Interlaboratory system to ensure and improve the quality of glassware calibration and use in a large laboratory

This paper describes the implementation and methodology of an interlaboratory system that ensures the quality of glassware calibration and use in a large laboratory. The interlaboratory system involves periodic comparisons between laboratories with evaluations and improvements made over time. Two similar items are calibrated in each exercise according to a detailed calibration procedure. The reference value is traceable to the international system supplied by a metrology laboratory. The results are evaluated as normalized errors and analyzed by Youden graphs. The calibration procedure is presented. An interlaboratory experiment is described in which 7 participating laboratories performed calibrations of 2 volumetric flasks. The reported results, the interlaboratory evaluation, and the actions taken are presented.     

Use of reference materials in coastal monitoring quality assurance

The NOAA National Status and Trends (NS&T) Program determines the current status of, and changes over time in the environmental health of U.S estuarine and coastal waters. Concentrations of organic and inorganic contaminants are determined in bivalves, bottom-dwelling fish and sediments. The quality of the analytical data generated by the NS&T Program is over-seen by the performance-based Quality Assurance Project, which is designed to document sampling protocols, analytical procedures, and laboratory performance, and to reduce intralaboratory and interlaboratory variation. All NS&T cooperating laboratories are required to participate in yearly intercomparison exercises. The analysis of reference materials, such as the National Research Council of Canada's Certified Reference Materials (CRMs) and National Institute of Standards and Technology's (NIST) Standard Reference Materials (SRMs), and of control materials, is required. Because of the need for marine matrix reference materials and standards, NOAA contributed to the production of eight NIST SRMs and seven internal standard solutions. Analytical data from all control materials and all matrix reference materials are reported to the Program office.     

Collaborative study to improve the quality control of trace element determinations in polymers. Part 1. Interlaboratory study

In order to control the quality of trace element determinations in polymer, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project of which the final aim is to certify polymer reference materials for their contents of a range of trace elements. The first part of this project consisted in an interlaboratory study which aimed at testing the feasibility of preparation of candidate polymer reference materials and to detect and remove most of the pitfalls observed in trace element determinations. This paper presents the results of this interlaboratory study carried out prior to the certification campaign. Received: 22 April 1999 / Revised: 21 June 1999 / Accepted: 21 June 1999     

Collaborative study to improve the quality control of trace element determinations in polymers. Part 1. Interlaboratory study

In order to control the quality of trace element determinations in polymer, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project of which the final aim is to certify polymer reference materials for their contents of a range of trace elements. The first part of this project consisted in an interlaboratory study which aimed at testing the feasibility of preparation of candidate polymer reference materials and to detect and remove most of the pitfalls observed in trace element determinations. This paper presents the results of this interlaboratory study carried out prior to the certification campaign. Received: 22 April 1999 / Revised: 21 June 1999 / Accepted: 21 June 1999     

The external quality assurance of phylloquinone (vitamin K1) analysis in human serum

The vitamin K external quality assurance scheme (KEQAS) aims to assist in the harmonization of phylloquinone (vitamin K₁) analysis in order to improve the comparability of clinical and nutritional studies. Serum samples were despatched to 17 groups from eight countries during 2000–2006. Using pilot data (1996–1999), an analytical performance target of 20% absolute difference from the all‐laboratory trimmed mean (ALTM) was assigned and formed the basis for interlaboratory comparison. Assay specificity, analytical bias and assay performance were evaluated. From 21 batches of samples distributed, 414 results were reported of which 2.7% were outliers. The mean interlaboratory absolute difference from the ALTM was 21.7% with 47% of groups consistently meeting the performance target. The mean interlaboratory coefficient of variation was 29.6%. The false positive rate for phylloquinone depleted samples was high at 35%. Bias was found to be independent of HPLC‐detector type (fluorescence vs electrochemical). Assay characteristics for the measurement of phylloquinone in human serum compare favourably with methods for analytes at equivalent concentrations. The high proportion of false positive results suggest that poor assay specificity at low phylloquinone concentrations is a common problem, which in the clinical setting could lead to underreporting of vitamin K deficiency. Copyright © 2009 John Wiley & Sons, Ltd.     

The BIOREMA project—Part 2: International interlaboratory comparison for biodiesel test methods

The results of an interlaboratory comparison, using various measurement methods to carry out biodiesel testing, are presented and the findings are discussed. The interlaboratory comparison was organised within the framework of an EU-funded project called BIOREMA. A general overview of the project and results of an interlaboratory comparison on bioethanol are published as Part 1 and 2 of this series of papers. In the study presented here, reference values, provided by national metrology institutes and expert laboratories, were used for evaluating the results. Consensus values, derived from the results of all participants, were used to assess any bias between the results from the national metrology institutes and testing laboratories. The emphasis in this interlaboratory comparison was not the performance rating of the individual laboratories, but recognising and interpreting differences caused by the measurement methods applied. For most biodiesel parameters, a good agreement of measurement results was found among different methods, and between the consensus and reference values. The study material was a rapeseed oil fatty acid methyl ester, for which it was demonstrated that it is feasible to prepare and characterise reference materials for biodiesel with well-established reference values for many parameters.     

Metrology in laboratory medicine – Reference measurement systems

 The medical laboratory must provide results of measurements that are comparable over space and time in order to aid medical diagnosis and therapy. Thus, metrological traceability, preferably to the SI, is necessary. The task is formidable due to the many disciplines involved, the high production rate, short request-to-report time, small sample volumes, microheterogeneity of many analytes, and complex matrices. The prerequisite reference measurement systems include definition of measurand, unit of measurement (when applicable), consecutive levels of measurement procedures and calibrators in a calibration hierarchy, international organizations, reference measurement laboratories, dedicated manufacturers, written standards and guides for the medical laboratory, production of reference materials, internal and external quality control schemes, and increasingly accreditation. The present availability of reference measurement procedures and primary calibrators is shown to be insufficient to obtain international comparability of all types of quantity in laboratory medicine. Received: 19 April 2000 / Accepted: 3 July 2000     

From GUM to alternative methods for measurement uncertainty evaluation

Since the advent of the Guide to the expression of Uncertainty in Measurement (GUM) in 1995 laying the principles of uncertainty evaluation numerous projects have been carried out to develop alternative practical methods that are easier to implement namely when it is impossible to model the measurement process for technical or economical aspects. In this paper, the author presents the recent evolution of measurement uncertainty evaluation methods. The evaluation of measurement uncertainty can be presented according to two axes based on intralaboratory and interlaboratory approaches. The intralaboratory approach includes “the modelling approach” (application of the procedure described in section 8 of the GUM, known as GUM uncertainty framework) and “the single laboratory validation approach”. The interlaboratory approaches are based on collaborative studies and they are respectively named “interlaboratory validation approach” and “proficiency testing approach”.     

The use of centrally prepared reagents in an external quality experimental trial.

The authors provide the results of a short-term experimental trial in external quality assessment in 42 clinical laboratories conducted by the Mexican Ministry of Health. Assay kits for glucose, urea, and creatinine were prepared by the Ministry. The results may prove useful to organizers of external quality assessments in third-world countries who may opt for this strategy to improve performance. The laboratories performed the tests on reconstituted lyophilized control serum, also prepared by the Ministry. All three assays were performed manually using colorimetric methods. On the basis of their intralaboratory precision (coefficients of variation less than 8%, 8-12%, and greater than 12% for high, medium, and low precision, respectively), 12 laboratories demonstrated high precision for all three tests. Eight laboratories showed medium and low precision for different tests, while the other 22 fell in between. The results showed that the strategy of using centrally prepared reagents to improve interlaboratory agreement did not work well for urea and creatinine, but met expectations for glucose. The laboratories achieved an interlaboratory coefficient of variation of 10% for glucose in this first trial.     

The EC Standards, Measurements and Testing Programme in support of the quality control of waste analysis

Projects funded within the EC Standards, Measurements and Testing Programme (SM&T) of the European Commission aim to contribute to the harmonization and improvement of methods and measurements carried out within the European Union and hence to the comparability of data necessary for e.g. trade activities, monitoring of environment, food and health control, etc. This goal may be achieved by e.g. the organization of interlaboratory studies and certifications of reference materials, the development of new methods and pre-normative research. Examples of projects undertaken in support of the quality of waste analysis are given in this paper, covering different aspects, namely interlaboratory study and certification of extractable trace metals in sewage sludge amended soil reference materials, pre-normative research for the characterisation of stabilized waste (interlaboratory study), and development of field-measurement device for the monitoring of waste water quality; this paper gives also an account of a network aimed at harmonising leaching/extraction tests used for environmental risk assessment. Finally, the main topics of the workshop on Standards, Measurements and Testing for Solid Waste Management are given in the annex, along with a list of participants.     

Multielement trace determination in SiC powders: assessment of interlaboratory comparisons aimed at the validation and standardization of analytical procedures with direct solid sampling based on ETV ICP OES and DC arc OES

The members of the committee NMP 264 “Chemical analysis of non-oxidic raw and basic materials” of the German Standards Institute (DIN) have organized two interlaboratory comparisons for multielement determination of trace elements in silicon carbide (SiC) powders via direct solid sampling methods. One of the interlaboratory comparisons was based on the application of inductively coupled plasma optical emission spectrometry with electrothermal vaporization (ETV ICP OES), and the other on the application of optical emission spectrometry with direct current arc (DC arc OES). The interlaboratory comparisons were organized and performed in the framework of the development of two standards related to “the determination of mass fractions of metallic impurities in powders and grain sizes of ceramic raw and basic materials” by both methods. SiC powders were used as typical examples of this category of material. The aim of the interlaboratory comparisons was to determine the repeatability and reproducibility of both analytical methods to be standardized. This was an important contribution to the practical applicability of both draft standards. Eight laboratories participated in the interlaboratory comparison with ETV ICP OES and nine in the interlaboratory comparison with DC arc OES. Ten analytes were investigated by ETV ICP OES and eleven by DC arc OES. Six different SiC powders were used for the calibration. The mass fractions of their relevant trace elements were determined after wet chemical digestion. All participants followed the analytical requirements described in the draft standards. In the calculation process, three of the calibration materials were used successively as analytical samples. This was managed in the following manner: the material that had just been used as the analytical sample was excluded from the calibration, so the five other materials were used to establish the calibration plot. The results from the interlaboratory comparisons were summarized and used to determine the repeatability and the reproducibility (expressed as standard deviations) of both methods. The calculation was carried out according to the related standard. The results are specified and discussed in this paper, as are the optimized analytical conditions determined and used by the authors of this paper. For both methods, the repeatability relative standard deviations were <25%, usually ~10%, and the reproducibility relative standard deviations were <35%, usually ~15%. These results were regarded as satifactory for both methods intended for rapid analysis of materials for which decomposition is difficult and time-consuming. Also described are some results from an interlaboratory comparison used to certify one of the materials that had been previously used for validation in both interlaboratory comparisons. Thirty laboratories (from eight countries) participated in this interlaboratory comparison for certification. As examples, accepted results are shown from laboratories that used ETV ICP OES or DC arc OES and had performed calibrations by using solutions or oxides, respectively. The certified mass fractions of the certified reference materials were also compared with the mass fractions determined in the interlaboratory comparisons performed within the framework of method standardization. Good agreement was found for most of the analytes.     

Lifetime of the traceability chain in chemical measurement

Since the uncertainty of each link in the traceability chain (measuring analytical instrument, reference material or other measurement standard) changes over the course of time, the chain lifetime is limited. The lifetime in chemical analysis is dependent on the calibration intervals of the measuring equipment and the shelf-life of the certified reference materials (CRMs) used for the calibration of the equipment. It is shown that the ordinary least squares technique, used for treatment of the calibration data, is correct only when uncertainties in the certified values of the measurement standards or CRMs are negligible. If these uncertainties increase (for example, close to the end of the calibration interval or shelf-life), they are able to influence significantly the calibration and measurement results. In such cases regression analysis of the calibration data should take into account that not only the response values are subjects to errors, but also the certified values. As an end-point criterion of the traceability chain destruction, the requirement that the uncertainty of a measurement standard should be a source of less then one-third of the uncertainty in the measurement result is applicable. An example from analytical practice based on the data of interlaboratory comparisons of ethanol determination in beer is discussed. Received: 5 October 2000 Accepted: 3 December 2000     

Metrology in chemistry – a public task

 The importance of analytical chemistry is increasing in many public fields, and the demand for reliable measurement results is growing accordingly. A measurement result will be reliable only if its uncertainty has been quantified. This can be achieved only by tracing the result back to a standard realizing the unit in which the measurement result is expressed. The National Metrology Institutes (NMIs) can contribute to the reliability of the measurement results by developing measuring methods, and by providing reference materials and standard measuring devices. In fields in which the comparability of measurement results is of particular importance, they establish traceability structures. Responding to the globalization of trade and industry the International Committee for Weights and Measures (CIPM) agreed on an arrangement on the mutual recognition of calibration certificates (CIPM MRA) issued by the NMIs. Received: 19 April 2000 / Accepted: 28 July 2000     

External calibration in gas chromatography-combustion-isotope ratio mass spectrometry measurements of endogenous androgenic anabolic steroids in sports doping control

An alternative calibration procedure for the Gas Chromatography–Combustion–Isotope Ratio Mass Spectrometry (GC–C–IRMS) measurements of the World Antidoping Agency (WADA) Accredited Laboratories is presented. To alleviate the need for externally calibrated CO₂ gas for GC–C–IRMS analysis of urinary steroid metabolites, calibration using an external standard mixture solution of steroids with certified isotopic composition was investigated. The reference steroids of the calibration mixture and routine samples underwent identical instrumental processes. The calibration standards bracketed the entire range of the relevant δ¹³C values for the endogenous and exogenous steroids as well as their chromatographic retention times. The certified δ¹³C values of the reference calibrators were plotted in relation to measured m/z¹³CO₂/¹²CO₂ (i.e. R(45/44)) mass spectrometric signals of each calibrator. δ¹³C values of the sample steroids were calculated from the least squares fit through the calibration curve. The effect of the external calibration on δ¹³C values, using the same calibration standards and set of urine samples but different brands of GC–C–IRMS instruments, was assessed by an interlaboratory study in the WADA Accredited Laboratories of Sydney, Australia and Athens, Greece. Relative correspondence between the laboratories for determination of androsterone, etiocholanolone, 5β-androstane-3α,17β-diacetate, and pregnanediacetate means were SD(δ¹³C) = 0.12‰, 0.58‰, −0.34‰, and −0.40‰, respectively. These data demonstrate that accurate intralaboratory external calibration with certified steroids provided by United States Antidoping Agency (USADA) and without external CO₂ calibration is feasible and directly applicable to the WADA Accredited Laboratories for the harmonization of the GC–C–IRMS measurements.     

An international interlaboratory study for the production of a sewage sludge certified reference material for routine use in inorganic quality control

Two existing interlaboratory schemes are used to certify a sewage sludge reference material. Data from the analysis (As, Cd, Cr, Cu, Pb, Hg, Ni and Zn) of the material using routine procedures, US EPA and Netherlands NEN, plus INAA and IDMS and an interlaboratory comparison in Eastern Europe have been examined. The Dutch results show significantly lower analytical results for As for the graphite furnace technique compared to HG-AAS, probably due to matrix-effects. The differences between the Dutch and USA results for Cr and Ni suggest that the USEPA 3050A digestion method for dissolution of the metals is less aggressive for this material compared to aqua regia destruction. For international comparability of analytical data it is essential to harmonize method dependent dissolution/extraction techniques. The preparation of reference materials which mimic real samples and certification by ILS result in useful materials for quality control.     

The practical advantages of hospital quality systems such as NIAZ/PACE

 The Netherlands Institute for Accreditation of Hospitals (NIAZ) was established at the end of 1998. It was founded by the PACE foundation, the Society of University Hospitals, the Netherlands Association of General Hospitals and the Society of Medical Specialists in the Netherlands. Since then in the Netherlands 19 pilot accreditations have been performed based upon 35 NIAZ-PACE standards for hospital departments and functions, and the overall standard 'quality system'. The aims and methods of the accreditation system were inspired by examples from the other side of the Atlantic, especially from Canada. The characteristics are: voluntary-based, self-evaluation, peer-review and aiming at continuous improvement of quality of care. Received: 15 April 2000 · Accepted: 15 April 2000     

Quality assurance in analytical chemical laboratories: Towards harmonization and integration of current standards

This article presents the results of a comparative study of the main quality assurance (QA) and good laboratory practice (GLP) regulation systems and standards for analytical chemical laboratories currently being applied in Europe. A growing number of laboratories are being confronted with the need to cope with two or more of these systems, which involves separate audits and inspections for certification and accreditation. As these regulatory systems have essentially the same aims, there is an increasing interest in harmonization of QA and GLP guidelines. As a first step in exploring the possibilities of harmonization, similarities and differences of the current systems, compiled in the form of cross reference tables, have been analyzed (from a laboratory practice point of view) by a study group of EURACHEM, The Netherlands. The conclusions of this study have recently been endorsed by the Committee of EURACHEM Europe.     

The BIOREMA project—part 1: Towards international comparability for biofuel analysis

There is an increasing demand to accurately measure the quality of biofuel products (e.g. biodiesel and bio-ethanol). This demand is driven in Europe by directives promoting the use of renewable sources of energy and worldwide by national and international legislation setting out quality requirements for these fuels. Until now, there has been no international consensus on the minimum technical specifications to ensure biofuel quality. Furthermore, it is unclear which reference materials and measurement techniques are needed to provide the quality assurance and quality control framework to underpin these legislative requirements. As part of the European Commission’s 7th Framework Programme, the BIOREMA project (REference MAterials for BIOfuel specifications) demonstrated the feasibility of preparing biodiesel and bio-ethanol reference materials with reference values traceable to the international system of units for a range of parameters at levels relevant to technical specifications. However, the project concluded also that further research is needed to improve the current measurement capabilities for some parameters. Within the BIOREMA project, two global interlaboratory comparisons were carried out, using the biodiesel and bio-ethanol test materials prepared during the feasibility stage of the project, as well as two biodiesel standard reference materials from the National Institute of Standards and Technology (NIST, USA). The exercises showed that the measurement capabilities of the field laboratories were in many cases satisfactory, whereas for other laboratories the availability and regular use of certified reference materials would likely enhance the measurement capabilities for many of the parameters studied. A general overview of the BIOREMA project is presented in this paper. The details of the production of the two types of BIOREMA reference materials, and the results of the interlaboratory comparison for the bio-ethanol and biodiesel study materials, are discussed in parts 2 and 3 of this series of papers.     

Harmonized protocol and certified reference material for the determination of extractable contents of phosphorus in freshwater sediments – A synthesis of recent works

An analytical protocol for the determination of the extractable phosphorus contents in freshwater sediments has been harmonized through interlaboratory studies in the frame of the Standards Measurements and Testing Program of the European Commission. A homogeneous and stable sediment reference material has been prepared and certified on the basis of this protocol named SMT protocol, and will be available in spring of 2001. The SMT protocol, together with the reference material, are useful tools in the field of water management, especially at a time when quality assurance and data comparability are of paramount importance in laboratory analysis. The knowledge of the bioavailable forms of phosphorus is important not only for sediments but also for sludge and soils. Therefore, the SMT protocol could be extended to these materials and new CRMs could be prepared. The SMT protocol was used in a study of a reservoir, which allowed to calculate the P stock, therefore helping to predict the restoration delay of the lake. The paper describes the protocol and the CRM, and gives a brief outline of the case study. Received: 14 November 2000 / Revised: 25 January 2001 / Accepted: 31 January 2001