Grantee Research Project Results

2006 Progress Report: Polar Organic Compounds in Fine Particles from the New York, New Jersey, and Connecticut Regional Airshed

EPA Grant Number: R832165
Title: Polar Organic Compounds in Fine Particles from the New York, New Jersey, and Connecticut Regional Airshed
Investigators: Mazurek, Monica
Institution: Rutgers
EPA Project Officer: Chung, Serena
Project Period: January 1, 2005 through December 31, 2007 (Extended to December 31, 2009)
Project Period Covered by this Report: January 1, 2006 through December 31, 2007
Project Amount: $449,150
RFA: Source Apportionment of Particulate Matter (2004) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air

Objective:

Fine particles in urban atmospheres are composed of highly complex mixtures of organic compounds spanning large ranges of molecular weight and compound group classifications. However, nearly 50% of the organic carbon mass collected as fine particles cannot be analyzed using current molecular level mass spectrometric analytical methods (e.g., gas chromatography/mass spectrometry, GC/MS) due to low volatility in the gas chromatographic system. Liquid Chromatography Mass Spectrometry (LCMS) is an emerging technology to study polar organic compounds extracted from fine particles. The main goals of this project are: 1) to identify and measure the ambient abundances of polar organic compounds (acids and bases) found as PM_2.5 in the NY, NJ and CT regional airshed using LCMS chemical analysis; 2) to measure and identify both known and potential secondary organic aerosol source markers found within the fine particle acidic organic fraction; and 3) to screen the SOAP filter polar extracts for highly polar molecular markers from primary sources of urban fine particles.

Progress Summary:

We have focused this period on the quantitation of key groups of atmospheric polar organic compounds using a LCMS ion trap instrument with Atmospheric Photochemical Ionization (APPI) and Electrospray Ionization (ESI). C2 to C10 diacids and the CARB DNPH carbonyl standard component mixture (13 components) were analyzed principally by LCMS APPI. Standard solutions were prepared and analyzed as 5-point calibration series. In addition, measurement precision was investigated for each standard component by injecting the standard 10 times at each level for the 5-point calibration curves. Instrument stability was evaluated throughout the calibration sequences using a negative ion check standard (nitrophenol) from May 2006 to July 2007. The results from these injections indicated instrument drift and instability over the course of a run sequence (~2-3 days) was occurring under both APPI and ESI negative mode conditions. The average % RSD for the nitrophenol responses was 28.4% + 6.3% with a standard deviation of 8.5.

Use of an internal standard injected with standard solutions also demonstrated high variability and lack of precision. For example, we injected nitrophenol-d5 (IS) and the California Air Resources Board (CARB) 13-component carbonyl standard. The run period was ~2.5 days with sixty injections of the CARB standard. A 60% difference was noted between the highest and lowest Rfs calculated for acrolein. The %RSD was 16.2% with a standard deviation of 4.33%. If one was running actual samples using Rfs for acrolein over the run period indicated, standards bracketing shortly before and after the sample run would need to be averaged to produce a single Rf for acrolein present in the sample. This task makes the data analysis step much more complicated, time consuming and subjective, since where one chooses to begin and end the Rf averaging would have to be determined based on multiple injections and constant generation of adequate statistical information on which to make informed decisions. This step increases analysis time and cost per sample. Typically, 6 to 10 injections per sample must be performed in order to begin to evaluate a sample for target organic compounds. One injection is insufficient given the variability of the response factor for the target compound and drifting instrument response.

Because of low instrument stability and precision for the LCMS ion trap instrument based on these extensive calibration and precision studies, we decided the instrument could not provide data of sufficient quality for the SOAP 2002–2003 network fine particle samples. The decision to switch to GCMS analysis with BSTFA (with TMCS) derivatization occurred in September 2006. We worked on method optimization for the BSTFA process. The conversion must be performed under anhydrous conditions to reduce hydrolysis of the trimethylsilyl ether derivatives. The procedure was scaled to 50μl to 100μl sample volumes in microvials that were inserted directly into the GCMS autosampler. Standard solutions for sugars, aromatic acids, polyols, aromatic acids and alcohols, and oxo and hydroxyl carboxylic acids were evaluated for conversion efficiency with the BSTFA derivatization step. All can be successfully converted, including oxalic acid and the oxo and hydroxyl carboxylic acids. Successful calibrations with the standards were carried out by GCMS. RSDs for the response factors were generally 5% to 10%. The instrument check standards indicate the stability of the GCMS instrument over several months.

Fine PM samples collected for the SOAP 2002-2003 network have been analyzed as trimethylsilyl ethers. In addition, the SOAP-NY sampling networks are scheduled for GCMS analysis from 8/2007 to 10/2007. Conversion of the polar organic fraction to trimethylsilyl ethers will be performed immediately prior to analysis. Sugars (including levoglucosan), aromatic acids, polyols, sterols, phytosterols, diacids, oxoacids, and hydroxyacids will be screened in each SOAP filter composite. Seasonal and spatial concentration trends will be determined for these suites of polar compounds. In addition, levoglucosan and cholesterol markers will be added to source receptor modeling for the SOAP network samples using CMB-MM (version 8.2).

Future Activities:

Research in Year 3 will focus on MS interpretation and data reduction of approximately 50 polar organic target molecular markers in the SOAP fine particle samples (~90 total samples). These marker compounds are indicators of emission sources such as wood smoke, motor vehicles, meat cooking and vegetation. Secondary compounds represented by the hydroxyl acids and oxo acids will be screened also in the SOAP network samples.

Journal Articles:

No journal articles submitted with this report: View all 15 publications for this project

Supplemental Keywords:

ambient air, atmosphere, sources, particulates, PAHs, organics, analytical, measurement methods, LCMS, northeast, Atlantic coast, midatlantic, New York, NY, New Jersey, NJ, Connecticut, CT, EPA Region 2,, RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Air Quality, particulate matter, air toxics, Environmental Chemistry, Air Pollution Effects, Chemicals, Monitoring/Modeling, Environmental Monitoring, Atmospheric Sciences, Engineering, Chemistry, & Physics, Environmental Engineering, particle size, atmospheric particulate matter, health effects, air quality modeling, mass spectrometry, aerosol particles, motor vehicle emissions, human health effects, PM 2.5, wood combustion, atmospheric particles, air quality models, airborne particulate matter, particulate emissions, air modeling, air sampling, gas chromatography, thermal desorption, air quality model, emissions, benzene, particulate matter mass, human exposure, particle phase molecular markers, particle dispersion, aerosol analyzers

Progress and Final Reports:

Original Abstract

2005 Progress Report

2007 Progress Report

2008 Progress Report

Final Report