Trace elements reference materials

A further important requirement in selecting the starting material is that, after all the processing has been done to produce the end product, a large amount should remain to permit meaningful use of this material over a period of several years. Most producers do not provide details of how much is available for distribution. The IAEA, for its part, has adopted the criterion that, for a trace element reference material, at least 50 kg of the final end product should be produced. In practice, however, some of the reference materials already issued by the IAEA have been produced in amounts as small as 15 kg, and sometimes less (for human hair, HH-1, only 300 g was produced, with the consequence that stocks were exhausted very quickly). 

The primary and immediate need is for a trace metal reference material, but a certified reference material would provide even greater benefits. A technique based on isotope dilution with detection by inductively-coupled plasma mass spectrometry (ICP-MS) (Wu and Boyle, 1998) most clearly meets the traceability criteria required for a certified reference material. Although useful for iron and several other metals, isotope dilution is not possible for monoisotopic elements like cobalt, so other techniques must also be used. Indeed, it is advisable that several techniques be used to certify a trace metal reference material. 

National Institute of Standards and Technology (NIST). The NIST is the source of many of the standards used in chemical and physical analyses in the United States and throughout the world. The standards prepared and distributed by the NIST are used to caUbrate measurement systems and to provide a central basis for uniformity and accuracy of measurement. At present, over 1200 Standard Reference Materials (SRMs) are available and are described by the NIST (15). Included are many steels, nonferrous alloys, high purity metals, primary standards for use in volumetric analysis, microchemical standards, clinical laboratory standards, biological material certified for trace elements, environmental standards, trace element standards, ion-activity standards (for pH and ion-selective electrodes), freezing and melting point standards, colorimetry standards, optical standards, radioactivity standards, particle-size standards, and density standards. Certificates are issued with the standard reference materials showing values for the parameters that have been determined. 

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. 

Throughout this book the use of a number of standard analytical samples is recommended in order that practical experience may be gained on substances of known composition. In addition, standard reference materials of environmental samples for trace analysis are used for calibration standards, and pure organic compounds are employed as standard materials for elemental analysis. 

In a similar way there has been a passing reference to a cobalt oxychloride cement (Prosser et ai, 1986). No explicit details of the fabrication or chemical behaviour of this material were provided, but the ingredients were listed among series of acids and bases for forming cements as agents for the sustained release of trace elements to grazing animals. The implication of this paper was that cobalt oxide would function as the base... 

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),... 

The number of samples of reference material needed is a commercial issue in the first place. An important variable is the number of samples likely to be sold during the lifetime ( shelf life ) of the reference material. As the lifetime is a function of the intrinsic stability of the material, this variable also affects the amount of raw material is needed. For instance, microbiological materials have limited intrinsic stability, and therefore their lifetime is expected to be shorter than for a dry sediment certified for trace elements. So, under the assumption of an equal number of sam-... 

Muntau H (1980) Measurement quality improvements by application of reference materials. In Brattee P and Schramel P, eds. Trace Element Analytical Chemistry in Medicine and Biol-ogy, PP707-726. Walter de Gruyter Co Berlin New York. 

Versieck J, Vanballenberghe L, de Kesel A, Baeck N, Steyart H, Byrne AR and Sunderman FW Jr. (1988) Certification of a second-generation biological reference material (freeze dried human serum) for trace element determinations. Anal Chim Acta 204 63-75. 

Bogershausen W, Cicciarelli R, Gercken B, Konig E, Krivan V, Muller-Kaeer R, Pavel J. Seltner H, Schelcher J 1997) Pure graphite as a reference material for the determination of trace elements - an interlaboratory collaborative study. Fresenius J Anal Chem 357 266-273. 

Fraser CA, Gardner GJ, Maxwell PS, Kubwabo C, Guevremont R, Siu KWM, Berman SS (1995) Preparation and certification of a biological reference material (CARP-i) for polychlorinated dibenzo-p-dioxin and dibenzofliran congeners. Fresenius J Anal Chem 352 143-147. Gardiner PE (1993) Consideration in the preparation of biological and environmental reference materials for use in the study of the chemical speciation of trace elements. Fresenius J Anal Chem 345 287-190. 

KuRFiiRST U, Grobecker KH, Stoeppler M (1984) Homogeneity studies in biological reference and control materials with solid sampling and direct Zeeman-AAS. In Schramel P, Bratter P, eds. Trace Element Analytical Chemistry in Medicine and Biology, Vol. 3, pp 591-601. de Gruyter, Berlin. 

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. 

Versieck j, Hoste j, Vanballenberghe L, De Kesel A, Van Renterghem DJ (1987) Collection and preparation of a second generation biological reference material for trace element analysis. J Radioanal Nucl Chem 113 299-304. 

Yoshinaga j, Morita M, Okamoto K (1997) New human hair certified reference material for methylmercury and trace elements. Fresenius J Anal Chem 357 279-283. 

Byrne AR, Deemelj M, Kosta L, and Tusek-Znidaric M (1984) Radiochemical neutron activation analysis in standardization of trace elements in biological reference materials at the nanogram level. Mikrochim Acta [Wien] 1 119-126. 

De Goeij JJM, Kosta L, Byrne AR, and Kucera J 1983) Problems in current procedures for establishing recommended values of trace-element levels in biological reference materials, illustrated by IAEA Milk Powder A-ii. Anal Chim Acta 146 161-169. 

Delfanti R, Di Casa M, Gallorini M, and Orvini E (1984) Five years activity in determining trace elements for the certification of standard reference materials by neutron activation analysis. Mikrochim Acta [Wien] L239-250. 

International Atomic Energy Agency and United Nations Environment Programme (1995) Survey of Reference Materials, Volume i Biological and Environmental Reference Materials for Trace Elements, Nudides and Micro-contaminants. IAEA-TECDOC-854, IAEA, Vienna. 

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. 

Wise SA, Schantz MM, Poster DL, Lopez de Alda MJ, and Sander LC (2000) Standard reference materials for the determination of trace organic constituents in environmental samples. In Barcelo D, ed. Sample Handling and Trace Analysis of Pollutants Techniques, Applications and Quality Assurance, pp 649-687. Elsevier Science Publishers, Amsterdam, The Netherlands. Yoshinaga Y, Morita M, and Okamoto K (1997) New human hair certified reference material for methylmercury and trace elements. Fresenius J Anal Chem 357 279-283. 

Fajgelj a, Radecki Z, Burns KI, Moreno Bermudez J, De Regge PP, Danesi PR, Bojanowski R (1999). Intended use of the IAEA reference materials. Part I Examples on reference materials for the determination of radionuclides or trace elements. In Fajgelj A, Parkany M, eds. 

IAEA-TECDOC-854 (1995) Survey of reference materials. Vol. i Biological and environmental reference materials for trace elements, nuclides and microcontaminants. IAEA, Vieima. IAEA-TECDOC-88o (1996) Survey of Reference Materials. Vols. i and 2. International Atomic Energy Agency, Vienna, Austria. 

Kurfurst U, Pauwels J, Grobecker KH, Stoeppler M, Muntau M (1993) Micro-heterogeneity of trace elements in reference materials - determination and statistical evaluation. Fresenius J Anal Chem 345 112-120. 

Taylor A (1996) Reference materials and analytical standards to stimulate improved laboratory performance Experience from the external quality assessment scheme for trace elements in biological samples. Mikrochim Acta 123 251-260. 

Identification of sources of analytical bias in method development and method validation is another very important application of reference materials in geochemical laboratories. USGS applied simplex optimization in establishing the best measurement conditions when the ICP-AES method was introduced as a substitute for AAS in the rapid rock procedure for major oxide determinations (Leary et al. 1982). The optimized measurement parameters were then validated by analyzing a number of USGS rock reference samples for which reference values had been established first by classical analyses. Similar optimization of an ICP-AES procedure for a number of trace elements was validated by the analysis of U S G S manganese nodule P-i (Montaser et al. 1984). 

Ihnat M (1988) Biological and related reference materials for determination of elements. In McKenzie HA, Smythe LE, eds. Quantitative Trace Analysis of Biological Materials, pp 739-760. Elsevier Science Publishers, Amsterdam. 

Pearce NJG, Perkins WT, Westgatb JA, Gorton MP, Jackson SE, Neal CR, Chenery SP (1997) A compilation of new and pubUshed major and trace element data for NIST SRM 610 and SRM 612 partially certified glass reference materials. Geostds Newslett The Journal of Geostandards and Geoanalysis 21 115-144. 

In his survey of the use of CRMs in food related publications on the subject of trace elements for the years 1990-1996, Jorhem (1998) checked 82 papers published in five international journals. He found that in 42 papers there was no mention of CRM results and assumed that no CRMs were used. He wrote Since the importance of incorporating CRMs in the AQA-activities today is well recognized, it is surprising that firstly so many laboratories still do not use CRMs and secondly that scientific journals accept papers describing analytical results without the use of reference materials, as part of the verification of the analytical results . 

For example trace elements in milk powder are not consumed as milk, and moisture in transformer oil is not used in transformers, yet matrix reference materials based on milk are imported as food and are subject to health certification requirements and sometimes import quotas. Likewise a matrix based on oil is identified as fuel or lubricating oil and is both classified as a hazardous material and subject to mineral oil tax. These problems arise because RMs are frequently incorrectly classified by specific title of their matrix (as Reference Material of Trace Elements in Rice is classified as rice) and not as reference material which is the intended use. 

IAEA (1985) [Muramai SU Y, Parr RM] Survey of currently available reference materials for use in connection with the determination of trace elements in biological and environmental materials. Report IAEA/RL/128, International Atomic Energy Agency, Vienna, Austria. 

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