Interlaboratory Experiment Research Articles

Certified reference materials of agricultural products and foods bearing radioactivity from the Fukushima nuclear accident

Certified reference materials (CRMs) for food analysis were developed in an inter-laboratory experiment for validation of measurement of radiocesium in foodstuffs. Since 2012, five series of CRMs were developed, including for brown rice grain, soybean powder, beef flake, shiitake mushroom powder and marine fish (meat and bone parts). This paper discusses the strategy of development, including choice of CRMs developed and the preparation and certification procedures applied for CRM development. In particular, some detailed data are presented for the most popular CRMs developed: brown rice grain, soybean powder and beef flake.

Применение стандартных образцов для анализа результатов измерения удельной мощности магнитных потерь в листовых образцах из анизотропной электротехнической стали, полученных различными методами

The article presents the results of an interlaboratory experiment evaluating the differences in the results obtained by different methods of measuring of specific power of magnetic losses of sheet specimens of oriented electrical steel. Measurements were carried out both with the installation CICL-2 that implements measurement method using field coils and a standardized method with calculation of field magnitude from the current value in the magnetizing winding, and with the measuring systems with different design of yokes implementing a standardized method. The article analyzes the experimental data obtained in order to assess the comparability of measurement results for systems with different design of the closing yoke.

Shear and flexural characterization of grid-reinforced asphalt pavements and relation with field distress evolution

The use of geogrids at the interface of asphalt layers is currently adopted to improve pavement performance in terms of rutting, fatigue and reflective cracking. Several test methods have been proposed in order to simulate the complex mechanical behavior of reinforced pavements and assist practitioners in the selection of the appropriate reinforcement product. A particular subject of debate is the evaluation of geogrid effects in terms of both flexural strength and interlayer bonding. In this context, an interlaboratory experiment has been organized as part of the RILEM TC 237-SIB/TG4 with a twofold objective: to compare the predictive effectiveness of different experimental approaches and to analyze the behavior of different geogrid types. For this purpose two experimental reinforced test sections have been realized, the first one to prepare samples for the interlaboratory experiment, the second one to analyze the geogrid field performance under heavy traffic conditions. This paper describes the test results obtained by one participating laboratory on double-layered asphalt samples extracted from the first experimental section and compares them with the periodic visual observation of the reflective cracking evolution occurred in the second test section. The laboratory tests were performed following a specific testing protocol that combines interlayer shear tests, repeated loading tests in a four-point bending configuration and quasi-static three-point bending tests, in order to investigate the overall performance of double-layered asphalt systems. Results have shown that geogrid reinforcement does not noticeably influence the flexural stiffness and strength in the pre-cracking phase, whereas the crack propagation speed can be significantly reduced and the failure behavior may change from quasibrittle to ductile, depending on the interlayer shear resistance. Laboratory results were confirmed by periodic visual observation of field performance in terms of reflective cracking evolution.

Proficiency testing of pH and electrolytic conductivity measurements of groundwater: a case study of the difference between consensus and metrologically traceable values

A proficiency testing (PT) scheme was designed for measurements of pH and electrolytic conductivity (EC) of groundwater in Israel. A groundwater sample was used for preparation of test items fit-for-intended-use. The interlaboratory experiment was organized taking into account changes of the test item properties which occurred after sampling due to presence of CO2 in the groundwater. A total of 34 PT participants reported pH measurements results, while 29 of them reported results of EC measurements. The pH results were normally distributed. However, a significant bias of the pH consensus value of the PT participants from the metrologically traceable certified value (obtained by the National Physical Laboratory of Israel) was detected. This bias was caused by the drift of the measurement response due to water stirring and CO2 degassing from the sample during the measurement process. The bias of the EC consensus value from the metrologically traceable one was negligible, in spite of an abnormal distribution of the EC results of the PT participants.

Critical values of Mandel’s h and k, the Grubbs and the Cochran test statistic

According to ISO 5725-2 (1994), measurement results obtained in an interlaboratory experiment are inspected for consistency by plotting Mandel’s h and k statistics and for outliers by application of the Grubbs test and the Cochran test. Critical values of these statistics for significance levels α=5% and α=1% and for some numbers p of laboratories and n of repeated measurements in the laboratories are supplied in ISO 5725-2 without reference to methods for their calculation. In this paper, exact formulae for the critical values of Mandel’s h and k and approximate formulae for the critical values of the Single Grubbs test, the Double Grubbs test and the Cochran test are derived.

Chemometric and biological validation of a capillary electrophoresis metabolomic experiment of Schistosoma mansoni infection in mice

Metabonomic and metabolomic studies are increasingly utilized for biomarker identification in different fields, including biology of infection. The confluence of improved analytical platforms and the availability of powerful multivariate analysis software have rendered the multiparameter profiles generated by these omics platforms a user-friendly alternative to the established analysis methods where the quality and practice of a procedure is well defined. However, unlike traditional assays, validation methods for these new multivariate profiling tools have yet to be established. We propose a validation for models obtained by CE fingerprinting of urine from mice infected with the blood fluke Schistosoma mansoni. We have analysed urine samples from two sets of mice infected in an inter-laboratory experiment where different infection methods and animal husbandry procedures were employed in order to establish the core biological response to a S. mansoni infection. CE data were analysed using principal component analysis. Validation of the scores consisted of permutation scrambling (100 repetitions) and a manual validation method, using a third of the samples (not included in the model) as a test or prediction set. The validation yielded 100% specificity and 100% sensitivity, demonstrating the robustness of these models with respect to deciphering metabolic perturbations in the mouse due to a S. mansoni infection. A total of 20 metabolites across the two experiments were identified that significantly discriminated between S. mansoni-infected and noninfected control samples. Only one of these metabolites, allantoin, was identified as manifesting different behaviour in the two experiments. This study shows the reproducibility of CE-based metabolic profiling methods for disease characterization and screening and highlights the importance of much needed validation strategies in the emerging field of metabolomics.

Precision study on capillary electrophoresis methods for metacycline

A CE method for metacycline (MTC) determination was investigated in an inter-laboratory experiment. Many problems were encountered in this study, most of which were related to the transfer of the method to different CE equipment. The reported problems could be classified into different categories: problems related to the precision, to the parameters in the protocol, and to the MTC peak shape. As the peak shape problem was partially responsible for the poor precision, a new CE method was developed in order to obtain a good MTC peak shape on all equipment. The precision of this new method for MTC determination was examined in an intermediate precision study, where the influence of the factors "time" and "equipment" was investigated. Although the new method could be transferred to different instruments, the precision remained poor mainly due to the contributions of the between-replicate and the between-injection variances.

Sets and Uncertainty

Arguments are presented indicating coincidence between the concepts of uncertainty and precision, and also on the undesirability of using the uncertainty propagation law for estimating dispersion. It is possible to estimate the reproducibility without performing an interlaboratory experiment and ways are characterized for estimating the closeness between the actual (or true) value of a measured quantity to the measurement result in the presence of influencing factors.

Testing for bias between the Kjeldahl and Dumas methods for the determination of nitrogen in meat mixtures, by using data from a designed interlaboratory experiment

Bias between the Dumas and the Kjeldahl methods for the determination of protein nitrogen in food was studied by conducting an interlaboratory study involving 40 laboratories and 20 different test materials. Biases were found to be small and statistically significant only for the chicken test materials, where a bias of 0.020 ± 0.004% m/m was detected.

Determination of uncertainty in analytical measurements from collaborative study results on the analysis of a phenoxymethylpenicillin sample

The correct interpretation of a measurement result requires knowledge about its uncertainty. Depending on the conditions under which the analyst is operating, different operational definitions of uncertainty have been proposed. They include: within-laboratory uncertainty, reproducibility uncertainty, bias-included uncertainty and absolute uncertainty. Here we consider the evaluation of the reproducibility uncertainty derived from the results obtained in an inter-laboratory experiment. Nine laboratories participated in an inter-laboratory study for the analysis of phenoxymethylpenicillin. The analyses consisted of a Karl–Fischer water determination, an acid–base titration to assay phenoxymethylpenicillin and a liquid chromatography (LC) method to determine 4-hydroxyphenoxymethylpenicillin and other impurities. The experimental set-up allowed to obtain for each determination s r 2 and s L 2 as estimates of the repeatability variance ( σ r 2) and the between-laboratory variance ( σ L 2), respectively. The reproducibility uncertainties for the different assays were then derived from these estimates.

Optimization of an interlaboratory program for the certification of a multi-element plagiogneiss reference material

A sample of garnet-biotite plagiogneiss, GBPg-1 is currently being developed as a certified reference material at the Vinogradov Institute of Geochemistry. It was used as the sample that was distributed round 7 of International Proficiency Testing Program (GeoPT7) and was analyzed by 76 geoanalytical laboratories around the world. Twenty Russian laboratories involved in the interlaboratory experiment also analyzed GBPg-1. The resultant analytical data obtained from these two experiments has allowed GBPg-1 to be certified as a state standard sample for 50 elements. It also enabled a comparison of the quality of data developed by the Russian and international geoanalytical laboratories, to optimize the outcome of this interlaboratory experiment.

Testing of Neutron Data Libraries in Application to Reactor Pressure Vessel Dosimetry

Different neutron data libraries frequently used in reactor pressure vessel dosimetry and related applications were compared and tested using activation measurement data from the international interlaboratory ex-vessel experiment at the Russian type pressurized water reactor Balakovo-3. Besides different data for the neutron transport calculations also different dosimetry cross section files were investigated. At simple testing models the impact of frequently used group approximations on neutron and gamma fluence parameters was studied by comparison of DORT and MCNP calculation results. The fast neutron results relevant for pressure vessel embrittlement agree reasonably for different libraries and calculation methods but the results for low energy neutrons as well as for deep penetrations differ strongly in many cases.

Adsorptive enrichment and thermal desorption of low-boiling oxygenated compounds—possibilities and limitations

Laboratory experiments have been performed to examine the potential of adsorptive enrichment thermal desorption and gas chromatography for the analysis of low molecular-weight oxygenated compounds in gaseous samples. The experiments were conducted with test atmospheres containing, for example, acetaldehyde, propionaldehyde, acrolein, methacrolein, and acetone. The suitability of the graphitized carbon blacks Carbotrap X and Carbograph 5 for sampling these compounds was tested. In this context the influence of humidity on the recovery of the analytes and on the storage stability of the loaded adsorbent tubes over a period of seven days under different storage conditions was investigated. Losses of up to 60% propionaldehyde and acrolein were observed for Carbotrap X, even immediately after sampling. In contrast Carbograph 5 seems promising for the sampling of low molecular-weight oxygenated compounds, although with some limitations. The laboratory investigations were proved by use of an interlaboratory experiment.

Multi-elemental characterization of the atmospheric aerosols in frames of interlaboratory experiment

The influence of aerosols on the quality of the air, atmospheric processes and climate on the local, regional and global scales is defined by the particle's dimension spectra and morphology, as well as chemical composition and element contents. As for elemental composition, it varies between % and ppt. It creates some problems for analytical provision of the atmospheric aerosols investigations. To analyze aerosols samples on Whatman-41 filters, different analytical techniques have been applied: instrumental neutron activation analysis (INAA), synchrotron radiation X-ray fluorescence (SRXF), atomic-absorption and optical atomic-emission spectrometry (OES). Interlaboratory comparisons of analytical data have been used to estimate the true values for aerosol's elemental characterization. The results of statistical evaluation of data produced are discussed.

Characterisation of protected denomination of origin cheeses: relationships between sensory texture and instrumental data

Relationships between sensory and instrumental measurements of cheese texture have been explored through an interlaboratory experiment in the framework of a European FLAIR pro- gramme (SENS, Concerted Action no. 2, contract AG RF 025). Ten very different samples of each of the two cheese varieties, Appenzeller, a Swiss serni-hard cheese, and Parmigiano Reggiano, an Ita- lian very hard cheese, were analysed using biochemicaI, rheological and sensory methods. The rela- tional study is one of the first using hannonised methods. Results have shown thar sensory data can be related to instrumental data. Partialleast square regression appears use fui to relate sensory texturai properties from instrumental data. The approach is recommended for similar investigations of other cheese varieties. © Inra!EIsevier, Paris.

New zircon fission-track ages from New Zealand Quaternary tephra: an interlaboratory experiment and recommendations for the determination of young ages

Fission-track dating, of zircons from five Pleistocene tephra in the Wanganui Basin, North Island, New Zealand, has been carried out independently in two different laboratories. The results from each are statistically identical even though there were some differences in laboratory techniques. The resulting ages confirm recent isothermal plateau fission-track (ITPFT) ages on two of these tephra, but with increased precision. The weighted mean ages (± 1σ) are: Potaka Tephra, 0.97 ± 0.04 Ma (4 determinations); Rewa Pumice, 1.00 ± 0.06 Ma (3 determinations); Mangapipi Ash, 1.26 ± 0.08 Ma (2 determinations); Pakihikura Pumice, 1.66 ± 0.07 Ma (4 determinations); and the Vinegar Hill Tephra, 1.73 ± 0.08 Ma (3 determinations). These new results further constrain the time control in this important Pleistocene section which contains many cyclothems reflecting climatic and tectonic influences. This study illustrates well the pitfalls that can occur when dating such young material using single-crystal techniques. The difficulties of determining when etching is optimal, the presence of detrital grains and their subsequent removal from the data set are described, as well as a recommendation that a minimum of 15 crystals, but optimally at least 20, be counted before calculating the final age. It may also be necessary to plot running means of the single-crystal ages to determine when the final age has been approached.

Results of an interlaboratory experiment for the 1988 fission track workshop on a putative apatite standard for internal calibration

In March–April 1988 an apatite (sample 88-5) with a homogeneous spontaneous track density around 3 × 10 6 tr cm -2 was distributed for analysis among the interested laboratories in the scope of the forthcoming Fission Track Dating Workshop at Besançon, France. The apatite was distributed in two aliquots. The first aliquot was intended to be analysed with the normal procedure of each analyst. The second, which was annealed and pre-irradiated with a precisely determined thermal neutron fluence, enabled an additional analysis with the POP method. The reported results of the independent analyses exhibit a rather large variation, but the results obtained with the pre-irradiated aliquots are quite consistent. To a certain extent, this can be ascribed to the simplicity of the POP method and its low sensitivity to variations in track revelation and observation. In addition to primary age standards, the apatite 88-5 provides a good supplementary standard for calibration, especially if apatites from older crystalline rocks are to be dated. Averaging the results based on the pre-irradiated aliquots, a provisional fission track reference age of 184 ± 15 Ma is attributed to this apatite.

Reproducibility of electromigration measurements

The reproducibility of median-time-to-failure (t 50 ) measurements was determined in an interlaboratory experiment in which 11 laboratories and a reference laboratory took part. Each laboratory used a method of its choosing to test equivalent samples under the same conditions of current density and oven temperature. The between-laboratory reproducibility of t 50 measurements normalized to one metallization temperature was dependent on current-density stress: at 1.0 MA /cm2it was within 15 percent, while at 2.5 MA/cm2it was generally within 50 percent. The primary source for variability is in estimating the temperature rise of the test metallization due to joule heating. Recommendations are given for the design and test of electromigration test structures to improve the reproducibility of t 50 measurements.

The Assay of Uranium and Plutonium in Reprocessing Input Solutions by Isotope Dilution Mass Spectrometry: Results of the Isotope Dilution Analysis Measurement Evaluation Programs

For analytical methods to be applied to international safeguards, precision and accuracy must be well established. With this objective an interlaboratory measurement evaluation program— “IDA-80,” which determined the elemental and isotopic content of the input solutions to reprocessing plants—was carried out with the participation of 33 laboratories from 15 countries or international organizations. It was guided jointly by the Central Bureau for Nuclear Measurements (CBNM) and the Kernforschungszentrum Karlsruhe (KfK) under the auspices of the European Safeguards Research and Development Association and with the support of the International Atomic Energy Agency. The element concentrations and isotopic compositions of all test materials were characterized by CBNM and the U.S. National Bureau of Standards to a high accuracy. The evaluation of more than 60000 analytical data reported by the participating laboratories yielded detailed estimates of the isotopic measurement capability of the laboratories for uranium and plutonium isotopes as well as for uranium and plutonium element assay by isotope dilution mass spectrometry. It also identified a number of sources of error. Compared to the results obtained in the “IDA-72” interlaboratory experiment—a similar program organized earlier by KfK with the participation of 22 laboratories from 13 countries or international organizations—considerable improvement of isotope dilution analysis over the last decade is shown.

Quantitative XPS: The calibration of spectrometer intensity—energy response functions. 2—Results of interlaboratory measurements for commercial instruments

AbstractAn interlaboratory experiment to establish X‐ray photoelectron spectrometer intensity–energy response functions has been completed. The measurements made by fifteen participants give results for seven instrument models from four manufacturers. Two methods of determining the response function are tested: (i) by peak area measurement and (ii) using the background data from wide scan spectra from reference foils of Cu, Ag and Au. The peak area data show excellent reproducibility, and area ratios, when corrected for instrument response functions, are consistent to a standard deviation of 4% for Ag and Au between all instruments and conditions. The response functions relative to the VG Scientific ESCA 3 Mk II are proportional to En where, in the constant ΔE mode, n = −;0.20±0.03 for the Leybold LHS10, −0.15±0.10 for the Perkin–Elmer PHI 550, 0.00±0.03 for the VG Scientific ESCA 3, and 0.20±0.02 for the VG Scientific ESCALAB I and II. The AEI/Kratos ES 200B/300 gives a complex, but defined, function. In the constant ΔE/E mode the latter instrument gives n in the range 1.3 to 2.0 and the VG Scientific ESCALAB II 1.79±0.05.