ISO 5725 and GUM: comparison and comments

We compare the approach to measure uncertainties proposed in ISO 5725 and GUM from a statistician point of view. In particular we give some warnings to the application of the expanded uncertainty introduced in GUM when the input variables are few and we report some considerations on the relevant role of the interactions among the input variables in the measurement equation as well as the role of statistical design of experiments to measure uncertainties.

Uncertainty in photometric analysis: a case study

A procedure for estimation of measurement uncertainty of photometric analysis based on the ISO GUM method is presented. Two variations of the procedure—for the calibration graph and the standard addition method, respectively—are discussed. The variations are based on mathematical models involving 64 and 80 input quantities, respectively. The uncertainty of the result strongly depends on changes in experimental details. These dependencies are explored for a practical example of determination of the iron content of aluminum. The importance of taking uncertainty from sample preparation into account in uncertainty estimation is stressed. The number of effective degrees of freedom is calculated and discussed. The examples are available as GUM Workbench files in the Electronic Supplementary Material.Electronic Supplementary Material  Supplementary material is available for this article at .

Accounting for bias in measurement uncertainty estimation

Generic issues and current approaches in the evaluation of bias studies with respect to estimation of measurement uncertainty are discussed, focusing on two main scenarios. In the first, for a within-laboratory assessment of a fully developed uncertainty budget, bias studies are carried out to verify the pre-established performance of a measurement procedure, and design corrective actions if necessary. In the second scenario, for an estimation of measurement uncertainty from within-laboratory validation data, bias studies are carried out to calibrate the whole measurement procedure and evaluate its performance, more specifically to estimate the uncertainty of measurement by combination of bias and precision estimates.

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Food anaphylaxis

    Figure Avoidance is the primary measure in food allergy confirmed

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Correlation between repeated measurements: bane and boon of the GUM approach to the uncertainty of measurement

With measurement uncertainty estimation accounting for all relevant uncertainty contributions, the results of measurements using the same procedure on different objects or samples may no longer be considered as being independent, and correlations have to be taken into account. For this purpose, a simple approximation for the estimation of covariances is derived and applied to the estimation of uncertainty for some basic combinations of two measurement results. This covariance estimate is also applied to the estimation of uncertainty for the mean value of the results of replicate measurements on the same object or sample.

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed. Graphical Abstract  

A note on Michael Weisberg’s: challenges to the structural conception of chemical bonding

Michael Weisberg’s recent 2007 paper on the chemical bond makes the claim that the chemical notion of the covalent bond is in trouble. This note casts doubts on that claim.

Do we need to rethink collaborative trials?

The currently recommended design of collaborative trials (interlaboratory method performance studies) is examined in relation to the usefulness of the resulting statistics. It is suggested that larger experiments, without duplicate analysis, would be more informative.

Irreversible structural changes in cryogenic mechanically milled isotactic polypropylene

The influence of cryogenic mechanical milling on the structure and the thermal behavior of isotactic polypropylene was investigated by means of wide-angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. The results presented show that structural changes caused by mechanical milling at cryogenic temperatures are only partly reversible. The decrease in the degree of crystallinity as determined by differential scanning calorimetry with increasing milling time is attributed to a reversible transformation of the initial morphology into a nanostructured morphology, consisting of small fragments of the original isotactic polypropylene lamellae. During recrystallization from the molten state, there still exists an influence of the previous milling treatment, leading to significantly changed crystallization behavior. The reason for this behavior might be a decrease in the molecular weight or a change in the molecular weight distribution or the formation of long-chain branched polypropylene molecules induced by cryogenic mechanical milling.

A novel Ce<Superscript>III</Superscript>-cyclam type complex and its redox chemistry in aqueous solutions

A new Ce^III complex was synthesized by mixing the ligand “dioxocyclam” with Ce^III ions at pH 8.0 and its redox properties were investigated.

Encapsulating of single quantum dots into polymer particles

Single semiconductor quantum dots were embedded into polymer particles with diameters below 0.1 μm by an emulsion polymerization procedure or via a secondary dispersion approach. The photoluminescence properties of the nanocrystals are retained upon encapsulation, as demonstrated by fluorescence confocal microscopy.

The OIML and the purpose of international recommendations

This article was presented to the CITAC workshop in Wellington, New Zealand on 3 May 2004. It explains the role of the Organisation Internationale de Métrologie Legalé (OIML) and work carried out to promote harmonisation in the field of legal metrology—the part of metrology relating to activities which result from statutory requirements and concern measurement, units of measurement, measuring instruments and methods of measurement and which are performed by competent bodies. It also discusses the publications issued to achieve harmonisation. The article also discusses New Zealands recent elevation to full membership of the OIML and the commitment to make the membership work to the benefit of the whole New Zealand measurement industry.

Measurement uncertainty and the use of reference materials

The use of (certified) reference materials and quality control materials can form a suitable basis for evaluating measurement uncertainty of routine measurements. In particular when these materials are used for quality control purposes, it is not always evident how the quality control data can be used in the uncertainty budget of a routine measurement. Current guidance documents on the evaluation of measurement uncertainty and the use of reference materials treat this subject only in part, or in very generic terms. ISO/REMCO has established a new working group that will provide practical guidance and examples on how to use quality control data in the evaluation of measurement uncertainty. A short introduction to the subject is given.

Chemistry, commentary, and community: discussion of “an examination of the vaporization enthalpies and vapor pressures of pyrazine, pyrimidine, pyridazine, and 1,3,5-triazine” by Lipkind and Chickos

Vaporization enthalpies for the isomeric diazines were discussed within the context of recent measurements and estimation techniques. It is suggested that pyridazine shows enigmatic behavior.

Core-shell structured electrode materials for lithium ion batteries

Recent progress in studies of several types of core-shell structured electrode materials, including TiO₂/C, Si/C, Si/SiO _x , LiCoO₂/C, and LiFePO₄/C nanocomposites, including details of their preparation and their electrochemical performance is briefly reviewed. Results clearly show that the coating shell can effectively prevent the aggregation of the nanosized cores, which are the electrochemically active materials. In addition, the diffusion coefficients of lithium ions can be increased, and the reversibility of lithium intercalation and deintercalation is improved. As a result, the cycling behavior is greatly improved. The reviewed results suggest that core-shell nanocomposites are a good starting point for further development of new promising electrode materials.

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The non-integer cyclovoltammetric electron-exchange numbers of reversible redox reactions of adsorbates

Allowing for the interfacial potential distribution it can be shown that the apparent faradaic electron number, n_app, of ad-layers of chemically modified electrodes and the surface redox valency, n, relating to the slope of the peak potential/pH response [Huck (2002) J Solid State Electrochem 6:534] are at least identical, having the same thermodynamic origin. n_app is calculated from the cyclovoltammetric (CV) peak areas above the interpolated base line. At for proton-coupled surface redox reactions, the influence of the potential drop of the diffuse double layer disappears because the capacitor of the corresponding equivalent circuit becomes shortened by proton transfer, whereby the otherwise non-integer n_app or n values now approach the integer electron numbers, n, of the Nernst equation.

Exhaust gas analysers and optimised sampling, uncertainties and costs

Decision-making in the conformity assessment of exhaust gas analysers with due account of measurement uncertainty and limited sampling is considered. Risks of incorrect decisions where test results lie in the vicinity of a specification limit are assessed in terms of percentage probability and the costs of measurement and environmental consequences, with examples based on the metrological requirements on these analysers stipulated in the new EU Measurement Instrument Directive. An optimised uncertainty methodology is proposed for the first time in legal metrology based on quantitative testing of new instruments for type approval and initial verification, and gives valuable insight into traditional rules limiting uncertainty in conformity assessment in general. Further, an analysis of subsequent verification of exhaust gas analysers in use in society, leads to a new optimised uncertainty methodology based on attribute sampling.

The meaning of ‘concentration’

Terminology within a small laboratory community can be informal without danger of misunderstanding, but communication with a wider audience and not least in publications, needs unequivocal terms for defined concepts. As an example, the many meanings of “concentration” are explored to present a systematic nomenclature, including a concept diagram.

Formation of novel 1,3-thiazole- and 1,2-thiazole-fused aporphines and study on the simultaneously occurring benzothiazole–benzisothiazole-type isomerization

Abstract  The synthesis and acid-catalyzed rearrangement of novel thiazolomorphinandienes have been presented. An isomerization was observed simultaneously with the backbone transformation. An extensive study was performed to determine the major effects of the isomerization of 2′-alkyl- and aryl-substituted thiazoloapocodeines into 3′-alkyl- and arylisothiazoloapocodeines. The obtained results provided another practical example of the reversible benzisothiazole–benzothiazole-type isomerization emphasizing the determining role of the thermal effects in the occurrence of these isomerization products. The obtained experimental results and the proposed mechanism were in agreement with the calculated DFT data. Graphical abstract  

Preparation, structural, and optical features of two-dimensional cross-linked DNA/gold-nanoparticle conjugates

The formation and the optical features of two-dimensional aggregates formed by DNA-directed immobilization and cross-linking of bifunctional DNA–gold nanoparticles at flat gold substrates are analyzed. The samples are structurally characterized by atomic force microscopy to evaluate the particle size, the particle densities, and the degree of aggregation. The optical characteristics determined by UV/visible measurements are correlated with the structural features observed.