ASCOS Pre-Expedition Workshop Contributing Efforts to ASCOS using the Proton Transfer Reaction Technique for VOC Analysis M. Müller, M. Graus, A. Wisthaler, A. Hansel Institute of Ion Physics and Applied Physics, University of Innsbruck, Austria

ASCOS Pre-Expedition Workshop Proton Transfer Reaction: CompoundProton affinity [kcal/mol] Argon 88.2 Oxygen100.6 Nitrogen118.0 CO129.2 CO Water165.2 Formaldehyde170.4 Benzene179.3 Methanol180.3 Ethanol185.6 Toluene187.4 Xylene190.0 DMS198.6 Chemical ionization: H 3 O + + VOC →VOCH + + H 2 O Reaction controlling parameter: Proton affinity PA PA VOC > PA H2O ΔE= PA H2O - PA VOC PA of main air compounds to low → no PTR ionization Most volatile organic compounds (VOCs) can be detected Reaction energy is mostly lower than molecule bonding energies → hardly any fragmentation expected → soft ionization method

ASCOS Pre-Expedition Workshop PTR-MS: H2OH2O H 2 O + O + H + OH + H3O+H3O+H3O+H3O+H3O+H3O+H3O+H3O+ VOC VOCH + e–e– H3O+H3O+ H3O+H3O+ H3O+H3O+ Proton transfer reaction when PA(VOC)>PA(H 2 O) Reaction: H 3 O + + VOC → VOCH + + H 2 O

Most hydro carbons and derivates  Terpenes  Aromatics Photo oxidation products and other oxyVOCs  Ketones  Aldehydes  Alcohols Aerosol precursors  DMS and oxidation products (DMSO)  High molecular species (semi volatile) What do we detect: ASCOS Pre-Expedition Workshop

Advantages: Compact organic trace gas analyser Mostly non dissociative ionization Excellent sensitivity Low limit of detection ~10 pptv Performance Summary PTR-MS: Disadvantage: Poor selectivity ASCOS Pre-Expedition Workshop

M. Graus, M. Müller, A. Wisthaler, A. Hansel Time of Flight Signal PTR Drift TubeTOF-MS Pulser Detector Sample Inlet Acquisition Timing HR PTR-TOFMS:

ASCOS Pre-Expedition Workshop Performance Example I: m/z= m/z=79.055

ASCOS Pre-Expedition Workshop Performance Summary HR PTR-TOFMS: Detects all ions in one instant Separation of isobars is possible Identification of the elemental composition High sensitivity Low pptv range LOD m/z= m/z=79.055

Planed Innsbruck’s contributions to ASCOS: Analysis of solved VOCs in sea water: Surface µ-layer samples Surface layer samples Heli profiles of VOCs VOC air mass characterization Aerosol collection (5 stage BCI) and analysis for organic compounds Continuous measurements 6-8 SilcoCan off- line sampling technique HLC-Setup Molekular mass HLC for identification quantitativ Off-line thermal desorption analysis

EGU General Assembly 2008 Why off-line heli profiles using 6-8 SilcoCans? Lets look at some AOE 2001 data!

EGU General Assembly 2008 AOE Results by Armin Wisthaler: Expected SilcoCan Data

EGU General Assembly 2008 AOE Results by Armin Wisthaler: Expected SilcoCan Data Very low DMS concentration => high signal/noise High precision data  low signal/noise  Whole mass scans possible  Isobaric identification possible (TOF)

EGU General Assembly 2008 THANK YOU