cyclic peroxides have been identified by capillary gas chromatography followed by mass spectrometry (GC-MS). By using a saturated hydroperoxy cyclic peroxide as a synthetic model, the thermal decomposition pathways have been elucidated. Main cleavage occurs between the peroxide ring and the carbon-bearing hydroperoxide group. Volatiles produced were generally similar to those from corresponding monohydroperoxides. New volatiles identified included methyl furan octanoate, methyl ketones, and conjugated diunsaturated aldehyde esters. The general fragmentation observed between the peroxide ring and the hydroperoxide-bearing carbons is sufficiently predictable that it can be used as a tool for the structural characterization of hydroperoxy cyclic peroxides. Hydroperoxy cyclic peroxides from autoxidized and photosensitized oxidized methyl linolenate are suggested as important precursors of volatiles that may affect flavor quality of lipid-containing foods.     

Simultaneous determination ofSonchus arvensis L. triterpenes by gas chromatography-mass spectrometry

Sonchus arvensis L. or sow thistle has proved an excellent source of pentacylic triterpenes; triterpenes account for about 6% of the crude lipid extract or 0.2% of the dried plant. Composition of the triterpenoid fraction, as indicated by gas chromatography of the corresponding acetates, was α-amyrin (9%), β-amyrin (21%), lupeol (13%), taraxasterol (24%) and pseudo-taraxasterol (12%). A single, long-chain alcohol (16%) was also present. The nature of the triterpenoids was defined using gas chromatography and gas chromatography-mass spectrometry (GC/MS) and confirmed by direct comparison with authentic samples. The use of combined GC/MS proved extremely valuable in the simultaneous analysis of a mixture of triterpene acetates and greatly reduced the time needed to phytochemically evaluate these compounds.     

溶剂型胶粘剂中多环芳烃的气相色谱-质谱法检测

建立了溶剂型胶粘剂中16种PAHs(多环芳烃)含量的GC-MS(气相色谱-质谱)检测方法。分别优化了样品的萃取溶剂、净化方式和浓缩过程。研究结果表明:样品经过前处理后,可采用SIM(选择离子扫描)模式和内标法对PAHs进行定量分析;该检测方法的线性相关系数均大于0.999,检出限为0.001~0.020 mg/kg,用加标回收率法确定了该检测方法的精密度为1.54%~8.91%(n=7),16种物质的回收率为83.13%~104.32%;该检测方法具有准确、高效之特点,适用于胶粘剂中PAHs含量的定量检测。     

气相色谱-质谱法检测喷胶中卤代烃及烷烃含量

以正十一烷为内标物,采用气相色谱-质谱(GC-MS)法建立了喷胶中卤代烃及烷烃含量的检测方法。研究结果表明:各目标化合物的校正曲线在浓度为5~400μg/mL范围内呈良好的线性关系,其线性相关系数均超过0.999 0,平均回收率为89.06%~103.36%,相对标准偏差(RSD)为0.97%~4.13%;该方法具有良好的重现性和较高的灵敏度,在部分市售喷胶中进行验证时,所得结果令人满意。     

Volatile products from room temperature autoxidation ofcis,cis-6, 9-octadecadiene. Analysis by combined gas chromatography-mass spectrometry

The volatile products from autoxidation at ambient temperature ofcis,cis-6, 9-octadecadiene have been analyzed by combined capillary gas chromatography-mass spectrometry (Cap GC-MS). The compounds of interest from a mechanistic viewpoint were pentane, pentanal, hexanal, 1-pentanol, octane, 2-heptenal, octanal, and nonanal. Other compounds which appear to be secondary reaction products were 2-pentylfuran, 3-hexen-1-ol, amyl formate, hexyl formate, and octyl formate. Agricultural Research Service, USDA.     

气相色谱-质谱法测定化妆品中16种邻苯二甲酸酯

建立了气相色谱-质谱法同时测定化妆品中16种邻苯二甲酸酯的分析方法。在邻苯二甲酸酯质量浓度为0.1 mg/L~100 mg/L范围内,该方法测得的峰面积值与邻苯二甲酸酯的质量浓度的线性关系良好。线性相关系数均大于0.99,检出限为0.5 mg/kg,回收率为83.3%~121.8%,相对标准偏差为0.5%~6.4%。