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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.10, #3)
New approach to calibrating conductivity meters in the low conductivity range by Petra Spitzer; Bruno Rossi; Yves Gaignet; Stéphane Mabic; Uwe Sudmeier (pp. 78-81).
There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 μS cm−1 at 25.0 °C, resistivity >1 MΩ cm at 25.0 °C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.
Keywords: Electrolytic conductivity; High purity water; Calibration; Primary methods; Metrology in chemistry
A review of interference effects and their correction in chemical analysis with special reference to uncertainty by Michael Thompson; Stephen L. R. Ellison (pp. 82-97).
This paper reviews matrix effects and interference in chemical analysis and the methods by which analytical chemists reduce their effects to either negligible or minimal magnitude. The aim is to provide a framework for estimating the contribution to uncertainty due to these effects in analysis, with or without the application of procedures for correcting them. The general characteristics of matrix effects and interference are discussed, and general principles for the estimation of uncertainty associated with matrix effects are introduced. The principal techniques available to minimise matrix effects are described, together with methods of uncertainty estimation where appropriate.
Use of the Eurachem guide on method validation for determination of uranium in environmental samples by M. S. Al-Masri; Y. Amin (pp. 98-106).
Three analytical methods for determination of uranium in environmental samples by a fluorescence technique have been validated and compared in accordance with the Eurachem Guide on method validation. The first method depends on uranium separation from iron using the mercury anode technique; in the other two methods uranium is separated from iron on an anion exchange column by use of either a solution of hydrochloric acid containing ascorbic acid and hydrazine hydrate or a dilute sulfuric acid solution. Detection limits, repeatability, reproducibility, and recovery coefficient were the main validation characteristics. The results showed that better statistical values can be achieved by using the third method. Control charts for in-house control samples and international intercomparison samples have also shown that the third method is more statistically stable with time. In addition, uncertainties of measurement were estimated and compared for the three methods. It was found that the Eurachem Guide and comparison of quality statistical validation data can be good tools for selection of the appropriate method for an application.
Keywords: Method validation; Determination; Uranium; Fluorimeter; Environmental samples
A case study in the practical estimation of measurement uncertainty by Michael Gluschke; Jörg Wellmitz; Peter Lepom (pp. 107-111).
This case study is written for analytical laboratories, in order to give support to the implementation of the concept of measurement uncertainty for routine measurements. The aim is to provide a practical, understandable and common way of performing measurement uncertainty calculations, based mainly on pre-existing quality control and validation data. Practical examples taken directly from environmental laboratory monitoring are presented and explained. However, the approach is very general and should be applicable to most testing laboratories in the chemical field. Following the protocol of evaluation illustrated in the case study, it is possible to ensure that most relevant uncertainty components associated with the method are covered. Contributions associated with sampling, homogenisation, sub-sampling, and so on, are, however, excluded.
Keywords: Measurement uncertainty; Replicate analyses; Certified reference material; Relative reproducibility; Intercomparison studies
Acceptability limits based on biology goals in haematology EQAS by Milan Skitek (pp. 112-115).
The current situation in defining and setting criteria used to determine acceptability limits in haematology external quality assessment schemes (EQAS) is discussed. This report also addresses the control materials and experiences used when determining the suitability of home-made material for complete blood count (CBC), which involves testing a small scheme of about 100 participants with different analytical systems based on a single principle for the attainment of quality specifications. By studying the biological variation in haemocytometry using home-made EQA control blood in a controlled study that employed only haematological analysers based on the electrical impedance (Coulter) principle, we have assessed whether total error goals are achieved for the following parameters: white blood cell (WBC), red blood cell (RBC), and platelet (Plt) counts, concentration of haemoglobin (Hb), and mean cell volume (MCV) in a simple single challenge external quality assessment scheme. We found that we could not attain the biological goals for MCV, RBC and Plt in a haematology EQAS that uses the single analytical principle; even minimum performance based upon the calculation of 1.65[0.75CVI] + 0.375[CVI2 + CVG2]1/2 (p<0.05) is not achievable. For the other two parameters, the minimum (Hb) required for desirable performance (Lkci), given by 1.65[0.50CVI] + 0.25[CVI2 + CVG2]1/2 (p<0.05), is achievable, but the optimum performance of 1.65[0.25CVI] + 0.125[CVI2 + CVG2]1/2 (p<0.05) is not attainable for all five basic haemocitometry parameters. Besides acceptability limits, the control materials used for CBC and the target values used in haematology EQAS are discussed from a practical point of view in order to improve quality.
Keywords: External quality assessment scheme; Haematology; Biological variation
Quality management education over the Internet by Leif Halbo; Ketil Lund; Hans Arne Froystein (pp. 116-120).
We describe a program for continuing education in “Quality management and metrology”. It may be followed by class lectures, by videoconference or by individual distance learning over the Internet. An important feature for students who attend classes is visits to selected institutions for demonstrations of quality management in practice. For students using distance learning, multimedia presentations containing a total of 2 h of video and supporting documentation is the alternative to the visits. The program is aimed at personnel from all fields, and its emphasis is on the generality of quality principles, attitudes and motivation for quality thinking, measurements in quality work, as well as the use of system audits and other elements of quality management in related fields.
Keywords: Quality management; Metrology; Distance learning; Continuing education; Multimedia teaching
The increasing demands of quality assurance in chemical testing by John Buckingham (pp. 121-122).
The chemical and microbiological testing community is going through a rather difficult period of change. Publication of ISO/IEC 17025 (General requirements for the competence of Calibration and Testing Laboratories, 1999) [1] is placing additional demands on testing laboratories to ensure traceability and estimate uncertainty in their measurements. At the same time, laboratories must remain mindful of the need to provide relevant, timely and economic services to their clients. International Accreditation New Zealand (IANZ) and its accredited laboratories are currently focussing on establishing realistic methods for ensuring traceability to national and international standards and estimating measurement uncertainty. To this end, IANZ recognizes that it has an important role in providing as much advice and assistance as possible, not only to its accredited chemical laboratories but also to all those contemplating accreditation in New Zealand.
Keywords: Accreditation; Chemical testing; Measurement; Traceability; Uncertainty
The OIML and the purpose of international recommendations by John Barker (pp. 123-124).
This article was presented to the CITAC workshop in Wellington, New Zealand on 3 May 2004. It explains the role of the Organisation Internationale de Métrologie Legalé (OIML) and work carried out to promote harmonisation in the field of legal metrology—the part of metrology relating to activities which result from statutory requirements and concern measurement, units of measurement, measuring instruments and methods of measurement and which are performed by competent bodies. It also discusses the publications issued to achieve harmonisation. The article also discusses New Zealand’s recent elevation to full membership of the OIML and the commitment to make the membership work to the benefit of the whole New Zealand measurement industry.
Keywords: OIML; International recommendations; International documents; Technical committees; New Zealand
Comparative analysis of laboratory accreditation in Bulgaria, Lithuania, Slovakia and Serbia and Montenegro by Mića Jovanović (pp. 125-129).
The development of an internationally recognized laboratory accreditation process, accompanied by a mutual recognition agreement (MRA), is an issue of great interest in Central and Eastern European countries. This paper presents a comparative analysis of laboratory accreditation in Bulgaria, Lithuania, Slovakia and Serbia and Montenegro. The basic analysis technique was preliminary laboratory accreditation assessment (PLAA). The analysis data were obtained via a questionnaire issued from January to June 2004, with the participation of accreditation bodies. Results from the study are presented in four sections: accreditation body standards, accreditation body organization, assessors and proficiency testing, and inter-laboratory comparisons. Research results for the countries were accessed using PLAA techniques and conformity/non conformity statements. The analysis verified that PLAA can provide low cost, rapid assessment of the key influencing factors in laboratory accreditation bodies.
Keywords: Laboratory accreditation; Mutual recognition agreement; Accreditation assessment for Bulgaria, Lithuania, Slovakia and Serbia and Montenegro