Grantee Research Project Results

2007 Progress 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 Period Covered by this Report: March 6, 2007 through March 5,2008
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:

Briefly describe the objectives for the project.

A new cost effecting instrument is capable of analyzing the semi-volatile organic and inorganic gas phase precursors.

Approach:

The heart of these instruments is a 2D ion mobility spectrometer able to perform continuous gas-phase chemical analysis. The mobility cell separates ions in space, as does a DMA. The resulting spatial current distribution is recorded by a linear array of electrometers. Key to the viability of the mobility spectrometer is recent progress in CMOS active pixel sensors and multiplexed electrometer arrays. Arrays of 1000 electrometers are commercially available with sensitivities down to hundreds of electrons. Hamamatsu or another vender will provide these multiplexed electrometer arrays modified from their linear image sensors. Thus, the ion mobility cell and electrometer array are able to measure the concentration of gas phase components with 1-10 s temporal resolution. Pre-conditioning the sample enables particulate and gaseous analysis.

For PM analysis, ambient air is sampled through PM2.5 or PM10 cyclones. Sample air flow is carefully controlled to provide reliable cut point precision. The sample is then drawn through silica gel and activated carbon denuders where the gas phase components are removed. The sample is then heated to evaporate semi-volatiles. These vapors and the non-volatile particle components are drawn through a ⁶³Ni beta source where the vapors are ionized. The sample is then drawn into an ion mobility cell where the ions are analyzed. The remaining particle components leave the ion mobility cell and are available for further composition analysis.

Progress Summary:

Progress Summary/Accomplishments: Provide brief statements covering work status and preliminary results, emphasizing findings and their significance to the field, their relationship to the goals of the project, and their relevance to protection of the environment and human health. This discussion should include potential practical applications.

More experiments were done by TSI supplied 20-channel electrometer with different cross flow ion mobility drift cell including Delrin block and improved stacked PCB configuration to help charge dissipation and protect signal from outside EM signal. Several chemicals include pyridine, ethyl alcohol, SF6 were investigated with various carriers gas such as nitrogen and argon. Argon as carrier gas gave more strong signal than Nitrogen which was better than air. By using stacked PCB design, more ion clusters were identified than Delrin block. Repeatability and resolution were improved also. Experimental data reinforced our initial calculation published on international journal of mass spectrometry. The moisture and applied voltage potential were calibrated to more accuracy value. Lots of effort was spent on the 256-channel electrometers and hands on experience on electrometer were built for future work.

Expected Results:

In summary, a 2D ion mobility spectrometer will be combined with standard PM and gaseous sampling components to develop instruments for analyzing gas phase precursors and the semi-volatile organic and inorganic composition of PM with 10 second temporal resolution – much faster than current instruments enabling analysis of pollutant transients that may be extremely detrimental to health.

Future Activities:

Describe the major objectives and focus for the subsequent reporting period, including any expected hanges in the project schedule.

Dr. Zhang has taken a job in government. Dr. Zhao will continue the work when his current research responsibilities are complete.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views
Other project views:	All 5 publications	1 publications in selected types	All 1 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	Zhang M, Wexler AS. Cross flow ion mobility spectrometry: theory and initial prototype testing. International Journal of Mass Spectrometry 2006;258(1-3):13-20.	R832836 (2006) R832836 (2007) R832836 (2008)	Full-text: Science Direct Exit Abstract: Science Direct Exit Other: Science Direct PDF Exit

Supplemental Keywords:

Keywords are extremely important for information retrieval. There is no need to duplicate terms used in the summary of progress. See the attached file, example Keywords, for sample 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

Relevant Websites:

Identify any Web site that has been established as part of the project or that reflects related research and publications associated with the principal investigators.

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.