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.
