吸附/一级热解吸/气相色谱联用测定室内空气中的挥发性有机物

本文以高聚物TenaxTA动态吸附,一级热解吸/毛细管气相色谱法联用测定室内空气中的挥发性有机物。优化了热解吸温度和热解吸时间,建立了苯、甲苯、乙酸正丁酯、乙苯、对二甲苯、苯乙烯、邻二甲苯、正十一烷等8种典型有机污染物的外标定量曲线,各化合物线性范围为103,相关系数R为0.9983～0.9999,最低检出浓度可达2×10-4mg/m3;考察了方法的重复性、热解吸率和残留率,并分析了实际空气样品。     

热脱附-气相色谱-质谱法测定空气中挥发性有机物

提出了热脱附-气相色谱-质谱法测定空气中54种挥发性有机物含量的方法。用HP-INNOWAX毛细管色谱柱分离,电子轰击离子源全扫描和选择离子检测模式检测。54种挥发性有机物的方法检出限在0.11～0.28μg.m-3之间。回收率在85%～107%之间,相对标准偏差(n=7)小于15%。     

Isolation and Determination of Volatile Organic Compounds from Water by Dynamic Purge-and-Trap Technique Coupled with Capillary Gas Chromatography

The preconcentration technique of purge-and-trap has been investigated in the present work for quantitative adsorption of volatile organic pollutants purged from water samples. A dynamic purging device with variable volume size has been constructed and tested to purge different concentrations of organic compounds. With Tenax GR as the adsorbent, a dynamic purge-and-trap technique was developed combining on-column preconcentration procedures using ambient trapping/thermal desorption/cryogenic focusing/back-flash injection prior to separation and determination using capillary gas chromatography. Various aromatic compounds in water were determined, giving linear working ranges over five orders of magnitude from 0.02 to 5000 µg/L. The analytical procedures were optimized under the assistance of ultrasonication with results validated for the determination of organic contaminants in underground water and tap water, giving over 93% recoveries and a detection limit of 0.01 µg/L, two orders of magnitude lower than those obtained using commercial available instruments with on-line configuration to minimize cross-contamination. The technique provides a potential automated method for in situ monitoring of volatile organic compounds in water.     

MOFs with Open Metal(III) Sites for the Environmental Capture of Polar Volatile Organic Compounds

Metal–Organic Frameworks (MOFs) with open metal sites (OMS) interact strongly with a range of polar gases/vapors. However, under ambient conditions, their selective adsorption is generally impaired due to a high OMS affinity to water. This led previously to the privilege selection of hydrophobic MOFs for the selective capture/detection of volatile organic compounds (VOCs). Herein, we show that this paradigm is challenged by metal(III) polycarboxylates MOFs, bearing a high concentration of OMS, as MIL-100(Fe), enabling the selective capture of polar VOCs even in the presence of water. With experimental and computational tools, including single-component gravimetric and dynamic mixture adsorption measurements, in situ infrared (IR) spectroscopy and Density Functional Theory calculations we reveal that this adsorption mechanism involves a direct coordination of the VOC on the OMS, associated with an interaction energy that exceeds that of water. Hence, MOFs with OMS are demonstrated to be of interest for air purification purposes.     

Reactivity of Carbon Adsorbents Used to Determine Volatile Organic Compounds in Atmospheric Air

The surface reactivity of carbon adsorbents (carbon molecular sieves and graphitized carbons) used for analysis of volatile organic compounds in atmospheric air was studied using ¹⁸O as a labelling agent. The carbon adsorbent surface activated in a stream of inert gas at 350°C and then exposed to air is very active chemically. Apparently peroxide structures are formed. Owing to this activity the integrity of some analytes, for example dienes and alcohols, among others, is compromised. The active surface can react with the volatile organic compounds analyzed and even initiate free-radical polymerization. The consequences in analytical practice are discussed.     

在线测量大气挥发性有机物的冷阱浓缩/热解析仪的研制

研制了一种只用-10C低温的冷阱浓缩/热解析仪,用于大气中C2和C2以上挥发性有机物的在线检测.以碳分子筛TDX-01和石墨化炭黑为吸附剂,将大气挥发性有机物富集在吸附管内,通过对吸附管直接加热快速热解析后,样品随载气直接进入气相色谱仪进行分离分析,不需二级冷阱或者二次浓缩.对10种挥发性有机物的检测显示,测定结果的相...     

Evaluation of Coriolis Micro Air Sampling to Detect Volatile and Semi-Volatile Organic Compounds

There are several analytical procedures available for the monitoring of volatile organic compounds (VOCs) in the air, which differ mainly on sampling procedures. The Coriolis micro air sampler is a tool normally designed for biological air sampling. In this paper, the Coriolis micro bio collector is used to evaluate its ability to sample organic contaminants sampling and detecting them when combined GC-MS. We also compare the use of the Coriolis micro with a standardized sampling method, which is the use of a lung box with a Nalophan^® bag. The results show that the Coriolis micro sampling method is suitable for the sampling of organic contaminants. Indeed, the Coriolis micro allows to sample and detect mainly semi-volatile molecules, while the lung box/Nalophan^® bags allow to sample more volatile molecules (highly volatile and volatile). These results were confirmed in the controlled air lab with a slight difference with the field. The simultaneous use of the both techniques allow to sample and detect a larger number of molecules with specific physicochemical properties to each sampling technique. In conclusion, the Coriolis micro can sample and detect volatile organic compounds present in air. We have shown that the development of alternative sampling methods and the use of non-target analysis are essential for a more comprehensive risk assessment. Moreover, the use of the Coriolis micro allows the detection of emergent molecules around the Thau lagoon.     

Self-Doped n-Type Quinoidal Compounds with Good Air Stability and High Electrical Conductivity for Organic Electronics

Air stable n-type conductive molecules with high electrical conductivities and excellent device performance have important applications in organic electronics, but their synthesis remains challenging. Herein, we report three self-doped n-type conductive molecules, designated QnNs, with a closed-shell quinoidal backbone and alkyl amino chains of different lengths. The QnNs are self-doped by intermolecular electron transfer from the amino groups to the quinoidal backbone. This process is ascertained unambiguously by experiments and theoretical calculations. The use of a quinoidal structure effectively improves the self-doping level, and thus increases the electrical conductivity of self-doped n-type conductive molecules achieved by a closed-shell structure from<10⁻⁴ S cm⁻¹ to>0.03 S cm⁻¹. Furthermore, the closed-shell quinoidal structure results in good air stability of the QnNs, with half-lives>73 days; and Q4N shows an electrical conductivity of 0.019 S cm⁻¹ even after exposure to air for 120 days. When applying Q6N as the cathode interlayer in organic solar cells (OSCs), an outstanding power conversion efficiency of up to 18.2 % was obtained, which represents one the best results in binary OSCs.     

室内空气中总挥发性有机物（TVOC）检验方法的探索

使用TVOC混合标准溶液对气相色谱法检测室内空气样品中总挥发有机物的方法进行了探索。改进后的色谱分析时间为26.1min,比GB/T 18883-2002方法（52min）缩短了25.9min,TVOC各物质峰分离度高于99%,检测精密度相对标准偏差在1.05%至2.89%之间,回收率在95%到102%之间,检出限为0.020μg。     

富勒烯烟炱的吸附性及其在大气挥发性有机物分析中的应用

研究了富勒烯烟炱对挥发性有机物(VOCs)的吸附作用.17种VOCs气体在烟炱上的比保留体积V_g²⁰为17.4～2634L/g.富勒烯烟炱充填的吸附管对VOCs气体的吸附-热脱附回收率在40.8%～117%之间,大部分为(100±20)%.结果表明,富勒烯烟炱能够用于吸收和富集大气中痕量的VOCs     

室内空气中挥发性有机化合物污染及检测方法

室内空气中挥发性有机污染物的释放严重影响了室内空气质量,本文较详细的叙述了这些有机污染物的来源、种类及处理方法等,并对空气中VOCs的采集和检测方法作以介绍,阐述了不同机制的热解吸仪与气相色谱联用时的优缺点及其应用．     

Application of a Self-developed Proton Transfer Reaction-Mass Spectrometer to On-line Monitoring Trace Volatile Organic Compounds in Ambient Air

Real-time and on-line monitoring volatile organic compounds(VOCs) are valuable for real-time evalua- ting air quality and monitoring the key source of pollution. A self-developed proton transfer reaction-mass spectrometer(PTR-MS) was constructed and applied to on-line monitoring trace VOCs in ambient air in Hefei, China. With the help of a self-developed catalytic converter, the background signal of the instrument was detected and the stability of the instrument was evaluated. The relative standard deviation of signal at m/z 21 was only 0.74% and the detection limit of PTR-MS was 97 part per trillion(97×10^-12, volume ratio). As a case of the air monitoring in Hefei, the ambient air at Dongpu reservoir spot was on-line monitored for 13 d with our self-developed PTR-MS. Meanwhile, a solid-phase micro-extraction(SPME) technique coupled to gas chromatography-mass spectrometry/mass spectrometry (GC-MS/MS) was also used for the off-line detection of the air. The results show that our self-developed PTR-MS can be used for the on-line and long-term monitoring of VOCs in air at part per trillion level, and the change trend of VOCs concentration monitored with PTR-MS was consistent with that detected with the conventional SPME-GC-MS. This self-developed PTR-MS can fully satisfy the requirements of air quality monitoring and real-time monitoring of the key pollution sources.     

Advanced Methodologies for Sampling and Analysis of Toxic Organic Chemicals in Ambient Outdoor,Indoor, and Personal Respiratory Air

Many different kinds of sampling devices and analytical techniques are required to assess the potential adverse effects of toxic air pollutants on human health and the ecosystem. The U.S. Environmental Protection Agency has an on-going research and development program designed to provide the necessary tools to monitor air quality both outdoors and indoors and to measure personal respiratory exposures. Particular emphasis in recent years has been placed on real-time and integrative methods for neutral and polar volatile organic chemicals (e.g., chlorinated hydrocarbons, single-ring aromatics, alcohols, aldehydes, ethers, thiols, nitriles) and semi-volatile organics (e.g., polynuclear aromatics, nitrated aromatics, pesticides, phenols). Samplers capable of obtaining sufficient quantities of chemicals for ultratrace analyses and sometimes bioassay, that are also quiet, unobtrusive and user-friendly, are being developed and evaluated for indoor, outdoor, and personal monitoring. New analytical techniques such as matrix-isolation GC/FTIR, and supercritical fluid extraction and chromatography are being adapted to characterize collected samples.     

Combination of a Mid-infrared Hollow Waveguide Gas Sensor with a Supported Capillary Membrane Sampler for the Detection of Organic Compounds in Water

A Fourier transform infrared (FT-IR) spectroscopy based gas sensor for continuous analysis of liquid phase samples has been developed, coupling a short hollow waveguide (HWG) gas cell with a supported capillary membrane sampler (SCMS) probe. Passing an inert carrier gas through the thin-walled tubular silicon membrane enables the permeation of volatile organic compounds (VOCs) present in aqueous solution and facilitates their continuous and quantitative detection in the infrared hollow fiber by multiple internal reflection spectroscopy. The sensitivity of the sensor system has been determined at the ppb (μg/L) concentration level and the response time ranges from few minutes to 30 min, depending on the analyte and the permeation properties of the sampling membrane.

The experimental set-up consists of Bruker Vector 22 FT-IR spectrometer with an externally aligned 50 cm long silica HWG coupled to the SCMS, which is immersed into a glass flask filled with analyte solution and kept under constant stirring.

Aqueous solutions of benzene, toluene, xylene isomers and chloroform were qualitatively and quantitatively analyzed confirming the feasibility of this sensor approach for environmental analysis.     

多孔膜萃取/微捕集方法及在线测定水中挥发性有机物

基于多孔膜萃取水中挥发性有机物和微捕集技术,构建了一套水中挥发性有机物(Volatile OrganicCompounds,VOCs)样品前处理装置,可自动、在线、连续完成水中挥发性有机物萃取、富集、热解析,传输给气相色谱分离检测。实验分别对膜萃取材料、萃取温度、萃取时间、吹扫气流速等进行了系统优化,并用于氯仿、1,2-二氯甲烷、四氯化碳、三氯乙烯、甲苯、四氯乙烯、乙苯、氯苯、苯乙烯9种挥发性有机物的检测。研究结果表明,采用膜萃取/微捕集装置,与气相色谱联用,在萃取温度60℃,萃取时间30 min,吹扫气流速8 mL/min条件下,采用氢焰离子化检测器(Flame ionization detector,FID),对氯代烃的检出限达到0.003～0.041μg/L,精确度为2.7%～13.0%,线性相关系数均大于0.9936,适用于在线检测水中挥发性有机物。     

Influence of Ca(OH)2 on the Extraction Efficiency of Nitroaromatic Compounds from Soils

High concentrations of TNT and related nitroaromatic compounds (NAC) can still be found in the soils. To evaluate the alkaline hydrolysis of NAC as a new remediation technology, two highly contaminated soils were treated under alkaline conditions using Ca(OH)₂ as base. However, instead of the expected decrease, a temporary or even permanent increase was observed for several NAC. The extent of the intensity was affected by Ca(OH)₂ concentration, suggesting the existence of desorption processes in the soil. The extent of the increase also depends on the soil investigated, the highest being observed with 1,3,5-trinitrobenzene (239 mg kg^?1 compared to the baseline concentration of 24 mg kg^?1) in the HTNT2 soil. This indicates incomplete NAC extraction and, hence, too low NAC concentrations measured in soils when conventional extraction procedures are used.     

催化燃烧去除VOCs污染物的最新进展

催化燃烧是目前最有效的处理挥发性有机物(VOCs)技术之一. 本文从催化剂活性组分、催化剂载体、有效组分颗粒大小、水蒸汽的影响及催化燃烧反应中的积碳等几个方面, 对近年来催化燃烧处理VOCs的研究进行了总结. 分析表明: 贵金属催化剂的研究主要着重于选择有效的载体和双组分贵金属催化剂; 非贵金属催化剂的研究主要集中在高活性的过渡金属复合氧化物、钙钛矿和尖晶石型等催化剂的研制, 还有这些活性组分粒径大小及载体对催化燃烧VOCs反应活性的影响;此外, 在实际应用中,水蒸汽和催化剂积碳失活等问题对催化燃烧VOCs的反应也有很大影响. 本文的评述将为选择合适的催化燃烧技术处理VOCs污染物提供一定参考.     

催化燃烧去除VOCs污染物的最新进展

催化燃烧是目前最有效的处理挥发性有机物(VOCs)技术之一. 本文从催化剂活性组分、催化剂载体、有效组分颗粒大小、水蒸汽的影响及催化燃烧反应中的积碳等几个方面, 对近年来催化燃烧处理VOCs的研究进行了总结. 分析表明: 贵金属催化剂的研究主要着重于选择有效的载体和双组分贵金属催化剂; 非贵金属催化剂的研究主要集中在高活性的过渡金属复合氧化物、钙钛矿和尖晶石型等催化剂的研制, 还有这些活性组分粒径大小及载体对催化燃烧VOCs反应活性的影响;此外, 在实际应用中,水蒸汽和催化剂积碳失活等问题对催化燃烧VOCs的反应也有很大影响. 本文的评述将为选择合适的催化燃烧技术处理VOCs污染物提供一定参考.     

催化燃烧去除VOCs污染物的最新进展

催化燃烧是目前最有效的处理挥发性有机物(VOCs)技术之一. 本文从催化剂活性组分、催化剂载体、有效组分颗粒大小、水蒸汽的影响及催化燃烧反应中的积碳等几个方面, 对近年来催化燃烧处理VOCs的研究进行了总结. 分析表明: 贵金属催化剂的研究主要着重于选择有效的载体和双组分贵金属催化剂; 非贵金属催化剂的研究主要集中在高活性的过渡金属复合氧化物、钙钛矿和尖晶石型等催化剂的研制, 还有这些活性组分粒径大小及载体对催化燃烧VOCs反应活性的影响;此外, 在实际应用中,水蒸汽和催化剂积碳失活等问题对催化燃烧VOCs的反应也有很大影响. 本文的评述将为选择合适的催化燃烧技术处理VOCs污染物提供一定参考.     

催化燃烧去除VOCs污染物的最新进展

催化燃烧是目前最有效的处理挥发性有机物(VOCs)技术之一. 本文从催化剂活性组分、催化剂载体、有效组分颗粒大小、水蒸汽的影响及催化燃烧反应中的积碳等几个方面, 对近年来催化燃烧处理VOCs的研究进行了总结. 分析表明: 贵金属催化剂的研究主要着重于选择有效的载体和双组分贵金属催化剂; 非贵金属催化剂的研究主要集中在高活性的过渡金属复合氧化物、钙钛矿和尖晶石型等催化剂的研制, 还有这些活性组分粒径大小及载体对催化燃烧VOCs反应活性的影响;此外, 在实际应用中,水蒸汽和催化剂积碳失活等问题对催化燃烧VOCs的反应也有很大影响. 本文的评述将为选择合适的催化燃烧技术处理VOCs污染物提供一定参考.