Single Aerosol Particle Analysis Using Aircraft Compatible Time-of-Flight Mass Spectrometers in Real Time (A-ATOFMS

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Single Aerosol Particle Analysis Using Aircraft
Compatible Time-of-Flight Mass Spectrometers in
Real Time(A-ATOFMS SPLAT II)
Suresh Regmi Literature Seminar Presentation CHEM
7800 November 9, 2009
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Objective

• To compare and contrast two TOF instruments (
  A-ATOFMS SPLAT II) developed for real time
  detection and analysis of single aerosol
  particles.

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Articles

• Development and characterization of an aircraft
  aerosol time-of-flight mass spectrometer
• Kerri A. Pratt, Joseph E. Mayer, John C. Holecek,
  Ryan C. Moffet, Rene O. Sanchez, Thomas P.
  Rebotier, Hiroshi Furutani, Marc Gonin, Katrin
  Fuhrer, Yongxuan Su, Sergio Guazzotti, and
  Kimberly A. Prather (University of California,
  San Diego, California).
• Anal. Chem. 2009, 81, 17921800
• SPLAT II an aircraft compatible,
  ultra-sensitive, high precision instrument for
  in-situ characterization of the size and
  composition of fine and ultrafine particles
• Alla Zelenyuk Juan Yang Eric Choi Dan Imre
  (Pacific Northwest National Laboratory, Richland,
  Washington).
• Aerosol Sci. Technol. 2009, 43, 411424,

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Why Study Aerosol?

• Human health
• air quality, airborne pathogen transport
• Energy balance of earth
• aerosol optical properties
• direct/indirect effects
• Cloud nucleation
• Geochemical cycles
• metals, nutrients, organics
• Acidification (sulfur, nitrogen)

http//www.ucar.edu/learn/1_1_1.htm
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Why Single Aerosol Particles in Real Time?

• Particle size is critical for health effects
• Chemical composition of a particle and mixed
• composition particles
• Individual particle size and composition
  represents its
• source.
• Prevents sampling artifacts / secondary
  pollutant
• formation during detection
• Real picture of the air you breathe

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Research Challenges

• Requires faster data acquisition speeds to
• provide high spatial resolution
• No sample collection (advantages and
• disadvantages)
• Difference in shape of the particles
• Enormous variety, complexity, and fragility of
• particles

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Why Aircraft Based Study ?

• Direct and indirect radiative forcing depend on
  
• aerosol vertical and horizontal profiles.
• Quantify the properties of particles as a
  function of
• altitude
• Horizontal distribution of particles, aircraft
  route
• selection
• Role of particles in cloud nucleation (Aerosol
  cloud
• interaction)

Low aerosol concentration
High aerosol concentration
http//earthobservatory.nasa.gov/Features/Aerosols
/
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Requirements for Aircraft Based Instrument

• Size of the instrument
• Weight of the instrument
• Vibration shielding
• Data acquisition

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Real Time -Single Aerosol Time of Flight Mass
Spectrometer
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Time of Flight Mass Spectrometer
Laser
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Aircraft-Aerosol Time of Flight Mass
Spectrometer (A-ATOFMS) Principal investigator
Dr. Kimberly Prather
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A-ATOFMS in Working Condition
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A-ATOFMS On Board
Power consumption- 1.4 kW
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A-ATOFMS Inside
7 10 -7 Torr
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Particle Sizing
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Ionization Laser Desorption
-
-


-





-


-

-

-
Extractors
266 nm NdYAG DI laser
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A-ATOFMS Separation and Detection
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A-ATOFMS
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Mass Spectra Organic Carbon - Sulfate - Nitrate
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Mass Spectra Dust - Sulfate - Nitrate
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Particle Concentration
)
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Conclusions

• Transportable and high data acquisition
• capability
• Real time source apportionment software
• Use of neutralizer
• Duel polarity mass analyzer
• Field tested in ground and on board

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Single Particle Laser Ablation Time of Flight
Mass Spectrometer II (SPLAT II)Principal
investigatorDr. Alla Zelenyuk
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Real Time -Single Aerosol Time of Flight Mass
Spectrometer
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SPLAT II Ready to Fly
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SPLAT II Inside
2.25 10-6 Torr

• Power consumption
• 3.5 kW
• Total wt 400 kg
• Dimension - 143 69.6
• 124.5 cm

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Particle Sizing
Spot 330 µm
532 nm, 300 mw
532 nm, 300 mw
Zelenyuk et al. Aerosol Sci. Technol. 2009_2
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Ionization Evaporation Laser Ablation

• Requires lower laser intensity
• Less fragmentation
• Flexibility for optimization

193 nm UV excimer laser, 8 ns pulse, 0.5-2
mJ/pulse, Focal spot- 550 750 µm
UV laser

IR laser
10.6 µm CO2 laser, 50 ns pulse, 110 mJ/pulse,
spot -1 mm
IR/UV ionization
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Mass Spectrum SPLAT II Vs. NIST
Trans-sobrerol 170 Lab
OC-Nitrate-Sulfate
70 ev EI ionization
Trans-sobrerol 170
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Mass Spectrum IR/UV Vs. UV
334 nm DOP- 390.56 Lab
OC-Nitrate-Sulfate
DOP - 390.56
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Mass Spectra Convair 580 Aircraft
Dust particle
Biomass burning particle
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Conclusion

• Transportable
• Can size over 500 particles and record up to
  100
• individual particles mass spectra per
  second
• Real time source apportionment software
• Can differentiate between spherical and
• aspherical particles
• Two step ionization process
• Field tested in ground and on board

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Summary/ Evaluation

• Both papers summarize an important scientific
• investigation
• Devoted in the development of instruments for
  real
• time detection and analysis of single aerosol
  particles
• Improved version of their predecessor
• Field as well as on board tested
• Ionization - major difference

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A-ATOFMS Vs. SPLAT II
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Instrumentation
Components A-ATOFMS SPLAT II
Neutralizer Yes No
Particle sizing Light scattering Light scattering
Ionization Single laser ablation IR/UV laser ablation
Ion separation Dual polarity Single polarity
Dynamic range 70 nm - 1000 nm 125 nm - 600 nm
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Ionization

• UV
• Hard ionization
• Irreproducible mass spectra
• Easier optics alignment
• Non-linear, multiphoton
• process
• Matrix and charge transfer
• effects

• IR/UV
• Soft /user controlled ionization
• Reproducible mass spectra/
• Independent of UV laser fluence
• Difficult optics alignment
• Linear relationships between the
• integrated mass spectral
• intensities and particle mass
• Less influence by matrix and
• charge transfer

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Dual Polarity Vs. Single Polarity TOF
Single polarity
Dual polarity
?
http//www.internetvibes.net/gallery/disney-pixar-
cars-images-from-the-cartoon/
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Evaluation - Suggestion

• Comparison with their own instrument
• Competition to show the instrument
• portable
• Stocked with TOF
• Why not Ion trap?

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Alternative to Time of Flight MS Ion Trap MS
Simpson et al. International Journal of Mass
Spectrometry 281 (2009) 140149
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Conclusions

• Online analysis of single particle size,
  chemical
• composition, density, and optical properties
• A-ATOFMS- more sensitive for detection limit and
• dynamic range
• SPLAT II- Reproducible mass spectra, accurate
  chemical
• composition, differentiate spherical and
  aspherical
• particles
• Ion trap instead of flight tube smaller,
  and lighter
• instrument

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Acknowledgement

• Dr. Gilman
• Dr. McCarley
• Dr. Murray
• Dr. Gilmans research
• group
• Audience