Metrology certified reference materials

The analysis was performed by SRXRF at the XRF beam-line of VEPP-3, Institute of Nuclear Physics, Novosibirsk, Russia. For accuracy control the International Certified Reference Materials were used. There were obtained all metrological characteristics, namely precision, accuracy and lower limits of detections. 

The Promochem Group was the first international specialist supplier of certified reference materials (CRMs) and pharmaceutical reference substances used in environmental, medical and trace element analysis. Their experience provides a viewpoint that echoes, reinforces and expands on many of the trends discussed above (Jenks 1997). From the middle of the 1980 s, sales of CRM by Promochem increased between 10 % and 20 % annually, depending on the market sector and application. Since then National and International Metrology Institutes, such as the now privatized U.K. Laboratory of the Government Chemist (LGC), the European and U.S. Pharmacopoeias, the E.U. IRMM and others have recognized that efficient distribution of RMs, backed by available technical support, is as important as production and certification. Thus, they have moved to spread their influence outside their national origins. The Web and e-commerce will continue to grow as major facilitators of better information dissemination and supply of CRMs. 

Certified Reference Material A reference material characterized by a metrolog-ically valid procedure for one or more specified properties, accompanied by a certificate that states the value of the specified property, its associated uncertainty and a statement of metrological traceability. 

Laboratories must use calibration standards that are metrological trace-ability to an embodiment of the unit in which they are expressed. This requires use of certified reference materials, usually to make up working standards that calibrate instruments in the laboratory. Implicit is that results will be expressed in common units, and while this is increasingly the case, the example of the Mars Climate Orbiter (chapter 1) should signal those still using versions of imperial units that it might be time to join the rest of the world and use SI units. 

There are some existing texts that cover the material in this book, but I have tried to take a holistic view of quality assurance at a level that interested and competent laboratory scientists might learn from. I am continually surprised that methods to achieve quality, whether they consist of calculating a measurement uncertainty, documenting metrological traceability, or the proper use of a certified reference material, are still the subject of intense academic debate. As such, this book runs the risk of being quickly out of date. To avoid this, I have flagged areas that are in a state of flux, and I believe the principles behind the material presented in this book will stand the test of time. 

Historically, there have been several ways of demonstrating metrological linkages of traceability. One of the earliest was for a reference laboratory to calibrate an artifact by measuring it and then provide it, along with certified results, to one or more laboratories so that they could also measure it and then compare their results with those of the reference laboratory. Later, distribution of certified reference materials, produced in lots by reference laboratories, provided an exactly analogous linkage for those kinds of materials amenable to production and certification in lots. 

National traceability or dissemination structures, internationally linked via comparison measurements under the CIPM Mutual Recognition Arrangement, are beginning to play a central role in establishing trace-ability of chemical measurements in practice. Reference materials are the most important transfer standards for disseminating traceability (more precisely the units of measurement) to the user level. Availability of certified reference materials with evidence of their metrological quality is, however, very limited. Great efforts are necessary to improve this situation. 

Abstract For ensuring the traceability and uniformity of measurement results, the main objectives of national metrology programmes in chemistry are to calibrate and verify measuring instruments, to evaluate the uncertainty of measurement results and to intercompare the analytical results, etc. The concept of traceability has developed recently in chemical measurements, thus, an attempt to implement the principles of metrological traceability especially by appropriateness calibration using composition certified reference materials (CRMs) is underlined. Interlaboratory comparisons are also a useful response to the need for comparable results. The paper presents some aspects and practices in the field of spec-... 

A traceability chain of the value carried by the IHRM to the value carried by the reference material with higher metrological status and sufficiently similar matrix (for example, a certified reference material CRM according to ISO Guide 30) is helpful in such a case. The chain is realized when the IHRM samples are analysed simultaneously with the CRM samples under the same conditions. This and other traceability chains necessary for the IHRM development are examined as the measurement information sources. 

The demand for Certified Reference Materials is much higher than the international infrastructure of metrology institutes can provide. National metrological institutes are often not well enough equipped for efficient production of these materials. 

The most recent definitions of reference materials (RM) and certified reference materials (CRM) were given in the International vocabulary of metrology - basic and general concepts and associated terms (VIMS) [1]. 

Emons, H. Policy for the statement of metrological traceability on certificates of ERM certified reference materials. ERM http //www.erm-crm.org/ERM products/policy on traceability/Docu ments/erm traceability statement policy final 5 may 2008.pdf. Accessed 15 May 20015... 

As written in the Eurachem Guide it is commonplace to confuse reference material with certified reference material [14], Unfortunately, the situation is even worse, as there are also some other terms used to describe the same, like standard material , reference standard , standard reference material etc. It is evident from the literature that in the International Vocabulary of General Terms in Metrology (VIM), at least twelve different terms associated with objects used to define, realise, conserve or reproduce a unit or a value of a quantity are used [1, 15], Up to now several approaches have been already made to uniform terminology in this field as it is essential for many reasons (traceability and consequently comparability being one of them) and it is hoping that... 

Certified reference material (CRM) A standard with a quantity value established to a high metrological degree, accompanied by a certificate detailing the establishment of the value and its traceability. Used for calibration to ensure traceability, and for estimating systematic effects. (Section 3.3)... 

Consider what the consequences of setting the probability level for acceptance of H0 at 90, 95, and 99% might be. As an example suppose an analytical method has been used to analyze a certified reference material for the element zinc, that is, a material whose amount of substance of zinc has been established to a high metrological standard with low measurement uncertainty, with a view to deciding if there is any significant systematic error in the method. The mean of n measurement results has been determined and suppose that the population standard deviation (a), and therefore the standard deviation of the... 

The calibration hierarchy is the sequence of calibrations from a reference to the final measuring system, where the outcome of each calibration depends on the outcome of the previous calibration [13]. This hierarchy requires that for measurements incorporating more than one input quantity in the measurement model (e.g., pH, 7), each input quantity must itself be metrologically traceable. In addition, each measurement and derived quantity is listed with an evaluated uncertainty that captures the uncertainties of the measurements and of the calibration hierarchy. Also, because the propagation of variances is additive, measurement uncertainty increases throughout the calibration hierarchy fiomthe RM (which is ideally a certified reference material aka CRM) to the sample. A statement describing the uncertainty is essential, as a measured quantity value unaccompanied by a measurement uncertainty is not only useless, but it is potentially dangerous because the measured value may be misinterpreted or misused. 

In the field of chemical measurement, certified reference materials (CRMs) and RMs are used as measurement standards. Depending on the metrological qualities of these standards, in certain fields CRMs provide a primary standard for a measurement system. 

Jakopic, R., Sturm, M., Kraiem, M. et al. (2012). Certified reference materials and reference methods for nuclear safeguards and security. INSINUME Sixth International Symposium on In Situ Nuclear Metrology as a Tool for Radioecology. Brussels, Belgium Joint Research Centre, Presentation. 

In the development of new analytical methods, the use of well-characterized reference materials can be invaluable in comparing measurement technologies, assessing potential sources of bias, and in method validation. Reference materials are also useful as controls for quality assurance. Reference materials produced by national metrology institutes are usually classified as certified reference materials (CRMs) ... 

Technology (NIST), formerly the National Bureau of Standards founded in 1918, is responsible for maintaining both scientific and commercial metrology in the United States. Its mission is to promote American innovation and competitiveness and supplies industry, academia and government with certified standard reference materials, including documentation for procedures, quality control, and materials for calibration. The German Institute for Standards (DIN) was founded in 1917 while in the United Kingdom the BSI was formed in 1901. 

Meanwhile, metrological institutions, such as the Institute of Reference Materials and Measurements (IRMM) in Geel, Belgium, and the Bundesanstalt fur Materialforschung und -priifung (BAM) (the Federal Institute for Materials Research and Testing) in Berlin, Germany, distribute certified spike solutions [18, 19], for example, for boron, uranium, plutonium, copper, and zinc. 

As in many previous PSA conferences, the metrology of particle characterisation by the electrical sensing zone method was again prominent [Berge, Feder and Jfefssang]. The emphasis these days is however on the mass calibration of the instrument, sometimes also using certified or standard reference materials... 

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