Application of chemical derivatization techniques combined with chemical ionization mass spectrometry to detect stabilized Criegee intermediates and peroxy radicals in the gas phase
Application of chemical derivatization techniques combined with chemical ionization mass spectrometry to detect stabilized Criegee intermediates and peroxy radicals in the gas phase
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DOI：
10.5194/amt-14-2501-2021
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发表时间：
2020-09
影响因子：
3.8
通讯作者：
Alexander Zaytsev;M. Breitenlechner;A. Novelli;H. Fuchs;D. Knopf;J. Kroll;F. Keutsch
中科院分区：
文献类型：
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作者：
Alexander Zaytsev;M. Breitenlechner;A. Novelli;H. Fuchs;D. Knopf;J. Kroll;F. Keutsch
抽象的。短命的高活性大气物种，如有机过氧基(RO2)和稳定克里吉中间体(SCI)，在控制大气中许多自然和人为痕量气体的氧化去除和转化方面发挥着重要作用。对这些组分的直接形态测量对于了解它们在大气中的去向和影响非常有帮助。介绍了利用化学衍生化和自旋捕获技术，结合H3O+和NH4+化学电离质谱仪(CIMS)，在实验室实验中在线测量SCI和RO2的方法。使用低质子亲和力的化学衍生化试剂，如贫电子的羰基，我们清除了从广泛的烯烃中产生的所有SCI，而不耗尽CIMS试剂离子。我们的测量结果与使用改进的主化学机理数值模拟的结果进行了比较，结果表明，该方法可以用于实验室实验中SCI的定量，检测下限为1.4×10~7分子cm−3，积分时间为30 S。通过对自旋陷阱与羟基自由基气相反应动力学的研究表明，自旋陷阱对大气中的自由基具有很高的反应性，并与之形成稳定的加合物。我们还证明，在实验室条件下，可以同时探测和定量自旋陷阱与SCI和RO2的加合物，检测下限为1.6×10~8分子cm−3，RO2物种的积分时间为30 S。自旋捕获可以防止激进的二次反应和循环，确保测量不会受到化学干扰的影响，并且可以用于在实验室研究中以及可能在环境大气中检测RO2物种。
Abstract. Short-lived highly reactive atmospheric species, such as organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), play an important role in controlling the oxidative removal and transformation of many natural and anthropogenic trace gases in the atmosphere. Direct speciated measurements of these components are extremely helpful for understanding their atmospheric fate and impact. We describe the development of an online method for measurements of SCIs and RO2 in laboratory experiments using chemical derivatization and spin trapping techniques combined with H3O+ and NH4+ chemical ionization mass spectrometry (CIMS). Using chemical derivatization agents with low proton affinity, such as electron-poor carbonyls, we scavenge all SCIs produced from a wide range of alkenes without depleting CIMS reagent ions. Comparison between our measurements and results from numeric modeling, using a modified version of the Master Chemical Mechanism, shows that the method can be used for the quantification of SCIs in laboratory experiments with a detection limit of 1.4×107 molecule cm−3 for an integration time of 30 s with the instrumentation used in this study. We show that spin traps are highly reactive towards atmospheric radicals and form stable adducts with them by studying the gas-phase kinetics of the reaction of spin traps with the hydroxyl radical (OH). We also demonstrate that spin trap adducts with SCIs and RO2 can be simultaneously probed and quantified under laboratory conditions with a detection limit of 1.6×108 molecule cm−3 for an integration time of 30 s for RO2 species with the instrumentation used in this study. Spin trapping prevents radical secondary reactions and cycling, ensuring that measurements are not biased by chemical interferences, and it can be implemented for detecting RO2 species in laboratory studies and potentially in the ambient atmosphere.