The application of data from proficiency testing to laboratory accreditation according to ISO 17025

Current methods of testing laboratories for their proficiency in reporting correct measurement results are liable to substantial errors of the second kind. This means that laboratories with deflated uncertainties are accepted as proficient, even though their reported measurement results pave the way for erroneous conclusions. Only by using E _n numbers based on an accepted reference value with the lowest possible uncertainty can the risk of recognising incorrect measurement results be kept at an acceptable level. Based on an actual set of proficiency test (PT)-data for the concentration of Pb in water, this paper compares PT results obtained by methods using E _n numbers with methods based on z-scores. Kaj Heydorn is a technical assessor at The Danish Accreditation and Metrology Fund (DANAK).     

Use of characteristic functions derived from proficiency testing data to evaluate measurement uncertainties

Interlaboratory comparisons show that reproducibility standard deviations are dependent on the concentration of the analyte. Many attempts have been made to model this. In this paper, ??characteristic?? functions are used for modelling the concentration dependence of the reproducibility standard deviations based on data from proficiency tests for water analysis. The characteristics of the resulting functions can be used for the estimation of measurement uncertainties at different concentration levels. These functions are especially useful to determine the concentration levels below which absolute uncertainties tend to be constant and above which the relative uncertainties are more constant. By comparing the characteristic functions of different analytical procedures for the determination of the same analyte, the performance of these procedures under routine application can be compared. Finally, these functions may be used to get an indication on the average quality of analytical result in a specific field to be used by regulators in order to formulate requirements in the legislation that are in accordance with current measurement quality.     

Estimates of uncertainty of measurement from proficiency testing data: a case study

The results obtained by a laboratory over a number of proficiency testing/external quality assessment schemes (PT/EQAS) rounds can give information on the uncertainty of its measurements for a given test, provided that conditions such as full coverage of the routine analytical range, traceability, and small uncertainty of the assigned values (compared to the spread of the results) are met and provided that systematic deviations and any other sources of uncertainty are considered. As organisers of the Italian EQAS (ITEQAS) in occupational and environmental laboratory medicine, we tested this hypothesis using as model data from well-performing laboratories taking part in ITEQAS for lead in blood over the last 2 years. We also investigated how different PT/EQAS features (frequency of trials and number of samples) would affect a laboratory estimate of its uncertainty. Such information can be helpful in improving PT/EQAS organisation and define, for a given test: (a) the state of the art of the uncertainty of current measurement procedures, (b) identify needs for improvement of analytical methodologies and (c) set targets for acceptable uncertainty values.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia.Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.     

Approaching target uncertainty in proficiency testing schemes: experience in the field of water measurement

Good correspondence between evaluations of the proficiency testing data for water measurements according to different scoring schemes was found as a result of implementation of the measurement quality according to the target uncertainty defined in the Drinking Water Directive. The accuracy of the evaluation is determined by the uncertainty of the assigned value, and this uncertainty should be in correspondence with the target uncertainty. Modification of the zeta-score by the thorough application of the target uncertainty is presented. It is convenient for generalised presentation of the proficiency testing data. The allowed bias is included as a linear term on the measured value scale, as it is treated in uncertainty analysis. The importance of implementation of the target measurement uncertainty in other fields of the routine measurements is indicated.     

The influence of a quality system according to ISO/IEC 17025 on the performance of Brazilian laboratories in proficiency testing in the environmental area

This paper presents a performance analysis of laboratories in proficiency testing (PT) with the main objective of evaluating whether having accreditation to ISO/IEC 17025 or not having an implemented quality system has an influence on the performance of these laboratories. This research was conducted with data from an accredited PT scheme of physical–chemical water analyses. Nine metals were considered in the analysis, with a total of 896 results. The performance indicator was z-score. The proposed analysis was conducted through statistical methods of analysis of variance, Dunnett’s test, Chi-square and cross-tabulation. It was verified that there is a significant difference between the performance of accredited laboratories, recognised laboratories, and laboratories that do not have an implemented quality system. It was established that an accredited or recognised quality system has a positive influence on the laboratory performance, resulting in a lower z-score (in module) and in a larger percentage of satisfactory results.     

Analytical performance is improved by regular participation in proficiency testing: an analysis of data from the Aquacheck proficiency testing scheme

Analysis of historical data from the Aquacheck proficiency testing scheme demonstrates improvement in the performance of participants correlated to the frequency of participation. Analysis of the spread of results returned by all participants, defined by the percentage relative standard deviation (RSD) and the performance (Z) scores awarded to the individual participants, indicates that the overall performance for the group of participants is consistent. However, when the frequency of participation is analysed, it can be clearly seen that those laboratories who participated in the majority of the distributions available reported 10–15% more acceptable (Z-scores between +2 and ?2) results than those labs who took part with a greatly reduced frequency. When ‘more difficult’ analytes are considered, those laboratories who participated in greater than 75% of available rounds reported up to 30% more acceptable results than those laboratories who participated in 25% or fewer, of the available rounds.     

The organization of proficiency testing in plant pathology (qualitative methods of analysis) according to the ISO/IEC 17043: example of the French national reference laboratory

The use of methods of analysis capable of producing reliable analytical results is a prerequisite to the effective control of quarantine plant pathogens. Proficiency testing is considered to be one of the most reliable ways to verify and coordinate analytical results. As a French national reference laboratory in plant pathology, the Anses Plant Health Laboratory organizes proficiency tests in order to ensure that officially approved laboratories (certified by government services) are capable of producing reliable analytical results for the detection of plant pathogens. Proficiency tests in plant pathology have a number of notable features including the processing of qualitative results. This paper presents the experience of the Anses Plant Health Laboratory’s Unit for Tropical Pests and Diseases (LSV-RAPT) as an organizer of proficiency tests in plant pathology. The LSV-RAPT has gained recognition for the methodology it has developed in the form of accreditation as a proficiency testing provider according to the ISO/IEC 17043. The methodology can be applied to many other disciplines that use qualitative detection methods.     

A review of proficiency testing scheme in Republic of Korea: in the field of water analysis

For regulatory purposes, it is often required to check the quality of environmental chemical analyses by routine proficiency testing (PT). In this study, the PT scheme of environmental laboratories in Republic of Korea has been reviewed. Especially, real water-based reference materials (RMs) were prepared and distributed for PT schemes. The consensus values from the PT were calculated by robust statistics with its standard uncertainties. The relative bias between the reference values and the consensus values was used as one of the indicators for the determination of the assigned values. The relationship between the performances of the laboratories, expressed by Z scores, and the concentration levels of the RMs were also revealed.     

State of water in inverse micelles of Aerosol OT,according to IR spectroscopic data

Leningrad State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 4, pp. 81–85, July–August, 1991.     

Regular participation in proficiency testing provides long term improvements in laboratory performance: an assessment of data over time

Data from various proficiency testing schemes, operated by LGC Standards, was collated and reviewed to determine whether regular involvement within third party, proficiency testing, either over a prolonged period of time or via multiple participation, had improved the performance of those laboratories taking part. Three statistical evaluations were applied to historical PT results, a review of improvements over time, demonstrated by the evaluation of satisfactory performance scores achieved, a review of the relative robust standard deviations obtained from multiple methods and a focused review of one analyst participating in proficiency testing over a prolonged period of time. In each case the data indicated that long term participation and evaluation via proficiency testing had resulted in consistent and sustained improvements in laboratory performance.     

State of the structural hydroxyl groups in minerals of the kaolinite group according to infrared spectroscopic data

An interpretation of the IR spectra of kaolinite, dickite, and nacrite is proposed, based on the concept of resonance interaction of two intrasurface hydroxyl groups, and their manifestation in the spectrum as a split doublet 30 cm^–1 and by the individual vibration of a third intrasurface OH-group. The structural identification of each band in the IR spectra of the kaolinite minerals is given. It was demonstrated that thermal dehydroxylation under vacuum of kaolinite occurred in two stages with activation energies of 43 and 84 kJ/mole. The activation energy of proton delocalization of the structural hydroxyl groups of kaolinite has been evaluated (E 13 kJ/mole). The contribution of the energy of the interlayer hydrogen bonds (AH 28 kJ/mole) to the total cohesion energy of adjoining layers of kaolinite (E_c 165 kJ/mole) was calculated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 73–81, January–February, 1985.     

Use of uncertainty estimates as reported by participants in proficiency testing for the evaluation of their results: pros and cons

The aim of this paper is to study the measurement uncertainties reported in proficiency tests (PTs) using examples from PTs in the environmental sector and to compare the obtained measurement uncertainty estimates using different approaches. In addition, the paper focusses on the differences between the z-score and the zeta score. Since the year 2000, the Finnish Environment Institute has asked participants to report analytical methods as well as measurement uncertainties in connection with PT results. The measurement uncertainties of the assigned value have also been evaluated. On the basis of the results, the measurement uncertainties reported by the participants varied greatly. Participants often reported underestimated measurement uncertainties, but overestimated uncertainties were also reported. At the moment, it seems as if performance assessment should be based on the z-score because of a number of significant over- and underestimated measurement uncertainties. The zeta score should be used for information and educational purposes mainly.     

Quality control in extended measurement campaigns: selection of contract laboratories by proficiency testing exemplified for the trace analysis of anilines in groundwater

An interlaboratory comparison for the determination of aniline, nine methylated anilines and chlorinated anilines in contaminated groundwater (each compound between 1 µg L^?1 and 750 µg L^?1) was conducted as proficiency test for the selection of contract laboratories for a groundwater monitoring campaign. For the 13 participants, two different test sample series were prepared from a stabilized real case groundwater. Series A was the groundwater as sampled in the field and series B was prepared from series A by spiking with selected anilines. Homogeneity and stability investigations revealed that contaminated groundwater provides a viable basis for the preparation of ring test samples for the determination of anilines. Analytical procedures were limited to the standardized liquid–liquid extraction or solid-phase extraction in combination with gas chromatography/mass spectrometry (DIN 38407-16:1999). The robust consensus values were evaluated according to the standardized protocol of DIN 38402-45:2013. Robust reproducibility standard deviations ranged largely between 20?% and 60?% depending on the analyte. The proficiency assessment of individual participants combined the qualitative aspect of correct peak identification with the quantitative determination of individual concentrations within set limits in a unified approach. It could be shown that the accreditation status of laboratory and the existence of a standardized analytical procedure do not substitute a problem-related proficiency assessment of potential contractors.     

Conversion of ethanol on HZSM-5 modified zeolite, according to data from in situ spectrokinetic studies

The conversion of ethanol on zeolite catalysts is studied spectrokinetically in situ. Ethoxy groups and polyene structures (compaction products) are found to be key intermediates on the studied catalysts under reaction conditions. Ethoxy groups are shown to convert into diethyl ether by a bimolecular mechanism at relatively low temperatures in the presence of ethanol in the gas phase. The character of the conversion of ethoxy groups is found to change at temperatures above 200°C: they become a source for the formation of surface polyene structures, which in turn are converted into a complex combination of hydrocarbons.     

A comparison in the evaluation of measurement uncertainty in analytical chemistry testing between the use of quality control data and a regression analysis

The evaluation of measurement uncertainties has been widely applied to the calibration of measurement instruments, whereas its application to tests, despite increasing requirements, is a more recent phenomenon. The generalization of the evaluation of measurement uncertainties to tests has been a gradual process, in line with changes in the requirements of the normative framework that regulates the accreditation of tests laboratories and also as the perceived good practices have evolved. The sole identification of the relevant sources of uncertainty was followed by the requirement to provide a simplified estimate of the measurement uncertainty, and it is now an accepted requirement to properly evaluate the expanded measurement uncertainty associated with any tests. In this study, the evaluation of measurement uncertainty associated with the determination of sulfate in water will be attempted using a procedure that includes linear regression, with the regression parameters provided with associated uncertainties, and a Monte Carlo method applied as a validation tool of the conventional mainstream evaluation method, concerning the approximations in terms of linearization of the model and the assumed shape of the output distribution introduced by this approach.     

Implementation of a quality assurance system according to GMP and ISO 9001:2008 standard for radiopharmaceutical production in a public research centre

The production of pharmaceuticals is one of the most highly regulated fields in terms of quality. The body of good manufacturing practice (GMP) represents the standard required by law; GMP embraces the guidelines that regulate all activities related to the production and quality control of medicinal products for human and veterinary use. This paper deals with the implementation of a quality management system (QMS) in compliance with GMP and ISO 9001 standards for the production and distribution of radiopharmaceuticals in a public research institute. The production of 2-[18F]fluoro-2-deoxy-d-glucose has been implemented according to GMP standards and has been licensed by the national Authority in 2007. In 2010, a project to orient the system??s GMP compliance to ISO 9001 standards has been approved. A QMS conforming to ISO 9001:2008 should be considered an important additional step in terms of quality, because ISO 9001 also takes into account economic and financial aspects, design and development aspects and introduces management review for measurement and analysis of the process with the aim of improving performances. The harmonization between GMP and ISO has been defined following the Pharmaceutical Quality System Q10 guideline developed by International Conference on Harmonization.     

Dynamic structure of organic compounds in solution according to NMR data and quantum chemical calculations: II. Styrene

The dynamic structure of styrene has been studied with the goal of obtaining detailed information on the internal rotation parameters. A potential energy surface has been constructed for the rotation of the vinyl group about the single bond in terms of the second-order Møller–Plesset perturbation theory with aug-cc-pvtz basis functions, and conformational dependences of ⁿ J _HH have been calculated at the FPT DFT (B3LYP) level of theory with basis functions of the same type. The vibration-averaged coupling constants have been compared with the experimental values reliably determined in this work. A high efficiency of the proposed dynamic model for structural studies of organic molecules with ultrafast internal rotation dynamics has been demonstrated.