Further, the reproducibility standard deviations among laboratories performing pulverisation were on average in very good agreement with the prediction of the Horwitz model. Use of sonication showed no effect on the HEtG extraction yield. Inter-laboratory comparisons of hexenuronic acid measurements in kraft eucalyptus pulps using a UV-Vis spectroscopic method. The pulp samples were produced in a laboratory at kappa numbers of approximately 14, 20, and The hexeneuronic acid contents of the three pulps were Interlaboratory comparison for the determination of the soluble fraction of metals in welding fume samples.
There is interest in the bioaccessible metal components of aerosols, but this has been minimally studied because standardized sampling and analytical methods have not yet been developed. An interlaboratory study ILS has been carried out to evaluate a method for determining the water-soluble component of realistic welding fume WF air samples. Replicate samples were generated in the laboratory and distributed to participating laboratories to be analyzed according to a standardized procedure.
Within-laboratory precision of replicate sample analysis repeatability was very good. Reproducibility between laboratories was not as good, but within limits of acceptability for the analysis of typical aerosol samples. These results can be used to support the development of a standardized test method.
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A consortium of European enterprises and research institutions has been engaged in the Feed-Code Project with the aim of addressing the requirements stated in European Union Regulation No. Accordingly, an interlaboratory trial was set up to compare the performance of different assays based either on optical microscope or DNA analysis for the qualitative and quantitative identification of the composition of compound animal feeds. A tubulin-based polymorphism method, on which the Feed-Code platform was developed, provided the most accurate results.
The present study highlights the need for the performance of ring trials for the determination of the botanical composition of animal feeds and raises an alarm on the actual status of analytical inaccuracy. An interlaboratory comparison programme on radio frequency electromagnetic field measurements: the second round of the scheme. The second round of an interlaboratory comparison scheme on radio frequency electromagnetic field measurements has been conducted in order to evaluate the overall performance of laboratories that perform measurements in the vicinity of mobile phone base stations and broadcast antenna facilities.
The participants recorded the electric field strength produced by two high frequency signal generators inside an anechoic chamber in three measurement scenarios with the antennas transmitting each time different signals at the FM, VHF, UHF and GSM frequency bands. In each measurement scenario, the participants also used their measurements in order to calculate the relative exposure ratios.
The results were evaluated in each test level calculating performance statistics z-scores and En numbers. Subsequently, possible sources of errors for each participating laboratory were discussed, and the overall evaluation of their performances was determined by using an aggregated performance statistic. A comparison between the two rounds proves the necessity of the scheme. Published by Oxford University Press. For Permissions, please email: journals. Interlaboratory comparison of extraction efficiency of pesticides from surface and laboratory water using solid-phase extraction disks.
A continuation of an earlier interlaboratory comparison was conducted 1 to assess solid-phase extraction SPE using Empore disks to extract atrazine, bromacil, metolachlor, and chlorpyrifos from various water sources accompanied by different sample shipping and quantitative techniques and 2 to compare quantitative results of individual laboratories with results of one common laboratory. Three replicates of a composite surface water SW sample were fortified with the analytes along with three replicates of deionized water DW.
A nonfortified DW sample and a nonfortified SW sample were also extracted. All samples were extracted using Empore C 18 disks. After extraction, part of the samples were eluted and analyzed in-house. Duplicate samples were evaporated in a 2-mL vial, shipped dry to a central laboratory SDC , redissolved, and analyzed. Overall, samples analyzed in-house had higher recoveries than SDC samples. Laboratory x analysis type and laboratory x water source interactions were significant for all four compounds.
Seven laboratories participated in this interlaboratory comparison program. No differences in atrazine recoveries were observed from in-house samples analyzed by laboratories A, B, D, and G compared with the recovery of SDC samples. In-house atrazine recoveries from laboratories C and F were higher when compared with recovery from SDC samples. However, laboratory E had lower recoveries from in-house samples compared with SDC samples. For each laboratory, lower recoveries were observed for chlorpyrifos from the SDC samples compared with samples analyzed in-house.
Bromacil recovery was study. Three laboratories showed no differences in metolachlor recovery; two laboratories had higher recoveries for samples analyzed in-house, and two other laboratories showed higher metolachlor recovery for SDC samples. Laboratory G had a higher. In this inter-laboratory comparison the gas-fluid-mineral reactions of three samples of rock-forming minerals have been investigated by 11 experimental labs. The reported results point to robust identification of the major processes in the experiments by most groups.
The comparison of experimental setups and procedures as well as of data corrections identified potential improvements for future gas-fluid-rock studies. Flow cytometry FC aids in characterization of cellular and molecular factors involved in pathologic immune responses. Although FC has potential to facilitate early drug development in inflammatory bowel disease, interlaboratory variability limits its use in multicenter trials. Standardization of methods may address this limitation. We compared variability in FC-aided quantitation of T-cell responses across international laboratories using three analytical strategies.
Peripheral blood mononuclear cells PBMCs were isolated from three healthy donors, stimulated with phorbol myristate acetate and ionomycin at a central laboratory, fixed, frozen, and shipped to seven international laboratories.
Permeabilization and staining was performed in triplicate at each laboratory using a common protocol and centrally provided reagents. Median cell percentages were calculated across triplicates and donors, and reported for each condition and strategy. The coefficient of variation CV was calculated across laboratories. Between-strategy comparisons were made using a two-way analysis of variance adjusting for donor.
Mean interlaboratory CV ranged from 1. Mean interlaboratory CV differed significantly across strategies and was consistently lower with CG. An interlaboratory comparison of sizing and counting of subvisible particles mimicking protein aggregates. Accurate counting and sizing of protein particles has been limited by discrepancies of counts obtained by different methods. Twenty-three laboratories from industry, government, and academic institutions participated.
The circulated samples consisted of a polydisperse suspension of abraded ethylene tetrafluoroethylene particles, which closely mimic the optical contrast and morphology of protein particles. Differences between instrument manufacturers were not statistically significant for light obscuration but were significant for flow imaging. Purpose An interlaboratory comparison of radiation dosimetry was conducted to determine the accuracy of doses being used experimentally for animal exposures within a large multi-institutional research project. The background and approach to this effort are described and discussed in terms of basic findings, problems and solutions.
Methods Dosimetry tests were carried out utilizing optically stimulated luminescence OSL dosimeters embedded midline into mouse carcasses and thermal luminescence dosimeters TLD embedded midline into acrylic phantoms. Conclusions For the dosimetrically non-compliant laboratories, the relatively high rates of dosing errors were problematic, potentially compromising the quality of ongoing radiobiological research. This dosimetry effort proved to be instructive in establishing rigorous reviews of basic dosimetry protocols ensuring that dosing errors were minimized.
Schouten, Stefan; Hopmans, Ellen C. Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers GDGTs are the TEX86 TetraEther indeX of 86 carbon atoms paleothermometer for sea surface temperature reconstructions and the BIT Branched Isoprenoid Tetraether index for reconstructing soil organic matter input to the ocean.
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Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques.
BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility ranging from 0. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the. Interlaboratory study of a liquid chromatography method for erythromycin: determination of uncertainty.
Erythromycin is a mixture of macrolide antibiotics produced by Saccharopolyspora erythreas during fermentation. A new method for the analysis of erythromycin by liquid chromatography has previously been developed. It makes use of an Astec C18 polymeric column. After validation in one laboratory, the method was now validated in an interlaboratory study. Validation studies are commonly used to test the fitness of the analytical method prior to its use for routine quality testing. The data derived in the interlaboratory study can be used to make an uncertainty statement as well.
The relationship between validation and uncertainty statement is not clear for many analysts and there is a need to show how the existing data, derived during validation, can be used in practice. Eight laboratories participated in this interlaboratory study. The set-up allowed the determination of the repeatability variance, s 2 r and the between-laboratory variance, s 2 L.
Combination of s 2 r and s 2 L results in the reproducibility variance s 2 R. It has been shown how these data can be used in future by a single laboratory that wants to make an uncertainty statement concerning the same analysis. Interlaboratory comparability of serum cotinine measurements at smoker and nonsmoker concentration levels: A round-robin study.
Jacob, Peyton; Holiday, David B. Introduction: Cotinine, the primary proximate metabolite of nicotine, is commonly measured as an index of exposure to tobacco in both active users of tobacco and nonsmokers with possible exposure to secondhand smoke SHS. A number of laboratories have implemented analyses for measuring serum cotinine in recent years, but there have been few interlaboratory comparisons of the results. Among nonsmokers exposed to SHS, the concentration of cotinine in blood can be quite low, and extensive variability in these measurements has been reported in the past.
Methods: In this study , a group of seven laboratories, all experienced in serum cotinine analysis, measured eight coded serum pools with concentrations ranging from background levels of about 0. All laboratories used either gas—liquid chromatography with nitrogen—phosphorus detection or liquid chromatography with mass spectrometric detection. Results: All seven laboratories reliably measured the cotinine concentrations in samples that were within the range of their methods. Discussion: We conclude that present methods of chromatographic analysis of serum cotinine, as used by these experienced laboratories, are capable of providing accurate and precise results in both the smoker and the nonsmoker concentration range.
Interlaboratory comparison program for nondestructive assay of prototype uranium reference materials.
The objectives of the program were to evaluate the reliability of NDA techniques as applied to nuclear safeguards materials control and accountability needs and to investigate the feasibility of providing practical NDA scrap and waste reference materials for use throughout the nuclear safeguards community.
Synthetic calcined ash, cellulose fiber, and ion-exchange resin simulate selected uranium scrap and waste forms which are often encountered in fabrication and recovery operations. The synthetic calcined ash represents an intermediate density inorganic matrix while the cellulose fiber and ion-exchange resin are representative of low-density organic matrices. Nineteen prototype reference samples, plus three empty containers, one to accompany each set, was circulated to the participants between August and May In addition, participants could opt to perform modular configuration measurements using containers from Sets IIA and IIB to simulate non-homogeneously dispersed uranium in waste containers.
All data were reported to NBL for evaluation. Ultra-trace analysis of 41Ca in urine by accelerator mass spectrometry: an inter-laboratory comparison. Analysis of the ratios assayed by accelerator mass spectrometry AMS shows that there is no statistically significant difference in the ratios.
Further, Bayesian analysis shows that the uncertainties reported by both facilities are correct with the possibility of a slight under-estimation by one laboratory. Finally, the chemistry procedures used by the two facilities to produce CaF2 for the cesium sputter ion source are robust and don't yield any significant differences in the final result. Objectives: Flow cytometry FC aids in characterization of cellular and molecular factors involved in pathologic immune responses. Methods: Peripheral blood mononuclear cells PBMCs were isolated from three healthy donors, stimulated with phorbol myristate acetate and ionomycin at a central laboratory, fixed, frozen, and shipped to seven international laboratories.
Results: Mean interlaboratory CV ranged from 1. The increasing hospital-to-hospital transmission of multiple drug-resistant bacteria is a major concern for bacteriology laboratories involved in nosocomial infection control. The interlaboratory reproducibility of pulsed-field gel electrophoresis PFGE for Pseudomonas aeruginosa typing was evaluated by asking four hospital laboratories two in Lyon, one in Brest, and one in Marseille to study 11 P.
These two methods led to similar epidemiological conclusions. However, centralization of the data showed poor center-to-center reproducibility due to inadequate standardization of the procedure. The main objectives were to map the state of the science in passively sampling sediments, identify sources of variability, provide recommendations and practical guidance for standardized passive sampling, and advance the use of passive sampling in regulatory decision making by increasing confidence in the use of the technique.
The study was performed by a consortium of 11 laboratories and included experiments with 14 passive sampling formats on 3 sediments for 25 target chemicals PAHs and PCBs. The remaining variability was primarily due to factors not related to passive sampling itself, i. Tilling, Robert I. Some determinations of major-element constituents agree within analytical uncertainty, whereas others exchibit significant bias. These differences are ascribed in part to a complex combination of calibration assumptionsand mineralogical and particle-size effects inherent in the use of pressed rock-powder pellets in the analytical procedure of the MTU laboratory.
Knowledge of such change is needed for understanding petrogenetic history and for such related studies as evaluation of volcanic hazards. The Thermofisher CarboPac SA10 anion-exchange column enables isocratic separation of monosaccharides, sucrose and cellobiose in approximately 7 minutes. Additionally, use of a low-volume 0. The technique's robustness, linearity, and interlaboratory reproducibility were evaluated and showed excellent-to-acceptable characteristics.
While these two methods showed good agreement a statistical comparison found significant quantitation difference between them, highlighting the difference between selective and universal detection modes. Inter-laboratory comparison of the in vivo comet assay including three image analysis systems. To compare the extent of potential inter-laboratory variability and the influence of different comet image analysis systems, in vivo comet experiments were conducted using the genotoxicants ethyl methanesulfonate and methyl methanesulfonate.
Tissue samples from the same animals were processed and analyzed-including independent slide evaluation by image analysis-in two laboratories with extensive experience in performing the comet assay. The analysis revealed low inter-laboratory experimental variability. Neither the use of different image analysis systems, nor the staining procedure of DNA propidium iodide vs. In addition, relatively high stability of the staining intensity of propidium iodide-stained slides was found in slides that were refrigerated for over 3 months. In conclusion, following a thoroughly defined protocol and standardized routine procedures ensures that the comet assay is robust and generates comparable results between different laboratories.
Single particle inductively coupled plasma-mass spectrometry spICP-MS is an emerging technique that enables simultaneous measurement of nanoparticle size and number quantification of metal-containing nanoparticles at realistic environmental exposure concentrations. Such measurements are needed to understand the potential environmental and human health risks of nanoparticles. Before spICP-MS can be considered a mature methodology, additional work is needed to standardize this technique including an assessment of the reliability and variability of size distribution measurements and the transferability of the technique among laboratories.
The general agreement in particle size between spICP-MS measurements and measurements by six reference techniques demonstrates the reliability of spICP-MS and validates its sizing capability. However, the precision of the spICP-MS measurement was better for the larger 60 nm gold nanoparticles and evaluation of spICP-MS precision indicates substantial variability among laboratories, with lower variability between operators within laboratories.
Global particle number concentration and Au mass concentration recovery were quantitative for RM but significantly lower and with a greater variability for RM Statistical analysis did not suggest an optimal dwell time, because this parameter did not significantly affect either the measured mean particle size or the ability to count nanoparticles. Finally, the spICP-MS data were often best fit with several single non-Gaussian distributions or mixtures of Gaussian distributions, rather than the more frequently used normal or log-normal distributions.
Sample integrity evaluations and inter-laboratory comparisons were conducted in application of U. As advances in analytical separation techniques, mass spectrometry instrumentation, and data processing platforms continue to spur growth in the lipidomics field, more structurally unique lipid species are detected and annotated. The lipidomics community is in need of benchmark reference values to assess the validity of various lipidomics workflows in providing accurate quantitative measurements across the diverse lipidome.
LipidQC addresses the harmonization challenge in lipid quantitation by providing a semiautomated process, independent of analytical platform, for visual comparison of experimental results of National Institute of Standards and Technology Standard Reference Material SRM , "Metabolites in Frozen Human Plasma", against benchmark consensus mean concentrations derived from the NIST Lipidomics Interlaboratory Comparison Exercise. Inter-laboratory comparison of multi-locus variable-number tandem repeat analysis MLVA for verocytotoxin-producing Escherichia coli O to facilitate data sharing.
However, as yet there is no common allelic or profile nomenclature to enable laboratories to easily compare data. We found all but two isolates were identical in profile in the two laboratories, and repeat units were homogeneous in size but some were incomplete. This work has enabled us to realize the potential of MLVA as a portable, highly discriminatory and convenient subtyping method. Experimental design of an interlaboratory study for trace metal analysis of liquid fluids.
The accurate determination of trace metals and fuels is an important requirement in much of the research into and development of alternative fuels for aerospace applications.
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Recognizing the detrimental effects of certain metals on fuel performance and fuel systems at the part per million and in some cases part per billion levels requires improved accuracy in determining these low concentration elements. Accurate analyses are also required to ensure interchangeability of analysis results between vendor, researcher, and end use for purposes of quality control.
Previous interlaboratory studies have demonstrated the inability of different laboratories to agree on the results of metal analysis, particularly at low concentration levels, yet typically good precisions are reported within a laboratory. An interlaboratory study was designed to gain statistical information about the sources of variation in the reported concentrations. Five participant laboratories were used on a fee basis and were not informed of the purpose of the analyses. The effects of laboratory, analytical technique, concentration level, and ashing additive were studied in four fuel types for 20 elements of interest.
The prescribed sample preparation schemes variations of dry ashing were used by all of the laboratories. The analytical data were statistically evaluated using a computer program for the analysis of variance technique. An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using heptane as a food-simulating solvent for oily or fatty foods, based on the Japanese Food Sanitation Law for food contact products.
Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. In the official method, heating for evaporation was done with a water bath. In most laboratories, the test solutions were heated until just prior to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method.
The results demonstrated that there was no significant difference between heptane and these two leaching solutions. For four participants out of 13, the uncertainties of CCT, calculated using traditional methods, not accounting for correlations, would be too small. The reason for the failure of traditional uncertainty calculation is spectral correlations, producing systematic deviations of the same sign over certain wavelength regions.
The results highlight the importance of accounting for such correlations when calculating uncertainties of spectrally integrated quantities. Measuring the glycemic index of foods: interlaboratory study. Many laboratories offer glycemic index GI services. We assessed the performance of the method used to measure GI. The laboratories reported the results of their calculations and sent the raw data for recalculation centrally. The trial was registered at clinicaltrials. Nanomaterials are increasingly being used in polymer composites to enhance the properties of these materials.
Here we present results of a pilot inter-laboratory study to simulate the effects of weathering on the potential release of multiwalled carbon nanotubes MWCNT from thei Umezawa, Taku; Brenninkmeijer, Carl A. The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories.
To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. First European interlaboratory comparison of tetracycline and age determination with red fox teeth following oral rabies vaccination programs.
The first European interlaboratory comparison of tetracycline and age determination with red fox Vulpes vulpes tooth samples was organized by the European Union Reference Laboratory for rabies. Performance and procedures implemented by member states were compared. These techniques are widely used to monitor bait uptake in European oral rabies vaccination campaigns. A panel of five red fox half-mandibles comprising one weak positive juvenile sample, two positive adult samples, one negative juvenile sample, and one negative adult sample were sent, along with a technical questionnaire, to 12 laboratories participating on a voluntary basis.
Analysis of the technical questionnaires in parallel with test results suggested that all laboratories cutting mandible sections between the canine and first premolar obtained false results. All the laboratories using longitudinal rather than transverse sections and those not using a mounting medium also produced false results. Section thickness appeared to affect the results; no mistakes were found in laboratories using sections interlaboratory trials underline the importance of using standardized procedures for biomarker detection in oral rabies vaccination campaigns.
Several changes can be made to improve analysis quality and increase the comparability of bait uptake frequencies among member states. Interlaboratory comparison for the measurement of particle size and zeta potential of silica nanoparticles in an aqueous suspension. The Institute for Reference Materials and Measurements has organised an interlaboratory comparison ILC to allow the participating laboratories to demonstrate their proficiency in particle size and zeta potential measurements on monomodal aqueous suspensions of silica nanoparticles in the nm size range.
The main goal of this ILC was to identify competent collaborators for the production of certified nanoparticle reference materials. Most of the laboratories submitted particle size results obtained with centrifugal liquid sedimentation CLS , dynamic light scattering DLS or electron microscopy EM , or zeta potential values obtained via electrophoretic light scattering ELS. The results of the laboratories were evaluated using method-specific z scores, calculated on the basis of consensus values from the ILC.
The standard deviations of the corresponding laboratory mean values varied between 3. From the received test reports, a large discrepancy was observed in terms of the laboratory's quality assurance systems, which are equally important for the selection of collaborators in reference material certification projects. International Organisation for Standardization, Geneva, b.
The absence of measurement uncertainty values in the reports, for. Viral reservoirs represent an important barrier to HIV cure. Accurate markers of HIV reservoirs are needed to develop multicenter studies. For evaporation, a water bath was used in the official method, and a hot plate in the modified method.
In most laboratories, the test solutions were heated until just prior to evaporation to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods, regardless of the heating equipment used. Interlaboratory comparison of mineral constituents in a sample from the Herrin No. Approximately 20 kg of the Herrin No. Clair County, Ill. A kg portion was ground to mesh, homogenized, and riffled into splits of g each.
Homogeneity of these splits was confirmed by moisture, ash, and sulfur analyses of six randomly selected splits. Splits of the Herrin No. Low-temperature plasma oxidation was used to isolate inorganic matter for quantitative chemical and mineralogical analysis. Despite a wide variation in ashing conditions, only minor variations in ash yields were obtained; these variations were attributed to differences in operating temperature and moisture content. Mineralogical analyses of low-temperature ash LTA concentrates prepared by five different laboratories indicated variations within the limits of analytical error.
Good interlaboratory agreement was obtained for most major, minor, and trace elements despite differences in analytical procedures and in the type of sample analyzed coal, high-temperature ash, or LTA. Discrepancies between analyses for zinc, strontium, manganese, and iron may be attributed to sampling inhomogeneity problems. Mossbauer spectroscopy showed that approximately 44 percent of the pyritic sulfur was lost through weathering in the first year after preparation of the interlaboratory sample.
Leymarie, Nancy; Griffin, Paula J. One of the principal goals of glycoprotein research is to correlate glycan structure and function. Such correlation is necessary in order for one to understand the mechanisms whereby glycoprotein structure elaborates the functions of myriad proteins. The accurate comparison of glycoforms and quantification of glycosites are essential steps in this direction.
Mass spectrometry has emerged as a powerful analytical technique in the field of glycoprotein characterization. As part of the ABRF Glycoprotein Research Group study , we explored the use of mass spectrometry and ancillary methodologies to characterize the glycoforms of two sources of human prostate specific antigen PSA. PSA is used as a tumor marker for prostate cancer, with increasing blood levels used to distinguish between normal and cancer states.
The glycans on PSA are believed to be biantennary N-linked, and it has been observed that prostate cancer tissues and cell lines contain more antennae than their benign counterparts. Thus, the ability to quantify differences in glycosylation associated with cancer has the potential to positively impact the use of PSA as a biomarker. We performed an interlaboratory study to determine the ability of different laboratories to correctly characterize the differences between glycoforms from two different sources using mass spectrometry methods.
We used clustering analysis and ancillary statistical data treatment on the data sets submitted by participating laboratories to obtain a consensus of the glycoforms and abundances. The results demonstrate the relative strengths and weaknesses of top-down glycoproteomics, bottom-up glycoproteomics, and glycomics methods. An interlaboratory comparison of dosimetry for a multi-institutional radiobiological research project: Observations, problems, solutions and lessons learned.
An interlaboratory comparison of radiation dosimetry was conducted to determine the accuracy of doses being used experimentally for animal exposures within a large multi-institutional research project. Dosimetry tests were carried out utilizing optically stimulated luminescence OSL dosimeters embedded midline into mouse carcasses and thermal luminescence dosimeters TLD embedded midline into acrylic phantoms.
Outliers were most notable for OSL-based tests, while multiple tests by 'non-compliant' laboratories using orthovoltage X-rays contributed heavily to the wide variation in dosing errors. For the dosimetrically non-compliant laboratories, the relatively high rates of dosing errors were problematic, potentially compromising the quality of ongoing radiobiological research. Interlaboratory study of the ion source memory effect in 36Cl accelerator mass spectrometry. Understanding and minimization of contaminations in the ion source due to cross-contamination and long-term memory effect is one of the key issues for accurate accelerator mass spectrometry AMS measurements of volatile elements.
The focus of this work is on the investigation of the long-term memory effect for the volatile element chlorine, and the minimization of this effect in the ion source of the Dresden accelerator mass spectrometry facility DREAMS. For this purpose, one of the two original HVE ion sources at the DREAMS facility was modified, allowing the use of larger sample holders having individual target apertures.
Additionally, a more open geometry was used to improve the vacuum level. To evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison had been initiated. Besides investigating and comparing the individual levels of long-term memory, recovery time constants could be calculated.
The tests show that all four sources suffer from long-term memory, but the modified DREAMS ion source showed the lowest level of contamination. Compositional analysis of biomass reference materials: Results from an interlaboratory study. Biomass compositional methods are used to compare different lignocellulosic feedstocks, to measure component balances around unit operations and to determine process yields and therefore the economic viability of biomass-to-biofuel processes. Four biomass reference materials RMs NIST — were prepared and characterized, via an interlaboratory comparison exercise in the early s to evaluate biomass summative compositional methods, analysts, and laboratories.
Having common, uniform, and stable biomass reference materials gives the opportunity to assess compositional data compared to other analysts, to other labs, and to a known compositional value. We sent samples of the four biomass RMs to 11 academic, industrial, and government laboratories, familiar with sulfuric acid compositional methods, for recharacterization of the component reference values. We report the median values and the expanded uncertainty values for the four RMs on a dry-mass, whole-biomass basis.
The original characterization data has been recalculated using median statistics to facilitate comparisons with this data. Here, the major components were not statistically different in the recharacterization which suggests that the biomass materials are stable during storage and that additional components, not seen in the original. Reduced strength of attachment of the encapsulant resulting from the outdoor environment, including ultraviolet UV radiation, may decrease photovoltaic PV module lifetime by enabling widespread corrosion of internal components.
To date, few studies exist showing how the adhesion of PV components varies with environmental stress. We have conducted an interlaboratory experiment to provide an understanding that will be used to develop climatic specific module tests. Factors examined in the study included the UV light source lamp type , temperature, and humidity to be proposed for use in accelerated aging tests. Shear strength, shear strain, and toughness were measured using a mechanical load-frame for the compressive shear test, with subsequent optical imaging and electron microscopy of the separated surfaces.
Interlaboratory study of a method for determining nonvolatile organic carbon in aquifer materials. The organic carbon fraction in aquifer materials exerts a major influence on the subsurface mobilities of organic and organic-associated contaminants. The spatial distribution of total organic carbon TOC in aquifer materials must be determined before the transport of hydrophobic organic pollutants in aquifers can be modeled accurately. We have tested a new analytical method designed to improve the accuracy and precision of nonvolatile TOC quantitation in geologic materials that also contain carbonate minerals.
Four authentic aquifer materials and one NIST standard reference material were selected as test materials for a blind collaborative study. Nonvolatile TOC in these materials ranged from 0. Sample replicates were digested with sulfurous acid, dried at 40?? C, and then combusted at ?? Participants did not have enough time to become proficient with the new method before they analyzed the test materials. A seventh laboratory successfully used an alternative method that analyzed separate liquid and solid fractions of the acidified sample residues.
Liquid chromatographic determination of histamine in fish, sauerkraut, and wine: interlaboratory study. An interlaboratory study of the liquid chromatographic LC determination of histamine in fish, sauerkraut, and wine was conducted. Diminuted and homogenized samples were suspended in water followed by clarification of extracts with perchloric acid, filtration, and dilution with water. After LC separation on a reversed-phase C18 column with phosphate buffer pH 3. Results from one participant were excluded from statistical analysis.
For all samples analyzed, repeatability relative standard deviations varied from 2. Reduced optical transmittance of encapsulation resulting from ultraviolet UV degradation has frequently been identified as a cause of decreased PV module performance through the life of installations in the field. The present module safety and qualification standards, however, apply short UV doses only capable of examining design robustness or 'infant mortality' failures.
Essential information that might be used to screen encapsulation through product lifetime remains unknown. For example, the relative efficacy of xenon-arc and UVA fluorescent sources or the typical range of activation energy for degradation is not quantified. The solar-weighted transmittance, yellowness index, and the UV cut-off wavelength, determined from the measured hemispherical transmittance, are examined to provide understanding and guidance for the UV light source lamp type and temperature used in accelerated UV aging tests.
Index Terms -- reliability, durability, thermal activation. Reduced optical transmittance of encapsulants resulting from ultraviolet UV degradation has frequently been identified as a cause of decreased PV module performance through the life of service in the field. Urine cytology is used in the evaluation of hematuria or to follow patients with known urothelial neoplasia. To investigate the performance characteristics of urinary cytology challenges in the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytopathology.
Participant responses from to were evaluated for the reference diagnoses of high-grade urothelial carcinoma HGUC , squamous cell carcinoma, adenocarcinoma, and benign diagnoses including polyomavirus infection and ileal loop urine. Responses were compared for differences in sample preparation conventional, liquid based, and cytospin and participant type laboratory, pathologist, cytotechnologist. There were 96 responses 46 pathologists [ Of the malignant reference diagnoses, However, of adenocarcinoma challenges For the benign cases, the most common diagnostic pitfall was overinterpretation of ileal loop urines of ; 6.
For the general diagnosis of positive for malignancy, cytotechnologists performed slightly better that pathologists Although the participants performed well in accurately classifying cases as benign and malignant, there were difficulties with the correct identification of adenocarcinoma and. Layered samples with known binary compositions of Irganox and either Irganox or Fmoc-pentafluoro-L-phenylalanine in each layer were manufactured in a single batch and distributed to more than 20 participating laboratories.
Participants using XPS provided volume fractions within 0. Participants using ToF-SIMS either made no attempt, or used various methods that gave results ranging in error from 0. Error was predominantly caused by inadequacy in the ability to compensate for primary ion intensity variations and the matrix effect in SIMS. Matrix effects in these materials appear to be more pronounced as the number of atoms in both the primary analytical ion and the secondary ion increase. We provide recommendations for identifying and compensating for matrix effects. Finally we demonstrate, using a simple normalization method, that virtually all ToF-SIMS participants could have obtained estimates of volume fraction that were at least as accurate and consistent as XPS.
Layered samples with known binary compositions of Irganox and either Irganox or Fmoc-pentafluoro-l-phenylalanine in each layer were manufactured in a single batch and distributed to more than 20 participating laboratories. The samples were analyzed using argon cluster ion sputtering and either X-ray photoelectron spectroscopy XPS or time-of-flight secondary ion mass spectrometry ToF-SIMS to generate depth profiles.
Participants were asked to estimate the volume fractions in two of the layers and were provided with the compositions of all other layers. Using the participants' data we show that organic SIMS matrix effects can be measured and are remarkably consistent between instruments. Finally, we demonstrate, using a simple normalization method, that virtually all ToF-SIMS participants could have obtained estimates of volume fraction that were at least as accurate and consistent as XPS. The members of the committee NMP "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. 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. An intercomparison exercise on the determination of Am, Cm and Cf in urine was performed. Since it was designed with regard to emergency preparedness, the detection limit for each nuclide was set to 0. Most of the participating laboratories were established bioassay laboratories.
However, some laboratories that routinely determine Am only in environmental samples were also invited in order to explore their potential for emergency bioassay analysis. Another aspect of the intercomparison was to investigate the performance of all laboratories concerning the chemical yields of the Am tracer in comparison with Cm and Cf. In summary, both types of laboratories showed good results.
There was a negative bias for the results of Cm and Cf, which can be explained by slightly different radiochemical behaviours of americium, curium and californium and which is in agreement with results reported in the literature. Byrne, David C. An identical study was conducted independently at the U. The Howard Leight Airsoft premolded earplug was tested with twenty subjects at each of the four participating laboratories.
The occluded fit of the earplug was maintained during testing with a soundfield-based laboratory REAT system as well as all three headphone-based fit-test systems. For each of the fit-test systems, the average A-weighted attenuation across the four laboratories was not significantly greater than the average of the ANSI sound field method. Individual labs exhibited a range of agreement from less than a dB to as much as 9. Factors such as. Inter-laboratory comparison of turkey in ovo carcinogenicity assessment IOCA of hepatocarcinogens.
In three independent laboratories carcinogens diethylnitrosamine, DEN, 4- N-methyl-N-nitrosamino 3-pyridyl butanone, NNK and non-carcinogens N-nitrosoproline, nicotine were evaluated in turkey eggs for in ovo carcinogenicity assessment IOCA. Compounds were injected into aseptic fertilized eggs. All laboratories were able to distinguish unequivocally the hepatocarcinogen-exposed groups from those exposed to non-carcinogens or the vehicle controls, based on the pre-specified evaluation parameters: tumor-like lesions, pseudoglandular areas and FAH.
In addition to focal changes, only the carcinogens induced hepatocellular karyomegaly. Lower doses of the carcinogens, which did not induce FAH, were sufficient to induce hepatocellular karyomegaly. After exposure to 4 mg DEN, gall bladder agenesis was observed in all fetuses. The IOCA may be a valuable tool for early investigative studies on carcinogenicity and since it does not use rodents may complement chronic rat or mouse bioassays. Test substances that are positive in both rodents and fertilized turkey eggs are most probably trans-species carcinogens with particular significance for humans.
The good concordance observed among the three laboratories demonstrates that the IOCA is a reliable and robust method. Interlaboratory comparison of three microbial source tracking quantitative polymerase chain reaction qPCR assays from fecal-source and environmental samples. During summer and early fall , 15 river samples and 6 fecal-source samples were collected in West Virginia. These samples were analyzed by three laboratories for three microbial source tracking MST markers: AllBac, a general fecal indicator; BacHum, a human-associated fecal indicator; and BoBac, a ruminant-associated fecal indicator.
The aim was to assess interlaboratory precision when the three laboratories used the same MST marker and shared deoxyribonucleic acid DNA extracts of the samples, but different equipment, reagents, and analyst experience levels. The term assay refers to both the markers and the procedure differences listed above. Interlaboratory precision was best for all three MST assays when using the geometric mean absolute relative percent difference ARPD and Friedman's statistical test as a measure of interlaboratory precision.
Adjustment factors one for each MST assay were calculated using results from fecal-source samples analyzed by all three laboratories and applied retrospectively to sample concentrations to account for differences in qPCR results among labs using different standards and procedures. This was a small study and two of the MST assays had 52 percent of samples with concentrations at or below the limit of accurate quantification; hence, more testing could be done to determine if the adjustment factors would work better if the majority of sample concentrations were above the quantification limit.
An interlaboratory round robin study was conducted on the tensile strength of SiC—SiC ceramic matrix composite CMC tubular test specimens at room temperature with the objective of expanding the database of mechanical properties of nuclear grade SiC—SiC and establishing the precision and bias statement for standard test method ASTM C The mechanical properties statistics from the round robin study and the precision statistics and precision statement are presented herein.
The data show reasonable consistency across the laboratories, indicating that the current C—13 ASTM standard is adequate for testing ceramic fiber reinforced ceramic matrix composite tubular test specimen. However, the method was not validated for all key STX-group toxins, and procedures to quantify some of them were not provided. With more STX-group toxin standards commercially available and modifications to procedures, it was possible to overcome some of these difficulties.
This paper reports the study design and the results obtained. The performance characteristics for dc-GTX2,3 intralaboratory and interlaboratory precision, recovery, and theoretical quantification limit were evaluated. The mean recoveries obtained for dc-GTX2,3 were, in general, low The performance of the participant laboratories in the application of this method was compared with that obtained from the original collaborative study of the method. However the overall quantitative performance obtained with the method was poor for certain toxins.
Mixture effects in samples of multiple contaminants - An inter-laboratory study with manifold bioassays. Chemicals in the environment occur in mixtures rather than as individual entities. Environmental quality monitoring thus faces the challenge to comprehensively assess a multitude of contaminants and potential adverse effects.
Effect-based methods have been suggested as complements to chemical analytical characterisation of complex pollution patterns. The regularly observed discrepancy between chemical and biological assessments of adverse effects due to contaminants in the field may be either due to unidentified contaminants or result from interactions of compounds in mixtures.
Bridging has the opposite effect: decrease in resistance by creating alternative simple paths for current flow. The formation of deposits can cause, just like metal loss, a loss of electrical conductivity and, thus, make an electrical contact unusable. It can also act mechanically, to render parts, such as ball bearings, ineffective because of it not being able to turn adequately.
All main tests proposed to date address purely metal loss, although bridging can mask their results. In the remainder of this paper, thus, smoke corrosivity by metal loss will simply be labelled corrosion, for expediency's sake. The combination of acid gases combine with water causes corrosion of metals. Originally, thus, acid gases were believed to be the only entities capable of causing corrosion.
Thus, corrosive potential of smoke was deterrnined based simply on rankings of acid gas emission following combustion of the materials in a hot tube furnace, under an air flow. The water soluble effluents were captured and the solutions titrated for their acid gas content HC1, HBr, HF , acidity or conductivity. In practice, decisions were often taken based purely on chemical composition: i. It has since been found that smoke corrosivity can occur with halogen-free smoke, and that it can, under certain conditions, be larger than that due to halogens It used a range of combustible materials, and exposure conditions designed to simulate some of the wide range of conditions potentially found in an area affected by an accidental fire.
The effectiveness of some simplistic anti-corrosion treatments was also evaluated. Table 1 lists the materials used. The targets 5 steel and 2 copper for each bum were exposed for 1 h in a L chamber the NBS Smoke Density Chamber fully lined with Teflon sheeting, to minimize HC1 decay on the walls. Steel coupons were laid on the chamber floor while the copper mirrors were placed in a plastic holder.
In half the experiments the chamber air temperature was near ambient, while in the other half the chamber was heated to ca. Each steel coupon was treated differently, to simulate a particular fire scenario. The day after exposure, two of the steel coupons were taken out of the chamber, post-treated and returned to it. At the end of the 28 days, the steel coupons were mechanically stripped of corrosion debris and weighed to determine metal loss gravimetrically.
Copper mirror corrosion was determined based on the metallic copper remaining on the mirror after exposure.
Interlaboratory Evaluation of Smoke Density Chamber. Final Report. | NIST
All the materials tested caused metal loss, as did even the simple presence of warm humidity. The highest overall corrosion was found on steel coupons placed, in the warm chamber, on the hot plate Figure 1. The amount of metal lost in the warm chamber was fairly constant, irrespective of the material burnt, with no correlation with the chemical composition of the fuels. In particular, metal loss resulting from chlorinated material smoke did not correlate with acid gas emission Figure 2 , nor did it, as a whole, appear to be more corrosive than the smoke from the group of halogen free materials.
Moreover, the most corrosive smoke was due to nylon combustion. The single set of conditions under which HCI emission directly correlated with corrosion level was: steel coupons on ice Figure 2 , an unrealistic exposure, but which is often simulated during testing. Immediately after exposure, these particular steel coupons were covered with abundant water droplets, while no other coupons were similarly wet, indicating that the condensed moisture promoted condensation of HCI. The corrosion of steel coupons at room temperature did not correlate well with HCI emission Figure 2.
In general, in the warm environment, the most corrosive smoke appeared to be that of nylon. There is, not yet, a clear explanation for some of these unusual results. Rankings of the corrosive tendency of the smoke of all the materials tested in this series depend on the way in which smoke corrosivity is analyzed, as reflected by the cross-overs in Figure 3. Legends: Untr, untreated; Ice, steel coupon on ice bag during exposure; Oily, treatment with machine oil pre-exposure; TSP, treatment with trisodium phosphate solution post-exposure; WD40, treatment with WD40 oil post-exposure; HOT: steel coupon lying on hot plate during exposure.
Legends as in Figure 1. The additional current needed to reequilibrate the circuit was measured with a corrosometer Rohrback CK3 and converted into equivalent metal loss in A. Copper mirror metal loss was assessed by resistance increase at 1 h, end of exposure, and after 1, 3, 7, 14, 21 and 28 days and by copper dissolution as before. The targets were exposed in the warm chamber, with no treatments. Results in Figure 4 comparing three measurement methods show that a there is no simple correlation between the degree of acidity emitted and smoke corrosivity of copper and b there is a rough degree of correlation between the various targets, although they do not correlate exactly.
The copper mirror resistance results at 28 days agree reasonably well with the copper mass loss data, as do the Rohrback probes at 1 day agree with the copper mirror resistance results at 1 day. The Rohrback probes are much less sensitive, have a greater range before going off scale, can be used for continuous, or at leastfrequent,measurements, and thermal effects are nunimized by the reference arm.
Rohrback probes are also made for higherranges,up to 45, A, although the fabrication procedure is different. Figure 5 shows a useful feature of keeping targets post-exposure: there are substantial crossovers between materials when smoke corrosivity is measured at different times after exposure, with copper targets. It is obvious that there is no direct correlation between pH of smoke and smoke corrosivity. Table 2. The effect of oxygen was investigated with three burning modes: unconfined samples free bum , samples confined within an open fire box confined burn or samples within a fire box, with the opening restricted to a slit closed burn.
Figure 7 shows corrosion results at 3 days post-exposure. This suggests that corrosive potential may change with environmental temperature. Very few other series of large scale tests have been conducted to investigate corrosion. Any small scale test should correlate with the type of results found here. This issue is, as yet, undetermined for any of the proposed smoke corrosivity tests.
One set of experiments, with personal computers, will be discussed later 7. In the test the resistance of a copper printed circuit exposed to smoke is measured before and after exposure. Figure 8: Effect of ambient temperature on corrosion of copper mirrors by nylon smoke, in full scale burns, using copper mirrors, after 1 h exposure, at free burn conditions. In the test a small material sample mg is mixed with polyethylene mg and placed within a 20 L chamber, conditioned to very high relative humidity and slightly elevated temperature. The target is a copper printed circuit board, at a total area of ca.
Combustion resultsfromrapid application of an intense flux, rapidly raising the sample temperature to ca. Water soluble combustion products are condensed onto the target, water-cooled to a temperature below that of the bulk of the chamber. The test apparatus is limited to testing of materials and is incapable of addressing corrosion by products. For chlorinated materials, CNET test results were found recently 3 to closely parallel those of two acid gas tests: hot tube furnace, as used by the Canadian Standards Association, 9 and the faster "coil" test 5, The CNET test, however, is much less sensitive to smoke corrosivity by other halogenated materials, particularly fluorinated ones.
This illustrates that there are still some problems to overcome with the test. It is worth mentioning, however, that no other tests have, as yet, undergone such scrutiny. The main overall problems with the CNET test are solvable: a the use of forced condensation, which means that the effects of non water-soluble products is lost, b the lack of post-exposure and c a very intense fire module. Some minor problems associated with the CNET test include the excessive time required to clean Table 4.
The good fire performance of a tested material does not yield any advantages in the test itself, because of the forced combustion in the presence of polyethylene. Finally, test results can be difficult to interpret because the copper "lines" in the circuit board are so close that there often is a combination of resistance increase due to metal loss and resistance decrease due to bridging.
The most serious problem with the CNET test, however, was found when the results of tests on over 20 materials were compared with those using surrogate tests: no parallels with acid gas emission were found, The tests suggested that the only outliers were materials based on p o l y v i n y l chloride. On the other hand, materials containing bromine, and especially fluorine, seemed to be statistically almost indistinguishable from those containing no halogen.
Some of the logic for using either one has recently been discussed 3 , and smoke corrosivity performance tests of both kinds are being considered for standardization. It has a plastic exposure chamber ca. However, it is not actually static, as the smoke circulates, impelled through a set of channels communicating the combustion and exposure chambers. The apparatus is suitable to measure corrosive potential of products, if small representative samples can be placed in the holder. The Rohrback targets used differ from the printed circuit boards used for the CNET test in that they have much larger gaps between copper runs, so that bridging is extremely unlikely.
The test apparatus can accommodate other targets, including full scale equipment, such as a small computer. This test is generally referred to as the DIN smoke corrosivity test. Some recent work has been published regarding this proposal, using steel coupons and CNET targets The smoke then exposes a variety of targets. There is, as yet, insufficient published information on the test procedure to be able to discuss its relevance to full-scale smoke corrosivity or its repeatability or reproducibility.
Researchers at Underwriters Laboratories modified the sampling technique, in order to obtain high concentrations of corrosive species This concept has since been developed into the ASTM D standard also known as the cone corrosimeter , the first smoke corrosivity consensus standard fully approved, in The instrument, like the radiant apparatus described above, is now commercially available. It consists of a conical heater hence its name which radiates heat input to a horizontal sample, on a load cell, an exhaust system and a corrosion sampling system.
The corrosion sampling system takes an aliquot of the smoke from directly above the combustion zone and sends it to an 11 L polycarbonate exposure chamber. The samples are 0. Smoke passes through the exposure chamber for a period of time dependent on sample mass loss rate