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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.7, #1)
Implementing the GUM in the certification of reference materials: the revision of ISO Guide 35 by A.M.H. van der Veen (pp. 2-6).
The availability of certified reference materials, certified in accordance to the GUM is an important tool for the proper estimation of measurement uncertainty in routine analysis. Many CRMs may suffer from incomplete or wrongly estimated uncertainties, mainly due to lack of guidance on how to implement the GUM in the production of CRMs. In particular the inclusion of the impact of inhomogeneity and instability in the uncertainty budget is often missing. The ongoing revision of ISO Guide 35 aims to fill this gap in providing guidance how (batch) inhomogeneity and instability can be translated into measurement uncertainty. The structure of the current ISO Guide 35 has been maintained as far as possible, but major parts underwent revision to become better aligned with GUM and ISO Guide 34 (2000).
Keywords: Keywords Certification; Reference materials; Measurement uncertainty
Metrological role of neutron activation analysis. IB. Inherent characteristics of relative INAA as a primary ratio method of measurement by W. Tian; B. Ni; P. Wang; L. Cao; Y. Zhang (pp. 7-12).
This is the second part of a paper which deals with the advantages and disadvantages of relative instrumental neutron activation analysis concerning traceability and uncertainty, and the current scope and possible future extensions of neutron activation analysis as a primary ratio method. The first part of this paper has been published in this Journal [1].
Keywords: Keywords Instrumental neutron activation analysis; Primary ratio method; Uncertainty; Traceability
Uncertainty and other metrological parameters of peroxide value determination in vegetable oils by I. Kuselman; E. Kardash-Strochkova; Y. I. Tur’yan (pp. 13-18).
Measurement uncertainty in the proposed redox-potentiometric methods for peroxide value (PV) determination in vegetable oils is evaluated in comparison with uncertainty in the standard methods. The methods determine all peroxides in oils, in terms of milliequivalents per kg of sample (meq/kg), that oxidize potassium iodide (KI) under the conditions of the test. The standard methods are based on KI oxidation by the oil test portion and volumetric titration of the liberated iodine, while the proposed methods are using redox-potentiometric iodine determination without titration. As far as fresh refined oils have PV≤0.5 meq/kg, the limit of detection (LOD) and limit of quantitation (LOQ) of the methods are important. An approach to assess the LOD and LOQ using uncertainty calculation was applied. It is shown how important is the influence of the solvents purity on the values of LOD and LOQ.
Keywords: Key words Peroxide value; Vegetable oils; Uncertainty of measurements; Limit of detection; Limit of quantitation
Preparation and analysis of a reference material for the measurement of oxygen in copper by B. Lange; H. Kipphardt; S. Recknagel; K. A. Meier (pp. 19-23).
The preparation and analysis of the oxygen mass fraction of three pure copper reference materials (BAM-379/1, BAM-379/2, BAM-379/3) intended for the calibration of spark emission spectrometry are described here. Data of homogeneity testing and round robin certification in collaboration with 12 independent laboratories from metalworking industry and research are reported. Problems with the establishment of traceability in this special case are discussed.
Keywords: Keywords Determination of oxygen; Copper; Reference material; Certification
Report of the Study Group ”Quality Assurance and Accreditation” to the DAC-FECS
by W. Wegscheider (pp. 24-24).
The flexible scope of accreditation by B. Steffen (pp. 25-28).
The scope of accreditation for testing laboratories can inhibit, in certain cases, their quick response to customers needs, if the scope is too rigid with regard to the modification of test methods and the introduction of new ones using the same measurement principles. Document EA-2-05 published by the European Cooperation for Accreditation describes possibilities to allow flexibility in accredited laboratories. Several examples of a flexible scope are given.
Rules for stating when a limiting value is exceeded by J. M. Christensen; E. Holst; E. Olsen; P. T. Wilrich (pp. 28-35).
The paper describes rules for stating whether a measurement result indicates that the value of the measurand, e.g. the concentration of a substance in the blood, is in conformity or not in conformity with given specifications. Examples of the intended applications are control of doping in sports, alcohol level in drivers’ blood, trace metals levels in workers’ blood, the proportion of gold in alloys, certain ingredients in food products and pesticides in drinking water. When limiting value(s) have been established a permissible measurand value is said to be in conformity and a non-permissible value it is said to be in non-conformity. One of the following three statements is asserted: Statement A: The value of the measurand is beyond any reasonable doubt in conformity, Statement B: The value of the measurand is beyond any reasonable doubt in non-conformity, Statement C: Neither conformity nor non-conformity could be demonstrated. The test can be performed as either a one-stage or a two-stage procedure. A two-stage procedure is recommended as especially appropriate when a cheap and fast screening method can be used in the first stage. For normally distributed measurements, a freeware computer program, conform1e.exe, is available for the calculations of the probabilities for Statements A, B and C.
Keywords: Keywords Conformity testing; Compliance testing; Limiting values; Uncertainty of measurements; Harmonization
CRM CZ 6008a Human urine: total protein, creatinine, stress indicators and their metabolites
by I. Sperlingová (pp. 35-35).