Citation: ZHANG Qiang-Ling, ZOU Xue, LIANG Qu, ZHANG Ya-Ting, YI Ming-Jian, WANG Hong-Mei, HUANG Chao-Qun, SHEN Cheng-Yin, CHU Yan-Nan. Development of Dipolar Proton Transfer Reaction Mass Spectrometer for Real-time Monitoring of Volatile Organic Compounds in Ambient Air. Chinese Journal of Analytical Chemistry, 2018, 46(4): 471-478. doi: 10.11895/j.issn.0253-3820.171234 [复制]
Development of Dipolar Proton Transfer Reaction Mass Spectrometer for Real-time Monitoring of Volatile Organic Compounds in Ambient Air
大气中挥发性有机物（VOCs）能参与光化学反应，导致臭氧和气溶胶等二次污染物的产生，实时精准地监测VOCs对于大气污染成因研究具有重要意义。在质子转移反应质谱（PTR-MS）研究基础上，本工作研制一套用于大气VOCs实时在线监测的双极性质子转移反应质谱仪（Dipolar proton transfer reaction mass spectrometer，DP-PTR-MS）。相比单一反应离子H3O+的常规PTR-MS，DP-PTR-MS中有正负3种反应离子（H3O+、OH-、（CH3）2COH+），可根据实际检测需要选择切换，提高定性能力，并有效扩展检测范围。其中，H3O+反应离子用于检测质子亲和势大于H2O的VOCs；OH-反应离子可与H3O+反应离子配合识别VOCs，还可用于检测CO2等无机物；（CH3）2COH+反应离子可在排除干扰的情况下准确检测NH3。利用6种标准气体测定DP-PTR-MS检出限和灵敏度，结果表明，DP-PTR-MS对甲苯的检出限为7×10-12（V/V），对氨气的灵敏度为126.0 cps/10-9（V/V）。利用DP-PTR-MS对合肥市区大气VOCs开展连续78 h实时在线监测验证实验，结果表明，DP-PTR-MS可对大气中10-12（V/V）量级VOCs进行长期实时在线监测，可作为大气污染成因研究和痕量VOCs排放监测的重要工具。
Volatile organic compounds (VOCs) in ambient air can participate in photochemical reactions, which lead to the generation of secondary pollutants such as ozone and aerosol. So real-time and accurate monitoring of atmospheric VOCs plays an important role in the study of the causes of air pollution. On the basis of proton transfer reaction mass spectrometry (PTR-MS) research, a novel dipolar proton transfer reaction mass spectrometer (DP-PTR-MS) for real-time and on-line monitoring atmospheric VOCs was developed. Compared with the conventional PTR-MS with one kind of reagent ion H3O+, DP-PTR-MS had three kinds of reagent ions H3O+, OH-, (CH)2COH+, which could be switched according to the actual detection need. So DP-PTR-MS can improve the qualitative ability and expand the detection range effectively. The reagent ion H3O+ can be used for detecting VOCs whose proton affinities are greater than that of H2O. The reagent ion OH- can be used to identify VOCs cooperating with the reagent ion H3O+, and can also be used for detecting some inorganic substances such as CO2. The reagent ion (CH3)2COH+ can be used for accurately detecting NH3 under interference elimination circumstances. The limit of detection (LOD) and sensitivity of DP-PTR-MS were measured by using six kinds of standard gases. The results showed that the LOD for detecting toluene was 7×10-12 (V/V) and the sensitivity for detecting ammonia has reached 126 cps/10-9(V/V). The ambient air in Hefei city was on-line and real-time monitored for continuous 78 hours with DP-PTR-MS. The results showed that the newly developed DP-PTR-MS could be used for long-term and real-time monitoring atmospheric VOCs with the concentration of 10-12(V/V) level. DP-PTR-MS is an important tool for the study of the causes of atmospheric pollution and the monitoring of trace VOCs emissions.
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