NYC-WTC_000182790

NYC 9/11 Public Portal Document

- Pace Analytical Services, Inc. 1700 Elm Street, Suite 200 Pace Analytical' Minneapolis, MN 55414 Phone: 612.807.1700 www.pacslabs.eam REPORT OF; CHEMICAL ANALYSES Fax: 612.607.6444

PROJECT: PCDD/PCDF ANALYSES DATE; December 3, 2001

PAGE; 7 REPORT NO: 01-1051099

results

The results from the analyses are presented in the following:

Appendix A - Documentation Appendix B - PCDD/PCDF Analysis Results

DISCUSSION

The recoveries of the isotopically-labeled PCDD/PCDF internal standards in the sample extracts generally ranged from 40-109% and indicate a level of efficiency through the extraction and enrichment steps that is considered typical for this matrix. With the exception of three standards, which were affected by interferences, all of the internal standard recoveries for this project were within the target limits for this method. Also, since the quantifications of the native 2,3,7,8- substituted isomers were based on isotope dilution, the data were automatically corrected for variation in recovery and accurate values were obtained.

; A laboratory method blank was prepared and analyzed with the sample batch as part of our routine quality control procedures. The results, found at the beginning of Appendix B, show the blank to contain selected PCDD and PCDF isomers. Several of the samples contained these isomers at levels similar to those seen in the blank and are flagged "B" on the data summary sheets. In general, levels less than ten times the background are not considered statistically different from the background.

' Laboratory spike samples were also prepared with the sample batch by extracting a clean wipe that had been fortified with native standard materials. The results, found at the end of Appendix B, show that the spiked native compounds were recovered at 90-135% with relative percent differences of 0.0-16.9%. This indicates high degrees of accuracy and precision for these determinations. It should be noted that one internal standard was recovered slightly above the target limit for this method and is flagged "P" on the data summary sheet.

REPORT OF LABORATORY ANALYSIS This report shall not be reproduced, except in lull, without the written consent of Pace Analytical Services, Inc.

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NYC-WTC_000182797