稳定性同位素内标-吹扫捕集-气相色谱-质谱联用分析水中硫化物

建立稳定性同位素内标-吹扫捕集-气相色谱-质谱联用法(GC-MS)分析多种水体中硫化物,为预警异味水质突发事件和开展相关研究奠定基础。水样脱氯过滤后,加入同位素内标与氯化钠,吹扫捕集装置40℃氮气吹扫10 min,200℃脱附2 min,吹扫流量40 mL/min。色谱柱:DB-624,进样口温度270℃,分流比20∶1,载气高纯He,流速3.8 mL/min。升温条件:35℃(5 min),6℃/min升至120℃,20℃/min升至210℃。传输线(AUX)温度为280℃。质谱条件:离子源温度230℃,四极杆温度150℃,电子能量70 eV。以保留时间和质谱全扫描方式进行定性分析,质量范围m/z 45~450;选择离子监测定量;基质加标验证方法的准确度与精密度。乙硫醇、二甲基硫和二甲基二硫在0.6~21.3μg/L范围内线性良好。ET,DMS和DMDS的检出限分别为0.088,0.13和0.10μg/L。5种水体高、低浓度加标,回收率为90.7%~118.0%,RSD为2.7%~9.8%。本方法采用稳定同位素内标法,具有较好的准确性、稳定性和实用性,可用于地表水、地下水和生活饮用水等多种水体中含硫嗅味物质的分析。     

吹扫捕集-气相色谱/质谱联用测定土壤中挥发性石油烃

建立了吹扫捕集-气相色谱/质谱联用测定土壤中挥发性石油烃的分析方法。实验优选出了NaHSO_4作为样品的保存试剂,优化了吹扫-捕集条件和气相色谱质谱条件;GC条件:色谱柱60 m×0.32 mm×1.8μm RTX-502.2,进样口温度190℃,分流比20:1,程序升温;MS条件:EI源,离子源温度200℃,接口温度220℃,扫描范围40~350 amu/s。方法的线性范围为0.20~300 ng/g,相关系数均在0.995以上,检出限为0.03~0.38 ng/g。方法标准添加样品回收率为90.3%~108%;RSD为1.8%~8.8%。该方法适合于土壤样品中挥发性石油烃的分析检测。     

吹扫捕集-原子荧光光谱与同位素稀释质谱法结合测定海水中痕量汞

建立了吹扫捕集-原子荧光光谱,结合同位素稀释质谱法测定海水中痕量汞的高准确度的分析方法,以HNO_3消解样品,通过吹扫捕集、金柱吸附的方式实现痕量汞与高盐基体的分离并进一步富集,与电感耦合等离子体质谱联用,采用同位素稀释质谱法进行准确测定。对影响样品准确测定结果的消解用HNO_3体积、消解时间、SnCl_2用量、基体影响、本底控制等因素进行了选择和优化。吹扫捕集-同位素稀释质谱法的检出限为3.7 pg/g。在优化的条件下,分别对国际比对海水样品和采自渤海、舟山岛附近海水中的总汞含量进行了6次测定,国际比对样品海水测定结果的相对标准偏差为4.11%。在30 pg/g和50 pg/g加标水平上,海水样品的加标回收率分别为98.1%和104%。以国际比对海水样品测定为例进行了不确定度评定,测定结果的扩展不确定度5%(k=2),为常规海水和国际比对、海水标准物质等样品中痕量汞的高准确度测定提供了有力的技术手段。     

常温吹扫捕集-气相色谱法测定海水中氧化亚氮

建立了海水中氧化亚氮的常温吹扫捕集-气相色谱检测方法。对吹扫捕集系统的条件进行了考察,优化结果如下:捕集温度30℃,脱附温度250℃,吹扫时间10min,吹扫气流速20mL/min。等实验条件进行了优化。本方法操作简单、灵敏、重现;检出限达2.8×10-10mol/L,标准工作曲线的线性相关系数大于0.9995(n=5);曲线斜率的相对标准偏差为2.8%(n=5);回收率为93.93%±3.1%(n=5)。用此方法测定了厦门近海表层海水样品中氧化亚氮的浓度。     

银离子固相萃取-程序升温大体积进样-气相色谱法定量分析市售巧克力中的饱和烷烃矿物油

建立了银渍硅胶固相萃取柱离线(Ag-SPE)净化,程序升温进样-气相色谱-氢火焰离子化检测器(PTV-GC-FID)定量分析巧克力中饱和烷烃矿物油(MOSH)的方法.以正己烷浸泡提取巧克力中的MOSH,离心后取1 mL上清液,过0.3％ Ag渍硅胶SPE柱净化,氮吹浓缩,定容至0.2 mL,注入GC分析; GC的进样口程序升温过程:初始温度45℃,保持1 min(分流比200∶1),以250℃/min升温至360℃(分流阀关闭2 min),并保持27 min(分流比100∶1); 进样量40 μL; 柱温箱升温程序为:35℃保持3 min,以25℃/min升温至350℃,以5℃/min升温至370℃,保持10 min,载气为高纯氮气,流速1.3 mL/min(压力60 kPa); FID温度为380℃.结果表明,本方法的MOSH定量限为0.5 mg/kg,加标回收率为84.9％～108.6％,相对标准偏差(RSD)为0.2％～1.5％.运用本方法对25个市售巧克力样品中的MOSH含量进行了测定,3个样品未检出,其余22个样品中MOSH含量为1.09～8.15 mg/kg(其中C16～C35 的含量为0.56～4.43 mg/kg),有3个样品含量高于5.00 mg/kg,为严重污染样品.本方法操作简便,检出限低,适用于巧克力中MOSH的定量测定.     

吹扫捕集-气相色谱-质谱法测定土壤和地下水中四氢呋喃

建立吹扫捕集-气相色谱-质谱法测定土壤和地下水中四氢呋喃。最佳的吹扫捕集条件:吹扫温度为40℃,吹扫时间为15 min,脱附温度为250℃,脱附时间为2 min。四氢呋喃的质量浓度在10～200μg/L范围内与色谱峰面积线性关系良好,相关系数不小于0.990。土壤和地下水中四氢呋喃的检出限分别为1.5、1.4μg/L,标准样品平均加标回收率分别为84.5%、77.2%,测定结果的相对标准偏差分别为3.3%、5.8%(n=6)。该方法适用于土壤和地下水中四氢呋喃含量的检测。     

吹扫捕集-气相色谱-质谱法测定水和土壤中的甲基叔丁基醚含量

提出了测定水和土壤中甲基叔丁基醚(MTBE)的吹扫捕集-气相色谱-质谱法。水和土壤样品按相关标准采集后于25℃保存,吹扫捕集参数选定如下:1吹扫时间为11min;2脱附时间和温度分别为190℃,2min。经气相色谱分离后采用电子轰击离子源和选择离子扫描模式进行质谱分析。在水和土壤样品中MTBE的质量浓度在一定范围内与其峰面积呈线性关系,MTBE在上述2种样品中的检出限(3S/N)分别为0.10μg·L~(-1),0.26μg·kg~(-1)。按标准加入法进行回收试验,测得回收率在87.6%~103%之间,测定值的相对标准偏差(n=5)在2.3%~7.2%之间。     

气相色谱法测定茄尼醇中有机溶剂残留量

建立了测定茄尼醇中甲醇、正已烷、乙腈残留量的气相色谱法.样品和对照品均以异丙醇为溶剂,四氢呋喃为内标物. 色谱柱HP-5MS石英毛细管柱(5%苯基硅氧烷-95%甲基聚硅氧烷,30 m×0.25 mm×0.25 μm);检测器FID. 程序升温方式:初温80 ℃,保持5 min,以8 ℃/min升温至120 ℃,保持10 min;汽化室温度200 ℃;进样口温度250 ℃;高纯N2气为载气,流速2.0 mL/min;进样量2 μL.     

热解吸-气相色谱法测定植物源挥发性有机物

以Tenax-TA、Carboxen 1000和Carbosieve SⅢ为采样管填充料,将植物源挥发性有机物吸附于采样管内,样品通过二次热解吸仪解吸后,随载气进入气相色谱仪,采用氢火焰离子化检测器(FID)测定,建立了利用二次热解吸仪与气相色谱联用技术测定植物挥发性有机物的分析方法。载气N2流速为30 mL/min,60℃下吹扫吸附管2 min,然后在250℃下解吸吸附管5 min,冷却1 min后,在275℃下解吸聚焦管3 min,样品经传输线进入气相色谱。气相色谱载气N2压力为190 kPa,FID检测器温度280℃;进样口温度225℃;初始柱温40℃,停留5 min,以2℃/min升温至120℃,保留1 min,然后以20℃/min升温至200℃,保留10 min。方法重现性好,精密度高,线性相关系数大于0.99;检出限均低于9×10-9g/L;解吸效率大于96%,适用于植物源挥发性有机物的测定。     

吹扫捕集/气相色谱-质谱联用测定水中挥发性有机物

随着生态环境的变化和工业的发展,有毒有害化学品正在威胁着人们的饮水安全。我国对饮用水中有机污染物的监测正在逐步重视和加强,一些研究表明饮用水中挥发性有机物种类较多,含量较高[1,2]。因此,笔者对吹扫捕集/气相色谱-质谱联用测定水中挥发性有机物的方法进行了验证,并对9种饮用水中挥发性有机物的净化效果进行了研究。1实验部分1.1主要仪器与样品气相色谱-质谱联用仪:6890-5973型,美国Agilent公司;吹扫捕集仪:Tekmar3100型,美国Tekmar公司;自来水(编号1),开水(编号2),两种市售瓶装纯净水(编号3、4),某净化器净化后热,冷水(编号5、6),矿物质水(编号7),市售桶装纯净水(编号8),地下饮用水(编号9)。1.2分析条件[1,3]毛细管色谱柱:HP-5型(30m×0.32mm,0.25μm);升温程序:柱温120℃,保持3min,以20℃/min升至160℃,保持2min,再以20℃/min升至200℃,保持1min;载气:氦气,纯度大于99.999%,恒流控制1.0mL/min;分流进样,分流比为10∶1。进样口温度:200℃;传输线温度:280℃;四级杆温度:150℃。扫描范围...     

顶空-气相色谱-飞行时间质谱鉴定分析饮用水中的异味成分

使用顶空-气相色谱-飞行时间质谱结合差异化分析软件鉴定分析出了饮用水中的异味物质。质谱数据通过逐级筛查，降低化合物数量，通过T检验和倍数变化统计分析查找差异显著的化合物，利用结构解析确定异味成分为乙醛。通过正交试验优化了加热时间、加热温度、样品量和加盐量等因素。检出限和定量限分别为0.0033和0.010 mg/L，线性范围为0.010~0.500 mg/L，相关系数R²=0.997。对实际样品进行了检测，分析了产生异味的原因，并对相应的生产加工工艺提出了合理化建议。该方法简便、快速、灵敏，适用于鉴定分析饮用水中的异味成分。     

Development of taint and odour in cellulosic carton-board packaging systems

Unsaturated lipids exist in carton-board used for food packaging and can be the precursors of odorous compounds. The linoleic acid component may be in the form of a free acid, an alkyl ester derivative or a triglyceride. Oxidation proceeds via a free radical route to produce aldehydes, ketones, alcohols, furans, lower fatty acids, alkenes and alkanes, the majority of which are odorous. The aldehydes, in particular, have very low odour and taste detection thresholds, needing to be present only in very small amounts in a packaging material to cause a taint problem. Static headspace GC/MS analyses have identified a number of odorous compounds formed from the oxidation reactions. These oxidation reactions are affected to various extents by a number of factors that include temperature and the presence of photosensitising agents. Ultra-violet (UV) curable inks are commonly used in the printing of cellulosic carton-board packaging materials. These inks contain photoinitiators that have the potential to affect the rate and the extent of oxidation of unsaturated lipids, resulting in the formation of odorous compounds within the cellulosic carton-board matrix.     

Determination of odorous mixed chloro-bromoanisoles in water by solid-phase micro-extraction and gas chromatography-mass detection

A headspace-solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) method has been proposed for the simultaneous determination of odorous trihalogenated anisoles in water. Parameters affecting efficiency of HS-SPME procedure, such as the selection of the SPME coating, extraction time, temperature and ionic strength were optimized. The commercially available polydimethylsiloxane (PDMS 100 microm) fiber appears to be the most suitable for the simultaneous determination of these compounds. Run-to-run precision with relative standard deviations (R.S.D.s) between 5 and 15% were obtained for most of the compounds except for 2,5-dicloro-6-bromo-anisole, 2,3-dibromo-6-chloroanisole, pentachloro- and pentabromoanisole (>20%). The method was linear over two orders of magnitude, and detection limits were compound dependent and ranged from 0.03 ng/L for 2,4,6-trichloroanisole to 0.25 ng/L for 2,3-dibromo-6-chloroanisole. The HS-SPME-GC-MS procedure was tested using real samples and relatively good standard deviations were obtained when using p-iodoanisole as internal standard for quantification. This is the first time that the individual identification of odorous trihalogenated chloro-bromoanisoles has been reported, being HS-SPME-GC-MS a suitable method for simultaneous determination of these compounds in water at concentration levels below their odor limit of detection.     

Simultaneous determination of odorous volatile organic compounds with gas chromatography and a thermal desorber: A case study on methyl ethyl ketone, methyl isobutyl ketone, butyl acetate, toluene, and xylene

In this study, a series of experiments were conducted to examine the feasibility of the gas chromatographic approach for the quantification of several odorous volatile organic compounds (VOCs) in environmental samples which included methyl ethyl ketone, isobutyl alcohol, methyl isobutyl ketone, and butyl acetate plus benzene, toluene, and xylene (namely, BTX). The gaseous working standards (WS) of seven compounds were initially calibrated at varying concentration ranges by direct injection (DI) into GC injector. The detection properties of these compounds were then tested with a thermal desorber (TD). The relative sensitivities of three aromatic VOCs differed greatly between DI and TD methods. In contrast, four polar VOCs tend to consistently exhibit relative enhancement in response factors with increasing molecular mass (an exception of butyl acetate), regardless of method. The TD-based analysis was reliable enough to detect all target VOCs below their odor threshold values with their detection limit (DL) values. This TD method, when tested against a number of environmental samples collected from several industrial facilities, confirmed the presence of these odorous VOCs at a wide concentration range.     

Chemical causes of the typical burnt smell after accidental fires

The components responsible for the typical burnt smell that occurs after accidental fires (e.g. in buildings) were identified. For this purpose, samples of odorous materials were taken from different real fire sites. Their volatile fractions were analysed by means of thermal desorption, headspace analysis and solid-phase microextraction (SPME) combined with gas chromatography–mass spectrometry (GC/MS). Measurements performed with SPME gave the highest number of analytes as well as the highest signal intensities. A divinylbenzene/carboxen/polydimethylsiloxane SPME fibre was found to be the most suitable for this task. To distinguish the odour-active compounds from the ca. 1,400 identified volatiles concentrated by SPME, an olfactory detection port was attached to the GC/MS and the column effluent was assessed by panellists. The results revealed that eleven odorous compounds were present in most of the investigated samples: acetophenone, benzyl alcohol, 4-ethyl-2-methoxyphenol, 2-hydroxybenzaldehyde, 2-hydroxy-5-methylbenzldehyde, 2-methoxyphenol, 2-methoxy-4-methylphenol, 2-methylphenol, 3-methylphenol, 4-methylphenol and naphthalene. Their odour activities were confirmed in additional olfactory experiments, and the relative ratios of these eleven compounds were determined. Based on these ratios, standard solutions that presented an intense odour with typical characteristics of the burnt smell were produced.     

Novel multi-gas chromatography-olfactometry device and software for the identification of odour-active compounds

The aim of this work was to devise a novel fully computerised chromatography-olfactometry system where eight sniffers detect volatile compounds obtained from a single chromatographic separation. The technical options taken to implement this system are described in detail. The new methods and software developed and applied to analyse data obtained by gas chromatography-olfactometry and mass spectrometry (GC-O/MS) are presented. We found that 46 odorous zones could be detected by a panel of eight sniffers during the 35min of the analysis of the volatile compounds extracted from a cheese by purge-and-trap. Synchronisation of olfactometry and mass spectrometry data enabled us to propose 44 structures to account for 44 out of these 46 odorous zones.     

溶剂萃取GC-MS法测定纺织衣物中的异味物

采用溶剂萃取法提取纺织品中的土腥霉味化合物二甲萘炕醇(GSM)、2-异丁基-3.甲氧基吡嗪(IBMP)和2-甲基异茨醇(MIB),用气相色谱-质谱法测定其含量.考察了溶剂二氯甲烷和正己烷的提取效果以及提取时间、温度、溶盐因素对提取回收率的影响.结果表明:正己烷的提取效果优于二氯甲烷,采用正己烷提取剂.温度控制在60-8...     

Headspace solid-phase microextraction-gas chromatography--mass spectrometry analysis of the volatile compounds of Evodia species fruits

In this study the investigation of the aroma compounds of dried fruits of Evodia rutaecarpa (Juss.) Benth. and E. rutaecarpa (Juss.) Benth. var. officinalis (Dode) Huang (i.e. E. officinalis Dode) (Rutaceae family) was carried out to identify the odorous target components responsible for the characteristic aroma of these valuable natural products. To avoid the traditional and more time-consuming hydrodistillation, the analyses were carried out by means of headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The SPME headspace volatiles were collected using a divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fiber. The extraction conditions were optimized using a response surface experimental design to analyze the effect of three factors: extraction temperature, equilibrium time and extraction time. The best response was obtained when the extraction temperature was around 80 degrees C, equilibrium time near 25 min and extraction time close to 18 min. Analyses were performed by GC-MS with a 5% diphenyl-95% dimethyl polysiloxane (30 m x 0.25 mm I.D., film thickness 0.25 microm) capillary column using He as the carrier gas and a programmed temperature run. The main components of the HS-SPME samples of E. rutaecarpa (concentration >3.0%) were limonene (33.79%), beta-elemene (10.78%), linalool (8.15%), myrcene (5.83%), valencene (4.73%), beta-caryophyllene (4.62%), linalyl acetate (4.13%) and alpha-terpineol (3.99%). As for E. officinalis, the major compounds were myrcene (32.79%), limonene (18.36%), beta-caryophyllene (9.92%), trans-beta-ocimene (6.04%), linalool (5.88%), beta-elemene (7.85%) and valencene (4.62%).     

A simple and fast sampling method for the characterization of volatile compounds released byNezara viridula

Summary A simple method is described for the collection of volatile compounds from a biological matrix and for their subsequent GC-MS analysis. (E)-2-decenal and (E)-2-decenyl acetate odorous compounds from bugs of theNezara viridula species were detected together with n-dodecane and n-tridecane hydrocarbons as carriers. The chemical composition of the secretions of the bugs collected in the Veneto region corresponds to one obtained from the same American pentatomidae.     

Analysis of odorous trichlorobromophenols in water by in-sample derivatization/solid-phase microextraction GC/MS

The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization headspace solid-phase microextraction method (HS-SPME).The analytical procedure involved their derivatization to methyl ethers with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating, derivatization–extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 μm and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs) run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol (22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water.