CRMs

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. 

In compounds, the important oxidation numbers of Cr are +2, +3, and +6. In all of these states the chromium ions are colored and, in fact, the element got its name from this property (ichroma is the Greek word for color). The +2 state is not frequently encountered but it can be made quite easily as the beautiful blue chromous ion in solution by dripping a solution containing CrM over metallic zinc. Air has to be excluded since O rapidly converts Cr1-5 back into Cr. ... 

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. 

Bureau of Analysed Samples Nickel Steel, No. 222 is suitable this steel contains about 3.5 per cent of nickel (BCS-CRM 222/1, ECRM 154/1). 

Note. Feldspar (Potash), No. 29dG available from the Bureau of Analysed Samples (BCS-CRM 376). 

British Chemical Standard BCS-CRM No. 225/2 Ni-Cr-Mo steel is suitable for practice in this determination. 

The values of para positions, are thus available from pX measurements of benzoic acids. One cannot so easily extend the correlation to ortho groups, however, because steric effects are superimposed on the electronic effects under study. Table 10-1 presents a list3 of crm and ap values. Note that the groups considered as electron-withdrawing relative to H have positive <7 values, and vice versa. Thus, we have a(p-CF ) — +0.54 and cr(/n-CHi) = —0.069. 

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). 

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). 

From the mid 1980 s the rise of Quahty Standards, Total Quahty Management and Accreditation schemes created a booming demand for RMs and CRMs. Thus, the use and production of matrix RMs rapidly increased the new IAEA database lists 56 producers from 22 cormtries and about 1640 RMs. The 1998 Comar database, which covers a much wider scope, hsts more than 200 producers and around 10 000 RMs see Chapter 8 for more details. 

The demand for RMs and CRMs continues to grow. As traditional chemical analysis moves into biochemistry and molecular biology the demand for RMs does not abate the only question is what is next Chapter 9 considers these, and other future issues critically. 

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