Abstract Oxidation products of α-pinene represent a fraction of organic matter in the environmental aerosol. α-pinene is one of most abundant monoterpenes released in the atmosphere by plants, located typically in boreal, temperate and tropical forests. This primary compound reacts with atmospheric oxidants, such as O3, O2, OH radicals and NOx, through the major tropospheric degradation pathway for many monoterpenes under typical atmospheric condition. Although several studies identified a series of by-products deriving from the α-pinene photo-oxidation in the atmosphere, such as pinic and cis-pinonic acid, the knowledge of the mechanism of this process is partially still lacking. Thus, the investigation of the distribution of these acids in the different size aerosol particles provides additional information on this regard. The aim of this study is twofold. First, we aim to improve the existing analytical methods for the determination of pinic and cis-pinonic acid in aerosol samples, especially in terms of analytical sensitivity and limits of detection (LOD) and quantification (LOQ). We even attempted to increase the knowledge of the α-pinene photo-oxidation processes by analysing, for the first time, the particle-size distribution up to nanoparticle level of pinic and cis-pinonic acid. The analysis of aerosol samples was carried out via high-performance liquid chromatography coupled to a triple quadrupole mass spectrometer. The instrumental LOD values of cis-pinonic and pinic acid are 1.6 and 1.2 ng L−1 while LOQ values are 5.4 and 4.1 ng L−1, respectively. Samples were collected by MOUDI II™ cascade impactor with twelve cut-sizes, from March to May 2016 in the urban area of Mestre-Venice (Italy). The range concentrations in the aerosol samples were from 0.1 to 0.9 ng m−3 for cis-pinonic acid and from 0.1 to 0.8 ng m−3 for pinic acid.

中文翻译：

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α-蒎烯在粗、细和超细气溶胶中的光氧化产物：一种新的高灵敏度 HPLC-MS/MS 方法

摘要 α-蒎烯的氧化产物是环境气溶胶中有机物的一部分。α-蒎烯是植物在大气中释放的最丰富的单萜之一，通常位于北方、温带和热带森林中。在典型的大气条件下，这种主要化合物与大气氧化剂（如 O3、O2、OH 自由基和 NOx）发生反应，通过对流层中许多单萜的主要降解途径。虽然一些研究确定了一系列源自大气中 α-蒎烯光氧化的副产物，如松香酸和顺式松香酸，但对该过程的机制仍部分缺乏了解。因此，对这些酸在不同尺寸气溶胶颗粒中的分布的调查提供了关于这方面的额外信息。这项研究的目的是双重的。首先，我们旨在改进现有的测定气溶胶样品中松香酸和顺式松香酸的分析方法，特别是在分析灵敏度和检测限 (LOD) 和定量 (LOQ) 方面。我们甚至试图通过首次分析松果酸和顺式松香酸的纳米颗粒水平的粒度分布来增加对 α-蒎烯光氧化过程的了解。气溶胶样品的分析是通过与三重四极杆质谱联用的高效液相色谱法进行的。顺式松香酸和松酸的仪器 LOD 值为 1.6 和 1.2 ng L-1，而 LOQ 值分别为 5.4 和 4.1 ng L-1。样品由 MOUDI II™ 级联撞击器收集，具有十二个切割尺寸，2016 年 3 月至 5 月在梅斯特-威尼斯（意大利）市区。气溶胶样品中顺式松香酸的浓度范围为 0.1 至 0.9 ng m-3，松酸的浓度范围为 0.1 至 0.8 ng m-3。