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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. Objective. - PowerPoint PPT Presentation
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Single Aerosol Particle Analysis Using Aircraft Compatible Time-of-Flight Mass
Spectrometers in Real Time(A-ATOFMS & SPLAT II)
Suresh RegmiLiterature Seminar Presentation
CHEM 7800November 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 spectrometerKerri 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, 1792–1800
SPLAT II: an aircraft compatible, ultra-sensitive, high precision instrument for in-situ characterization of the size and composition of fine and ultrafine particlesAlla Zelenyuk ; Juan Yang ; Eric Choi ; Dan Imre (Pacific Northwest National Laboratory, Richland, Washington). Aerosol Sci. Technol. 2009, 43, 411–424,
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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)
http://earthobservatory.nasa.gov/Features/Aerosols/
Low aerosol concentration
High aerosol concentration
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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
particle collection/
focusing
Particle sizing
IonizationMass analysis
Detection
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Time of Flight Mass Spectrometer
ReflectronFlight tubeIonization chamber
Detector
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 BoardPower consumption- 1.4 kW
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A-ATOFMS : Inside
7 × 10 -7 Torr
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Particle Sizing
Aerosol particle
Aerodynamic lens
SkimmersLaser
PMT
Po 210 neutralizer
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Ionization: Laser Desorption
266 nm Nd:YAG DI laser
+-
++
+
++
+
-
-
-
-
- ++
++-
Extractors
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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 investigator
Dr. Alla Zelenyuk
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Real Time -Single Aerosol Time of Flight Mass Spectrometer
particle collection/
focusing
Particle sizing
Ionization
Mass analysis
Detection
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SPLAT II : Ready to Fly
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SPLAT II : Inside
Power consumption 3.5 kW Total wt – 400 kg
Dimension - 143 × 69.6 × 124.5 cm
2.25 × 10-6 Torr
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Particle Sizing
Zelenyuk et al. Aerosol Sci. Technol. 2009_2
532 nm, 300 mw
532 nm, 300 mw
Spot 330 µm
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Ionization: Evaporation + Laser Ablation
IR/UV ionization
Requires lower laser intensity Less fragmentation Flexibility for optimizationUV laser
IR laser
+ + ++ + +
10.6 µm CO2 laser, 50 ns pulse,110 mJ/pulse, spot -1 mm
193 nm UV excimer laser,8 ns pulse, 0.5-2 mJ/pulse,Focal spot- 550 × 750 µm
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Mass Spectrum : SPLAT II Vs. NIST
OC-Nitrate-Sulfate
Trans-sobrerol 170 Lab
Trans-sobrerol 170 70 ev EI ionization
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Mass Spectrum : IR/UV Vs. UV
OC-Nitrate-Sulfate
334 nmDOP- 390.56 Lab
DOP - 390.56
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Mass Spectra: Convair 580 Aircraft
Biomass burning particle
Dust 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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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
Ionization
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Dual Polarity Vs. Single Polarity TOF
?
http://www.internetvibes.net/gallery/disney-pixar-cars-images-from-the-cartoon/
Dual polaritySingle polarity
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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) 140–149
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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. Gilman’s research group• Audience