388 research outputs found
Introduction to electrochemistry
No full textAn excellent way into the subject'- New Scientist Introduction to Electrochemistry is the first major new text in the field in recent years. The author takes the student from the basics through to a level suitable for beginning a post-graduate course. The chapters cover theory from electrolytes through electrodes to cells, both equilibrium and dynamic. Applications and methods are given great emphasis, and the second part of the text focuses on these aspects with coverage of electrosynthesis, electroanalytical chemistry, industrial electrochemistry, batteries and corrosion. Scattered throughout the text are panels of historical and anecdotal information illustrating unusual and often amusing aspects of electrochemistry not normally presented to the student. This, plus the highly readable style adopted by Brynn Hibbert, and his use of fully worked problems at the end of each chapter, make Introduction to Electrochemistry the ideal undergraduate textbook choice. Introduction to Electrochemistry is part of the Macmillan Physical Sciences Series
Human being as a part of measuring system influencing measurement results
No full textThe role of human being as a part of a measuring system in a chemical analytical laboratory is discussed. It is argued that a measuring system in chemical analysis includes not only measuring instruments and other devices, reagents and supplies, but also a sampling inspector and/or analyst performing a number of important operations. Without this human contribution, a measurement cannot be carried out. Human errors, therefore, influence the measurement result, i.e., the measurand estimate and the associated uncertainty. Consequently, chemical analytical and metrological communities should devote more attention to the topic of human errors, in particular at the design and development of a chemical analytical/test method and measurement procedure. Also, mapping human errors ought to be included in the program of validation of the measurement procedure (method). Teaching specialists in analytical chemistry and students how to reduce human errors in a chemical analytical laboratory and how to take into account the error residual risk, is important. Human errors and their metrological implications are suggested for consideration in future editions of the relevant documents, such as the International Vocabulary of Metrology (VIM) and the Guide to the Expression of Uncertainty in Measurement (GUM)
Use of gas chromatograms of the essential leaf oils of the genus Eucalyptus for taxonomic purposes: E. subser. Euglobulares (Blakely)
No full textPeter J. Dunlop, Caroline M. Bignell, D. Brynn Hibbert and M. I. H. Brooke
IUPAC/CITAC Guide: Evaluation of risks of false decisions in conformity assessment of a substance or material with a mass balance constraint (IUPAC Technical Report)
No full textA Bayesian multivariate approach to the evaluation of risks of false decisions on conformity of chemical composition of a substance or material due to measurement uncertainty is adapted to cases for which the composition is subject to a mass balance constraint. The constraint means that sum of the actual (“true”) values of the composition component contents under conformity assessment is equal to 1 (or 100 %) or another positive value less than 1 (less than 100 %). As a consequence, the actual values of the component contents are intrinsically correlated. Corresponding measured values of the component contents are correlated also. Any correlation can influence evaluation of risks of false decisions in conformity assessment of the substance or material chemical composition. A technique for appropriate evaluation of the relevant risks, including evaluation of the conformance probability of a subject or material composition, is discussed for different scenarios of the data modeling, taking into account all observed correlations. A Monte Carlo method is applied in the R programming language for the necessary calculations. Examples of evaluation of the risks are provided for conformity assessment of chemical composition of a platinum-rhodium alloy, pure potassium trioxidoiodate, a sausage, and synthetic air
Advanced methods for assessment of chemical compositions of multicomponent substances or materials and their categorical property values
No full textRisk of a false decision on conformity of an environmental compartment due to measurement uncertainty of concentrations of two or more pollutants
No full textRisks of false decisions in conformity assessment of an environmental compartment due to measurement uncertainty of concentrations of two or more pollutants are discussed. Even if the assessment of conformity for each pollutant in the compartment is successful, the total probability of a false decision concerning the compartment as a whole might still be significant. A model of the total probability of a false decision, formulated on the base of the law of total probability, is used, for example, for a study of test results of total suspended particulate matter (TSPM) concentration in ambient air near to three independent stone quarries located in Israel, as the sources of the air pollution. Total probabilities of underestimation of TSPM concentration (total risk of the inhabitants) and overestimation (total risk of the stone producers) are evaluated as a combination of the particular risks of air conformity assessment concerning TSPM concentration for each quarry. These probabilities characterize conformity of the TSPM concentration in the region of the quarries as a whole. Core code developed in R programming environment for the calculations is provided
Risk of false decision on conformity of a multicomponent material when test results of the components' content are correlated
No full textThe probability of a false decision on conformity of a multicomponent material due to measurement uncertainty is discussed when test results are correlated. Specification limits of the components' content of such a material generate a multivariate specification interval/domain. When true values of components' content and corresponding test results are modelled by multivariate distributions (e.g. by multivariate normal distributions), a total global risk of a false decision on the material conformity can be evaluated based on calculation of integrals of their joint probability density function. No transformation of the raw data is required for that. A total specific risk can be evaluated as the joint posterior cumulative function of true values of a specific batch or lot lying outside the multivariate specification domain, when the vector of test results, obtained for the lot, is inside this domain. It was shown, using a case study of four components under control in a drug, that the correlation influence on the risk value is not easily predictable. To assess this influence, the evaluated total risk values were compared with those calculated for independent test results and also with those assuming much stronger correlation than that observed. While the observed statistically significant correlation did not lead to a visible difference in the total risk values in comparison to the independent test results, the stronger correlation among the variables caused either the total risk decreasing or its increasing, depending on the actual values of the test results
Bioanalytical Chemistry
No full textThis chapter provides a terminology of bioanalytical chemistry in general and analysis of biomacromolecules in particular. The vocabulary given in this chapter is largely taken from Labuda et al. “Terminology of bioanalytical methods (IUPAC Recommendations 2018)”,1 which becomes the immediate source reference for definitions of terms in this chapter that are not otherwise attributed. Reference to secondary sources follow the entry as “see also:” Terms are taken from the IUPAC Recommendations published in 1994 covering mostly the analytical terminology related to body fluids, enzymology, and immunology.2 Selected terms related to bioanalysis are included within recommendations and reports devoted to the unit “katal”,3 biotechnology,4 clinical chemistry,5 toxicology,6,7 medicinal chemistry,8,9 proteomics,10 electrochemical biosensors,11,12 and physical organic chemistry.13 Definitions of some terms have been updated here with respect to new reports and considerations, and a number of new terms has been introduced particularly on the topics of “–omics”, DNA analysis and studies of the interactions between biomolecules. Terms from earlier IUPAC Recommendations that are replaced by ref. 1 are not otherwise referenced but can be found as references in ref. 1
Total risk of a false decision on conformity of an alloy due to measurement uncertainty and correlation of test results
No full textTotal risk (probability) of a false decision on conformity of an alloy due to measurement uncertainty and correlation of test results is quantified. As an example, a dataset of test results of a PtRh alloy is studied when contents of four components of the alloy composition are under control. There are specification limits for contents of 1) Pt and 2) Rh; 3) three precious impurities - Au, Ir and Pd, and 4) eight impurities, both precious Au, Ir, Pd, and non-precious Fe, Pb, Si, Sn, Zn. Test results of 100 batches of the alloy produced at the same plant, obtained by X-ray fluorescence and optical atomic emission spectrometry methods at the plant laboratory, were in the dataset. The Pt content was tested based on the mass balance. Measurement uncertainties of the test results are estimated summarizing data of validation reports of the measurement procedures for different elements/analytes. These test results are correlated because of the natural chemical origin of the raw materials used in the alloy production and mass balance constraints. Correlations between test results for two pairs of the components (Pt vs. Rh, and the three vs. the eight impurities) were strong. To assess the correlation effects on the total risk, the study was performed for two scenarios considering 1) correlated test results for all four components, and 2) practically uncorrelated test results for two components only - Rh and the eight impurities. A multiparameter Bayesian approach was applied for total risk evaluation, where the observed correlations are taken into account within the experimental correlation matrix. This matrix influenced all subsequent multivariate calculation results. It was shown that simplification of the testing by reducing the number of components under control leads to a significant increase of the probability of a false decision on conformity of an alloy batch randomly drawn from a statistical population of such batches. Core of the developed R code, used for the risk calculations, is presented
Specific risks of false decisions in conformity assessment of a substance or material with a mass balance constraint – A case study of potassium iodate
No full textA methodology for the Bayesian evaluation of total specific risks of false decisions on conformity of a substance or material due to measurement uncertainty was developed using Monte Carlo simulations, taking into account the mass balance constraint of the data. As a case study, the measurement results (measured values and associated measurement uncertainty) obtained for testing a potassium iodate batch, being considered as a candidate reference material of potassium iodate purity, were analyzed and discussed for different models of the prior probability density function and the likelihood function. Different scenarios of the risks related to determination of potassium iodate purity were studied, when the direct or indirect test method is applied, as well as when both are used simultaneously
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