Interlaboratory Experiment Research Articles

New Certified Reference Material of Tungsten Concentrate for Developing Multielement Analysis Techniques

A new multielement certified reference material of tungsten concentrate (GSO 11541–2020) – wolframitehubnerite concentrate (hard-alloyed), KVG(T) was developed. Its metrological characteristics were established via results of interlaboratory experiment. The analytical results were obtained at the testing laboratories of 13 scientific and manufacturing organizations of Russia, Belarus, Kazakhstan, and Uzbekistan using single-element chemical analysis methods (gravimetric, spectrophotometry, atomic absorption spectrometry, etc.), as well as modern multielement methods (atomic emission spectrometry with arc discharge or inductively coupled plasma, inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry). The mass fraction values for ten elements certified; for eleven elements recommended; and for 39 elements, as well as hygroscopic and crystallization water, are given as information data. This CRM is intended for certification and validation of single and multielement methods, as well as quality assurance in analysis of the ores and products of their processing in mining, metallurgical, and chemical industries and in scientific research. The information potential of GSO 11541–2020 is higher than that of imported reference materials.

Assessment of the Equivalence of Methods for the Determination of the Vapor Pressure of Oil and Oil Products

Current regulatory documents in Russia establish the need for testing laboratories to determine such parameters as saturated vapor pressure using the Reid method, air saturated vapor pressure, total vapor pressure of crude oil. In analytical practice, appropriate reference materials are used for measurement quality control, method validation, metrological traceability establishment, and other purposes. In addition, the calculation of various vapor pressure equivalents using correlation equations (DVPE – dry vapor pressure equivalent, RVPE – Reid vapor pressure equivalent, etc.) is regulated by appropriate methods for determining vapor pressure. Vapor pressure is a method-dependent parameter; so many producers of reference materials use interlaboratory experiment as a way to establish a certified value. Thus, when conducting an interlaboratory experiment in the process of certification of reference materials, it was revealed that laboratories can incorrectly interpret the obtained experimental data – consider values of the air saturated vapor pressure, total vapor pressure and even calculated vapor pressure equivalents as the Reid vapor pressure. To solve this problem, the authors of this work set the goal of assessing the equivalence of methods for determining the vapor pressure of oil and oil products used in testing laboratories in order to identify the key characteristics of the stated methods and assess their equivalence. The article discusses methods the vapor pressure determination using an automatic vacuum chamber and a Reid bomb. Various matrices of reference materials (hydrocarbons, gasoline, commercial oil, gas condensate) were investigated, and the calculated vapor pressure equivalents were obtained and compared. It was shown that the air saturated vapor pressure, dry vapor pressure equivalent, Reid vapor pressure equivalent, and total vapor pressure cannot be equated to the saturated vapor pressure values determined by the Reid method. A comparative assessment of methods for determining the vapor pressure of oil and oil products used in testing laboratories can be of assistance to developers of regulatory documents for oil, gas condensate, and motor gasoline, revealing the need to separate the requirements for vapor pressure parameters of the considered objects of analysis and providing empirical material.

Method for Measuring the Mass Fraction of Soybean Trypsin Inhibitor: Features of Development and Certification

Modern industrialization increases the requirements for the accuracy of identifying allergens, especially those that have a negative impact – soy trypsin inhibitor (STI). Correct determination of the presence of STI in food products containing soybeans is key for product safety control and labeling. The authors set a goal to develop and certify a method for measuring the mass fraction of STI using an enzyme-linked immunosorbent assay – a technique that may increase the specificity of the method and avoid false-negative results. The object of research was a method for analyzing food allergens – an enzyme-linked immunosorbent assay carried out with a set of reagents produced by XEMA LLC. In the process of developing the measurement method, the main methodological factors influencing the accuracy of the measurement results were optimized: sample weight, time of its extraction, time and speed of sample centrifugation, ratio of supernatant liquid to ELISA buffer, incubation temperature, interaction time of the allergen-antibody complex with the coloring agent, the wavelength for measuring absorbance, and the maximum time for measuring absorbance after introduction of the stop reagent. The developed method was tested during an interlaboratory experiment with the participation of 5 laboratories. Metrological characteristics were established in accordance with RMG 61–2010. The proposed method was certified in accordance with the requirements of GOST R8.563-2009, No. 102–FZ. The method has a wide range of quantitative determination of the mass fraction of STI from 0.5 to 25.0 μg/kg (ppb) with a detection limit of 0.1 μg/kg (ppb) and a relative error of 40 %. Based on the results of the research, the Federal Information Fund for Ensuring the Uniformity of Measurements (FIF) registered a certified method for identifying and quantifying the content of non-infectious food allergens of plant protein origin in samples of all types of food products and objects related to the requirements for food products, swabs taken from working surfaces during production control using reagent kits for an enzyme-linked immunosorbent assay produced by XEMA LLC No. FR.1.31.2022.43884. The method is intended for use in testing laboratories involved in monitoring the quality and safety of manufactured products; it can be used to confirm product compliance with the mandatory requirements established in the Technical Regulations of the Customs Union TR CU022/2012.

Приготування і характеризація референс-матеріалу для визначення загального вмісту та рухомих форм металічних елементів у ґрунтах

Reference material of soil for determination of total content of copper, iron, manganese, nickel, and zinc, according to ISO 11466-2001, and for the operationally defined method of determination of exchangeable forms of these elements according to series of standards DSTU 4770, with ammonium acetate as an extractant is prepared and characterized. The studied material demonstrated sufficient homogeneity to exchangeable forms of metals and for the total content of copper, nickel, and zinc. The homogeneity of the material to manganese and iron is insufficient due to the presence of these metals in non-uniformly distributed magnetic microparticles (<10 μm). An interlaboratory experiment, performed to obtain assigned values of the sample characteristics, demonstrated sufficiently good agreement between the laboratories. An uncertainty of the assigned value corresponds to 30–50% for exchangeable forms of copper and nickel and 10–13% for exchangeable forms of iron, manganese, and zinc. An expanded uncertainty of assigned values of the total content of copper, nickel, and zinc is sufficient for the application of the material for methods validation and internal quality control.

The interlaboratory comparisons role in the Ukrainian metrology system functioning

It is considered the usage of interlaboratory comparisons for the assuring of national metrology system functioning in the part of national measurement standards recognition (international standards comparisons), development and support the system of the units dissemination (the measurements methods evaluation and reference materials certification by interlaboratory experiment) and the calibration, testing and medical laboratories competence confirmation while their accreditation (proficiency testing). The information on valid European Proficiency Testing System EPTIS is presented. The programs for different types of laboratory studies are considered. The approaches to participants functioning evaluation are presented for the proficiency testing while calibration programs. The recommendations by international documents concerning laboratory activities monitoring reliability are presented.

Interlaboratory experiment design in the production of reference materials (ICRM) and statistical processing of the results obtained

Institute for Certified Reference Materials (ICRM) is a leading manufacturer of certified reference materi­als (CRM) for ferrous metallurgy. The entire process of CRM production from the purchase of a material to the certificate issuance takes about two years. The determination of the metrological characteristics is the longest stage of CRM production. The metrological characteristics of reference materials, are evaluated, as a rule, according to the results of an interlaboratory experiment and, in addition, in combination with a comparison method. The interlaboratory experiment arranged by ICRM, involves at least 10 competent analytical laboratories. The interlaboratory comparative tests are also carried out to test the qualification of laboratories. Since 2017, ICRM has been accredited by the Federal Accreditation Service as a profi­ciency provider of interlaboratory comparison.

Multiple stress creep and recovery test for bituminous binders – influence of several key experimental parameters

The Multiple Stress Creep and Recovery test is recognised to better characterise the high-temperature property of bituminous binders than the traditional methods, especially for polymer modified bitumen (PmB). However, some experimental parameters may affect the test results, such as the preloading, measurement location, stress level. In this study, the effects of these parameters were evaluated through an interlaboratory experiment. Four bituminous binders were short-term aged and analysed by five different laboratories. The variability in most results met the requirements of the European standard, while some failed to pass the American precision criteria. The preloading at 0.1 kPa with ten cycles was found to have a recordable impact on PmB samples, but a less significant effect was observed for the unmodified ones. With the measurement locations, the influence is limited compared to other parameters. As for stress sensitivity, higher stresses lead to remarkable differences.

Results of an interlaboratory experiment on metrological certification of a soil sample certified for the content of trace elements-metals

Results of an interlaboratory experiment on metrological certification of a soil sample certified for the content of trace elements-metals

Estimation and predictors of the Omega-3 Index in the UK Biobank.

Information on the Omega-3 Index (O3I) in the United Kingdom (UK) is scarce. The UK-Biobank (UKBB) contains data on total plasma n3-PUFA% and DHA% measured by NMR. The aim of our study was to create an equation to estimate the O3I (eO3I) from these data. We first performed an inter-laboratory experiment with 250 random blood samples in which the O3I was measured in erythrocytes by GC, and total n3 % and DHA% were measured in plasma by NMR. The best predictor of eO3I included both DHA% and a derived metric, the total n3 %-DHA%. Together these explained 65 % of the variability (r = 0·832, P < 0·0001). We then estimated the O3I in 117108 UKBB subjects and correlated it with demographic and lifestyle variables in multivariable-adjusted models. The mean eO3I was 5·58 % (sd 2·35 %) in this UKBB cohort. Several predictors were significantly correlated with eO3I (all P < 0·0001). In general order of impact and with directionality (-, inverse and +, direct): oily-fish consumption (+), fish oil supplement use (+), female sex (+), older age (+), alcohol use (+), smoking (-), higher waist circumference and BMI (-), lower socioeconomic status and less education (-). Only 20·5 % of eO3I variability could be explained by predictors investigated, and oily fish consumption accounted for 7·0 % of that. With the availability of the eO3I in the UKBB cohort, we will be in a position to link risk for a variety of diseases with this commonly used and well-documented marker of n3-PUFA biostatus.

Application of direct and indirect methods for determining the mass fraction of the main component in flotation potassium chloride

The article is devoted to the comparison of two approaches to determining the purity of metal salts on the example of a complex in composition object - flotation potassium chloride. The results of determining the mass fraction of the main component (potassium chloride) in flotation potassium chloride obtained by direct (using the coulometric titration method with correction for anions titrated with the determined chloride ion and an excess of cations) and indirect (according to the scheme 100% minus the amount of impurities with regard to their species) methods. It is shown that direct and indirect methods give well consistent results: (96.08 ± 0.17) % and (96.11 ± 0.12) %, respectively. Also, the measurement results obtained using the standard installations considering the uncertainty are well consistent with the certified value of the mass fraction of potassium chloride (96.11 ± 0.11) %, obtained based on an interlaboratory experiment in laboratories that perform measurements in accordance with GOST 20851.3. The feature of the direct and indirect methods implemented in this work is the construction of a model of the chemical composition of the analysed object based on a priori and experimental data using two basic principles when summing up the content of impurities: the conditions of material balance and the principle of electroneutrality.

Development of reference materials for gas permeability

The article presents the development of reference materials of gas permeability of rocks (imitators) with traceability to Get 210–2019: State Primary Standard of Units of Specific Adsorption of Gases, Specific Surface Area of Pores, Specific Volume of Pores, Dimension of Pores, Open Porosity, and Coefficient of Gas Permeability of Solid Substances and Fabricated Materials. At the time of the beginning of this study, in the system of metrological assurance of gas permeability coefficient measurements, there were only reference materials of an approved type with traceability to the measurement results obtained in an interlaboratory experiment using gas permeability analyzers that were calibrated using the same reference materials, and reference materials with traceability to the State Primary Standard were absent. As a result, in the metrological practice of gas permeability measurement, there was no stable basis for comparison. This fact prompted the authors to research work in this area. The article considers the key stages of the process of reference materials development: analysis of similar reference materials of an approved type, selection of the starting material for reference materials, performing experimental research, and determining, on the basis of this research, the metrological characteristics of reference materials. Ceramic cylinders based on aluminum oxide were used as the starting material for reference materials; the method to measure the gas permeability coefficient is based on the method of stationary filtration. Measurements of the gas permeability coefficient were carried out on samples with different gas permeability using nitrogen and helium gases. Based on the results of these measurements, for each sample, the gas permeability coefficients were calculated at the given reverse pore pressure and the absolute gas permeability coefficient. As a result of the study, a set of reference materials of gas permeability of rocks (imitators) GSO 11546–2020 / GSO 11550–2020 was approved, the range of certified values is (0.1 10 –3 – 5) μ m 2 , and the expanded uncertainty of certified values Uo (k = 2, P = 0.95), is 3 %. The authors believe that the GSO 11546–2020 / GSO 11550–2020 dataset will ensure metrological traceability and reliability of gas permeability coefficient measurements. As a result, it will bring practical relevance to a petrophysical research laboratory.

Development of food industry metrological assurance complex

The paper considers the contribution of experts from the Laboratory of Metrology of Moisture Measurement and Reference Materials to the improvement of the food industry metrological assurance system. The information on the results of the development of forty types of reference materials (RM) for the composition of various nutrition, food staples and nutritional supplement in the period 2008-2020 is generalized. The development of each new RM type included preparation of the material, research for its stability and homogeneity, and determination of certified value with the appliance of State primary (GET 173) and secondary (GVET 176-1) standards, as well as primary reference measurement procedures and conducting the interlaboratory experiment for checking the applicability of the RM. The creation in 2008 of GET 173 was accompanied by the development of RMs for the composition of grains and dry milk product. The approval in 2010 of GVET 176-1 allowed to add in the RM the certified value for the mass fraction of nitrogen (protein). As a result of successful participation in comparisons, UNIIM got 6 items of calibration and measurement capabilities on measurements of mass fraction of nitrogen in glycine, milk powder, grain, egg powder, cereal and feed-stuff in the BIPM database. 35 types of RM for the composition of dairy and meat products, egg powder, infant food, oil and starch products together with the development of primary reference measurement procedures for measurement of fat, crude fat, ash and carbohydrates mass fraction were created between 2016 and 2019. Moreover, the RM for the composition of nutritional supplement (glycine, melamine, cystine) and dairy products for metrological assurance of IR-analysers as well as RM for the composition of reconstituted milk were developed for the control of measurement results by the enzyme-linked immunosorbent assay (ELISA). Developed RM were systemized on fields of the appliance of Technical regulations of Customs Union and the sectors of the international food triangle model. These RMs allow providing the measurement uniformity of the identification indicators and the nutritional value of food products and food staples.

Центральна лаборатория КХВ ПАТ «АрселорМіттал Кривий Ріг» у сучасних умовах.

THE CENTRAL LABORATORY OF COKE PRODUCTION AT PJSC «ARCELORMITTAL KRYVYI RIH» IN PRESENT-DAY CONDITIONS © O.P. Chernousova, N.V. Mukina (Coke Production of PJSC «ArcelorMittal Kryvyi Rih», 50095, Dnipropetrovsk region, Kryvyi Rih, Kryvorizhstal str., 1, Ukraine), A.Yu. Martynova, PhD in Technical Sciences (State Enterprise "Ukrainian State Research Coal Chemical Institute (UHIN)", 61023, Kharkov, Vesnina st., 7, Ukraine) The article discusses the scientific and methodological organization of analytical control at the coke production of PJSC "ArcelorMittal Kryvyi Rih" (CP AMKR), as well as the results of ongoing scientific and methodological measures to ensure confidence in the results of measurements carried out in the central laboratory (CL CP AMKR). Thus, the CL CP AMKR was one of the first in the industry to put into use the test installation "KARBOTEST", which allows without the involvement of third parties to carry out important laboratory research and enables the laboratory staff to quickly develop recommendations for optimizing the composition of coal charges and improving the quality of coke. The unit is designed to test the coking process of coal mixtures and certain grades of coal concentrates under temperature conditions similar to those in coke oven batteries. CL CP AMKR introduces express methods for the analysis of chemical coking products and was one of the first to introduce a refractometric method for determining the mass fraction of distillate up to 180 ° C in crude benzene. The use of this method can significantly reduce the measurement time, avoiding the cumbersome distillation procedure, and reduce the sample volume for analysis from 100 cm3 to a few drops. In order to ensure the uniformity, quality of measurements and tests, the CL on an ongoing basis takes part in interlaboratory comparative tests of almost all types of raw materials and products entering and produced by it. These are the products that are stable over time in terms of their quality indicators, for example, coal coke, as well as products whose individual indicators can change over time (crude benzene, coal tar, etc.). Keywords: measurement, quality control, coal concentrates, coke, chemical products, qualification confirmation, experimental coking, uncertainty, interlaboratory experiment, accreditation. Corresponding author A.P. Chernousova, е-mail: Elena.Chernousova@arcelormittal.com

Термоаналитический межлабораторный эксперимент по идентификации материалов, веществ и средств огнезащиты

Проведен межлабораторный термогравиметрический эксперимент по идентификации огнезащитных составов интумесцентного типа. Использование дисперсионного анализа позволило установить значимость/незначимость различий в поведении исследуемых материалов при нагревании, выявить лаборатории, обладающие необходимыми компетенциями для проведения идентификации. Найдено, что применение различных водно-полимерных дисперсий даже близкого строения в составе огнезащитных материалов приводит к неидентичности их свойств. Представленный подход позволил однозначно установить неидентичность исследованных огнезащитных составов. The article deals with the problem of identification of materials, substances and means of fire protection according to GOST R 53293-09 using one of the methods of thermal analysis, namely, thermogravimetric analysis. The long-term practice demonstrated that the methodology presented in the standard did not always give a clear result when identifying objects. Therefore, the evaluation experiment was conducted simultaneously in several testing laboratories with the appropriate equipment. The tests were conducted in the laboratories of the FGBU VNIIPO EMERCOM of Russia, ANO «CISIS FMT», and two CCPS of the Lomonosov Moscow State University. The most complex and controversial objects for identification were studied, namely, thermally expanding (intumescent) flame retardants based on water-polymer dispersions, which are used to protect building structures in closed premises. The purpose of the work consists in more correctly identifying the differences in the samples of the identifier and the analyzed object by using methods of dispersion analysis (GOST R ISO 5725-1, 2-202) when processing the joint interlaboratory experiment. Thermogravimetric analysis of objects was performed in platinum crucibles on samples in the form of disks with a thickness of 0,2-0,3 mm, weight 5-7 mg, at a heating rate of 20 °C/min in the air flow (50-70 ml/min). As a result of the experiment, the significance/insignificance of differences between samples should be displayed. The opinion about the competence of the laboratories participating in the experiment was made. In each laboratory there were conducted two series of thermogravimetric tests in 30-700 °C temperature range including five parallel measurements in each series. Each independent single measurement for further processing was represented by the data array formed within the temperature range of 140-650 °C with a 5° step, in total 103 points in each measurement. The results were processed using Excel spreadsheets. In the context of dispersion analysis there were evaluated both mean values of conversion rates for all laboratories, and the convergence (repeatability) variance for each laboratory using the Student's test, and the inter-laboratory variance (reproducibility variance) using the Cochran’s С test. This procedure revealed the nature of the quasi-samples and established the identity/non-identity of the samples. The results of calculations are represented by the graphical dependence of the generalized average degrees of transformation of destruction processes of objects under the temperature as well as the difference between these characteristics for laboratories I-IV. The presented identification procedure allows both to uniquely solve the problem of significance/insignificance of differences between the test object and the identifier, and to distinguish samples that have a similar composition. The statistical characteristics of a single measurement are calculated. The convergence of parallel measurements for determination of statistical outliers is identified. Determination of the overall average difference for a series of degrees of transformation allows to calculate the Student's test and accept or reject the null hypothesis. The performance of the joint evaluative (interlaboratory) experiment allows not only to establish the significance/insignificance of differences in the behavior of the materials during heating, but also to identify laboratories that have the necessary competencies for identification. The case considered in this paper revealed that the use of various water-polymer dispersions of even close structure in the composition of fire-resistant materials leads to non-identity of their properties.

Development of alumina-based porosity reference materials for the mercury porosimetry method

This paper presents the results of a study on the development of alumina-based porosity reference materials (RMs), which are intended for controlling the accuracy of the measurement results obtained using the mercury porosimetry method. These mercury porosimetry RMs are being developed in the Russian Federation for the first time and are primarily intended for verification / calibration and testing for type approval of mercury porosimeters. The study of metrological characteristics was conducted using a reference system, which is to be included in the GET 210-2014 State Primary Measurement Standard for units of specific gas adsorption, specific surface area, specific volume and pore size of solid substances and materials. This reference system was calibrated prior to conducting the study with the use of external reference pressure sensors of the 2nd order at 0.6 MPa and 400 MPa, as well as a laboratory balance (special accuracy class 1) having a maximum weighing limit of220 g. In the course of conducted research work, procedures for reproducing and estimating the uncertainty of porosity characteristics using the mercury porosimetry method were developed. When estimating the PM metrological characteristics, the standard uncertainty, associated with the characterisation and heterogeneity of the studied materials (PM candidates), was evaluated. The standard uncertainty due to instability was disregarded due to the high stability of the alumina matrix. According to the results of the conducted studies, four types of alumina-based porosity PM were developed. Their pore sizes are of about -lOnm; -2,000 nm; -9,000 nm; -60,000 nm. The RMs with pore sizes of -10 nm; -2,000 nm were intended for use in controlling the accuracy of mercury porosimeters operating at high pressures, while the RMs with pore sizes of -9,000 nm; -60,000 nm were for controlling the accuracy of mercury porosimeters operating at low pressures. The developed RMs are different from their foreign counterparts, which are produced by BAM (Germany) and NIST (USA) metrological institutes. The standard uncertainty due to characterisation of the RMs in question was estimated, not by the method of interlaboratory experiment, but by a full analysis of the constraint equations taking into account all sources of uncertainty included in the equations on the basis of the Guide to the Expression of Uncertainty in Measurement. The conducted studies allowed the RM certified values to be traceable at this stage to the GET 3-2008 State Primary Measurement Standard for the mass unit (kilogram), the GET 101-2011 State Primary Measurement Standard for the pressure unit in the field of absolute pressure in the range 1×10 –1 – 7×10 5 Pa, the GET 43-2013 State Primary Measurement Standard for the pressure unit in the range 10-1600 MPa and the effective area of the piston-cylinder unit of dead weight testers in the range 0.05-1 cm 2. In addition, a reference material having a large pore size of -60,000 nm, which currently has no analogues elsewhere in the world, was characterised.

Estimation of the POD Function and the LOD of a Binary Microbiological Measurement Method from an Interlaboratory Experiment

Abstract Background: We deal with interlaboratory experiments (collaborative studies) in which k participating laboratories, selected randomly from a population of laboratories, use samples from one and the same material or matrix. They perform binary microbiological measurements for which the measurement results are either “0” (target microorganisms not detected) or “1” (target microorganisms detected). The performance of such a measurement method is described by its probability of detection (POD) function, i.e., the POD as a function of the contamination of the sample (CFU per gram or CFU per milliliter), or by the level of detection (LODp), i.e., the contamination level of the sample that is detected (measurement result “1”) with a specified probability p. Objective: We derive an approximate statistical analysis that is simple enough to be implemented in a spreadsheet application. Methods: Under the assumption of a Poisson distribution of the number of CFU in the samples, we estimate the mean POD function of the laboratories and the SD of the laboratory effect based on a complementary log-log model, a special case of the Generalized Linear Model in the special situation in which the contamination level is known by means other than the POD. The estimates are obtained by maximization of the Laplace approximation of the likelihood function. By simulation, a bias correction factor for the estimate of the SD is obtained. With the estimated POD function, LODs can be estimated. The model can also be used to evaluate the relative LOD of an alternative method with repect to a reference method. Results: The EXCEL program PODLOD-interlab_ver1.xls for this method of statistical analysis can be downloaded from http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich. Highlights: A simple approximate statistical method for the estimation of the POD and LOD is derived. The method also allows the estimation of the RLOD of an alternative method with respect to reference method. The method is implemented in an EXCEL program that can be downloaded from http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich.

Estimation of the POD Function and the LOD of a Binary Microbiological Measurement Method from an Interlaboratory Experiment.

Background: We deal with interlaboratory experiments (collaborative studies) in which k participating laboratories, selected randomly from a population of laboratories, use samples from one and the same material or matrix. They perform binary microbiological measurements for which the measurement results are either "0" (target microorganisms not detected) or "1" (target microorganisms detected). The performance of such a measurement method is described by its probability of detection (POD) function, i.e., the POD as a function of the contamination of the sample (CFU per gram or CFU per milliliter), or by the level of detection (LODp), i.e., the contamination level of the sample that is detected (measurement result "1") with a specified probability p. Objective: We derive an approximate statistical analysis that is simple enough to be implemented in a spreadsheet application. Methods: Under the assumption of a Poisson distribution of the number of CFU in the samples, we estimate the mean POD function of the laboratories and the SD of the laboratory effect based on a complementary log-log model, a special case of the Generalized Linear Model in the special situation in which the contamination level is known by means other than the POD. The estimates are obtained by maximization of the Laplace approximation of the likelihood function. By simulation, a bias correction factor for the estimate of the SD is obtained. With the estimated POD function, LODs can be estimated. The model can also be used to evaluate the relative LOD of an alternative method with repect to a reference method. Results: The EXCEL program PODLOD-interlab_ver1.xls for this method of statistical analysis can be downloaded from <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich">http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich</ext-link>. Highlights: A simple approximate statistical method for the estimation of the POD and LOD is derived. The method also allows the estimation of the RLOD of an alternative method with respect to reference method. The method is implemented in an EXCEL program that can be downloaded from <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="url" xlink:href="http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich">http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich</ext-link>.

Preparation and certification of certified reference materials of fish meat and ashed bone for determination of 90Sr and radiocesium after Fukushima Daiichi Nuclear Power Plant

Certified reference materials (CRMs) of the fish meat powder and the fish bone ash for validation of measurement of anthropogenic nuclides (134Cs, 137Cs and 90Sr) related the Fukushima Daiichi nuclear power plant accident were developed using an inter-laboratory comparison. This paper discusses the strategy of development including selection of raw material, the preparation and certification procedures applied for CRM production. In particular, some detailed data are presented for the homogeneity study and inter-laboratory experiment for the certification. The results of inter-laboratory comparison not only to certify CRMs but also showed analytical performance of the anthropogenic nuclides in Japanese laboratories.

A fully customizable MATLAB Framework for MSA based on ISO 5725 Standard

In this paper, a full featured MATLAB framework for Measurement System Analysis, fully compliant with the ISO 5725 Repeatability and Reproducibility (R&R) assessment is presented. While preserving the operations prescribed in the ISO standard, the software presents distinct improvements.First of all, all computations are made using exact closed-form formulae (instead of statistical tables) allowing a consistent analysis without limitations on the number of participating laboratories and measurements, and using custom significance levels of statistical tests. Second, a double threshold decision system for each test step has been implemented, helping the statistician to decide on the elimination of outliers/stragglers. Third, ANOVA analysis has been included.The software therefore, besides producing quickly and efficiently all the graphical and numerical results required in an inter-laboratory experiment, provide guidelines for properly updating the ISO 5725 standard.

Estimation and uncertainty analysis of dose response in an inter-laboratory experiment

An inter-laboratory experiment for the evaluation of toxic effects of NH2-polystyrene nanoparticles on living human cancer cells was performed with five participating laboratories. Previously published results from nanocytoxicity assays are often contradictory, mostly due to challenges related to producing a reliable cytotoxicity assay protocol for use with nanomaterials. Specific challenges include reproducibility preparing nanoparticle dispersions, biological variability from testing living cell lines, and the potential for nano-related interference effects. In this experiment, such challenges were addressed by developing a detailed experimental protocol and using a specially designed 96-well plate layout which incorporated a range of control measurements to assess multiple factors such as nanomaterial interference, pipetting accuracy, cell seeding density, and instrument performance. Detailed data analysis of these control measurements showed that good control of the experiments was attained by all participants in most cases. The main measurement objective of the study was the estimation of a dose response relationship between concentration of the nanoparticles and metabolic activity of the living cells, under several experimental conditions. The dose curve estimation was achieved by imbedding a three parameter logistic curve in a three level Bayesian hierarchical model, accounting for uncertainty due to all known experimental conditions as well as between laboratory variability in a top-down manner. Computation was performed using Markov Chain Monte Carlo methods. The fit of the model was evaluated using Bayesian posterior predictive probabilities and found to be satisfactory.