NIST SRMs

The set of Glass Standard Reference Material NIST SRM 610 - 614 was used for quantification of amount up to 45 trace elements in the synthetic oxide single crystals and natural quartzites. 

As an example of a standardless bulk analysis by SNMS, a measurement of the complex Ni-based Hasteloy metal (NIST SRM 2402) is presented in Figure 3 and Table 1, in which the composition determined from ion-current ratios (not RSF corrected) is compared to the certified chemical composition. 

Tab. 3.5 Certified values for 25 constituent elements in NIST SRM 2704, River sediment...

Multi-method certification of 25 elements with information provided on another 22 elements was performed in NIST SRM 2704 (Buffalo River sediment) by NIST laboratories with four co-operating laboratories from USA and Canada (Epstein et al. 1989). 

Tab. 3.7 Results for NIST SRM 1633a Coal Fly Ash using the self-verification principle of NAA (Byrne and Kucera 1997 Kucera et al. 1997)...

As an example of the capabilities of a combination of INAA and RNAA using a two group separation scheme for the simultaneous determination of As, Cd, Cu, Mo, Sb, Hg, and Se (Kucera and Soukal 1993), and a single separation procedure for vanadium determination (Byrne and Kucera 1991), Table 3.8 shows results for NIST-SRM-i573a Tomato Leaves that were obtained prior to certification of this material (Kucera 1995), and later on taken into consideration for deriving the NIST certified and information values (Becker 1995, personal communication). 

Tab. 3.8 INAA and RNAA results for NIST SRM-i573a Tomato Leaves (dry weight) (Kucera 1995)...

It can be concluded that, in the field of RM certification, NAA represents a major analytical technique contributing significantly to the certification of element contents in environmental and biological RMs, as was also pointed out earlier (Dyb-czynski 1980 1995), and also provides the bulk of the hterature data on NIST SRMs (Gladney et al. 1987,1993). NAA also has a similar position in the field of geological RMs (Roelandts 1991). It possesses unique quality assurance and self-verification aspects (Becker 1993 Byrne 1993 Byrne and Kucera 1997), though these in-built features are rarely exploited in fuU at present. It should be reahzed that the advanta-... 

A limited number of pure substances are available from NIST, primarily clini-cally-relevant compounds such as cholesterol, urea, uric acid, creatinine, glucose, cortisol, tripalmitin, and bilirubin (NIST SRM website). These compounds are certified for purity (greater than 99 %) and are used as primary calibrants in definitive methods for these clinical analytes (see below). Several additional pure substances are available for specific applications such as microchemistry, i.e. elemental composition (acetanilide, anisic acid, cystine nicotinic acid, o-bromobenzoic acid, p-fluoro-benzoic acid, m-chlorobenzoic acid), polarimetric standards (sucrose and dextrose), acidimetric standard (benzoic acid and boric acid). Only three pure substance NIST RMs are available for environmental contaminants, namely the chlorinated pesticides, lindane, 4,4 -DDT, and 4,4 -DDE. 

There are many similarities in the certification approaches used by NIST and BCR as well as major differences. Both the NIST and BCR approaches are based on results from multiple independent methods. For the NIST SRMs the measurements are generally all performed at NIST with emphasis on the independence of the methods, whereas the BCR relies on results from a large number of laboratories that may use different methods. The certification approaches used by NIST and BCR are described below using as an example the measurement of PAHs in an environmental matrix. 

Fig, 3.2 Analytical scheme used for the certification of PAHs in NIST SRM 1649a Urban Dust. 

National Institute of Standards and Technology, Standard Reference Materials Catalog, http // www.nist.srm... 

Tab. 4.4 Calculation of homogeneity factors for selected elements in NIST SRM 1648 based on experimental INAA results...

Fig. 4.4 Calibration curve for chromium, constructed from measurements of increasing intakes of five different CRMs NIST SRMs 1646 Estuarine sediment, certified content 76 + 3 mg/kg 1632a Coal, certified content 34.4 1.5 mg/kg BCR CRMs 141 Calcareous loam soil, indicative content 75 mg/kg, 142 Light sandy soil, indicative content 74.9 mg/kg and 143 Over fertilized soil, indicative content 228 mg/kg (Kurfiirst 1998b).

For the determination of As, Cd, Zn, Pb, Mn, Cu and Cr with solid sampling GF-AAS in a number of biological samples, calibration curves using one NIES CRM and three NIST SRMs were constructed and successfully used (Atsuya et al. 1987). 

Using the slurry-method and GF-AAS in Cu, Cr, Fe and Pb were determined in various pine needle samples, using NIST SRM 1575 Pine needles slurry as calibrant. Comparison of the obtained results showed good agreement with wet ashing (Carrion et al. 1988). 

Within collaborative work on element concentrations in a number of biological reference materials using solid sampling and other analytical methods, calibration of Cd, Cu, Pb and Zn in BCR CRM 185 Bovine liver with solid CRMs was performed for each element with a reference material of the same matrix, NIST SRM 1577... 

Mercury in various cement products was determined with a special mercury oven for solid samples. Calibration was performed with four BCR CRMs and one NIST SRM with different Hg content as well as with a reference solution and excellent agreement found (Bachmann and Rechenberg 1991). 

Thirty-four sets of data on D2S44 were sent to NIST. Nineteen laboratories also reported results on D4S139 (PH30), 17 tested D10S28, 16 laboratories examined D1S7 (MSi), and 12 provided results on D17S79 (Vi). The certified values (number of DNA base pairs) for SRM 2390 are shown on the NIST SRM 2390 Certificate. 

These three NIST SRMs have a number of important quality control applications for forensic DNA profiling, medical diagnostics and mutation detection. The main applications are summarized below ... 

Possible heteroplasmic site. This heteroplasmy seen in the mtDNA from the first CHR cell culture line is not seen in the mtDNA from the second CHR cell culture line. It is DNA from the second CHR cell culture line which is supplied in NIST SRM 3392. 

NIST SRM 2676d (pg/filter) Cd, Pb, Mn, Zn (three concentration levels)... 

Quartz on filter media in a clay matrix is also available from NIST. The SRM 2679a is certified for quartz at three levels 30.8, 80.2 and 202.7 [xg/filter respectively. Respirable silica in powder form is also issued by NIST SRMs 1878a and 1879a are crystalline silica materials with particles in the respirable range and they are intended for use in X-ray diffraction and infrared spectroscopy. 

Solvents or their metabolites are commonly determined by GC (Tokunaga et al. 1974) or GC-MS. In spite of the high importance of exposure to solvents, and the great number of determinations performed worldwide, reference materials for solvents in serum or urine are virtually non-existent. There are a number of reference materials used in occupational hygiene, for example the ethanol in water standard from NIST (SRM 1828a) is commonly used in the clinical laboratory. 

Other than NIST SRM 1589, PCBs in human serum, there are no reference materials for these compounds in urine or serum. A number of reference materials are available for environmental samples, food and agriculture. 

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