Characterisation of the Aerosol Collection Module (ACM) Dagmar Trimborn, John Jayne, Thorsten Hohaus

Transcription

1 Characterisation of the Aerosol Collection Module (ACM) Dagmar Trimborn, John Jayne, Thorsten Hohaus

2 ACM working principle Valve Cooler/ Heater 10-3 Torr 10-5 Torr 10-5 Torr Particle Inlet Aerodynamic Lense Turbo Pump Turbo Pump Turbo Pump Carrier Gas Detector

3 ACM working priciple a) Standby/Backflush b) Sampling Particle Beam Valve 3 PC Particle Beam Valve 3 PC To Detector Valve 1 Vent Valve 2 To Detector Valve 1 Vent Valve 2 Carrier Gas Carrier Gas c) Desorption & Injection Particle Beam Valve 3 PC Cleaning in backflush mode (standby) To Detector Valve 1 Vent Valve 2 Collecting in vacuum Desorption/Injection mode Carrier Gas

4 ACM - Tasks Optimising operating parameters Temperatures Cycle time Materials / setup Checks for Linearity, Detection limits, Artefacts

5 ACM Octadecane

6 ACM Octadecane

7 ACM Octadecane

8 ACM Octadecane 6x10 4 ~ 50 pg Octadecane TIC/arb. units retention time/ min Production of monodisperse Octadecane Aerosol (300nm) difficult Amount sampled here ~ 50 pg Octadecane For comparison: detection limits TAG: Hexadecane: 74 pg, Eicosane: 59 pg => comparable

9 ACM Octadecane x10 4 corrected peak area/arb. units mass/ng Column moved into transfer line REPRODUCIBILITY (Octadecane) Mass range: 2.5ng-20ng Still blank problem

10 Ambient samples: Tuesday, 06/10/08, hot and humid Probably also measured exhausts from hood 3.0x min 2462 blank w/o VV 2463 blank 12h 11min 2464 blank w/o VV 2465 ambient 9h 14min Unresolved area (UCM???) Small peaks TIC/ arb. units min min ret.time/min 40

11 Ambient samples: Average of mass spectra (t > min) 57 8x signal/arb. units column column m/z Mixture of many different organics: hydrocarbon likes (m/z= 57, 71, ) and (m/z= 55, 69, )

12 Ambient samples: Peak at 31.8min, background subtracted 57 4x C 32 H 66??? signal/arb. units m/z Spectra hydrocarbon like (NIST: C 32 H 66 ) but it is not because peak of C 32 H 66 at 35.3 min

13 Ambient samples: Comparision ACM - AMS 3.0x10 7 Area of ACM (time >=27min, subtracted background:002479)) vs mass collected with ARI III Area ACM/ arb. units line y=a+bx a = e+05 ± 8.53e+05 b = e+06 ± 1.66e+05 r= 0.986, r 2 = mass ARI III/µg Good linearity, ARI III: mass loadings up to 300 µg/m 3 Signal above line is not related to larger sample in experiment before

14 β-pinene SOA experiments Aerosol generation Air Air Salt solutions Aerosol Mass Spectrometer (Aerodyne) PTR-MS Organic Vapors Double wall system: Teflon FEP bag Aluminum walls Volume: 260 m 3 (7m x 7m x 5.3m) Surface: 250 m 2 APS 3321 SMPS 3071A Canister CPC 3022A Filter samples Mixing: Floor heater

15 β-pinene SOA experiments β-pinene experiment 600 ppb β-pinene (Sigma-Aldrich, 99% purity) 1000 ppb Ozone 40% RH Analytical equipment ACM-GC O 3 (UV absorption) AMS PTR-MS SMPS & CPC

16 β-pinene SOA experiments

17 β-pinene SOA experiments

18 β-pinene SOA experiments

19 β-pinene SOA experiments

20 β-pinene SOA experiments

21 β-pinene SOA experiments

22 β-pinene SOA experiments

23 β-pinene SOA experiments

24 β-pinene SOA experiments

25 Summary Experiments with Octadecane Difficulties producing monodisperse aerosol sensitivity ~ 50 pg Experiments with ambient aerosol at Aerodyne ACM sees ambient Some samples high mass loadings: probably measured exhausts from the hood Blank issues Linearity between ACM and AMS Experiments with SOA from β-pinene Nopinone detected in SOA Correlation of ACM peaks with AMS mass peaks Needs improvement in sensitivity

26 Outlook Optimize ACM: temperatures, times, coating Full characterization of sensitivity, linearity Switching automatically between blanks and experiments Further ambient experiments Coupling with other detectors such as PTR-MS

27 Thank you!