An automated system for near-real-time monitoring of trace atmospheric halocarbons.
An automated system for near-real-time monitoring of trace atmospheric halocarbons.
复制标题
用于近实时监测痕量大气卤化碳的自动化系统。
作者：
M. Bassford;Peter Simmonds;G. Nickless
描述了一种新的气相色谱定量测定大气中重要卤代烃的方法。目标化合物包括氯氟烃替代品、氯化溶剂和生物合成（自然产生的）有机卤素，以及大气中浓度在0.1至600 pptv(其中pptv =体积的1 / 10（-)(12)）之间的所有微量气体。超低浓度和相对较小的电子附着截面的结合使得这些化合物很难在典型的远程大气监测站的背景空气中进行常规测量。检测是通过使用吸附剂填充的微阱预先浓缩200毫升空气样品和通过氧掺杂串联两个检测器中的一个来增强电子捕获检测器的响应来实现的。氧掺杂专门针对电子附着率系数相对较差的卤代烃。本文详细描述了一种新型分析系统的构建、实验室试验和优化，随后在爱尔兰梅斯黑德的一个远程大气监测站进行了扩展的现场活动。每小时使用循环自动程序获取校准标准品或环境空气样本，无需使用低温预浓缩或重新聚焦。分析方法对目标化合物的总体精密度在0.3 ~ 1.5%之间。
A new gas chromatographic method developed to quantitatively determine important atmospheric halocarbons is described. Target compounds include replacement CFCs, chlorinated solvents, and biosynthesized (naturally produced) organohalogens, all trace gases in the atmosphere at concentrations ranging from 0.1 to 600 pptv (where pptv = 1 part in 10(-)(12) by volume). A combination of ultralow concentrations and relatively small electron attachment cross sections renders these compounds very difficult to routinely measure in the background air typical of remote atmospheric monitoring stations. Detection is achieved by preconcentration of a 200-mL air sample using an adsorbent-filled microtrap and enhancement of electron capture detector response by oxygen doping one of two detectors connected in series. Oxygen doping specifically targets halocarbons with relatively poor electron attachment rate coefficients. The work described here details construction of a novel analytical system, laboratory trials, and optimization followed by an extended field campaign at a remote atmospheric monitoring station, Mace Head, Ireland. A calibration standard or ambient air sample was acquired every hour using a cyclic, automated procedure without employing cryogenic preconcentration or refocusing. Overall precision of the analytical method for the target compounds is between 0.3 and 1.5%.