Laboratory explanation of PAH detection limit revision, March 2003

NYC 9/11 Public Portal Document

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Gilsenan, Michael From: Usbeck, Fred [[email protected] Sent: Wednesday. March 26. 2003 2:23 PM To: [email protected]; Theodorellys. Penny Cc: Radhakrishnan. Krish; Gilsenan. Michael; [email protected] ; Playez. Dave; Johnston. Mark Subject; RE: FW; Revised PAH results

Chuck

In response to your question about the change in the reporting limit for the PAH wipe samples:

Our normal PQL (practical quantitation limit) is 5 ug for each PAH for this method, however, our MDL (method detection limit) is 1 ug for each PAH. For this reason we did not need to rerun these samples - we went back to the raw data to verify that there weren't any "hits" above the 1 ug MDL for these samples, and reprinted the report with the revised reporting limit.

I will ask the guys in the lab to print a few chromatograms to demonstrate the new 1 ug DL and send them to Andrew at JLC. I'm sure he won't mind sharing these with you.

If you have any other questions please get back to me.

thanks! Fred

---- Original Message---- From: [email protected] [mailto:[email protected]] Sent: Wednesday, March 26, 2003 8:42 AM To: Theodorellys, Penny Cc: Radhakrishnan, Krish; Gilsenan, Michael; [email protected] ; Usbeck, Fred Subject: Re: FW: Revised PAH results

Penny,

Thanks for sending the revised PAH results. The detection limit seems to be the appropriate one, however I would need one additional piece of information from the laboratory to accept the results as valid. The additional information would be a letter (on the laboratory's letterhead) explaining the change in detection limits on the analytical reporting sheets with an attachment of one of the lab sheets/chromatographs that shows the detection limit used during the analysis. I am only requesting this because of the discrepancy highlighted below.

Based on the original PAH results that I received, it appears that the PAH samples were analyzed using a detection limit of 5 ug. The analyses were all conducted on March 10 and 11. The analytical results sheets had a date on top of the page of March 14. The revised PAH results that I received yesterday are identical to the previous results with the exception that the detection limit is now reported as 1 ug and the date at the top of the pages is March 24. The revised results have the same analysis dates and times as the previous samples. Based on the revised results, the only interpretation of this can be that the original analysis was in fact conducted with a detection limit of 1 ug, but erroneously reported as 5 ug, which would make reanalyzing the samples unnecessary (scenario 1). However, I was under the impression that the original detection limit used was 5 ug, and that the only way to get revised results at a detection limit of 1 ug would be to re-run the 1

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