Development of a Proton Transfer Reaction Linear Ion Trap for Fast Atmospheric Pollutant Detection

普渡大学的Paul Shepson教授和Scott McLuckey教授以及因斯布鲁克大学的Armin Hansel教授得到了分析和表面化学和大气化学项目的支持，以开发和评估一种快速灵敏检测大气污染物的新型仪器。这项研究的动机是来自植被的挥发性有机化合物以重要的方式参与对流层臭氧的产生，而对流层臭氧是一种重要的温室气体。因此，非常需要关于与森林生态系统交换气体的定量资料。该仪器被称为质子转移反应线性离子阱，是一个流管反应器和线性四极杆质谱仪的组合，具有独特的新设计，使用具有适当应用电位的端板，可以在四极杆的轴内捕获离子。分析物离子在允许与质子反应的流动管中产生，然后采样到质谱仪；已知的反应动力学可以在没有校准标准的情况下进行定量检测。然后，选定的离子可以用施加的交流电位激发，导致碰撞诱导解离，并获得MS/MS谱。利用涡流相关通量技术，通量测量将成为可能。该项目涉及质谱、仪器开发和大气化学方面的专家小组之间的合作努力。开发的仪器将在普渡大学进行测试，然后在密歇根州北部的一个森林地点进行现场测试，作为森林-大气相互作用大规模研究（PROPHET）的一部分。第一代仪器将用于测量生物源异戊二烯的氧化产物（甲基乙烯酮和甲基丙烯醛），并测量来自森林冠层的异戊二烯的通量。该项目有可能影响包括痕量探测和大气化学在内的几个领域。挥发性有机化合物（VOCs）在调节二氧化碳水平上升的影响方面的作用尚不清楚。因此，这项研究是理解和预测全球表面温度变化的重要因素。

Professors Paul Shepson and Scott McLuckey of Purdue University and Professor Armin Hansel of the University of Innsbruck are supported by the Analytical and Surface Chemistry and Atmospheric Chemistry Programs to develop and evaluate a novel instrument for fast and sensitive detection of atmospheric pollutants. The research is motivated by the fact that volatile organic compounds from vegetation participate in significant ways in the production of tropospheric ozone, which is an important greenhouse gas. There is thus a great need for quantitative information about exchange of gases with forest ecosystems. The instrument, called a Proton Transfer Reaction Linear Ion Trap, is a combination flow tube reactor and linear quadrupole mass spectrometer, with a unique new design that uses end plates with appropriate applied potentials that enable trapping of ions within the axis of the quadrupole rods. Analyte ions are produced in a flow tube that allows for reaction with protons, followed by sampling to the mass spectrometer; the known reaction kinetics can allow for quantitative detection without calibration standards. Selected ions can then be excited with an applied AC potential, resulting in collision induced dissociation, and acquisition of MS/MS spectra. Flux measurements will be possible using the eddy covariance flux technique. This project involves a collaborative effort between groups expert in mass spectrometry, instrument development and atmospheric chemistry. The developed instrumentation will be tested at Purdue and then field tested at a forest site in northern Michigan as part of a large-scale study (PROPHET) of forest-atmosphere interactions. The first generation instrument will be used to conduct measurements of the oxidation products (methyl vinyl ketone and methacrolein) of biogenic isoprene, and to conduct measurements of the fluxes of isoprene from the forest canopy. The project has the potential to impact several fields including trace detection and atmospheric chemistry. The role of volatile organic compounds (VOCs) in mediating the impacts of rising carbon dioxide levels is not well understood. This research is thus an important element in understanding and predicting global surface temperature changes.