Current best practice for traceability in testing laboratories,when certified reference materials are unavailable

Since the implementation of ISO/IEC 17025 in 2002, all accredited laboratories (at the least) need to establish traceability in all their tests and calibration methods. Traceabilty, though well understood in the calibration field (through an unbroken chain of comparisons to the International System of Units —SI), is less straight forward and not so well understood in the testing laboratories. Traceability in analytical and biological testing is found through the use of reference materials, and the validated steps of a test method. This article describes the possibilities to comply with the traceability requirement of ISO/IEC 17025 in testing laboratories , when certified reference materials are unavailable.Presented at the Second International Conference on Metrology—Trends and Applications in Calibration and Testing Laboratories, 4–6 November, 2003, Eilat, Israel     

External quality assessment schemes for clinical laboratories

 The clinical routine laboratory generally utilizes cheap, easy and rapid measurement procedures ("methods") in order to meet the requirement for the production of many analytical results (500–3000 per day) of hundreds of different types. The measurement procedures are optimized for the analysis of native patients' samples, but are frequently sensitive to deviation of the composition of the matrix from that in normal fresh samples. The inherent lack of stability of patient samples means that control samples need to be stabilized. The method of stabilization is critical. Furthermore, the method of "spiking" samples with pathological material is a matter of concern. Generally, minimally processed patients' samples should be used in external quality assessment (EQA) schemes. Consensus values are currently the most popular for use as a guide to the best results from participating laboratories in EQA schemes; these often work fairly well. However, the uncertainty and traceability of this type of value is unknown, and in some cases may even be misleading, tending to preserve bad routine methods when these are dominant in the participating laboratories. Reference measurement procedure (RMP) values are recommended to provide scientifically based information, to facilitate the proper choice of methods in the routine laboratories, and to validate the suitability of control materials in EQA schemes. The present paper provides selected examples from a study comparing consensus values with RMP values on lyophilized sera, and also presents results on a fresh frozen thawed serum for the study of commutability. Received: 8 November 1995 Accepted: 8 May 1996     

Total-reflection X-ray fluorescence analysis for semiconductor process characterization

Semiconductor process characterization techniques based on total-reflection X-ray fluorescence (TXRF) analysis are reviewed and discussed. One of the most critical factors in obtaining reliable determinations by TXRF is the reliability of the standard samples that are used. Conventional physisorption standard samples such as spin coat wafers have two potential drawbacks: reproducibility of depth profile and stability. A method of chemisorption called ‘immersion in alkaline hydrogen peroxide solution (IAP)’ was proposed that provides answers to these two problems. IAP standard samples were used to experimentally examine three methods of TXRF application: Straight-TXRF, VPD-TXRF, and Sweeping-TXRF. In the application of Straight-TXRF, the linearity of Cu at a level of 10⁹ atoms cm⁻² is examined. In the application of VPD-TXRF, test results of VPD-TXRF for both transition metals and light elements are shown. Finally, a new measurement protocol called Sweeping-TXRF is proposed to conduct whole-surface analysis without chemical preconcentration.     

Real-coded Genetic Algorithm for system identification and tuning of a modified Model Reference Adaptive Controller for a hybrid tank system

Modeling and controlling of level process is one of the most common problems in the process industry. As the level process is nonlinear, Model Reference Adaptive Control (MRAC) strategy is employed in this paper. To design an MRAC with equally good transient and steady state performance is a challenging task. The main objective of this paper is to design an MRAC with very good steady-state and transient performance for a nonlinear process such as the hybrid tank process. A modification to the MRAC scheme is proposed in this study. Real-coded Genetic Algorithm (RGA) is used to tune off-line the controller parameters. Three different versions of MRAC and also a Proportional Integral Derivative (PID) controller are employed, and their performances are compared by using MATLAB. Input–output data of a coupled tank setup of the hybrid tank process are obtained by using Lab VIEW and a system identification procedure is carried out. The accuracy of the resultant model is further improved by parameter tuning using RGA. The simulation results shows that the proposed controller gives better transient performance than the well-designed PID controller or the MRAC does; while giving equally good steady-state performance. It is concluded that the proposed controllers can be used to achieve very good transient and steady state performance during the control of any nonlinear process.     

Extrapolation-to-flight of aerodynamic heating measurements and determination of in-flight radiation-equilibrium surface temperature in hypersonic/high enthalpy flow conditions

The previously demonstrated success of the reference enthalpy concept in heat transfer prediction at hypersonic flow conditions is utilized herein to propose a cost-effective methodology for extrapolation-to-flight of Stanton number measurements (or baseline computational results), and the determination of radiation-equilibrium surface temperatures that develop on actual vehicle surfaces during hypersonic/high enthalpy flight conditions. The methodology couples the (analytical) generalized reference enthalpy solution with Euler computations (providing input data along the edge of thin boundary layers) and is, therefore, significantly cheaper and more efficient than the execution of full Navier–Stokes computations that are presently incorporated, particularly so in the thermo-chemically active high enthalpy flow regime. The validity of the proposed methodology is demonstrated in a first step by means of two-dimensional test cases, whereby extrapolated data accuracy is better than 20%.

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光纤陀螺的研究现状与发展趋势

论述了光纤陀螺的基本原理，性能特征和优势。介绍了光纤陀螺在军用民用领域的应用，分析了光纤陀螺的研制水平，进展，以及技术市场的发展趋势。     

An interlaboratory study to improve the quality of chemical and biological measurements in waste water

 Analyses of waste water are routinely performed to monitor the level of contamination. To verify the quality of such determinations the National Institute of Chemistry, with the support of the Ministry of Environment and Spatial Planning and the Slovenian Accreditation Agency, organizes interlaboratory comparisons. Over the last 3 years, five interlaboratory trials named "MPP-Waste Water" were organized. Each round attracted around 50 participants, mostly from Slovenia and some from abroad, which enabled the testing of SIST ISO methods or alternative methods. We prepared samples for determination of harmful substances that are important for the characterization of waste water; physico-chemical parameters (pH), global parameters – chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), metals (mercury, cadmium, copper, nickel, lead and chromium (VI)), nutrients (ammonia and total phosphorus), anions (chloride, nitrite, nitrate, sulphate) and toxicity to Daphnia magna. For the analysis of each parameter we prepared two samples at two different concentration levels. The materials used in the proficiency testing were carefully prepared and their homogeneity and stability were verified. The purpose of this scheme was to enable participants to check their day-to-day analytical performance. The results should enable the participants to improve the quality of their analyses.

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Received: 24 October 2002 Accepted: 2 January 2003

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Acknowledgments We would like to thank the Ministry of Environment and Spatial Planning and the Ministry for Education, Science and Sport for providing financial support. We would like to thank members of the Technical Committee: Mrs. Marjana Kovacˇicˇ, Dr. Katja Otrin-Debevc, Prof. Dr. Marjan Veber and Mrs. Boža Gregorc for their valuable support. Special thanks are due to Dr. Adrian Van der Veen who helped us in running the first PT.

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Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia

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Correspondence to M. Cotman     

Quality assurance in the microbiology laboratory

 The pertinent issues necessary for the establishment of quality assurance in the microbiology laboratory are discussed. Quality assurance is a planned system of control measures that enables management to ensure that the analytical data produced in the laboratory are valid. To introduce quality assurance, all activities in the laboratory that affect the production of analytical data must be documented and controlled. These include sampling, method selection, laboratory environment, equipment, reagents and media, staff, reference materials and internal and external quality control. Laboratory accrediation in accordance with EN45001 and ISO Guide 25 enables laboratories demonstrate to an external agency their ability to perform analytical work and produce valid analytical data. This gives creditability to the laboratory and allows management to have confidence in the data produced. Received: 6 June 1995 Accepted: 3 July 1995