Preprints
https://doi.org/10.5194/egusphere-2024-1203
https://doi.org/10.5194/egusphere-2024-1203
02 May 2024
 | 02 May 2024
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Optimizing Iodide-Adduct CIMS Quantitative Method for Toluene Oxidation Intermediates: Experimental Insights into Functional Group Differences

Mengdi Song, Shuyu He, Xin Li, Ying Liu, Shengrong Lou, Sihua Lu, Limin Zeng, and Yuanhang Zhang

Abstract. Iodide-Adduct time-of-flight chemical ionization mass spectrometry (I-CIMS) has been developed as a powerful tool for detecting the oxidation products of volatile organic compounds. However, the accurate quantification of species that do not have generic standards remains a challenge for I-CIMS application. To accurately quantify aromatic hydrocarbon oxidation intermediates, both quantitative and semi-quantitative methods for I-CIMS were established for intermediate species. The direct quantitative experimental results reveal a correlation between sensitivity to iodide addition and the number of polar functional groups (keto groups, hydroxyl groups, and acid groups) present in the species. Leveraging the selectivity of I-CIMS for species with diverse functional groups, this study established semi-quantitative equations for four distinct categories: monophenols, monoacids, polyphenol or diacid species, and species with multiple functional groups. The proposed classification method offers a pathway to enhance the accuracy of the semi-quantitative approach, achieving an improvement in R2 values from 0.50 to beyond 0.88. Overall, the categorized semi-quantitative method was utilized to quantify intermediates formed during the oxidation of toluene under both NO-free and NO-applied conditions, revealing the differential variations in oxidation products with varying levels of NOx concentration.

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Mengdi Song, Shuyu He, Xin Li, Ying Liu, Shengrong Lou, Sihua Lu, Limin Zeng, and Yuanhang Zhang

Status: open (until 14 Jun 2024)

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  • RC1: 'Comment on egusphere-2024-1203', Anonymous Referee #1, 15 May 2024 reply
Mengdi Song, Shuyu He, Xin Li, Ying Liu, Shengrong Lou, Sihua Lu, Limin Zeng, and Yuanhang Zhang
Mengdi Song, Shuyu He, Xin Li, Ying Liu, Shengrong Lou, Sihua Lu, Limin Zeng, and Yuanhang Zhang

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Short summary
This study introduces detailed and improved quantitation and semi-quantitation methods of Iodide time-of-flight chemical ionization mass spectrometry (I-CIMS) to measure toluene oxidation intermediates. It assesses the experimental sensitivity of various functional group species and their binding energy with iodide ions in I-CIMS. A novel classification approach improves semi-quantitative methods (R2 > 0.88) and reduces oxidation intermediate uncertainty to 15 %–45 %.