Between 300 and 500 mg of the NIST SRM
1649b urban dust was placed on one-eighth of a 150 mm prebaked quartz fiber filter, which was spiked with 1 [micro]L of a solution (0.5 ng x [micro][L.sup.-1]) of the recovery standards.
The recent release of a new generation of standardized 25-OH Vitamin D immunoassays, which are aligned to the NIST SRM
2972, leaves a perception that these assays show improved analytical performance.
Three certified standard reference materials (NIST SRM
1515 Apple leaves IAEA-336 Lichen and GBW-07605 Tea) were used.
The mean bias of the measured values to the assigned values of the NIST SRM
material was 0.3% (95% CI -1.4% to 2.1%) and 0.2% (95% CI -1.7 to 2.0%) for the male and female concentrations, respectively.
Laboratories are not required to purchase a NIST SRM
Most studies of the mutagenicity of DEPs have been conducted using NIST SRMs
(SRM 1650 or SRM 2975) in Salmonella (Hughes et al.
Accuracy has previously been established to be > 1% on the basis of analyses of NIST SRM
1400 bone ash (9.07 [micro]g/g ash weight) and SRM 1486 bone meal (1.335 [micro]g/g).
This has been shown in published comparisons as well on NIST SRM
certificates for SRM 1951a and 1951b (3-5).
External standardization for Pb was via the NIST SRM
981 isotopic standard and a certified Spex Pb standard (Spex Industries Incorporated, Edison, NJ) that had been independently isotopically characterized via thermal ionization mass spectrometry.
The standards will be disseminated as NIST SRM
4321d with the following specifications :
Because of the limited volumes of the NIST SRM
materials, measurements were done according to a reduced CLSI EP 5 protocol, i.e., duplicates on 5 independent days (n = 10) (31).
The prepared and standardized ultrapure, carrier-free [sup.209]Po solution standards were certified and will be disseminated as NIST SRM
4326a with the following specifications: