CRM materials

Epoxy Mortars Epoxies are the strongest resin mortars, have the best bond strength to other CRM materials, and resist many solvents, mild to moderate acids, non-oxidizing and alkaline media. Their useful pH range is about 2-14, and their thermal limit is approximately 230°F. Besides their excellent alkali and dilute acid resistance, epoxy mortars handle many organic chemicals and sodium hypochlorite at low temperatures. Epoxies should not be exposed to acetic acid and its esters. Epoxy mortars have the best physical and mechanical properties of all the resin mortars. 

These two ASTM committees have prepared and issued the standard specifications and test methods on CRM materials and components that are used throughout industry. 

Stability responding to needs may be better than large stocks of unrepresentative (and not used) CRMs. Materials have to be fit for purpose an example is the development of microbiological CRMs with certified values guaranteed at +/- 100%, which correspond to the present state-of-the-art and clearly fulfil a strong demand. 

In large organisations it is common for a general-purpose document management system to be implemented - in most cases it makes sense for CRM materials to harness these tools. A document management systan will typically set out the strategy for ... 

Over the last seventeen year s the Analytical center at our Institute amassed the actual material on the application of XRF method to the quantitative determination of some major (Mg, Al, P, S, Cl, K, Ti, Mn, Fe) and trace (V, Cr, Co, Ni, Zn, Rb, Sr, Y, Zr, Nb, Mo, Ba, La, Ce, Pb, Th, U) element contents [1, 2]. This paper presents the specific features of developed techniques for the determination of 25 element contents in different types of rocks using new Biaiker Pioneer automated spectrometer connected to Intel Pentium IV. The special features of X-ray fluorescence analysis application to the determination of analyzed elements in various types of rocks are presented. The softwai e of this new X-ray spectrometer allows to choose optimal calibration equations and the coefficients for accounting for line overlaps by Equant program and to make a mathematic processing of the calibration ai ray of CRMs measured by the Loader program. 

Many of these are also available as BCS Certified Reference Materials (CRM) supplied by the Bureau of Analysed Samples Ltd, Newham Hall, Middles borough, UK, who also supply EURONORM Certified Reference Materials (ERCM), the composition of which is specified on the basis of results obtained by a number of laboratories within the EEC. BCS Reference Materials are obtainable from the Community Bureau of Reference, Brussels, Belgium. In the USA similar reference materials are supplied by the National Bureau of Standards. 

In geochemistry, the introduction of RMs did not take place until 1951 but, once RM usage became a regular part of geochemical analysis, the consequences were not far short of amazing. For many years geochemical analysts had been concerned about the accuracy of their determinations of major elements in rocks, but it was the potential of emission spectrometry for the determination of trace elements which set off the production of the first rock Certified Reference Materials (CRMs),... 

Valuable contributions were made by two Canadian agencies, particularly by the National Research Council Canada (NRCC) who, from about 1976, provided marine and marine biological CRMs certified for metals, metal species and organic constituents (Berman 1984 Willie 1997). More recently their Halifax laboratories have issued a highly respected range of CRMs for the determination of shellfish toxins. Another Canadian producer, the National Water Research Institute (NWRI) specialized in marine (water and sedimentary) CRMs, and from the late 1980 s their matrix materials certified also for organic compounds (Chau et al. 1979 Lee and Chau 1987). 

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). 

A remarkable level of activity can be seen in China. The National Research Center for CRM (NRCCRM) was founded in 1980 and the certification and accreditation program for CBW RMs started in 1983 by co-operation with many Chinese Institutions. In 1993 around 60 RMs and CRMs were available (Chai Chifang 1993) and in 1999 the availability of about 1000 CRMs was reported, around 30 of them clinical, 100 environmental, 200 geological, and 300 metallic matrix materials (Rong and Min 1999). 

The definition of a certified reference material (CRM) is given in ISO Guide 30 (1992) and it forms the root of all other ISO Guides ... 

Most CRMs are so-called matrix-CRMs , identifying that they have been made from material sampled in nature. For these materials, it is impossible to come up with property values traceable to SI, as preparation steps carmot directly be related to that. At best, a comparison can be made among methods, from which usually one is the technically best established method, and the results of such a comparison may flow into the establishment of the property values and their respective uncertainties. 

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. 

These examples illustrate that, for many materials, the water content can be relatively high without leading to any material instability dmring shelf life, which depends on the water-bonding capacity of the material. When water is strongly retained, the water activity and thus the amount of free water will be low. It must be mentioned that this is quite contradictory to some former and still presently reported assumptions that the water content of CRMs should generally not exceed a rather low value, e.g. around 3 % for long-term stability of RMs. 

One example, a candidate matrix material of organotin species in marine water, had stability determined by storage for 120 days at 4°C in the dark, at ambient temperature, and exposed to daylight (Quevauviller and Donard 1991). Frequently storage at different temperatures over at least a i-year period are reported. Examples include organochlorine pesticides (OCPs) in BCR CRM 430, where pork fat was stored at -2o°C, -i-20°C, and -r37°C (van der Paauw et al. 1992). Storage at -20°C, -i-20°C, and -i-4o°C was performed for total and methyl Hg in BCR CRMs 463 and 464, tuna fish (Quevauviller et al. 1994), and metals in BCR CRM 600, EDTA and DTPA-extractable trace metal contents in calcareous soil (Quevauviller et al. 1998m). 

Griepink B, Maier EA, Muntau H, Wells DE (1991) Certified reference Materials chlorobiphe-nyls (lUPAC nos 28, 52, loi, 118,153 and 180) in dried sewage sludge - CRM 392. Fresenius J Anal Chem 339 173-180. 

Kramer GN, Oostra A, de Vos P, Conneely P (1997) The preparation of lyophilized tuna muscle samples for a feasibility study and for BCR candidate reference material CRM 669 rare earths. JRC-IRMM Report GE/R/MRM/14/97. 

Morabito R, Muntau H, Cofino W, Quevauviller Ph 1999) A new mussel certified reference material (CRM 477) for the quality control of butyltin determination in the marine environment. J Environ Monit 1 75-82. 

Pauwels J, Kureurst U, Grobecker KH, Quevauviller P (1993) Microhomogeneity study of BCR candidate reference material CRM-422 - cod muscle. Fresenius J Anal Chem 345 478-481. Pauwels J, Lambeety A, Schimmel H 1998a) Homogeneity testing of reference materials. Accred Qual Assur 3 51-55. 

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. 

Quevauviller Ph, Kramer KJM, Vinhas T (1996) Certified reference material for the quality control of cadmium, copper, nickel and zinc determination in estuarine water (CRM 505). Fresenius J Anal Chem 354 397-404. 

Trace elements in soils and sludges (CRMs 141R-146R 597) pp 225-232 (1998k) Chlorobi-phenyls in sewage sludge (CRM 392) pp 240-243 (1998I) Trimethyl-lead in urban dust (CRM 605) pp 274-278 In Production of Certified Reference Materials for Pollutants in Environmental Matrices. European Commission Report EUR 18157 EN, CCF Academic Press, Tarbes. 

Quevauviller Ph, Maier EA, Vercoutere K, Muntau H, Griepink B (1992a) Certified reference material (CRM 397) for the quality control of trace element analysis of human hair. Fresenius J Anal Chem 343 335-338. 

Quevauviller Ph, Vercoutere K, Griepink B (1992b) Certified reference materials (CRMs 398 and 399) for the quality control of major element determination in freshwater. Mikrochim Acta 108 195-204. 

VAN DER Paauw CG, Ribtveld AMJ, Maarse H, Griepink B, Maier EA (1992) Development of pork fat reference material for OCPs BCR-CRM 430. Part I. Preparation, homogeneity and stability. Fresenius J Anal Chem 344 297-300. 

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. 

The participants The range of participants should, whenever possible, be chosen in such a manner that widely different methods (based on different physical or chemical principles) can be used. The number of participants (recommended 15) should be sufficient to allow meaningful statistical processing of the results. When the laboratories feel the need for a CRM, either because the available calibrants are not comparable and a primary calibrant appears necessary for traceability, or because a reliable certified control material is needed but not available, then it is recommended that these laboratories do not plan a certification project entirely on their own, but that they involve laboratories having a background in traceability. 

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). 

---