A fully automated electrodynamical ion funnel proton transfer reaction mass spectrometer for the use on research and passenger aircraft

• Antragsteller: Dr. Detlev Sprung
• Fachliche Zuordnung: Physik und Chemie der Atmosphäre
• Förderung: Förderung von 2007 bis 2011
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 34119472

For more than five years proton-transfer-reaction mass spectrometers (PTRMS) for the detection of diverse organic compounds are successfully used for medical applications (e.g. breath analysis) and in atmospheric sciences. Since May 2005 a PTRMS for measuring acetone, acetonitrile, peroxyacetyl nitrate (PAN) and other compounds is installed in a modified airfreight container that is deployed onboard an Airbus A340-600 passenger aircraft of Lufthansa AG, project CARIBIC. The precision of the most sophisticated PTRMS currently is 30-200 pptv√Hz, depending on species and mixing ratio (1 pptv = 10-12 mol/mol). The desired precision (and accuracy) for the use on fast 2 moving aircraft in the upper troposphere and lower stratosphere, where the mixing ratios of the species of interest are in the order of 10-1000 pptv, is a factor of ~10 higher. A powerful technique to significantly improve the measurement uncertainty of PTRMS is expected to be the combination with an electro-dynamical ion funnel. In the present PTRMS, more than 95% of all ions get lost on the walls of the PTRMS reaction chamber (drift tube) and only ~1% of all primary ions finally reach the detector (quadrupole mass spectrometer). Ion funnels are systems that are able to guide ions almost quantitatively through ion drift regions where the pressure is about 1-10 hPa and thus the mean free path length below ~1mm. Objective of this proposal is to extent the PTRMS drift tube with an electro-dynamical ion funnel. The expected sensitivity improvement is in the order of 10. Until now, the ion funnel technique (proposed by Shaffer et al., 1997) has only been used for electrospray mass spectrometry and for molecule masses above ~200 amu. A few theoretical studies indicate that a modified ion funnel should be able to guide also light ions with masses as low as 20 amu through a drift tube. The proposed project consists of three phases: in year 1, a low-mass ion funnel and its rf power supply shall be developed, constructed and installed into a PTRMS; in year 2, the system shall extensively be tested in the laboratory under various conditions (pressures, ion funnel frequencies, DC, and AC voltages) and if necessary modified; and in year 3, an ion funnel PTRMS shall be flown onboard the CARIBIC Airbus and the data shall be analysed, inter alia, to quantify the improvement of the measurement uncertainty under field conditions.

• DFG-Verfahren: Sachbeihilfen