Grantee Research Project Results

Final Report: Ion Mobility Analysis of Particulate Matter and Gas Phase Precursors

EPA Grant Number: R832836
Title: Ion Mobility Analysis of Particulate Matter and Gas Phase Precursors
Investigators: Wexler, Anthony S.
Institution: University of California - Davis
EPA Project Officer: Chung, Serena
Project Period: March 6, 2006 through March 5, 2009 (Extended to March 5, 2011)
Project Amount: $372,168
RFA: Continuous Measurement Methods for Particulate Matter Composition (2005) RFA Text | Recipients Lists
Research Category: Particulate Matter , Air Quality and Air Toxics , Air

Objective:

A new cost-effective and portable instrument for analyzing the semi-volatile organic and inorganic gas phase precursors.

Summary/Accomplishments (Outputs/Outcomes):

The project has progressed slower than expected due to numerous difficulties designing the instrument, building it so that it is easily manufacturable, generating ions efficiently with minimal artifacts, and recording the ion signals. Details of our progress are enumerated below. In summary, we have a near-working prototype and continue to develop it in partnership with an analytical chemistry company that produces an electrometer array as part of their product line. This electrometer array was not available until recently and will facilitate successful testing and deployment of the CF-IMS in the near future.

Prior to this funding, a Cross-Flow Ion Mobility Spectrometer instrument was hypothesized and the theoretical basis for it was developed. During this grant:

A paper was published on the theoretical basis for the instrument and its testing in a low resolution configuration.
Many versions of a high-resolution prototype were built with the goal of testing a design that is cheap to manufacture. A version that uses a sandwich of printed circuit boards was settled on.
The ionizer in these versions was originally 63Ni, which caused a number of problems
1. since the source is a long-lived radionuclide, it had permitting and contamination problems.
2. the ionization efficiency was low because the mean free path for the beta particles was much larger than the container housing the foil.
3. the beta particles also ionize water which caused numerous artifacts in the spectra with multiple analyte-hydrates forming.
The 63Ni ionizer was replaced with a UV photoionization source which mitigated all of these problems.

e.Difficulties finding an electrometer array with sufficient sensitivity persisted. TSI loaned us a 22-channel electrometer but this was insufficient for the instrument since it uses macroscopic components. A new partnership has been developed with a company that manufactures an electrometer array on a chip

Dr. Zhang began this project since he had worked in it before under prior funding. Dr. Zhang left to join the California Air Resources Board. Dr. Collier commenced work on this project on September 1, 2009, and remained with the project until completion.

Expenditures were completed at the project completion.

Conclusions:

Inexpensive, real-time instruments enable much more spatially dense monitoring of ambient concentrations and real-time assessment of their temporal variability. These are very important to health effects studies and identifying sources. Although we were not able to complete development and testing of CF-IMS during the period of this grant, work on it continues.

The main objective for the subsequent work is to partner with a company that makes sensitive solid state electrometers for recording the CF-IMS ion signal. The agreement for this partnership is in place and we are rebuilding the low-voltage CF-IMS manifold to accommodate this electrometer array. Once completed, the company will visit us to help us use the array and debug the resulting instrument. A manuscript demonstrating capabilities, including sensitivity and resolution, will be written and submitted for publication. Testing of the CF-IMS and industry partnering to advance the design to field deployment continue.

Journal Articles:

No journal articles submitted with this report: View all 5 publications for this project

Supplemental Keywords:

Air, Scientific Discipline, Environmental Chemistry, Engineering, Chemistry, & Physics, Environmental Monitoring, aerosol particles, air sampling, air quality field measurements, chemical composition, chemical detection techniques, monitoring, field monitoring, atmospheric aerosols, particulate matter chemistry, atmospheric measurement

Progress and Final Reports:

Original Abstract

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.