Measurement traceability

The main requirements to the assurance of traceability are specified in Belarus in the law Assurance of Measurement Traceability . 

Matrix SRM s, Matrix SRM s can be used for a variety of functions. Taylor (71) reviewed the uses of matrix standards, which Include (a) method development and evaluation, (b) establishment of measurement traceability, and (c) assurance of measurement compatibility. During certification of these matrix SRM s, the selectivity of fluorescence... 

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. 

As stated on the slide, traceability should allow to trace the result of a measurement or the value of a standard through an unbroken chain of calibrations to stated references. Traceability is one key issue of ISO 17025. You find more on measurement traceability in chapter 10. 

Establishing the traceability of the measurement is one of the most important requirements in ISO/IEC 17025. Measurement traceability ensures that the measurements in different laboratories are comparable in space and time all over the world. Calibration and the use of certified reference material (see chapters 9, 10 and 14) is the central tool in establishing trace-ability. Therefore a laboratory must have programmes and procedures for both. 

In addition to the requirements listed in clause 5.10.2 of ISO/IEC 17025, calibration certificates shall include conditions under which the cahbration was carried out, the uncertainty on the result and information about the measurement traceability, which is necessary for the interpretation of calibration results. 

This gives an overview of metrology in analytical chemistry as well as describing the role of measurement traceability. The traceability part of the presentation is based on the CITAC position paper on measnrement traceability (Traceability in Chemical Measurement, Accred. (Jual. Assm. (2000) 5 388-389)... 

Focusing on the assignment of the reference value by measurement, there are several ways to achieve this. It can be done either by using one measurement method (usually this should be a primaiy method in order to be able to demonstrate measurement traceability and measurement uncertainty), or use of one method by several laboratories or several methods by one or several laboratories. 

South African Development Community Cooperation in Measurement Traceability (SADCMET) http //www.sadcmet.org/... 

In Australia there have been discussions as to how to make evidential breathalyzer measurements traceable to national or international standards. The amount of ethanol in a motorist is required by law to be less than a prescribed concentration, for many countries between 0.0 and 0.08 g per 100 mL blood. Recently there has been a move to change legislation to a limit of a given mass per 210 L of breath to avoid arguments about the blood/breath partition coefficient. As with any forensic measurement, metrological trace-ability is a key component of a successful prosecution. At present police buy standard solutions of ethanol in water from certifying authorities, with... 

The standard recognizes the factors that determine the correctness and reliability of test results human factors, accommodation and environment, methods, equipment, sampling, and the handling of test items. In this list, measurement traceability is mentioned, but in fact metrological traceability, with measurement uncertainty and method validation, are really subsumed in methods. (subsection 5.4). The effect of each of these factors on measurement uncertainty will differ considerably among kinds of tests. 

Pure substance RMs are used to derive the calibration factor Fc (see Fig. 1) and its uncertainty Uc for chemical measurements. Traceability of the amount of RM in a prepared standard solution is determined by the traceability of the purity certification, the mass measurement, and the volume measurements. For many trace chemical measurements the uncertainty (Uc) of the calibration derived from the pure substance RM is a small component of the final measurement un-... 

If reference materials are used for calibration or correction of calibration they establish traceability of chemical measurements. Traceability is the link or the vertical comparison between an analytical result and a national or international accepted standard, preferable a realization of the SI unit (see Fig. 7). 

In this example, internal consistency, over time, can suffice to assure production, with minimal analytical cost, of acceptable alloy. Indeed, portions of previous batches which have yielded high-quality materials and products can serve as measurement standards without the need for traceability to SI or national standards. Measurement traceability to a higher laboratory may be useful in attaining certain objectives, such as inter-plant comparisons and reaching agreement between producer and buyer laboratories, but, it is not essential to immediate quality assurance for production in a single plant. 

The concept of measurement traceability provides probably the most important strategy to achieve standardisation in laboratory medicine aimed at comparable measurement results regardless of the method, the measurement procedure (test kit) and of the laboratory where the analyses are carried out. 

According to the Vocabulary in Metrology (VIM) [2] and the Guide to the Expression of Uncertainty in Metrology (GUM) [3] measurement traceability is defined as... 

In line with the objectives of the CCQM Workshop, we have tried to suggest how measurement traceability can be disseminated to field laboratories. An important anticipated evolution in this respect is the fact that the stakeholders dealing with accreditation/metrology/edu-cation/standardization will need to collaborate much more closely to achieve measurable progress. 

One of the general requirements for evaluation of the competence of test laboratories is the realization of traceability of measurement results [1], Besides other measures, traceability is ensured by the availability of check and measuring standards. In the case of the determination of gas impurities in titanium- and aluminium-based alloys, reference samples (RSs) with a certified mass fraction of gas impurity to be determined serve as the above standards. 

Abstract In routine chemical measurements traceability can be achieved by using analytical instruments calibrated against primary reference materials. In the present work the calibration of a C02 non-dispersive infrared (NDIR) analyzer with measuring range 0 2000 mol/mol of C02 and a resolution of 5 mol/mol is reported. A procedure with working reference gas mixtures (WRMs) has been adopted, which requires seven calibration points. Primary reference gas mix-... 

---