Secondary Ion Chemistry Mediated by Ozone and Acidic Organic Molecules in Iodide-Adduct Chemical Ionization Mass Spectrometry
Secondary Ion Chemistry Mediated by Ozone and Acidic Organic Molecules in Iodide-Adduct Chemical Ionization Mass Spectrometry
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碘化物加合物化学电离质谱中臭氧和酸性有机分子介导的二次离子化学
DOI：
10.1021/acs.analchem.1c01486
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发表时间：
2021
影响因子：
7.4
通讯作者：
Zhang, Haofei
中科院分区：
文献类型：
--
作者：
Zhang, Wen;Zhang, Haofei
碘加合物化学电离质谱仪(I-CIMS)是大气化学界广泛使用的一种实时检测含氧挥发性有机化合物(OVOCs)的技术。在这项工作中，我们报道了在I-CIMS的离子-分子反应(IMR)区域中，由于强给氧体(如臭氧和过氧酸)与酸性OVOCs(如羧酸和有机氢氧化物)之间的相互作用而发生的二次离子化学。这种相互作用可以导致酸性有机分子(HA或HB)与[IO]−(例如，[HA+IO]−)和二聚体加合物([A+B+I]−)聚集，以及众所周知的碘簇合物([HA+I]−)。在流动管式反应器中，使用常见的化学标准以及α-蒎烯和异戊二烯的气相氧化产物对离子化学进行了探讨。结果表明，二次离子化学会导致对气相产物的分子组成和分布的错误解释，以及对元素O/C比的整体高估。然而，响应二次离子化学的不同程度的信号变化可能是了解OVOCs功能的线索。具体地说，在α-Pinene臭氧化体系中，在IMR中存在额外酸的情况下离子信号减弱的程度表明，在气相中产生的C9H14O4是过氧酸，而不是通常假设的Pinic酸。因此，我们认为二次离子化学在揭示有机官能团方面具有潜在的应用前景，这有助于更好地了解气相OVOCs的分子组成和其中的反应机理。
Iodide-adduct chemical ionization mass spectrometry (I-CIMS) is a widely used technique in the atmospheric chemistry community to detect oxygenated volatile organic compounds (OVOCs) in real time. In this work, we report the occurrence of secondary ion chemistry from interactions between a strong oxygen donor (such as O3and peracids) and acidic OVOCs (such as carboxylic acids and organic hydroperoxides) in the ion–molecule reaction (IMR) region of I-CIMS. Such interactions can lead to acidic organic molecules (HA or HB) clustering with [IO]−(e.g., [HA + IO]−) and dimer adducts ([A + B + I]−), in addition to the well-known iodide clusters ([HA + I]−). This ion chemistry was probed using common chemical standards as well as the gas-phase oxidation products of α-pinene and isoprene in a flowtube reactor. The results show that secondary ion chemistry can lead to misinterpretations of molecular compositions and distributions of the gas-phase products and an overestimation of the elemental O/C ratio overall. Nevertheless, the varying degrees of signal change in response to the secondary ion chemistry might be a clue to inform OVOCs’ functionalities. Specifically, in the α-pinene ozonolysis system, the extents of ion signal reduction in the presence of additional acids in the IMR suggest that C9H14O4produced in the gas phase is a peracid, rather than the often-assumed pinic acid. Thus, we suggest that the potential application of the secondary ion chemistry to inform organic functionalities is promising, which could help better understand the molecular compositions of gas-phase OVOCs and the reaction mechanisms therein.