NYC-WTC_000226877

NYC 9/11 Public Portal Document

Pace Analytical Services, Inc. 1700 Elm Street, Suite 200 ^ace Analyticar Minneapolis, MN 55414 Phone: 612.6071700 www.pacelabs.com REPORT OF: CHEMICAL ANALYSES Fax: 612.607.6444

PROJECT: PCDD/PCDF ANALYSES DATE: December 20, 2001

_ PAGE: 7 REPORT NO: 01-1051682

_ 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 ranged from 26-117% and indicate a level of efficiency through the extraction and enrichment , " steps that is considered typical to somewhat low for this matrix. With the exception of two 3 standards, all of the internal standard recoveries for the field samples were within the target liniits ■ 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 a trace level of non-2,3,7,8 substituted TCDD. Two of the samples contained this isomer at a level similar to that seen in the blank and are flagged "BJ" on the data summary sheets. In general, levels less than ten times the background are not considered statistically.different from the background.

3 A laboratory spike sample was 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 80-110%. This indicates a high degree of accuracy for these determinations.

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J a REPORT OF LABORATORY ANALYSIS This report shall not be reproduced, except in full, without the written consent of Pace Analytical Services, Inc. I CITY_21MC100_000490783 NYC-WTC_000226884