Certification of CRMs

Dybczynski, R., Danko, B., Polkowska-Motrenko, H. Some difficult problems still existing in the preparation and certification of CRMs. Fresen. J. Anal. Chem. 370, 126-130 (2001)... 

The required number of capsules to be used depends on how small the difference is between the certified fraction of negatives and the true laboratory fraction of negatives that must be detected. It also depends on a and p. Expressed into health and safety considerations, it means the smallest difference acceptable, which is of sufficient microbiological importance that it would be undesirable to fail to detect it. Large differences between the certified fraction and a true laboratory fraction of negatives can be detected with quite small numbers of capsules. To illustrate this the CRM with Listeria monocytogenes (CRM 595) will be considered. A certificate of CRM 595 is shown in Annex 3.4. The certified fraction of negatives for the presence-absence procedure based on the IDF method 143 is 1.2% [15]. When the laboratory analyses 10 capsules a true... 

SUMMARY OF THE TECHNIQUES USED IN THE CERTIFICATION OF CRM 505 Element Techniques... 

Further afield, in 1978 the Japanese National Institute for Environmental Studies (NIES) started the production of a series of biological and environmental matrix CRMs, certified for a number of trace elements (Okamoto and Fuwa 1985). Recently also the certification of metal species in some materials was reported (Okamoto and Yoshinaga 1999). 

Increasing activities for the production and certification of biological, environmental and geological CRMs from the late 1980 s have been also reported from Poland (Dybczyhski 1995) and the Czech Republic (Kucera et al. 1995,1998). 

The most important document, accompanying a CRM is its certificate. ISO Guide 31 (1981) provides guidance for the establishment of certificates, labeling of CRMs, and certification reports. The certificate contains among other information the certified values and their respective uncertainties. As important as this information is the traceability statement, which defines to what references the CRM is traceable. Ideally, a CRM is traceable to a suitable (combination) of SI units. This is not always possible, so other stated references may appear here. Especially when certifying matrix reference materials, making the measurements traceable to SI does not imply that the CRM is traceable to SI as well. The steps necessary to transform the sample into a state that can be measured may have a serious impact on the traceability of the values, and thus on the traceability statement. 

Quevauviller Ph, Drabaek I, Muntau H, Griepink B (1994) The certification of the contents (mass fractions) of total and methyl mercury in two tuna fish materials CRMs 463 and 464. 

Quevauviller Ph, Ebdon L, Harrison RM, Wang Y (1999) Certification of trimethyl-lead in an urban dust reference material (CRM 605). Appl Organomet Chem 13 1-7. 

Yeoman WB, Colinet E, Griepenk B (1985) the Certification of Lead and Cadmium in Three Lyophilized Blood Materials CRM No 194, 195, 196. European Commission Report EUR 10380 EN, Community Bureau of Reference, Brussels. 

Lichens accumulate trace elements from the atmosphere and thus are frequently used instead of air filters for pollution monitoring. Certification of nine elements (Al, As, Cd, Cr, Cu, Hg, Mo, Ni, Pb, and Zn) by a group of ii selected laboratories was performed in BCR CRM 482 (Lichen) after an inter-comparison on trace elements in samples of this material (Quevauviller et al. 1996b). 

Certification of the reference material (RM - CRM) by 10 labs using at least two different analytical techniques, e g. 

Fig. 3.3 General scheme used by the BCR for the certification of natural matrix CRMs...

BCR Analytical Approach for the Certification of PAHs in Natural Matrix CRMs Prior to the certification analyses for the CRM, each participating laboratory has to prepare standard solutions of the analytes to be determined from certified reference compounds (purity >99.0 %) to calibrate their instruments for response and response linearity (multiple point calibration), detection limit, and reproducibility. In the case of PAH measurements, reference compounds of certified purity are used as internal standards, which are not present at a detectable concentration in the matrix to be analyzed (e.g. indeno[i,2,3-cd]fluoranthene (CRM 267), 5-methylchrysene (CRM 081R), benzo[f ]chry-sene (CRM 046), picene (CRM 168), and/or phenanthrene-dio). 

Fig. 3.4 Results from the interlaboratory study used for certification of benzo[b]fluoranthene in BCR CRM 088 Sewage Sludge...

Christensen JM, Byrialsen K, Vercoutere K, Cornelis R, and Quevauviller Ph (1999) Certification of Cr(VI) and total leachable Cr contents in welding dust loaded on a filter (CRM 545). Fresenius J Anal Chem 363 28-32. 

LutherW, WinT, Vaessen HAMG, van de KampCG, Jekel AA, Jacob J, and Boenke A (1997). The certification of the mass fractions of pyrene, chrysene, benzo[fe]fluoranthene, benzo[o]pyrene, ben-zo[gW]perylene and indeno[i,2,3-cd]pyrene in two coconut oil reference materials (CRM 458 and CRM 459), BCR Information, Reference Materials. Report EUR 17545 EN, 61 pp. 

Quevauviller Ph, Herzig R. and Muntau H (1996b) Certified reference material of lichen (CRM 482) for the quality control of trace element biomonitoring. Sci Total Environ 187 143-152 Quevauviller Ph, Lachica M., Barahona E, Rauret G, Ure A, Gomez A, and Muntau H (1997) The certification of the EDTA-extractable contents (mass fractions) of Cd, Cr, Ni, Pb, and Zn and of the DTPA-extractable contents (mass fractions) of Cd and Ni in calcareous soil by the extraction procedures given CRM 600. EUR Report 17555 Quevauviller Ph. Maier EA, and Griepink B, eds. (1995) Quality Assurance for Environmental Analysis. Elsevier. Amsterdam. 

Veecoutere K, Cornelis R, Mees L, and Qubvauviller Ph (1998) Certification of the contents of the chromium(IIl) and chromium(VI) species and total chromium in a lyophOised solution (CRM 544). Analyst 123 965-969. 

The development of these CRMs has shown that it is possible to produce CRMs for public health microbiology and that whilst such a CRM can largely meet the ISO Guides requirements it does not completely satisfy all the requirements of CRMs. It has also demonstrated that their manufacture and certification places considerable challenges before the producers. 

The Standards, Measurements and Testing Programme of the European Commission launched a few years ago a project dealing with the development and, ultimately, the production of air filters realistically exposed to welding dust occurring during stainless steel welding (Christensen et al. 1999). This project resulted in the production and certification of a batch of 1100 filters for the Cr (VI) content (40.16 0.60 pg/g dust) (CRM 545). In addition, the total leachable Cr content ( 39.37 1.30 pg/g dust) was certified as a means to check for total Cr recovery. 

Ongoing projects include the certification of enzyme CRMs for GGT, LD, ALAT, CK-MB, ASAT, ALP and a-amylase at 37°C, according to adapted IFCC methods. 

The first four materials (IRMM/IFCC-452, 453, 454, 455) are expected to be released during 2000. Projects on the certification of reference materials for cardiac marker (myoglobin) and total protein concentration in serum are under discussion. Even so the number of available CRMs for clinical chemistry and occupational toxicology is still limited. This has to do with the complexity of physiological compounds (e.g. proteins), the instabihty (e.g. enzymes), or the volatility (e.g. solvents). 

Lamberty a, Kramer GN (1998) The Certification of the Mass Fraction of As, Cd, Cu, Mn, Pb, Se and Zn in Bovine Liver CRM 185R. European Commission, Report EUR 18841EN, Luxembourg. 

Pendlington aw, Meuree-Vanlaethem N, Brookes A (i<)g6) The Method Specific Certification of the Mass Fraction of Dietary Fibre in Lyophilised Haricot Beans, Carrot, Apple, Full Fat Soya Flour and Bran Breakfast Cereal Reference Materials CRMs 514, 515, 516, 317 and 518. European Commission Report EUR 17451 EN, Luxembourg. 

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