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Organic Characterization of Airborne Particles: Interlaboratory Comparison Studies and the Development of Standards and Reference Materials

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Abstract: Investigators characterizing and quantifying the organic compounds in particulate matter (PM) have completed the second interlaboratory comparison study. The first study used a subset of SRM1649a sieved to <63um(API) as an unknown sample, an extract of API, and SRM1649a for use as a control. For the second study, PM2.5 collected recently in Baltimore, MD (APII) was the unknown sample. The target analytes included polycyclic aromatic hydrocarbons(PAHs), nitrated-PAHs, alkanes (including hopanes and cholestanes), sterols, carbonyl compounds (ketones and aldehydes), acids (alkanoic and resin), phenols, and sugars. For the first and second study, 23 and 17 laboratories, respectively, reported. This is a performance-based study and laboratories used the methods they routinely use to analyze similar samples. The data received, following outlier testing, were then used to assign a consensus value to each analyte in the unknown samples. Results were used in the consensus value assignment only if the laboratory's results for SRM1649a were within 30% of the uncertainty limits of the certified values. Z-scores and p-scores have been determined for assessment of accuracy and precision. For these exercises, z-scores, which assess the difference between the result of the laboratory and the exercise assigned value, were calculated on the basis of 25% difference from the consensus value. For API, 65% of the data submitted were within 25% of the consensus values while for APII only 47% of the data submitted were within 25% of the consensus values. For the second study, the largest number of results reported for a chemical class was for 23 PAHs with 14 labs reporting. The next largest number of labs reporting other analyte classes was for alkanes (9), hopanes and cholestanes (6), carbonyl compounds (4), nitro-PAH (3), and phenols/sugars (2). The PAH concentrations for the APII sample of contemporary PM2.5 were similar to the concentrations found in SRM1649. The working group has reached consensus on a priority list for the development of calibration standards and internal standards.

This work has been funded by the US Environmental Protection Agency. It has been subjected to Agency review and approved for publication.
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Citation:Lewtas, J., S. A. Wise, and M. M. Schantz. Organic Characterization of Airborne Particles: Interlaboratory Comparison Studies and the Development of Standards and Reference Materials. Presented at International Symposium on Polycyclic Aromatic Compounds, Amsterdam, The Netherlands, September 21-25, 2003.
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Immediate Office
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Product Type: Abstrct/Oral
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Presented: 09/24/2003
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Related Entries:
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Bullet Item Biomarkers of PM Exposure to Combustion Source Emissions & Organic (Toxic) Components
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Last Updated on Monday, October 22, 2007
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