UE/ME-GC-MS提取分析普洱茶的挥发和半挥发性成分

采用超声波提取（UE）和微波萃取（ME）两种前处理方法提取普洱茶的挥发性成分,利用气相色谱-质谱（GC-MS）联用仪进行定性检测,并加入乙酸苯乙酯作为内标进行定量分析。结果表明：两种萃取方法共鉴定出挥发性成分88种,其中超声波萃取检测出79种,微波萃取检测出69种。普洱茶的主要挥发性成分有11,14,17-二十三碳烯酸甲酯、咖啡因、棕榈酸、维生素E、β-香树脂醇、植醇等。超声波萃取法得到的提取率较高,而微波提取法耗时较短,两者各有所长,应根据需要来选择。     

烟草中挥发性、半挥发性酸性成分的分析

烟草中富含有机酸,其中挥发性、半挥发性酸的种类和含量对烟草品质有较大影响。挥发酸含量适宜时,烟气吸味醇和,香气浓郁,清爽润喉,但含量高时,刺激性较大[1]。分析研究烟草中挥发性、半挥发性酸的种类和含量[2,2]对了解各种烟草内在质量有重要意义,对制定卷烟配方有重要指导意义。本文在同时蒸馏萃取处理后,采用选择离子检测(SIM)法对烟草中主要酸性成分进行定量分析,该法可有效排除干扰,并使灵敏度提高1～2个数量级[4],并用标准样品作了回收率试验。该法适合分析烟草中含18(及以下)个碳的一元酸,回收率在80%以上,相对偏差小于2%,线…     

固相微萃取结合气-质联用分析麻椒挥发性成分

以四川广元产的麻椒为原料,利用固相微萃取技术对麻椒中的挥发性成分进行提取,分别用装有HP-5ms和HP-INNOWAXms两种色谱柱的GC-MS进行分离与鉴定;采用质谱与保留指数进行定性,共鉴定出99种成分,其中烯烃类58种、醛类15种、醇类9种、酯类7种、酮类3种、其他烃类4种、其他化合物3种。采用面积归一化法确定了它们相对含量,含量较高的有芳樟醇、D-柠檬烯、β-崖柏烯、β-水芹烯、β-月桂烯、β-蒎烯、(-)-右旋吉玛烯、石竹烯、γ-萜品烯、3-崖柏烯、(Z)-β-罗勒烯、(1R)-(+)-α-蒎烯、(+)-3-蒈烯、(Z,Z,Z)-1,5,9,9四甲基-1,4,7环-十一碳三烯、萜品油烯。从鉴定出的挥发性成分的香气特征可知,烯烃类、醇类和醛类对麻椒的香气贡献较大。     

Comprehensive two-dimensional gas chromatography of volatile and semi-volatile components using a diaphragm valve-based instrument

A high-temperature configuration for a diaphragm valve-based gas chromatography (GCXGC) instrument is demonstrated. GCxGC is a powerful instrumental tool often used to analyze complex mixtures. Previously, the temperature limitations of valve-based GCxGC instruments were set by the maximum operating temperature of the valve, typically 175 degrees C. Thus, valve-based GCxGC was constrained to the analysis of mainly volatile components; however, many complex mixtures contain semi-volatile components as well. A new configuration is described that extends the working temperature range of diaphragm valve-based GCxGC instruments to significantly higher temperatures, so both volatile and semi-volatile compounds can be readily separated. In the current investigation, separations at temperatures up to 250 degrees C are demonstrated. This new design features both chromatographic columns in the same oven with the valve interfacing the two columns mounted in the side of the oven wall so the valve is both partially inside as well as outside the oven. The diaphragm and the sample ports in the valve are located inside the oven while the temperature-restrictive portion of the valve (containing the O-rings) is outside the oven. Temperature measurements on the surface of the valve indicate that even after a sustained oven temperature of 240 degrees C, the portions of the valve directly involved with the sampling from the first column to the second column track the oven temperature to within 1.2% while the portions of the valve that are temperature-restrictive remain well below the maximum temperature of 175 degrees C. A 26-component mixture of alkanes, ketones, and alcohols whose boiling points range from 65 degrees C (n-hexane) to 270 degrees C (n-pentadecane) is used to test the new design. Peak shapes along the first column axis suggest that sample condensation or carry-over in the valve is not a problem. Chemometric data analysis is performed to demonstrate that the resulting data have a bilinear structure. After over 6 months of use and temperature conditions up to 265 degrees C, no deterioration of the valve or its performance has been observed.     

柠檬果茶中游离态和键合态挥发性成分分析

以柠檬果茶为研究对象,建立了顶空固相微萃取前处理结合气相色谱质谱联用技术测定其中挥发性化合物的分析方法。采用开水冲泡对样品进行提取,通过Amberlite XAD-2大孔吸附树脂对柠檬果茶中的糖苷类挥发性组分键合,分离游离态和键合态化合物,甲醇溶剂作为洗脱剂对键合态化合物进行洗脱,Almondsβ-D-葡萄糖苷酶对其酶解。使用气质联用对样品中游离态和键合态挥发性成分进行检测,其结果根据数据库匹配和对比文献保留时间定性,内标法进行定量。结果表明,柠檬果茶中含有游离态物质24种,键合态物质16种,主要为(+)-柠檬烯、1-辛醇、橙花醇、(-)-4-萜品醇、alpha-松油醇等。方法为花果茶干燥工艺提供参考。     

A model p-T diagram for a ternary system with two semi-volatile and one highly volatile components

A model p-T diagram for a three-component system composed of two semi-volatile and one highly volatile components is developed. The phase equilibria and phase transitions are analyzed over a wide range of variable parameters. Isobaric T-x-y diagrams typical of real metal and salt systems with isothermal and polythermal sections are considered.     

Characterization of volatile components of tea flowers (Camellia sinensis) growing in Kangra by GC/MS

Volatile flavour components of tea flowers (Camellia sinensis) were isolated by two methods viz. simultaneous distillation extraction (SDE), supercritical fluid extraction (SFE), analyzed by GC and GC/MS and compared with headspace analysis (HS). The composition of the volatile components extracted by the three methods differed considerably. In SFE, phenylethanol (14.7%), linalool (7.9%), (E)-linalool oxide furanoid (3.5%), epoxy linalool (1.6%), geraniol (2.3%) and hotrienol (1.5%) were major components. m-Xylene (2.6%), (E)-linalool oxide pyranoid (5.4%), p-myrcene (5.2%), alpha-cadinol (4.3%) and methyl palmitate (2.9%) were major compounds isolated by SDE. 3-hexenol (2.1%) (E)-4,8-dimethyl-1,3,7-nonatriene (20.9%) and linalool (35.1%) are major components in headspace analysis. Acetophenone and pheromone germacrene D is detected in tea flowers by all the methods studied. Floral, fresh and fruity odour of tea flowers is retained by SFE as there is very little loss of heat sensitive volatiles in SFE. The flavour isolated from SFE has superior quality compared to SDE.     

An electrospray membrane probe for the analysis of volatile and semi-volatile organic compounds in water

A new membrane probe incorporating electrospray ionization (ESI) was designed, built and coupled to an ion trap mass spectrometer to detect low levels of semi-volatile organic compounds (SVOCs) in water. Similar to other membrane introduction mass spectrometry (MIMS) systems, the probe contains a capillary polydimethylsiloxane (PDMS) membrane to allow for the preferential permeation of small molecules but, in contrast, the interface uses a liquid/membrane/liquid interface rather than liquid/membrane/gas. The ESI source allows the probe to be operated at atmospheric pressure in positive or negative ionization mode and the lack of fragmentation in ESI allows for the simultaneous screening of many analytes with high sensitivity. The interface allows for the addition of additives to both the external and the internal liquid mobile phases to selectively improve permeation and/or the ionization efficiency of various classes of compounds. Characterization of the probe with methanol as the internal mobile phase showed that the signal for aniline optimized at 60 degrees C and an internal flow rate between 2-5 microL/min. The transfer of analyte through the membrane from water to methanol ensures a strong signal and robust electrospray for both positive and negative ion mode which is not typical when spraying pure water. Detection limits for aniline, pyridine and pentachlorophenol, and for the herbicides alachlor, atrazine, butachlor, metolachlor and simazine, were in the ppb to pptr range.     

A universal temperature controlled membrane interface for the analysis of volatile and semi-volatile organic compounds

A universal temperature controlled membrane interface (TCMI) has been constructed for hollow-fibre membranes. The membrane temperature is controllable in the range -70 to 250 degrees C using an electric heater and a flow of cooled nitrogen or helium gas. Volatile and semi-volatile organic compounds may be detected either by continuous diffusion across the membrane or by in-membrane pre-concentration followed by thermal desorption into the detector. The TCMI interface is demonstrated in combination with mass spectrometry and GC-MS, for the determination of VOCs and SVOCs in aqueous and air samples and for the on-line monitoring of a bioreactor.     

Time-weighted average sampling of volatile and semi-volatile airborne organic compounds by the solid-phase microextraction device

The ultimate goal of the chemist is to perform sample preparation, and analysis, if possible at the place where a sample is located rather than moving the sample to laboratory, as is common practice in many cases at the present time. This approach eliminates errors and time associated with sample transport and storage and therefore it would result in more accurate, precise and faster analytical data. In addition to portability, two other important features of ideal field sample preparation technique are elimination of solvent use and integration with a sampling step. A method is developed which addresses these requirements for the determination of time-weighted average concentration of gas phase compounds using a solid-phase microextraction device. Quantification of target analytes in air using this method can be carried out without external calibration. The volatile and semi-volatile organic compounds in air diffuse into the fiber coating which is retracted a known distance into its needle housing during the sampling period. The coatings used are poly(dimethylsiloxane) and poly(dimethylsiloxane)-divinylbenzene. The sampling rate at which gas phase analytes load onto the fiber is determined for a wide range of hydrocarbons. There is a good agreement between the theoretical and experimental sampling rates. Sampling time ranges from 1 min to 24 h depending on the coating used and its retraction distance. Effect of the flow-rate on the uptake rate by the fiber is studied. The method is tested in the field and compared with National Institute of Occupational Health and Safety Method 1550. Good agreement between the results is obtained.     

Simultaneous determination of non-volatile, semi-volatile, and volatile organic acids in tobacco by SIM-Scan mode GC-MS

A method for simultaneous determination of seven nonvolatile organic acids (NVOAs), five semivolatile organic acids (SVOAs), and twelve volatile organic acids (VOAs) in tobacco by synchronous SIM (Selected Ion Monitoring)-scan mode GC-MS was developed. The collection of NVOAs and SVOAs data was performed in full-scan mode, and that of VOAs data was carried out with SIM. Recoveries of NVOAs and SVOAs varied from 90.0 to 103.0%, and RSDs were less than 4.0%; recoveries of VOAs ranged from 89.5 to 99.3%, and their RSDs were less than 3.0%. Twelve tobacco samples were analyzed by the described method, and the results show that the method is applicable for the simultaneous determination of VOAs, NVOAs, and SVOAs in tobacco.     

Trace level analysis of volatile and semi-volatile organic compounds in water using a membrane/jet separator interfaced to an ion trap mass spectrometer

An ion trap mass spectrometer, equipped with a membrane/jet separator interface, is used for the direct detection of volatile and semi-volatile organic compounds in aqueous solutions. Aqueous sample is passed through a capillary membrane, the outside surface of which is continuously purged by helium. The permeate is pneumatically transported to the mass spectrometer via a jet separator which acts as an additional enrichment device. The performance and response characteristics of non-porous silicone and microporous polytetrafluoroethylene (PTFE) membranes are studied. The microporous membrane allows sufficient water to pass for it to be used as a reagent gas for chemical ionization. Both types of membranes provide detection limits in the parts per trillion (pptr) to parts per billion (ppb) range with a linear dynamic range of 3 orders of magnitude for some volatile organic compounds. Results show that there is no detectable matrix effect on response in the selected cases examined. The use of microporous membranes to analyze more polar compounds, such as 5-hydroxymethyl furfuraldehyde and lactic acid, is also demonstrated. The effects of other experimental parameters, such as membrane temperature and length, on sensitivity are also investigated.     

顶空气相色谱质谱法分析避蚊贴中挥发性成分

采用顶空-气相色谱-质谱联用技术分析鉴定了4种避蚊贴中的挥发性物质.样品经90℃、45 min顶空后,采用GC-MS进行定性分析.用面积归一化法得出各组分的相对含量.结果表明:经NIST质谱数据库检索和文献对照,样品Ⅰ、Ⅱ、Ⅲ和Ⅳ分别检出并确定了33、39、39和24种成分.样品Ⅰ、Ⅱ、Ⅲ和Ⅳ主要成分分别为桉树醇(相对...     

用电子鼻研究不同烘丝过程对卷烟挥发性成分的影响

采用电子鼻对卷烟烟丝挥发性组分进行分析,分别考察了前处理制样与电子鼻顶空平衡时间对结果的影响。确定采用三包卷烟的烟丝作为大样本,混合均匀后称取适量样品直接电子鼻分析,电子鼻顶空平衡温度为55℃。应用电子鼻在该参数下对不同烘丝方式和温度参数处理的卷烟烟丝挥发性成分进行气味指纹图谱和PCA分析,同连续流动法测定的常规化学成分结果作了比较,结果表明电子鼻能够反映规常规化学成分检测手段不能区分的不同烘丝过程带来的挥发性组分改变。     

Simultaneous determination of volatile and semi-volatile aromatic hydrocarbons in virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry

A reliable, simple and relatively fast method for the simultaneous determination of volatile and semi-volatile aromatic hydrocarbons in virgin olive oil was developed, based on headspace solid-phase microextraction (HS-SPME). The investigation regarded eco-contaminants such as alkylated monoaromatic hydrocarbons from C1- to C4-benzenes and light polyaromatic hydrocarbons up to four aromatic rings. Sampling and chromatographic conditions were optimized by using standard solutions in deodorized olive oil and the analytical performances of the method were determined. The proposed method was then applied to real samples of virgin olive oil were the target hydrocarbons could be identified and quantified. Several of them had not been previously quantified in virgin olive oil. Moreover, by the analysis of olive oil samples an additional number of C4-benzenes could be tentatively identified.     

Mechanisms effecting analysis of volatile flavour components by solid-phase microextraction and gas chromatography.

Quantitative properties of solid-phase microextraction (SPME) have been studied in order to investigate a simple and reliable method for analysing volatile flavour components in strawberries. Monitoring the chemical composition profile of berries will be of interest for the producers in order to optimise growth and storage conditions. By the use of SPME and capillary gas chromatography selected standard components were quantified with accuracy within +/-7% and a linear response were found in all concentration ranges studied, covering three orders of magnitude. Equilibrium constants that describe how various components are distributed between the three phases present, sample, headspace and fibre coating were determined. In the system studied, the majority of analytes remained in the sample. This means that repeated analysis can be performed from a single sample without significantly changing the results. The mass transfers of the flavour components, from the sample and into the fibre, were fitted to a transport model assuming that the rate-controlling step is diffusion within the fibre. The experimental results agreed well with the model for most of the components studied. The response for three of the components (geraniol, linalool and trans-2-hexenyl butanoate) did not agree with the model. These components were present in the gas phase in only minute amounts explaining the deviation from the model. Such components will require a long absorption time (longer than 30 min). For quantitative analysis, it is important to use a very precise pre-determined absorption period and well defined sampling conditions. Internal standards can be omitted.     

Optimized method avoiding solvent-induced response enhancement in the analysis of volatile and semi-volatile polyfluorinated alkylated compounds using gas chromatography-mass spectrometry

A method for the analysis of airborne (semi-)volatile polyfluorinated alkyl substances (PFASs) was optimized to avoid solvent-induced response enhancements as observed using ethyl acetate as extraction solvent (recoveries up to 300%, likely due to acetic acid as impurity). Of nine solvents tested, only the use of acetone, dichloromethane, methyl tert-butyl ether, and acetone:petroleum ether (1:1, v/v) resulted in recoveries below 100% and acetone:methyl tert-butyl ether (1:1, v/v) was chosen as suited extraction solvent. An appropriate GC capillary column and the application of mass-labelled internal standards appeared to be essential for these analyses. Instrumental limits of detection of <0.2 pg (dimethylperfluoroocatanesulfonamide, ethyl-[(2)H(5)]perfluorooctanesulfonamide, methyl-[(2)H(3)]perfluorooctanesulfonamide) to 8.2 pg (perfluorooctanesulfonamide) and LOQ of 0.4 pg (dimethylperfluoroocatanesulfonamide, ethyl-[(2)H(5)]perfluorooctanesulfonamide, methyl-[(2)H(3)]perfluorooctanesulfonamide) to 16.4 pg (perfluorooctanesulfonamide) were determined.     

Comparative analysis of volatile components from Clematis species growing in China

The volatile components between stems and roots and also among five Clematis species from China were studied and analyzed by gas chromatography-mass spectrometry (GC-MS) combined with alternative moving window factor analysis (AMWFA), a new chemometric resolution method. Identification of the compounds was also assisted by comparison of temperature-programmed retention indices (PTRIs) on HP-5MS with authentic samples included in our own laboratory database under construction. A total of 153 different compounds accounting for 86.6-96.5% were identified and significant qualitative and quantitative differences were observed among the samples. The major volatile components in different essential oils from Clematis species were n-hexadecanoic acid and (Z,Z)-9,12-octadecadienoic acid. Our work further demonstrated chemometric resolution techniques upon the two-dimensional data and PTRIs can provide a complementary and convenient method for fast and accurate analysis of complex essential oils.     

干黄芪中挥发性成分的提取与分析

为了确定干黄芪的特征香气成分,采用同时蒸馏萃取法对干黄芪中的挥发性成分进行提取,并考察了原料用量、浸泡时间和提取时间三个因素对结果的影响。在较优条件下对干黄芪中的挥发性成分进行提取,提取物通过GC-MS分析,结合计算保留指数和NIST11谱库检索,共鉴定出65种挥发性成分,其中包括醛类20种、醇类9种、烃类7种、酚类5种、酯类5种、杂环类5种、酮类4种、酸类2种、其他类8种。其中正己醛、2-戊基呋喃、丁香酚、正己醇、1-辛烯-3-醇、糠醛等挥发性成分对干黄芪的特征香气贡献较大。