顶空气相色谱法测定大蒜主要含硫化合物在烹饪后油脂中的含量

采用顶空毛细管气相色谱法/氢火焰离子化检测器,分析了大蒜中主要含硫化合物(如:二烯丙基硫醚、二烯丙基二硫醚、二烯丙基三硫醚)在烹饪后油脂中的含量变化。优化的色谱条件为以DM2WAX石英弹性毛细管色谱柱进行分离,平衡温度为403 K,搅拌速度为500 r/min,平衡时间为20 min。在所考察的浓度范围内,该方法呈现出良好的线性关系,相关系数大于0.999,检出限为0.001~0.025 mg/L,3种含硫化合物的平均回收率为97.1%~103.0%。     

冷柱头程序升温进样-气相色谱/质谱法研究新鲜大蒜中的有机硫化合物

采用冷溶剂提取新鲜大蒜中的有机硫化合物,结合冷柱头程序升温进样,对大蒜原始组分进行了气相色谱/质谱分析 。该法实现了从提取到色谱分离的“冷过程”,因而可以准确地鉴定大蒜提取液在热分解前的原始组分。分析结果表明, 在大蒜提取液中含有3-乙烯基-1,2-二硫杂-5-环己烯及其异构体2-乙烯基-1,3-二硫杂-4-环己烯两种主要组分以及少量 的S-甲基甲烷硫代亚磺酸酯、二烯丙基二硫醚、二烯丙基三硫醚。对大蒜的冷溶剂提取液和水蒸气蒸馏提取的大蒜油中 的有机硫化合物进行了比较,对一些主要有机硫化合物的形成进行了初步探讨。     

吹扫捕集-GC-MS-SIM法测定水中挥发性硫化合物

建立了水中的二硫化碳(CS2)、甲硫醚(DMS)和二甲二硫醚(DMDS) 3种挥发性硫化合物分析方法.采用吹扫-捕集对水中的被测成分进行预富集,然后导入GC-MS系统中在选择离子模式(SIM)下进行检测.CS2、DMS和DMDS 3种硫化合物分别在0.03～3.42 μg/L,0.17～2.72 μg/L和0.04～3.41 μg/L范围内线性关系良好,相关系数r分别为0.9967、0.9930和0.9959;在不同的浓度下,平行测定5次后的相对标准偏差均小于6.0%;方法检出限为3.75,11.33和2.10 ng/L.     

液相色谱-质谱联用银离子诱导电离分析大蒜粉剂中二烯丙基硫化物

烯丙基硫化物由于弱极性不电离,本实验利用Ag 柱后诱导电离对大蒜粉剂中的含硫化合物进行质谱定性,并以二烯丙基三硫醚为参比,对各种二烯丙基含硫化合物进行定量测定。采用甲醇-水梯度洗脱,色谱柱为W aters Symm etry C18(3.9 mm×150 mm,5μm)柱,流动相流速为0.5 mL/m in,30 m in实现良好分离。将1 mmol/L AgNO3衍生试剂以5μL/m in流速注入柱后管路,毛细管电压3 kV,正离子电离方式质谱检测。结果表明,含硫化合物的色谱行为符合“硫数规律”(lgk′=0.4276 0.0364n,r=0.9910);利用该类化合物摩尔吸光系数与二烯丙基三硫醚相近的原理,进行大蒜粉剂中含硫化合物定量分析,比硫酸钡重量法和银量定硫法更合理。     

自动顶空衍生化固相微萃取法测定啤酒中的老化醛类化合物

采用邻-五氟苯甲基羟胺(PFBOA)衍生,顶空固相微萃取(HS-SPME)和气相色谱质谱(GC-MS)测定啤酒中2-甲基丁醛、3-甲基丁醛、反-2-壬烯醛等8种老化醛类化合物.顶空固相微萃取采用65 μm PDMS/DVB纤维,先用纤维吸附PFBOA溶液,再将纤维插入装有2 mL啤酒的20 mL顶空进样瓶的顶空中在60 ℃萃取60 min,衍生和萃取都在自动进样器中进行.采用GC-MS检测,特征离子为m/z 181.8种羰基化合物在0.2～500 μg/L范围内线性关系良好,相关系数在0.990以上.检测样品的相对标准偏差为1.0%～15.7%,回收率为88%～103%.同时研究并讨论了萃取纤维、萃取温度、萃取时间、样品体积等因素对醛类萃取量的影响.该方法可用于啤酒保鲜期研究和产品质量控制.     

蒜油中几种有机多硫化合物质谱的研究

本文给出了大蒜挥发油中五种有机硫化合物的质谱图,通过质谱图解析,确定它们分别是1,2,3,4-四硫代环庚烷,1,2,3,4,5-五硫代环辛烷,二烯丙基四硫醚,二丙烯基四硫醚,5-烯丙基-1,2,3,4-四硫代环庚烷。     

二烯丙基硫醚化合物的合成

二烯丙基一硫醚（DS）,二烯丙基二硫醚（DDS）,二烯丙基三硫醚（DTS）和二烯丙基四硫醚（DTTS）等是大蒜提取液中的主要有效成分,具有十分广泛独特的生理药理活性。作者以甲酸、丙三醇为超始原料合成了这些化合物,烯丙基硫醚化合物总含量达83%,其中DDS,DTS含量分别达30%。产物均GC-MS鉴定确证。合成方法简单,原料易得,反应步骤少,实用性较强。     

黄原酸酯及二硫代硫酸酯与零价钯的反应

黄原酸烯丙基酯在Pd(pph₃)₄-dppe催化下,发生碳氧键断裂,放出气体硫化羰基(COS),生成烯而基硫醚。二硫代碳酸烯丙基酸在Pd(O)催化下,同样生成烯丙基硫。     

顶空气相色谱-质谱法快速测定废水中的α-甲基萘

建立顶空气相色谱–质谱法测定废水中α-甲基萘的含量。优化色谱、质谱及顶空条件,选用DB–624毛细管柱(30 m×0.32 mm,1.8μm),在柱流量1.5 mL/min条件下采用电子轰击电离源,全扫描定性,选择离子外标法定量。α-甲基萘的质量浓度在40～1 500 g/L范围内与其色谱峰面积呈良好的线性关系,相关系数大于0.999 5,当废水取样量为10.0 mL时,方法检出限为4.8μg/L。在3个不同加标水平下,实际废水样品中α-甲基萘的平均回收率为89.8%～97.6%,测定结果的相对标准偏差为1.5%～7.1%(n=6)。该方法快速灵敏、准确度高、重现性好,适用于废水样品中α-甲基萘的应急监测。     

顶空进样GC-SIM-MS测定硝唑尼特中溶剂残留甲醇含量

利用气相色谱-选择离子监测质谱联用仪(GC-SIM-MS)测定硝唑尼特样品中溶剂残留甲醇的含量,顶空进样,温度为70℃,时间为20 min.SIM定量离子m/z 32,参考离子m/z 31,30和29.甲醇质量浓度在0.5~100μg/m L内呈良好的线性(R~2=0.999 92).方法相对标准偏差为2.49%~4.85%,样品加标回收在94.5%~102.8%之间,检测限为0.5μg/m L,符合定量分析的要求.     

GC and Mass-Spectrometric Comparison of Organo Sulfur Compounds in Two Varieties of Iranian Garlic

Abstract

Garlic antibiotic action is well known; it is reputed to offer protection against coronary thrombosis and atherosclerosis exhibiting antioxidant and anticancer effects. ^1,2 In this work ¹ H NMR and gas chromatography in conjunction with mass spectrometry have been used for the identification and determination of these compounds in two varieties of Iranian garlic [Allium sativum var. sativum (I) and Allium sativum var. holmense (II)]. The organosulfur compounds in (I) exhibiting a concentration higher than 1% are diallyl sulfide (1.3%), diallyl disulfide (8%), methyl allyl disulfide (19%), methyl allyl trisulfide (3.2%), diallyl trisulfide (5.5%), diallyl tetrasulfide (2%), 2,3-dimethyl thiophen (1.8%), 5-methyl-1,2,3-thiadiazol (5%), and 1,2-ditiolan-3-carboxilic acid (1.5%). The amount of organosulfur compounds in (II) are diallyl disulfide (2%), methyl allyl trisulfide (6.3%), diallyl tetrasulfide (5%), and cyclopentanthiol (2.5%).     

Do garlic-derived allyl sulfides scavenge peroxyl radicals?

The chain-breaking antioxidant activities of two garlic-derived allyl sulfides, i.e. diallyl disulfide (1), the main component of steam-distilled garlic oil, and allyl methyl sulfide (3) were evaluated by studying the thermally initiated autoxidation of cumene or styrene in their presence. Although the rate of cumene oxidation was reduced by addition of both 1 and 3, the dependence on the concentration of the two sulfides could not be explained on the basis of the classic antioxidant mechanism as with phenolic antioxidants. The rate of oxidation of styrene, on the other hand, did not show significant changes upon addition of either 1 or 3. This unusual behaviour was explained in terms of the co-oxidant effect, consisting in the decrease of the autoxidation rate of a substrate forming tertiary peroxyl radicals (i.e. cumene) upon addition of little amounts of a second oxidizable substrate giving rise instead to secondary peroxyl radicals. The relevant rate constants for the reaction of ROO(.) with 1 and 3 were measured as 1.6 and 1.0 M(-1) s(-1), respectively, fully consistent with the H-atom abstraction from substituted sulfides. It is therefore concluded that sulfides 1 and 3 do not scavenge peroxyl radicals and therefore cannot be considered chain-breaking antioxidants.     

Comparative study of extraction techniques for determination of garlic flavor components by gas chromatography–mass spectrometry

Several sampling techniques based on steam distillation (SD), simultaneous distillation and solvent extraction (SDE), solid-phase trapping solvent extraction (SPTE), and headspace solid-phase microextraction (HS-SPME) have been compared for the determination of Korean garlic flavor components by gas chromatography–mass spectrometry (GC–MS). Diallyl disulfide (57.88%), allyl sulfide (23.59%), and diallyl trisulfide (11.40%) were found to be the predominant flavor components of garlic samples extracted by SDE whereas these components were at levels of 89.77%, 2.43%, and 3.89% when the same sample was extracted by SD, 97.77%, 0.17%, and 0.10% by SPTE, and 97.85%, 0.01%, and 0.01% by HS-SPME using the 50/30-m divinyl benzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber. Thermal degradation of components such as allyl methyl sulfide, dimethyl disulfide, and thiirane were observed for SDE and SD but not for SPTE or HS-SPME. HS-SPME had several advantages compared with SD, SDE, and SPTE—rapid solvent-free extraction, no apparent thermal degradation, less laborious manipulation, and less sample requirement. Five different fiber coatings were evaluated to select a suitable fiber for HS-SPME of garlic flavor components. DVB/CAR/PDMS was most efficient among the five types of fiber investigated.     

Identification and quantification of anticarcinogens in garlic extract and licorice root extract powder

Nine organosulfur compounds present in an aged garlic extract and two isoflavonoids and one triterpenoid present in a licorice root extract powder have been identified and quantified. Quantification involved solvent extraction and gas chromatographic – mass spectrometric analysis (garlic extract) or hydrolysis, solvent extraction, and liquid chromatographic analysis (licorice root extract powder). Although the garlic extract proved to be unstable and the concentration of the organosulfur compounds varied with time, one analysis of the extract gave the following results: methyl disulfide (0.607 μg/g), methyl trisulfide (0.181 μg/g), allyl sulfide (2.02 μg/g), allyl disulfide (0.784 μg/g), allyl trisulfide (0.795 μg/g), allyl methyl sulfide (1.64 μg/g), allyl methyl disulfide (0.411 μg/g), allyl methyl trisulfide (0.695 μg/g), and ethyl 2-propenesulfinate (11.4 μg/g). The analysis of the licorice root extract powder gave the following results: formononetin (1.92 mg/g), isoliquiritigenin (9.61 mg/g), and 18β-glycyrrhetinic acid (43.9 mg/g). Methods were successfully developed to quantify the same compounds in the serum of test animals which had consumed feed spiked with garlic extract or licorice root extract powder. Only the 18β-glycyrrhetinic acid could be detected in the sera of such animals, however. An effort was also made to determine serum levels of prostaglandin E2 to correlate its inhibition with levels of the dietary components, but the prostaglandin E2 levels were too low to measure.     

Copolymerization of diallyl isophthalate with methyl methacrylate and styrene in the presence of C60 fullerene

The involvement of fullerene in the radical copolymerization of diallyl isophthalate with methyl methacrylate or styrene results in a change in the relative activity of monomers owing to the interaction of C₆₀ with the allyl radical yielding a “quo;new,”quo; more active radical. This corresponds to the transition from degradative chain transfer to effective transfer to the allyl compound. It is of great importance that, at an amount of diallyl isophthalate in the monomer mixture of up to 10 mol %, C₆₀ fullerene is almost completely incorporated into macromolecules.     

GC-MS法测定大蒜中的挥发性物质

大蒜(AlliumsatiuvmL.)是多年生草本百合科植物大蒜的鳞茎,按皮的颜色不同可分为紫皮蒜和白皮蒜两种。大蒜原产于意大利的西西里岛,约在两千多年前传入我国。大蒜不仅是极佳的调味食品,而且还有很好的药用功能。近年来,科学家研究证明,大蒜是一种健康食品,有助人体防病保健、延年益寿,是药食兼优的佳品,对人体具有多种药用价值。大蒜具有一种强烈的蒜臭气味,这种特殊的气味由许多复杂的硫化物组成。这类有机硫化物可促进消化,健胃整肠,强化抗菌作用,消肿止痛,改善机体机能的功能,大蒜中还含有乙烷硫代磺酸乙酯和二烯丙基三硫化物等,能阻断强烈致癌物质亚硝胺类在胃部的形成和积累,可预防胃癌、食道癌、肝癌、鼻咽癌的发生。本试验采用"同时蒸馏-萃取方法"(simultaneousdistillationandextraction,SDE)提取白皮和紫皮大蒜的挥发性成分,经GC-MS分析,确定了化合物的化学组成和相对百分含量。     

Solid-phase Microextraction of Volatile Polar Compounds in Water

A method was developed for the analysis of volatile polar compounds in a water matrix using open cap vials Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC). Both SPME techniques – direct sampling and headspace – were tested. Optimization of experimental conditions – exposure time, desorption time, with headspace SPME in addition the influence of the temperature and ionic strength of the sample solution on compound sorption, and finally GC response – were investigated. The analytes were extracted by directly immersing the 85 μm polyacrylate fiber in the aqueous sample or in the headspace. The linear range of the preconcentration process and the precision were examined. The amount of polar analytes sorbed on the fiber was determined and was found to be concentration dependent; it amounted to 0.014–0.64% in the concentration range of 0.00425–425 ppm studied in aqueous solution for direct sampling SPME and to 0.011–2.76% for solutions of concentration 0.0425–255 ppm for headspace SPME. The limits of determination were ascertained. Headspace SPME was applied to the analysis of real-life samples.     

固相微萃取-气相色谱/质谱分析栀子花的头香成分

 分别用固相微萃取和动态顶空法分离栀子鲜花的头香成分,用GC/MS技术分析鉴定,并用GC/MS总离子流色谱峰的峰面积进行归一化定量。在固相微萃取方法中,共鉴定了54种化学成分,占总峰面积的99.98%。主要成分(质量分数)依次为金合欢烯（64.86%）、罗勒烯（29.33%）、芳樟醇（2.74%）、惕各酸顺式叶醇酯（1.34%）和苯甲酸甲酯（0.25%）等。经与动态顶空法的分析结果比较发现,固相微萃取法不仅操作简便,而且具有较高的采样灵敏度,获得的化学成分的信息量多于动态顶空法。     

Computational study of the thermal decomposition and the thermochemistry of allyl ethers and allyl sulfides

In spite of the several experimental and computational studies on the thermal decomposition of allyl ethers and allyl sulfides, there are still disagreements on aspects of the reaction mechanism, such as the true nature of the transition states and the grade of synchronicity of the reactions. This work presents a computational study of the gas-phase thermolysis reaction of allyl ethers and allyl sulfides substituted at α-carbon, at the M05-2X/6-31+G(d,p) level of theory and a temperature range from 586.15 to 673.15 K. The substituent groups were methyl, ethyl, n-propyl, i-propyl, allyl, benzyl and acetonyl. It was found that the sulfides react faster than the homologous ethers and that the substituent groups with the capacity of delocalize charge increase the reaction rate. Through natural bond orbital calculations, the transition states were characterized. The synchronicities and atomic charges of the studied reactions were determined. A computational study at the G3 level of theory on the thermochemistry of allyl ethers and sulfides was also carried out.     

Iridium-catalyzed carbonyl allylation by allyl ethers with tin(II) chloride

3-Alkoxypropenes, namely allyl ethers such as allyl butyl ether, allyl 2-hydroxypropyl ether, and diallyl ether, serve as reagents for the allylation of aldehydes with tin(II) chloride in the presence of a catalytic amount of [IrCl(cod)]₂ in THF and H₂O at 50 °C to produce the corresponding homoallylic alcohols.