2004 Progress Report: Aethalometric Liquid Chromatographic Mass Spectrometric InstrumentEPA Grant Number: R831074
Title: Aethalometric Liquid Chromatographic Mass Spectrometric Instrument
Investigators: Dasgupta, Purnendu K.
Institution: Towson University
Current Institution: The University of Texas at Arlington
EPA Project Officer: Chung, Serena
Project Period: September 1, 2003 through December 31, 2007 (Extended to December 31, 2008)
Project Period Covered by this Report: September 1, 2003 through December 31, 2004
Project Amount: $450,000
RFA: Measurement, Modeling, and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5) (2003) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Particulate Matter
The objectives of this research project are to fabricate, evaluate, and field test a new instrument that can perform liquid chromatographic mass spectrometric (LC-MS) analysis of the collected aerosol after in situ aethalometric measurements on the filter.
A membrane-based denuder coupled particle collector and ion analysis system was built and deployed in Bondville, Illinois. This instrument provides information on all major ionogenic gas composition and corresponding particle anionic compositions plus ammonium. Unlike previous instruments of this type, this instrument determines not only inorganic gases and particles, it provides measures of acetic, formic, and oxalic acids and the corresponding particle phase organic acid anions. Methanesulfonate has not been specifically tested, but it should be possible to resolve this. This instrument provides 40-minute time resolution, performs gradient ion chromatography, has a small footprint, and uses a modest sampling rate of 1.5 liters per minute and still attains limits of detection in the low ng/m3 range. Dionex Corporation has licensed patent rights of the membrane denuder used in this instrument from the University. A patent application has been filed.
A second instrument, which borrows largely in design aspects from this instrument but permits multiple solvent treatment and coupling to a quadrupole mass spectrometer, is presently under construction.
Another membrane-based device was developed for use in the first instrument. This microvolume device removes CO2 near-quantitatively from an aqueous stream. This device is expected to be extremely useful in future work. The de-CO2 device is being commercialized by Dionex Corporation and is presently in the beta-testing mode.
A size-selective multiple wavelength aethalometer has been developed. The data can be deconvoluted into size-dependent spectral absorption information of atmospheric fine particles. This inexpensive device can provide separate size-dependent contributions and resolve components to provide semiquantitative information (e.g., it can readily resolve brown West Texas dust from diesel soot). A more refined version that is based on a filter tape is being constructed. A substantial number of high volume filter samples from different regions of Texas (courtesy of Texas Commission on Environmental Quality) have been analyzed by LC-MS to judge what can be expected.
We also have looked at the ability of two types of carbon, which are both primarily EC by current thermo-optical measurements, to convert NO2 into nitrous acid. Fullerenes are relatively ineffective, and butane soot is more effective.
The “Composition of Atmospheric Particulate Matter” symposium was organized by Dr. Dasgupta, under the aegis of the Southeast Regional Meeting of the American Chemical Society in November 2004. He solicited and obtained funding from Dionex Corporation to fully fund the symposium, which was attended by a number of EPA scientists and other interested researchers, and featured Susanne Hering, George Allen, Rodney Weber, Richard Kamens and Rida Al-Horr (just graduated from Dr. Dasgupta’s group) as speakers.
We will continue efforts to develop a fully automated MS coupled instrument. A movable, self-advancing, tape-based, size-discriminating, multiwavelength aethalometer will be built. Conversion of NO2 to nitrous acid by soot derived from meaningful participation in the TexAQS II Air Quality Field Study (2005 and 2006) experiments will be sought.