ISSAOS 2008 l‘Aquila, September 2008 Aerosol Mass Spectrometry: General Principles and examples

1. ISSAOS 2008 l‘Aquila, September 2008 Aerosol Mass Spectrometry: General Principles and examples Hugh Coe School of Earth, Atmospheric and Environmental Sciences University of Manchester Reading: • D Murphy, The design of single particle laser mass spectrometers, in: Mass Spectrometry Reviews, 2007, 26, 150-165. • M. R. Canagaratna et al., Chemical and microphysical characterisation of ambient aerosols with the Aerodyne Aerosol Mass Spectrometer in: Mass Spectrometry Reviews, 2007, 26, 185-222. • H. Coe and J. D. Allan, “Aerosol Mass Spectrometry” in “Atmospheric techniques” ed D. E. Heard, Blackwell Scientific Publishing, 2006 • http://cires.colorado.edu/jimenez/ams-papers.html • thanks to Jose Jimenez for the slides showing component parts of aerosol mass spectrometers

2. General Outline • General Introduction – the advantages of Aerosol Mass Spectrometry • The component parts of an aerosol mass spectrometer • Examples of different mass spectrometric methods • Advantages and disadvantages of different mass spectrometric methods

3. General Outline • General Introduction – the advantages of Aerosol Mass Spectrometry • The component parts of an aerosol mass spectrometer • Examples of different mass spectrometric methods • Advantages and disadvantages of different mass spectrometric methods

7. General Outline • General Introduction – the advantages of Aerosol Mass Spectrometry • The component parts of an aerosol mass spectrometer • Examples of different mass spectrometric methods • Advantages and disadvantages of different mass spectrometric methods

8. thanks to Jose Jimenez for the slides showing component parts of aerosol mass spectrometers

9. Aerosol Inlets • Need to entrain aerosols from the atmosphere into a vacuum • Aerosol Inlets • Need to entrain aerosols from the atmosphere into a vacuum • Need to concentrate particles and remove the gas • 2.5 x 1019 molecules cm-3 in ambient air • 3.2 µg m-3 of particulate S = 10-7 moles m-3 of S • 6.2x1023x10-7x10-6=6.2x1010 molecules cm-3 • or around 2 ppb • Aerosol Inlets • Need to entrain aerosols from the atmosphere into a vacuum • Need to concentrate particles and remove the gas • 2.5 x 1019 molecules cm-3 in ambient air • 3.2 µg m-3 of particulate S = 10-7 moles m-3 of S • 6.2x1023x10-7x10-6=6.2x1010 molecules cm-3 • or around 2 ppb • May need to introduce a size dependent velocity onto the particles

13. Effects on beam width • non spherical particles may affect the ability of particle lens systems to focus the particle beam

19. Vaporization • Desorption/ionisation process can be coupled together • - This is certainly simpler but it is very difficult to quantify the mass of material detected • A two step process of desorption followed subsequently by ionisation provides a way of more easily quantifying mass • However, this comes at a price • - More volatile species may decompose • - Refractory material (NaCl, dust, soot) will not evapourate unless the temperature is very high • Vaporisation may be performed by • Thermal methods or • IR laser absorption

20. Ionization Ideally should: • Produce ions from either solid or liquid particles or the desorbed gas • Need to produce a high number of ions per molecule (high efficiency) • Ideally the number of ions produced is proportional to the number of molecules • The ionisation is selective and universal • The molecular fragmentation is reproducible

22. Laser Desorption/Ionisation: • The LDI process on particles is poorly understood • Laser wavelength is important • Sulphuric acid hard to ionise – due to transparency in UV • Dependent on laser beam cross sectional intensity • Laser pulse width dependence • In larger particles, not all particle may be ionized • Laser power density • -lower fluence reduces fragmentation • -higher fluence allows improved ionisation

27. Ion Trap • Can do MSn • Can investigate ion-molecule reactions

28. General Outline • General Introduction – the advantages of Aerosol Mass Spectrometry • The component parts of an aerosol mass spectrometer • Examples of different mass spectrometric methods • Advantages and disadvantages of different mass spectrometric methods

32. General Outline • General Introduction – the advantages of Aerosol Mass Spectrometry • The component parts of an aerosol mass spectrometer • Examples of different mass spectrometric methods • Advantages and disadvantages of different mass spectrometric methods

33. Advantages/Disadvantages of laser and thermal systems: • laser based systems: thermal systems: • can ionise a wide range of - Can be used to deliver • species quantitative mass information • -deliver single particle info - deliver information on the • and so enable estimates of particle ensemble • mixing state • -do not have consistent - Can be traced back to • ionisation and suffer shot to well characterised ionisation • shot variability libraries

34. Example: PALMS (Murphy et al NOAA)

35. Example: PALMS (Murphy et al NOAA) Murphy, D.M., Thomson, D.S. & Mahoney, T.M.J. (1998b) In situ measurements of organics, meteoritic material, mercury, and other elements in aerosols at 5 to 19 kilometers, Science, 282 (5394), 1664–1669.

36. Example: Dall’Osto et al (Birmingham) ATOFMS Identification of Hydroxymethanesulphonate during urban fog processing event REPARTEE experiment in central London ART-2a analysis based on a neural network algorithm was used to identify a number of different particle classes

37. Example: Dall’Osto et al (Birmingham) ATOFMS Identification of Hydroxymethanesulphonate during urban fog processing event

38. Example: Jim Smith (NCAR) Thermal Desorption Ionisation Chemical-Ionisation MS (TDICIMS) chemical analysis of ultrafine particles

39. Example: Jim Smith (NCAR) Thermal Desorption Ionisation Chemical-Ionisation MS (TDICIMS) chemical analysis of ultrafine particles

40. Example: Jim Smith (NCAR) Thermal Desorption Ionisation Chemical-Ionisation MS (TDICIMS) chemical analysis of ultrafine particles

41. Example: Jim Smith (NCAR) Thermal Desorption Ionisation Chemical-Ionisation MS (TDICIMS) chemical analysis of ultrafine particles

42. Example: Jim Smith (NCAR) Thermal Desorption Ionisation Chemical-Ionisation MS (TDICIMS) chemical analysis of ultrafine particles