Response of protonated, adduct, and fragmented ions in Vocus proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS)

IF 3.2 3区地球科学 Q2 METEOROLOGY & ATMOSPHERIC SCIENCES

Atmospheric Measurement Techniques Pub Date : 2024-01-12 DOI:10.5194/egusphere-2024-16

Fangbing Li, Dan Dan Huang, Linhui Tian, Bin Yuan, Wen Tan, Liang Zhu, Penglin Ye, Douglas Worsnop, Ka In Hoi, Kai Meng Mok, Yong Jie Li

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引用次数: 0

Abstract

Abstract. Volatile organic compounds (VOCs) affect secondary pollutant formation via active chemistry. Proton-transfer-reaction mass spectrometry (PTR-MS) is one of the most important techniques to study the highly variable spatial and temporal characteristics of VOCs. The response of protonated, adduct, and fragmented ions in PTR-MS in changing instrument settings and varying relative humidity (RH) requires rigorous characterization. Herein, dedicatedly designed laboratory experiments were conducted to investigate the response of these ions for 21 VOCs, including 12 oxygenated VOCs and two nitriles, using the recently developed Vocus PTR-MS. Our results show that the focusing ion-molecule reactor (FIMR) axial voltage increases sensitivity by three to four orders of magnitude but does not significantly change the fractions of protonated ions. Reducing the FIMR pressure, however, substantially increases fragmentation. Applying a high radio frequency (RF) amplitude radially on FIMR can enhance sensitivity by one to two orders of magnitude without affecting the protonated ion fractions. The change in big segmented quadrupole (BSQ) amplitude mainly affects sensitivity and protonated ion fraction by modifying ion transmission. The relationship between sensitivity and proton-transfer reaction rate constant is complicated by the influences from both ion transmission and protonated ion fraction. The protonated ions of most VOCs studied (19 out of 21) show less than 15 % variations in sensitivity as RH increases from ~5 % to ~85 %, except for some long-chain aldehydes which show a positive RH variation of up to 30 %. Our results suggest that the Vocus PTR-MS can reliably quantify the majority of VOCs under ambient conditions with varying RH. However, caution is advised for small oxygenates such as formaldehyde and methanol due to their low sensitivity, as well as for long-chain aldehydes for their slight RH dependence and fragmentation.

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质子化离子、加合物离子和碎片离子在 Vocus 质子转移反应飞行时间质谱仪（PTR-ToF-MS）中的反应

摘要。挥发性有机化合物（VOCs）通过活性化学作用影响二次污染物的形成。质子转移反应质谱法（PTR-MS）是研究挥发性有机化合物高度多变的时空特征的最重要技术之一。质子转移反应质谱（PTR-MS）中的质子化离子、加合物离子和碎片离子在改变仪器设置和相对湿度（RH）时的反应需要严格的特征描述。在此，我们利用最近开发的 Vocus PTR-MS 进行了专门设计的实验室实验，以研究 21 种挥发性有机化合物（包括 12 种含氧挥发性有机化合物和两种腈类）的这些离子的响应。结果表明，聚焦离子分子反应器（FIMR）轴向电压可将灵敏度提高三到四个数量级，但质子化离子的比例变化不大。然而，降低 FIMR 的压力会大大增加碎片的数量。在 FIMR 上径向施加高射频（RF）振幅可将灵敏度提高一到两个数量级，但不会影响质子化离子的分数。大分段四极杆（BSQ）振幅的变化主要通过改变离子传输来影响灵敏度和质子化离子分数。灵敏度和质子转移反应速率常数之间的关系因离子传输和质子化离子分数的影响而变得复杂。所研究的大多数挥发性有机化合物（21 种中的 19 种）的质子化离子在相对湿度从 ~5 % 增加到 ~85 % 时，灵敏度的变化小于 15 %，但一些长链醛类除外，它们的相对湿度正向变化高达 30 %。我们的研究结果表明，Vocus PTR-MS 可以在不同相对湿度的环境条件下可靠地量化大多数挥发性有机化合物。不过，由于甲醛和甲醇等小分子含氧化合物的灵敏度较低，以及长链醛类物质对相对湿度的依赖性较小和碎片较多，因此建议谨慎使用。

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来源期刊

Atmospheric Measurement Techniques METEOROLOGY & ATMOSPHERIC SCIENCES-

CiteScore

7.10

自引率

18.40%

发文量

331

审稿时长

3 months

期刊介绍： Atmospheric Measurement Techniques (AMT) is an international scientific journal dedicated to the publication and discussion of advances in remote sensing, in-situ and laboratory measurement techniques for the constituents and properties of the Earth’s atmosphere. The main subject areas comprise the development, intercomparison and validation of measurement instruments and techniques of data processing and information retrieval for gases, aerosols, and clouds. The manuscript types considered for peer-reviewed publication are research articles, review articles, and commentaries.