High-resolution mass spectrometry (HRMS) has become an indispensable tool in the characterization of organic aerosols (OA) providing information on air quality, health assessment, climate trends, reactions, and source apportionment. Spectra-derived lists of formulas and their relative abundances are used to compare ambient OA from different sources or to monitor secondary OA formation under controlled laboratory conditions in smog chamber experiments. Various techniques are implemented to visualize common and unique features, series of precursors, and products. The disadvantage of this conventional approach is in associating elemental compositions to specific compounds, while due to several analytical limitations, the structural information remains hidden. We argue that some of the conclusions derived from this data analysis can be misleading. In this study, we applied in-ESI source H/D exchange (HDX), which facilitated enumeration of labile protons in molecules behind elemental compositions of OA. We applied this technique to compare OA from three different locations representing urban, forest, and marine environments and to examine tentative chemical information derived from Kendrick mass defect (KMD) series analysis. Significant discrepancies were found between numbers of labile protons in protogenic functional groups and the stoichiometry of chemical reactions, which are associated with KMD series. Only a portion of chemical pairs matched target stoichiometries, which highlights the existing limitations in environmental applications of conventional formula-based HRMS data interpretation strategies.

中文翻译：

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降低有机气溶胶分子指纹图谱与 H/D 交换质谱法比较的不确定性


高分辨率质谱 （HRMS） 已成为有机气溶胶 （OA） 表征中不可或缺的工具，提供有关空气质量、健康评估、气候趋势、反应和来源分配的信息。光谱衍生的公式列表及其相对丰度用于比较来自不同来源的环境 OA 或在烟雾室实验中监测受控实验室条件下的继发性 OA 形成。实施了各种技术来可视化常见和独特的特征、一系列前驱体和产物。这种传统方法的缺点是将元素组成与特定化合物相关联，而由于一些分析限制，结构信息仍然隐藏起来。我们认为，从这种数据分析中得出的一些结论可能具有误导性。在这项研究中，我们应用了 ESI 源 H/D 交换 （HDX），这有助于计数 OA 元素组成后面的分子中不稳定质子。我们应用该技术来比较来自代表城市、森林和海洋环境的三个不同位置的 OA，并检查从 Kendrick 质量缺陷 （KMD） 系列分析得出的暂定化学信息。发现原生官能团中不稳定质子的数量与化学反应的化学计量之间存在显着差异，这与 KMD 系列相关。只有一部分化学对与目标化学计量相匹配，这突出了传统的基于公式的 HRMS 数据解释策略在环境应用中的现有局限性。