顶空固相微萃取-气质联用分析小麦储藏过程中挥发性成分变化

采用顶空固相微萃取(HS-SPME)和气相色谱-质谱联用(GC-MS)对不同储藏时间弱(强)筋小麦中的挥发性物质进行提取、鉴定与分析.选用复合萃取纤维二乙烯基苯-炭烯-聚二甲硅氧烷共聚物(DVB/CAR/PDMS)50 μm涂层,对萃取温度、时间、样品用量和解析时间进行优化.结果表明: HS-SPME测定挥发性物质的最佳前处理条件样品量20 g, 萃取温度75 ℃, 萃取时间60 min, 260 ℃条件下解析5 min;经鉴定分析小麦挥发性成分主要有烃类、醛类,其次为醇类、酮类;挥发性成分总含量在储藏6个月内均呈现先降后增的趋势.弱筋小麦的烃类挥发物相对量随储藏时间延长而快速增加,醛类相对含量先降后升,而酮类和醇类相对含量则逐渐下降;强筋小麦中除烃类相对含量呈先下降而后快速增加外,其余各类挥发物含量均与弱筋小麦呈现相同的规律.储藏6个月后,变化较明显的挥发性物质有己醇、己醛、2,6,10-三甲基-十二烷、十五烷和二十烷.     

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。     

固相微萃取和气质联用分析测定土壤中13种挥发性芳香烃

建立了固相微萃取(SPME)-气相色谱质谱法(GC-MS)测定土壤中13种挥发性芳香烃的方法.用SPME萃取土壤中的挥发性芳香烃,利用安捷伦5977A气相色谱-质谱进行分离检测,选用土壤基质修改液提高了目标化合物的回收率.13种芳香烃组分在5.0、10、20、40、50μg/kg土壤中质量浓度范围内呈线性关系,相关系数r2大于0.995,方法检测限小于1.0μg/kg,完全满足检测要求.     

卷烟主流烟气总粒相物中氨基甲酸酯类农药的前处理研究

采用Envi-carb/NH2复合柱净化,GC/MS法检测,对提取条件、净化条件和检测条件充分优化后,建立了卷烟主流烟气总粒相物中4种氨基甲酸酯类农药(久效威、甲奈威、克百威和抗蚜威)含量的快速分析方法.该方法的线性范围为0.01～10.0mg/L,相关系数(R)大于0.996 6,日内、日间相对标准偏差(RSD)均小于6.97%,检测限(LOD)均为10μg/L,样品的加标回收率均大于90.20%～92.80%.方法用于卷烟主流烟气总粒相物中氨基甲酸酯类农药含量的测定,结果令人满意.     

顶空-固相微萃取-气相色谱-质谱法测定烟气中挥发性和半挥发性成分

提出了顶空-固相微萃取-气相色谱-质谱法测定烟气中挥发性和半挥发性成分。结合信息量最大的原则,确定了固相微萃取时萃取纤维头为碳分子筛/聚二甲基硅烷萃取纤维头,萃取温度为70℃,萃取时间为60min。在气相色谱分离中用Agilent DB-1色谱柱为固定相,在质谱分析中采用全扫描模式。结果表明:共鉴定出107种成分,含量最大的成分是烟碱(18.07%),其次是新植二烯(11.46%),主要的3类挥发性和半挥发性成分依次为苯系物、酮类以及杂环类。     

固相微萃取/气相色谱-质谱联用技术测定燕窝中挥发性成分

该文以印尼产的燕窝为材料,使用固相微萃取(SPME)技术萃取燕窝中挥发性成分并以气相色谱-质谱(GC-MS)联用仪进行测定。考察了萃取头类型、萃取温度、萃取时间和解吸时间对固相微萃取(SPME)在燕窝挥发性成分测定中的影响。结果表明:以65μm聚二甲基硅氧烷/二乙烯基苯(PDMS/DVB)萃取头、在60℃下萃取60 min,解吸2 min的条件下,SPME/GC-MS技术可检出燕窝中挥发性成分醇、烃、醛、酯、醚类等化合物共82种。该方法具有操作简便、快速、重复性好和灵敏度高的特点,适用于燕窝中挥发性成分的测定。     

顶空固相微萃取-气质联用技术分析5种荷花的挥发性成分

采用顶空固相微萃取-气相色谱质谱联用(HS-SPME-GC-MS)技术分析测定了5个品种荷花中的挥发性成分.考察了不同萃取头和萃取温度对荷花挥发性成分萃取的影响,选用65μm PDMS/DVB SPME萃取头和25℃室温萃取荷花中的挥发性成分得到较好的萃取效果.应用峰面积归一化法测定各挥发性成分的相对含量,5个品种共鉴...     

发酵香肠成熟前后挥发性成分的固相微萃取-GC-MS分析

采用固相微萃取—气相色谱—质谱联用分析技术对发酵香肠挥发性成分进行了定性分析和峰面积相对含量的测定：结果表明,发酵香肠在成熟前(发酵结束时)的主要挥发性风味物质的成分为乙酸、3—羟基—2—丁酮、2—丁酮、1—羟基—2—丙酮等;成熟香肠的风味成分主要为乙酸、3—羟基—2—丁酮、2—丁酮、酯类物质、挥发性酚、醛类以及少量的烯及含氮化合物等。发酵香肠的风味发育赋予了该产品典型的感官风格。     

固相微萃取-气相色谱-质谱分析牡丹花的挥发性成分

用固相微萃取装置（SPME）顶空提取牡丹花的挥发性成分,采用气相色谱-质谱（GC-MS）联用技术定性分析不同品种牡丹花的挥发性成分,归一法计算其相对百分含量,同时对SPME与水气蒸馏提取效果进行了比较。10个品种牡丹花共检出34种成分,其中多数是烷烃。不同品种牡丹花的成分与相对百分含量不同,少量的醇、酯、烯等成为其特有成分。     

卷烟主流烟气气相物和总粒相物中有机酸的分析研究

以二氯甲烷-甲醇为萃取溶剂,N,O-双(三甲基硅基)三氟乙酰胺(BSTFA)为硅烷化试剂,采用配备氢火焰离子化检测器(FID)的气相色谱仪分别对卷烟主流烟气中气相物和总粒相物中甲酸、乙酸、硬脂酸等21种有机酸进行了定量分析。对样品主流烟气中气相物前处理硅烷化条件及有机酸萃取条件进行了优化,并采用气相色谱法对卷烟主流烟气中气相物和总粒相物中有机酸的含量进行了定量分析。该方法用于实际样品中挥发性有机酸分析时,回收率为88.12%～98.63%,相对标准偏差(RSD)为1.51%～8.38%。     

SPE-LC/MS/MS快速测定卷烟丝中的烟草特有亚硝胺类化合物

建立了卷烟丝中烟草特有亚硝胺类化合物(TSNAs)的SPE-LC/MS/MS分析方法,可一次性对卷烟烟丝中4种TSNAs进行定量分析.该方法弥补了传统的烟丝中TSNAs分析方法样品处理步骤多,检出限高,适应范围窄等缺点.4种TSNA的回收率的范围在95.7%～99.2%之间;相对标准偏差均小于8%;方法检出限均低于1.0 ng/g.可应用于国内外各类型卷烟的分析.     

Screening direct analysis of PAHS in atmospheric particulate matter with SPME

A direct headspace SPME method with PDMS fiber was developed for the determination of polynuclear aromatic hydrocarbons (PAHs) in atmospheric particulate matter collected in HiVol filter. The recovery obtained for PAHs lower than four congeners with the proposed method falls in the range 50-125% and DL was around 5-20 pg. The results obtained with standard reference materials (SRM 1649 and SRM 1650) for determination of PAHs showed acceptable agreement with the declared or certificated values.     

液相色谱-毛细管气相色谱/质谱离线联用分析烟草中的挥发性及半挥发性成分

建立了一种用于烟草样品中挥发性、半挥发性成分分析的液相色谱-毛细管气相色谱/质谱(LC-CGC/MS)离线联用方法。研究了LC-CGC/MS的分离机理。LC分析选用氨基分析柱(250 mm×2.0 mm, 5 μm)作为分析柱,正己烷-二氯甲烷-乙腈(90:6.6:3.4, v/v/v)作为流动相,对挥发性、半挥发性成分进行分离,收集得到5个馏分,并存放在5个氮吹瓶中。多次进样并收集相同时间段的馏分,氮吹浓缩至1 mL,然后分别进行CGC/MS分析,所用的CGC柱为DB-5MS(60 m×0.25 mm×0.25 μm)。结果显示,与直接采用CGC/MS分析相比,采用LC-CGC/MS分析复杂样本的效果更好,定性的可靠性更高。     

应用近红外光谱技术分析烟丝总糖和还原糖的研究

应用傅立叶变换近红外漫反射光谱仪,对同一品牌通过选择不同批号代表性好的卷烟烟丝样品,建立了卷烟烟丝总糖和还原糖的近红外定量分析数学模型,并对不同批号的分析样品进行检验,近红外预测值的平均相对误差为1.01%和0.77%,接近实测值,说明近红外光谱分析技术可用于卷烟烟丝生产质量指标的检测.     

New method to determine the total carbonyl functional group content in extractable particulate organic matter by tandem mass spectrometry

A functional group analysis method was developed to determine the quantitative content of carbonyl functional groups in atmospheric particulate organic matter (POM) using constant neutral loss scanning-tandem mass spectrometry (CNLS-MS/MS). The neutral loss method consists in monitoring the loss of a neutral fragment produced by the fragmentation of a precursor ion in a collision cell. The only ions detected are the daughter ions resulting from the loss of the neutral fragment under study. Then, scanning the loss of a neutral fragment characteristic of a functional group enables the selective detection of the compounds bearing the chemical function under study within a complex mixture. The selective detection of carbonyl functional groups was achieved after derivatization with pentafluorophenylhydrazine (PFPH) by monitoring the neutral loss of C(6)F(5)N (181 amu), which was characteristic of a large panel of derivatized carbonyl compounds. The method was tested on 25 reference mixtures of different composition, all containing 24 carbonyl compounds at randomly determined concentrations. The repeatability and calibration tests were satisfying as they resulted in a relative standard deviation below 5% and a linear range between 0.01 and 0.65 mM with a calculated detection limit of 0.0035 mM. Also, the relative deviation induced by changing the composition of the mixture while keeping the total concentration of carbonyl functional groups constant was less than 20%. These reliability experiments demonstrate the high robustness of the developed procedure for accurate carbonyl functional group measurement, which was applied to atmospheric POM samples.     

A random forest of combined features in the classification of cut tobacco based on gas chromatography fingerprinting

We applied the random forest method to discriminate among different kinds of cut tobacco. To overcome the influence of the descending resolution caused by column pollution and the subsequent deterioration of column efficacy at different testing times, we constructed combined peaks by summing the peaks over a specific elution time interval Δt. On constructing tree classifiers, both the original peaks and the combined peaks were considered. A data set of 75 samples from three grades of the same tobacco brand was used to evaluate our method. Two parameters of the random forest were optimized using out-of-bag error, and the relationship between Δt and classification rate was investigated. Experiments show that partial least squares discriminant analysis was not suitable because of the overfitting, and the random forest with the combined features performed more accurately than Naïve Bayes, support vector machines, bootstrap aggregating and the random forest using only its original features.     

Trace analysis of alkaline flavors in cut tobacco by heart‐cutting multidimensional GC–GC–MS

Tobacco is a complex chemical matrix. The analysis of trace alkaline flavors in tobacco is very difficult because of the limited peak capacity of monodimensional GC. In the present study, a home‐assembled twin‐oven GC–GC–MS system, with MS detection in both dimensions, has been applied to the analysis of 20 alkaline volatiles in a variety of cut‐tobacco samples. By transferring nine and six heart‐cuts from the first apolar column to the second polar column in two separate runs, the potential mutual interference of adjacent isomeric targets and the complex matrix could be removed. For comparative purposes, a systematic comparison of both quantification and qualification results for the cut‐tobacco sample as quality control was conducted between GC–GC–MS and GC–MS. The results showed that GC–GC–MS provided higher accuracy in peak assignment and quantification. And in GC–MS, the interferences of co‐elution had caused both low matched similarity in peak assignment and false‐negative/‐positive results in quantification for some targets. Advantages of the developed GC–GC–MS method in the analysis of alkaline flavors are its high resolving power, reliability, and simplicity.     

Analysis of inorganic mercury species associated with airborne particulate matter/aerosols: method development

This paper describes a method for speciation of Hg associated with airborne particulate matter. This method uses a mini-sampler for sample collection and analysis, thermal desorption for separating Hg species, and inductively coupled plasma mass spectrometry (ICP–MS) for identification and quantification of Hg. Coal fly ash spiked with different Hg compounds (e.g. Hg⁰, HgCl₂, HgO, and HgS) was used for qualitative calibration. A standard reference material with a certified value for Hg concentration was used to evaluate the method. When the temperature of the furnace was programmed at a linear rate of increase of 50° min^–1, different Hg compounds could clearly be separated. Three airborne particulate matter samples were collected in parallel in Toronto, ON, Canada and analyzed using this method. Reproducible results were obtained and Hg⁰, HgCl₂, HgO, and HgS species from these samples were detected.     

Capillary electrophoresis determinative and GC-MS confirmatory method for water-soluble organic acids in airborne particulate matter and vehicle emission

Urban fine airborne particulate matter (PM2.5) and vehicle emission samples were studied for water-soluble low-molecular-weight carboxylic acids using CE with indirect UV detection. Further identification of these acids was achieved using GC-MS as their butyl esters (after derivatization with BF3/butanol). Several dicarboxylic acids in the range C2-C10 including straight-chain, branched-chain, cis- and trans-unsaturated, and aromatic acids were confirmed by GC-MS. In addition, aromatic acids such as benzoate, phthalate, terephthalate, isophthalate, and 4-methylphtalate were present in such samples, but some of these were not well resolved by the used CE method. Oxocarboxylic acids (Cn(w) with n > 4) were also identified by GC-MS but not determined by CE due to lack of standards. The rapidity and simplicity of the CE method were clearly demonstrated, and the method was observed to be advantageous for routine monitoring of water-soluble organic acids in airborne PM2.5 and vehicle emission at low microg/L levels.     

An international round-robin study for the analysis of particulate semi-volatile organics by thermal desorption gas chromatography mass spectrometry

Thermal desorption gas chromatography mass spectrometry (TD-GC/MS) is becoming more commonly used for the quantification and identification of organic compounds in particulate matter (PM), including ambient and source PM such as diesel particulate matter (DPM). It has been proven as an alternative to the traditional solvent extraction (SE) method and liquid injection gas chromatograph mass spectrometry (LI-GC/MS). However, little information is available on how different types of TD-GC/MS systems compare to each other for analysis of real-world PM samples or to direct LI-GC/MS for analysis of PM components in a test solution. To address this, CanmetENERGY Characterization Laboratory initiated a round robin with the participation of 10 laboratories worldwide. Three sample types were analysed: (i) a test solution with a suite of pure compounds commonly found in PM, analysed by TD-GC/MS and LI-GC/MS; (ii) a DPM sample, analysed by TD-GC/MS and SE; and (iii) an ambient PM sample, analysed by TD-GC/MS. The first part of the study showed good overall performance and comparability between the different TD-GC/MS systems and LI-GC/MS method for the analysis of PM components in a test solution, with some variability of results due to system types and parameters used, concentration of calibration standards, and whether or not an internal standards was used. The analysis of the DPM sample showed greater variability between laboratories and methods as many PM components were present near the detection limit and matrix effects particularly affected the TD-GC/MS analysis of heavier n-alkanes. In the last part of the study, for the analysis of an ambient PM sample by TD-GC/MS, the analysis of variance showed good comparison between labs for polycyclic aromatic hydrocarbons (94% non-significant), but slightly lower for n-alkanes (68%) and biomarkers (57%).