A sensitive diffusion sampler for the determination of volatile organic compounds in ambient air |
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| Institution: | 1. Malvern Instruments Ltd, Grovewood Road, Malvern, Worcestershire, WR14 1XZ, UK;2. Paraytec Ltd, York House, Outgang Lane, Osbaldwick, York, YO19 5UP, UK;1. State Key Joint Laboratory of Environmental Simulation and Pollution Control, Beijing Key Laboratory for Emerging Organic Contaminants Control, School of Environment, Tsinghua University, Beijing, 100084, PR China;2. Environmental Programs, The Pennsylvania State University, 777 West Harrisburg Pike, Middletown, PA17057, USA;3. Energy and Environment International Centre, School of Energy and Power Engineering, Beihang University, Beijing, 100191, PR China;1. MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China;2. Research Center for Air Pollution and Health, Zhejiang University, Hangzhou 310058, China;3. Institute of Environmental Science, Zhejiang University, Hangzhou 310058, China;4. School of Engineering, Brown University, RI 02912, USA;5. Independent researcher, Espoo, Finland;1. Department of Environmental Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, PR China;2. Department of Civil Engineering, Huali College Guangdong University of Technology, Guangdong 511325, PR China |
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| Abstract: | We developed a diffusive sampling device (DSD-voc) for volatile organic compounds (VOCs) which is suitable for collection of low level VOCs and analysis with thermal desorption. This sampling device is composed of two parts, an exposure part made of a porous polytetrafluoroethylene (PTFE) filter, and an analysis part made of stainless-steel tubing. The DSD-voc collects VOCs through the mechanism of molecular diffusion. Collection is controlled by moving the adsorbent from the exposure part to the analysis part by changing the posture of the DSD-voc. Adsorbates in the DSD-voc were analyzed by GC/MS with a thermal desorption cold trap injector (TCT). The TCT has the advantage of being able to accept the entire quantity of VOCs. We connected a condenser between the DSD-voc and the trap tube to prevent moisture from freezing in the trap tube when the sampler was packed with strong adsorbent. We also examined the desorption efficiency for VOCs from several types of adsorbents (CarboxenTM 1000, CarbosieveTM G, Carbosieve S III, CarbotrapTM B, and activated carbon) over a wide range of temperatures. Carboxen 1000 was suitable for the determination of VOCs with a low boiling point range, from CFC12 to hexane, while Carbotrap B was suitable for VOCs from hexane to 1,4-dichlorobenzene. The limits of detection with Carboxen 1000 and Carbotrap B were 0.036–0.046 and 0.0035–0.014 ppb, respectively, for a sampling duration of 24 h. Coefficients of variation for concentrations of major VOCs ranged from 3.8 to 14%. It is possible to estimate atmospheric VOCs at sub-parts per billion (sub-ppb), with high sensitivity, by using both adsorbents in combination. |
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