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首页> 外文期刊>International journal of environmental analytical chemistry >Preparation of standard VOC mixtures for climate monitoring
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Preparation of standard VOC mixtures for climate monitoring

机译：制备用于气候监测的标准VOC混合物

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The growing need for global volatile organic compounds (VOC) data at trace level for industrial applications, domestic and working health, air quality and climate change is driving research towards the preparation of traceable and accurate standards for the VOC amount of substance fraction in gas phase.The World Meteorological Organization (WMO) has implemented a worldwide VOC monitoring programme, named Global Atmosphere Watch (GAW), which data quality objectives refer to an expanded uncertainty lower than 10% for VOC measurement at amount of substance fractions lower than 100nmol.mol(-1).Currently, gaseous standard atmospheres are prepared in high pressure gas cylinders, but they do not fulfil GAW requirements of accuracy and stability at ppb level, especially for oxygenated VOCs. Dynamic methods are proposed as an alternative to provide a stable amount of substance fraction of the mixture over time. Diffusion rate, dilution and carrier air flow rates, purity of air, VOC losses due to wall-interactions and leakages were considered as influence quantities of the VOC amount of substance fraction dynamically prepared in gas phase by the diffusion method. The contribution of the VOC losses to standard mixtures uncertainty and their sampling procedure are under study and a solution has not yet been proposed.In this paper, a conservative quantification of VOC losses is proposed, discussed and applied to a case study: a single stage dynamic dilutor with an acetone generation. An uncertainty budget was prepared to calculate target uncertainty for VOC losses due to leakages and VOC-wall interactions on Teflon((R)), Pyrex((R)) and stainless steel tubing. Teflon((R)) showed negligible interaction effects when the pipe was clean and long term effects were not considered. Uncertainty was not negligible for glass and stainless steel for which more accurate analyses are necessary. A leakage test was developed to assure negligible leakage contribution to uncertainty.
机译：对于工业应用，家庭和工作健康，空气质量和气候变化，对痕量水平的全球挥发性有机化合物（VOC）数据的需求日益增长，正推动着研究领域的发展，以为气相中的挥发性物质的VOC量制定可追溯和准确的标准世界气象组织（WMO）实施了一项名为全球大气监视网（GAW）的全球VOC监测计划，该数据​​质量目标指的是当物质分数低于100nmol.mol时，VOC测量的不确定性扩大到10％以下（-1）。目前，气态标准气氛是在高压气瓶中制备的，但它们不能满足GAW在ppb级精度和稳定性方面的要求，尤其是对于含氧VOC。提出了动态方法作为替代方案，以在一段时间内提供稳定量的混合物中的物质分数。扩散速率，稀释和载气流速，空气纯度，壁相互作用和泄漏引起的VOC损失被认为是通过扩散法在气相中动态制备的物质级分的VOC量的影响量。目前正在研究挥发性有机化合物损失对标准混合物不确定度的影响及其采样程序，但尚未提出解决方案。本文提出了一种挥发性有机化合物损失的保守量化方法，并将其应用于案例研究：单阶段动态稀释器，产生丙酮。准备了不确定性预算，以计算由于泄漏，特氟龙（Pyrex）和不锈钢管上的泄漏以及VOC-壁相互作用而导致的VOC损失的目标不确定性。当管道清洁时，特氟隆（R）的相互作用影响可忽略不计，并且未考虑长期影响。对于玻璃和不锈钢来说，不确定性是不可忽略的，因此必须进行更准确的分析。开发了泄漏测试以确保泄漏对不确定性的影响可忽略不计。

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