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首页> 外文期刊>International journal of mass spectrometry >VOC-OHM: A new technique for rapid measurements of ambient total OH reactivity and volatile organic compounds using a single proton transfer reaction mass spectrometer
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VOC-OHM: A new technique for rapid measurements of ambient total OH reactivity and volatile organic compounds using a single proton transfer reaction mass spectrometer

机译：VOC-OHM：一种使用单个质子转移反应质谱仪快速测量环境总OH反应性和挥发性有机化合物的新技术

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Measurements of total hydroxyl radical (OH) reactivity and volatile organic compounds (VOC) are necessary for improving our understanding of reactive emissions and atmospheric oxidation in air pollution and atmospheric chemistry studies. Proton transfer reaction mass spectrometers (PTR-MS) can measure ambient VOCs and the total ambient OH reactivity. However, till date this has always required deployment of two PTR-MS instruments, wherein one instrument measures ambient VOCs and the other instrument measures the total OH reactivity using the comparative reactivity method (CRM). Due to material (e.g. power, space) or financial constraints, deploying two PTR-MS instruments is not always possible and yet it is desirable to quantify both VOCs and OH reactivity. Here, we present a novel hyphenated technique christened VOC-OHM (for Volatile Organic Compounds-OH reactivity Measurement) that enables rapid ambient measurements of both VOCs and total OH reactivity using a single PTR-MS. The technique can provide more specificity for identification of compounds using a PTR-QMS through an estimate of the rate coefficient of the major isobaric contributor with the hydroxyl radical as shown in the case of rn/z=69 for isoprene and furan, which are nominal isobars but have rate coefficients that differ by one order of magnitude. It also demonstrates a new safer and portable substitute for pressurized zero air bottles that have been required thus far in CRM OH reactivity deployments. VOC-OHM successfully couples the typical VOC and CRM experimental set ups without undermining the PTR-MS's ability to measure either parameter. The design of the VOC-OHM system, its validation, optimization and results of field tests are described in detail. The VOC-OHM system measures the ambient VOCs and OH reactivity every hour for similar to 20 min durations each, with an ambient data gap of 13 min in between. Thus rapid temporal changes in the ambient chemical composition and reactivity are easily quantified. The sampling periods and VOC speciation achieved using VOC-OHM can be customized depending on user preferences, providing more options for the majority of users possessing a single PTR-MS. (C) 2014 Elsevier B.V. All rights reserved.
机译：测量总羟基自由基（OH）反应性和挥发性有机化合物（VOC）对于增进我们对空气污染和大气化学研究中对反应性排放物和大气氧化的理解是必要的。质子转移反应质谱仪（PTR-MS）可以测量环境VOC和总环境OH反应性。但是，迄今为止，这始终需要部署两台PTR-MS仪器，其中一台仪器使用比较反应性方法（CRM）测量环境VOC，另一台仪器测量总OH反应性。由于材料（例如电源，空间）或财务方面的限制，部署两种PTR-MS仪器并非总是可能的，但同时需要对VOC和OH反应性进行量化。在这里，我们介绍一种称为VOC-OHM（用于挥发性有机化合物-OH反应性测量）的新型联用技术，该技术能够使用单个PTR-MS快速测量VOC和总OH反应性的环境。该技术可以通过对主要异戊二烯贡献者具有羟基的速率系数进行估算，从而为使用PTR-QMS鉴定化合物提供更高的特异性，如异戊二烯和呋喃的rn / z = 69情况所示，这是标称值等压线，但速率系数相差一个数量级。它还展示了迄今为止零压力气瓶的一种新型的安全，便携的替代品，这是迄今为止CRM OH反应性部署中所需要的。 VOC-OHM成功地将典型的VOC和CRM实验设置结合在一起，而不会损害PTR-MS测量任一参数的能力。详细介绍了VOC-OHM系统的设计，其验证，优化和现场测试结果。 VOC-OHM系统每小时测量一次环境中的VOC和OH反应性，每次持续约20分钟，两者之间的环境数据间隔为13分钟。因此，可以容易地定量环境化学组成和反应性的快速时间变化。可以根据用户的喜好定制使用VOC-OHM获得的采样周期和VOC种类，从而为拥有单个PTR-MS的大多数用户提供更多选择。 （C）2014 Elsevier B.V.保留所有权利。

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