EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

Certificate 2581 http://patapsco.nist.gov/srmcatalog..7view_cert2gif.cfTn?certificate=2581

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Standard Reference Material® 2581 Powdered Paint Nominal O.S % Lead This Standard Reference Material (SRM) is intended for use in file evaluation of mefiiods and for the calibration of apparatus used to determine lead in paint. SRM 2581 is composed of paint collected firom the interior surfaces of housing. A unit consists of 35 g of powdered paint material, 99+% of whichpasses a 100 pm (No. 14^ sieve. The certified mass fraction of lead, given below, is based on measurements by isotope dilution inductively coupled plasma mass spectrometry (ID-ICPM^ with a minimum sample size of 100 mg. The certified value is reported on a dry basis (see Instructions for Drying.

Certified Mass Fraction

Lead Content; 0.419 % ±0.011 %

The uncertainty in the certified value is calculated as

where it is the combined standard uncertainty calculated according to the ISO Guide [1] and fc is a coverage factor. The value of is intended to represent at the level of one standi deviation, fixe combined effect of uncertainly components associated with material inhomogeneity and ID-ICPMS measurement uncertainty. In the absence of Type B uncertainties (which are negligible here in comparison with Type A), fixe expanded uncertainty (U) given is for a 95 % prediction interval The coverage factor; k “ 2.57, is the Students f-value for a 95 % prediction interval with 5 degrees of fieedom.

NOTICE AND WARNING TO USERS

Expiration of Certification: The certification of this SRM lot is valid within the measurement uncertainties specified until December 31, 2010, provided fixe SRM is handled and stored in accordance wifix file instructions given in this certificate (see Use). However, file certification will be nullified if the SRM is contaminated or modified.

Stability: This material is considered to be stable. NIST will monitor this material and will report any substantial changes in certification to file purchaser. Return of the attached registration card will facilitate notification.

Use: To relate analytical determinations to the certified value on this Certificate of Analysis, a minimum sample mass of 100 mg should be used and file sample should be dried according to the Instructions for Drying. Sample pr^aration procedures should also be designed to effect complete dissolution in order to relate file determined value to the certified value. This SRM must be stored in an air conditioned environment or similar cool and thy environment away from sunlight and fumes.

The support aspects involved in the preparation, certification, and issuance of this SRM were coordinated throu^ the Standard ReferenceMaterials Program by B.S. MacDonald.

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