Microengineered Mass Spectrometer for in-situ Measurement of Airborne Contaminants

EPA Grant Number: R824970C011
Subproject: this is subproject number 011 , established and managed by the Center Director under grant R824970
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EERC - Center for Airborne Organics (MIT)
Center Director: Seinfeld, John
Title: Microengineered Mass Spectrometer for in-situ Measurement of Airborne Contaminants
Investigators: Carr, William N. , Farmer, Kenneth R.
Institution: New Jersey Institute of Technology , Massachusetts Institute of Technology
Current Institution: New Jersey Institute of Technology
EPA Project Officer: Hahn, Intaek
Project Period:
Project Amount: Refer to main center abstract for funding details.
RFA: Center on Airborne Organics (1993) Recipients Lists
Research Category: Targeted Research

Objective:

The goal of this project is to develop a prototype microengineered mass spectrometer for in-situ measurement of airborne contaminants. This mass spectrometer uses standard silicon processing techniques to scale down the dimensions of an existing mass spectrometer to make it portable. It can be manufactured economically and has the potential to be integrated with more complex structures including transistor integrated circuits.

Approach:

The proposed device is fabricated using two silicon substrates, each approximately 1 cm by 1 cm. One of the substrates contains a novel microtip field emitter cathode electron source and ion extraction electrodes. The other provides ion collector, extraction and focusing electrodes. Gas molecules near the cathode are ionized by electrons generated by field emission. An electrostatic field and a uniform magnetic field of 3000 Gauss are used to establish separate trajectories for each ionized mass isotope. Each mass is collected at a different location on the ion collector plane and measured as a current through individual detector electrodes. Voltage supply levels between 0 and 50 V, and the 3000 Gauss magnetic field permit collection of ions up to 222 amu (radon). The minimum detectable density level for a given isotope is proportional to the active ionizing volume, and is limited by the input noise level of the ion collection detector circuits. From calculations, we expect to be sensitive to partial pressures below 10-11 Torr.

Rationale:

One of the stated objectives of the Center for Airborne Organics is to provide tools to reliably connect the identities and concentrations of airborne organic compounds with major emission sources by "developing and using improved techniques to sample and analyze emissions from sources and material in the air." This project directly addresses that objective. By developing a low-cost, portable mass spectrometer we expect ultimately to enable onsite testing at unprecedented levels. An important capability of the sensor is optimization for particular ions that can be identified as tracers for specific pollution source types. The information gained from both the increased and the more focused testing can be expected to impact all aspects of the Center's research, providing data and feedback for the synergistic work of the Center's other investigators. In addition, the prototype is expected to serve as leverage for significant external research and development funding, particularly in the drive toward hand-portable instruments.

Supplemental Keywords:

air, contaminant, emission., RFA, Scientific Discipline, Air, particulate matter, Environmental Chemistry, Atmospheric Sciences, Environmental Engineering, chemical characteristics, ambient measurement methods, microengineered mass spectrometry, air pollution, air sampling, in situ measurement, portable monitoring, sensor, aerosols

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  • Main Center Abstract and Reports:

    R824970    EERC - Center for Airborne Organics (MIT)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R824970C001 Chemical Kinetic Modeling of Formation of Products of Incomplete Combustion from Spark-ignition Engines
    R824970C002 Combustion Chamber Deposit Effects on Engine Hydrocarbon Emissions
    R824970C003 Atmospheric Transformation of Volatile Organic Compounds: Gas-Phase Photooxidation and Gas-to-Particle Conversion
    R824970C004 Mathematical Models of the Transport and Fate of Airborne Organics
    R824970C005 Elementary Reaction Mechanism and Pathways for Atmospheric Reactions of Aromatics - Benzene and Toluene
    R824970C006 Simultaneous Removal of Soot and NOx from the Exhaust of Diesel Powered Vehicles
    R824970C007 Modeling Gas-Phase Chemistry and Heterogeneous Reaction of Polycyclic Aromatic Compounds
    R824970C008 Fundamental Study on High Temperature Chemistry of Oxygenated Hydrocarbons as Alternate Motor Fuels and Additives
    R824970C009 Markers for Emissions from Combustion Sources
    R824970C010 Experimental Investigation of the Evolution of the Size and Composition Distribution of Atmospheric Organic Aerosols
    R824970C011 Microengineered Mass Spectrometer for in-situ Measurement of Airborne Contaminants