NYC-WTC_000202123

NYC 9/11 Public Portal Document

P3ce Analytical Services, Inc. 1700 Elm Street, Suite 200 'aceAnalyticar Minneapolis, MN 55414 Phone: 612.607.1700 www.paeelabs.com REPORT OF: CHEMICAL ANALYSES Fax: 612.607.6444

' PROJECT: PCDD/PCDF ANALYSES DATE: April 5, 2002

PAGE: 3 REPORT NO: 02-1055016

PCDD/PCDF Analyses (Cont.)

The mass spectrometer was operated in the electron impact ionization mode at a mass resolution of 10,000-11,000 (M/AM, 10 percent valley definition). This resolution is sufficient to resolve most interferences, such as PCBs, thus providing the highest level of confidence that the detected levels of PCDD/PCDF were not false positives resulting from interferences. Typical Operating parameters for the HRGC/HRMS analyses are summarized in Table 2.

The data were acquired by selected-ion-recording (SIR) using groups of ion masses similar to those described in USEPA Method 8290. The five groups corresponded to the tetrachlorinated through octachlorinated congener classes. Each group contained two ion masses for the PCDDs, two ion masses for the PCDFs, the corresponding ion masses from the two isotopically labeled internal standards, and the ion mass characteristic of the polychlorinated diphenylether (PCDE) which, if -- present, could cause false responses in the dibenzofuran channels.

Each group of ion masses also contained a lock mass which was used by the data system to automatically correct the mass focus of the instrument. The data system determined the centroid of the lock mass during each data acquisition cycle and corrected the mass focus of the analyte and internal standard ion masses to assure that the centers of the mass peaks were being ■ monitored.

The criteria used to judge positive responses for a PCDD/PCDF isomer included:

* Simultaneous response at both ion masses of the PCDD or PCDF * Signal-to-noise ratio equal to or greater than 2.5:1.0 for both ion masses * Chlorine isotope ratio within 1 5% of the theoretical value * Chromatographic retention time within 4-/- 2 seconds of the expected retention time * Chromatographic retention times within elution windows determined from analyses of standard mixtures * Absence of simultaneous response in the PCDF and PCpPE ion traces

A list of the exact ion masses monitored for the determination of PCDD/PCDF isomers and the -- PCDE interferences is presented in Table 3. Also included are the theoretical chlorine isotope ratios for the ten congener classes.

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

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