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This glossary provides a formal vocabulary of terms for concepts in surface analysis and gives clear definitions to those who utilize surface chemical analysis or need to interpret surface chemical analysis results but are not themselves surface chemists or surface spectroscopists.

Recommendations are given concerning the terminology of methods used in electroanalytical chemistry. Fundamental terms in electrochemistry are reproduced from previous PAC Recommendations, and new and updated material is added for terms in electroanalytical chemistry, classification of electrode systems, and electroanalytical techniques.

A brief review of the estimation of measurement uncertainty is given in the context of the measurement of solubilities and related thermodynamic parameters. Evaluation of measurement data — guide to the expression of uncertainty in measurement (known as the GUM) is the definitive treatise which uses a ‘bottom-up’ approach. However grouping components of measurement uncertainty with repeated independent measurements is encouraged. Examples are given of the measurement of solubility of oxygen in nickel-iron alloys, the solubility of whitlockite and the solubility of cadmium carbonate in aqueous systems.

A user-friendly MS-Excel spreadsheet is developed for evaluation of global consumer's and producer's risks in conformity assessment of chemical composition of a multicomponent material or object, when up to four component concentrations are under control. These risks are probabilities of incorrect conformity decisions related to a material batch (lot or similar) randomly drawn from a statistical population of such batches. The probabilities characterize the material quality globally, allowing the prediction of false decisions on conformity of a future batch, based on the future measurement results. The spreadsheet program evaluates risks using Monte Carlo simulations. As input data, the following need to be provided to the software: parameters of normal or lognormal distribution of actual (‘true’) values of the component concentrations (prior distribution); parameters of the distribution of measurements results at the actual value of the component concentration (likelihood function); and correlation matrices for couples of the actual components' concentrations under control and also for corresponding measurement results. The spreadsheet is validated by comparison of the risk estimates with those calculated in R programing environment by numerical integration of the relevant analytical formulae. The developed Excel file and a demonstration videos of its use are available as electronic supplementary material.

Recommendations are given concerning the terminology of concepts and methods used in spectroscopy in analytical chemistry, covering nuclear magnetic resonance spectroscopy, atomic spectroscopy, and vibrational spectroscopy. © 2021 IUPAC and De Gruyter. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. For more information, please visit: http://creativecommons.org/licenses/by-nc-nd/4.0/ 2021.

Current paleontological techniques to separate vertebrate fossils from encasing iron-rich cements by chemical means are limited by the low solubility of common iron(III) hydroxide oxides such as hematite and goethite. This study examines novel geochemical extractions capable of selectively dissolving iron(III) hydroxide oxides, in aqueous solutions of pH 9-11, without damaging fossilised bones or teeth (hydroxidecarbonate-apatite). This involves the siderophore ligands pyridoxal isonicotinoyl hydrazone (PIH), salicylaldehyde isonicotinoyl hydrazone (SIH), and acetohydroxamic acid (aHA), whose coordination complexes with iron(III) show exceptionally high formation stability constants. The methods have been tested on natural hematite and fossil containing samples from the Riversleigh World Heritage Area in Australia. Both 0.01 mol dm-3 aHA and 0.001 mol dm-3 PIH at pH 9.7 were able to dissolve over 0.1 mmol dm-3 of the goethite coating bone fragments.

Total 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.

Oxygen solubility in a series of binary austenitic Fe-Ni alloys has been measured at temperatures of 1000–1150 °C, under oxygen partial pressures corresponding to the Fe/FeO equilibrium. Oxygen activities controlled in Rhines packs or by flowing CO/CO2 gas mixtures yielded the same results within measurement uncertainty, showing that carbon has no effect at the levels used. The oxygen solubility dependence on Fe-Ni alloy composition is non-ideal, being strongly destabilised by the addition of nickel. Wagner's classical solution model is shown to represent the results well.

A technique for evaluation of risks of false decisions in conformity assessment of the chemical composition of sausages was developed based on a multivariate Bayesian approach, taking into account measurement uncertainty, correlation and mass balance constraint of the regulated contents of the sausage components. As a case study, a dataset of test results of chemical compositions of the sausage “Braunschweigskaya” (measured contents of fat, protein, moisture and salt) was used for evaluations of the risks. A total global consumer's risk of 0.006 and a total global producer's risk of 0.017, characterizing the production process in general, were evaluated using Monte Carlo simulations. The difference in the risk values indicates a clear preference of the consumer's interests over the producer's interests. The total specific consumer's and producer's risks, related to a (specific) sausage batch, were evaluated using normal approximations in the Bayesian model. The risk values obtained were much more significant when measured contents approached their tolerance/specification limits or exceeded them. The codes, written in the R programming environment, for calculations of both the total global and the specific risks are provided as electronic supplementary material to this paper.

A 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.

The illegal drug 3,4-methylenedioxymethylamphetamine, also known as MDMA, ecstasy or ‘E’, synthesised as the hydrochloride and then made into tablets, has organic impurities arising from manufacture that can be used to profile seized material. Knowing if two samples come from the same batch gives strategic information about the drug manufacturing trade. We report similarity measures (Pearson correlation coefficient, reported as the modified Pearson distance, and its Fisher transform) between impurity content of pairs of samples manufactured using four common reductive amination routes. Powder and tablets are compared using the n th root of GC–MS peak normalised areas of 8 or 31 impurities, ( n = 2, 3, 4, 5, 10). Overall using 31 compounds with 4th root pre-treatment gave the best discrimination. PtO 2 /H 2 , and Al/Hg reductions were completely discriminated among batches while NaBH 4 and NaBH 3 CN routes gave around 4% false assignments. Synthesis parameters were systematically altered to determine what parameters have significant effects on the overall purity of the product and on the impurity profiles. The amount ratio of methylamine and MDP2P, and the temperature control of the reaction mixture were both significant. Comparison of modified Pearson's distances ( r scaled to ∈[0–100]), the Fisher transform of r , and ROC curves are simple ways of providing initial evidence whether seized drugs originate from the same batch.

The 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).

After specific rules establishing whether a molecule is a ‘structural modification’ of a drug molecule, the analogue drug provisions in the various Acts legislated by States and the Commonwealth of Australia rely on rules that determine if a putative drug is ‘structurally similar’ to a dangerous or controlled drug listed by the Act. In some legislation there is a provision for a suitable expert to assert that the two structures are similar. A survey of more than 200 research chemists at UNSW Australia, who are not usually involved in legal matters, asked them to state whether six pairs of molecules were structurally similar or not. There is some correlation with Tanimoto similarity, a measure of similarity often used in pharmaceutical drug discovery, but the use of such an objective measure is not advocated at this time. The concepts of addition of groups, and of replacement of ring structures are discussed in the light of cases and of chemical and general definitions. Regularising the law with chemical u...

IUPAC is very interested in data, big or small. Its web site opens with the statement, “The International Union of Pure and Applied Chemistry (IUPAC) is the world authority on … many other critically-evaluated data.” While the ‘…’ covers compelling and widely popular topics, such as naming new elements, the mission of IUPAC to give its imprimatur for chemical data is of great importance to health, security, and trade in the world. In this article, after a review of present activities, we will contemplate how a comprehensive approach might be structured under IUPAC project rules and then look to the future in a world of ‘big data’ and ‘smart instruments’.

When components of a substance or material are subject to a mass balance constraint, test results of the components’ contents are intrinsically correlated because of the constraint. This so-called ‘spurious’ correlation is observed in addition to possible metrologically-related correlation of test results, and natural and/or technological correlation of the components’ contents. Such correlations may influence understanding of test results and evaluation of risks of false decisions, due to measurement uncertainty, in conformity assessment of the substance or material. The objective of the present paper is the development of a technique for appropriate evaluation of the risks. A Bayesian multivariate approach to evaluate the conformance probability of materials or objects and relevant risks is discussed for different scenarios of the data modelling, taking into account all observed correlations. A Monte Carlo method, including the mass balance constraint, written in the R programming environment, is provided for the necessary calculations.

4-Substituted 2-(4-X-2,5-dimethoxyphenyl)-N-[(2-hydroxyphenyl)methyl] ethanamine (25X-NBOH, X = Cl, Br, or I) are new psychoactive substances (NPS). Identification of these NBOH analogues by gas chromatography-mass spectrometry is difficult because they are found in very low concentrations in the blotting paper in which they are sold, and because of the thermolabile nature of NBOH. In the ion source of a mass spectrometer they break down to the known NPS 2,5-dimethoxy-4-Xphenethylamine (2C-X) thereby giving no indication of the initial compound present. We identify 25XNBOH by heptafluorobutyric anhydride (HFBA) derivatization and subsequent mass spectrometric analysis. The major peak is the bis-derivative where both the amine and phenol are derivatized, with a minor peak of the mono-derivative in which only the amine is derivatized. There is a small amount of degradation of 25X-NBOH to the 2C-X amine which is then derivatized to the amide in-situ. Reaction with HFBA is an efficient and simple derivatization that works well with NBOH and NBOMe analogs and is recommended for routine forensic analysis.

The integration of plasmonic nanoparticles into biosensors has the potential to increase the sensitivity and dynamic range of detection, through the use of single nanoparticle assays. The analysis of the localized surface plasmon resonance (LSPR) of plasmonic nanoparticles has allowed the limit of detection of biosensors to move towards single molecules. However, due to complex equipment or slow analysis times, these technologies have not been implemented for point-of-care detection. Herein, we demonstrate an advancement in LSPR analysis by presenting a technique, which utilizes an inexpensive CMOS-equipped digital camera and a dark-field microscope, that can analyse the λmax of over several thousand gold nanospheres in less than a second, without the use of a spectrometer. This improves the throughput of single particle spectral analysis by enabling more nanoparticles to be probed and in a much shorter time. This technique has been demonstrated through the detection of interleukin-6 through a core-satellite binding assay. We anticipate that this technique will aid in the development of high-throughput, multiplexed and point-of-care single nanoparticle biosensors.

Pt is usually not considered as an efficient catalyst for water oxidation. Here, we report a design-of-experiment approach for modelling the roughness of an electrochemically roughened Pt electrode for water oxidation. The results indicate significant interaction between oxidation and reduction potentials on surface roughness and the porous Pt exhibits greatly improved catalytic activity for oxygen evolution in acid which is comparable to the benchmark catalyst RuO₂.

Gas chromatograms and E.I. mass spectra of the parent compounds and seven heptafluorobutyric anhydride derivatised, 4-substituted 2-(4-x-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamines (25X-NBOMe), (x = Br, Cl, Me, Et, I, NO2,SMe; X = B, C, D, E, I, N, T2), 2-(2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamine (25H-NBOMe) and six other analogues are reported. Derivatisation allows determination of the mass of the molecular ion, and observation of characteristic fragmentation patterns. All the NBOMe compounds studied showed a McLafferty rearrangement in the E.I. mass spectrum that is diagnostic of a hydrogen atom that is six atoms removed from a π-bonded hetero-atom. The ease of this protocol makes this an important tool for the routine analysis of appropriately-structured new psychoactive substances in crime laboratories.

A new design for a membrane-free gas sensor modified with a thin layer of ionic liquid is described. The new approach uses miniaturized interdigitated microelectrodes for detecting gases having reversible electrochemistry, for example, dioxygen. Analyte molecules are reduced on the first working electrode, creating an intermediate species (e.g., superoxide, O2•–, from dioxygen) that can be reoxidized back to the original molecule at the second working electrode. The loop of redox reactions enhances the measured current, leading to high sensitivity (3.29 ± 0.06 nA cm–2 ppm–1) and low detection limit (LOD = 174 ppm). The gas sensor design was demonstrated to monitor typical concentrations of oxygen with good accuracy and precision. The enhancement in the current is characteristic only of gas molecules with reversible electrochemistry, which indicates that the proposed gas sensor can analyze these molecules with greater sensitivity over those with irreversible electrochemistry.

Electrochemical DNA biosensors composed of a redox marker modified nucleic acid probe tethered to a solid electrode is a common experimental construct for detecting DNA and RNA targets, proteins, inorganic ions, and even small molecules. This class of biosensors generally relies on the binding-induced conformational changes in the distance of the redox marker relative to the electrode surface such that the charge transfer is altered. The conventional design is to attach the redox species to the distal end of a surface-bound nucleic acid strand. Here we show the impact of the position of the redox marker, whether on the distal or proximal end of the DNA monolayer, on the DNA interface electrochemistry. Somewhat unexpectedly, greater currents were obtained when the redox molecules were located on the distal end of the surface-bound DNA monolayer, notionally furthest away from the electrode, compared with currents when the redox species were located on the proximal end, close to the electrode. Our results suggest that a limitation in ion accessibility is the reason why smaller currents were obtained for the redox markers located at the bottom of the DNA monolayer. This understanding shows that to allow the quantification of the amount of redox labeled target DNA strand that hybridizes to probe DNA immobilized on the electrode surface, the redox species must be on the distal end of the surface-bound duplex.

In 2009, the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) introduced the interval notation to express the standard atomic weights of elements whose isotopic composition varies significantly in nature. However, it has become apparent that additional guidance would be helpful on how representative values should be derived from these intervals, and on how the associated uncertainty should be characterized and propagated to cognate quantities, such as relative molecular masses. The assignment of suitable probability distributions to the atomic weight intervals is consistent with the CIAAW’s goal of emphasizing the variability of the atomic weight values in nature. These distributions, however, are not intended to reflect the natural variability of the abundances of the different isotopes in the earth’s crust or in any other environment. Rather, they convey states of knowledge about the elemental composition of “normal” materials generally, or about specific classes of such materials. In the absence of detailed knowledge about the isotopic composition of a material, or when such details may safely be ignored, the probability distribution assigned to the standard atomic weight intervals may be taken as rectangular (or, uniform). This modeling choice is a reasonable and convenient default choice when a representative value of the atomic weight, and associated uncertainty, are needed in calculations involving atomic and relative molecular masses. When information about the provenance of the material, or other information about the isotopic composition needs to be taken into account, then this distribution may be non-uniform. We present several examples of how the probability distribution of an atomic weight or relative molecular mass may be characterized, and also how it may be used to evaluate the associated uncertainty.

This is an Open Access Article. It is published by International Union of Pure and Applied Chemistry (IUPAC) under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence (CC BY-NC-ND). Full details of this licence are available at: http://creativecommons.org/licenses/by-nc-nd/4.0/

Platinum electrodes have been electrochemically roughened (roughness factors up to 430) and evaluated for use as neural stimulation electrodes. The roughened electrodes show superior interfacial properties with increasing surface roughness. The roughened electrode (fR = 250) has a charge injection limit of 1.0 mC cm(-2) (400 μs pulse width), which is superior to that of titanium nitride (0.87 mC cm(-2)) but comparable to that of carbon nanotubes (1.0-1.6 mC cm(-2)). The surface roughness can also be optimized for different neural stimulation applications based on the available charge density at a particular pulse width of stimulation. The roughened platinum electrodes demonstrated good mechanical stability under harsh ultrasonication and electrochemical stability under continuous biphasic stimulation, indicating the potential of this biological interface to be safe and stable.

Chemical scientists’ experiences with LabTrove., Electronic Laboratory Notebooks (ELNs) are progressively replacing traditional paper books in both commercial research establishments and academic institutions. University researchers require specific features from ELNs, given the need to promote cross-institutional collaborative working, to enable the sharing of procedures and results, and to facilitate publication. The LabTrove ELN, which we use as our exemplar, was designed to be researcher-centric (i.e., not only aimed at the individual researcher's basic needs rather than to a specific institutional or subject or disciplinary agenda, but also able to be tailored because it is open source). LabTrove is being used in a heterogeneous set of academic laboratories, for a range of purposes, including analytical chemistry, X-ray studies, drug discovery and a biomaterials project. Researchers use the ELN for recording experiments, preserving data collected, and for project coordination. This perspective article describes the experiences of those researchers from several viewpoints, demonstrating how a web-based open source electronic notebook can meet the diverse needs of academic researchers.

Ionic liquids (IL) have been regarded as promising electrolytes as substitutes for volatile aqueous or organic solvents for electrochemical gas sensors. However, ILs are viscous, and the slow diffusion of gas molecules leads to poor sensitivity and sluggish response times. Herein, we describe a strategy using an array of microstrips of IL containing magnetic nanoparticles as nanostirrers for enhanced mass transport and gas sensing. Magnetic CoFe2O4 nanoparticles are synthesized and dispersed in a hydrophobic IL [BMP][Ntf2]. First, the convection effect of the IL dispersion was studied using the reversible redox couple ferrocene/ferrocenium ion. In a rotating magnetic field, steady-state currents for oxidation of dissolved ferrocene are three to five times greater than that in an unstirred solution. Then, the IL dispersion is micropatterned onto a gold electrode using microcontact printing. A self-assembled monolayer was printed onto a gold surface creating 70 μm wide hydrophobic lines with a 30 μm gap between them. Upon applying the IL dispersion into the gap, a 30 μm wide array of microstrips was successfully fabricated. The system is demonstrated as an oxygen sensor in the range of volume fraction of O2 of 50-500 ppm giving a linear calibration with a sensitivity of 1.94 nA cm-2 ppm-1.

Risks 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.

Ionic liquids are “designer-solvents” that are promising candidates for substituting conventional aqueous/organic solvents in gas sensors. This is due to their unique set of properties, such as high ionic conductivity, great chemical and thermal stability, and low vapour pressure. The latter property is important in order to fabricate a membrane-free gas sensor. Direct contact between the gas analytes and the electrolyte medium (solvent) is preferable in order to enhance the overall performance (response time and sensitivity) of the gas sensor. Recent surges in publications, reports, and books have suggested increasing research interests towards this class of “smart” solvents. This chapter summarises the recent developments in ionic liquids-based gas sensor designs, for example electrochemical, optical, and mass-based. The performance of each gas sensor design to detect specific gas analyte was compared in terms of their sensitivity, response time, and limit of detection.

The 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.

RATIONALE Mass spectrometric identification of compounds in chromatography can be obtained from molecular masses from soft ionization mass spectrometry techniques such as field ionization (FI) and fragmentation patterns from hard ionization techniques such as electron ionization (EI). Simultaneous detection by EI and FI mass spectrometry allows alignment of the different information from each method. METHODS We report the construction and characteristics of a combined instrument consisting of a gas chromatograph and two parallel mass spectrometry ionization sources, EI and FI. When considering both ion yield and signal-to-noise it was postulated that good-quality EI and FI mass spectra could be obtained simultaneously using a post-column splitter with a split fraction of 1:10 for EI/FI. This has been realised and we report its application for the analysis of several complex mixtures. RESULTS The differences between the full width at half maximum (FWHM) of the EI and FI chromatograms were statistically insignificant, and the retention times of the chromatograms were highly correlated (r2 =0.9999) with no detectable bias. The applicability and significance of this combined instrument and the attendant methodology are illustrated by the analysis of standard samples of 13 compounds with diverse structures, and the analysis of mixtures of fatty acids, fish oil, hydrocarbons and yeast metabolites. CONCLUSIONS This combined dual-source instrument saves time and resources, and more importantly generates equivalent chromatograms aligned in time, in EI and FI (i.e. peaks with similar shapes and identical positions). The identical FWHMs and retention times of the EI and FI chromatograms in this combined instrument enable the accurate assignment of fragment ions from EI to their corresponding molecular ions in FI. Copyright © 2014 John Wiley & Sons, Ltd.

When a measured value of a property of a material or object differs from the upper or lower specification limit (actual or ‘true’ value) by the expanded measurement uncertainty or more, there is the clear decision on the material conformity or nonconformity - ‘white’ or ‘black’. In the interval from the measured value to the specification limit, covered by the expanded measurement uncertainty (‘grey zone’), risks of false decisions on conformity increase. Several kinds of the risks, named ‘shades of grey’, should be taken into account. For a multicomponent material there are four kinds of particular risks for each property value of the material (e.g. component concentration or content), and four kinds of total risks related to the material as a whole. Therefore, for n > 1 properties under control for the material conformity assessment one can distinguish 4(n +1) kinds of risks of false decisions – shades of grey.

Horse racing authorities impose a limit on the concentration of plasma 'total carbon dioxide' (TCO2), typically 36 mM with action taken above 37 mM, as measured by an electrochemical gas analyzer. It is of interest to understand the distribution of TCO2 in a 'normal' population of racehorses and determine probabilities of members of this population exceeding these current regulatory and action limits. TCO2 levels in equine plasma samples have been modelled for 12 months (2011-2012) of thoroughbred (3076 measurements) and standardbred (3788 measurements) data in Australia. The two populations have a common seasonal pattern, while the non-seasonal distributions differ. A single Gaussian distribution about the seasonal pattern explains the thoroughbred data, but there is evidence for a second Gaussian component for the standardbred horses. A Gaussian mixture model for standardbred horses gave a main component that matched the thoroughbred distribution, which was centred about 30.2 mM, and a smaller (about 20 % of the total density) Gaussian centred at 32.3 mM. The existence of a second, higher-meaned population of standardbred horses points to increased use of alkalinizing salts among a minority of trainers, whom still, however, maintain mostly legal levels of TCO2. Identification of this group can be used to direct intelligence-based testing with a view to limiting use of these products. Probabilities of exceeding limits are affected by seasonality, but the current rules remain conservative.

We report a systematic study of the effects of types and positions of amino acid residues of tripeptides on the formation constants logβ, acid dissociation constants pKa, and the copper coordination modes of the copper(II) complexes with 27 tripeptides formed from the amino acids glutamic acid, glycine, and histidine. logβ values were calculated from pH titrations with l mmol L(-1):1 mmol L(-1) solutions of the metal and ligand and previously reported ligand pKa values. Generalized multiplicative analysis of variance (GEMANOVA) was used to model the logβ values of the saturated, most protonated, monoprotonated, logβ(CuL) - logβ(HL), and pKa of the amide group. The resulting model of the saturated copper species has a two-term model describing an interaction between the central and the C-terminal residues plus a smaller, main effect of the N-terminal residue. The model supports the conclusion that two copper coordination modes exist depending on the absence or presence of His at the central position, giving species in which copper is coordinated via two or three fused chelate rings, respectively. The GEMANOVA model for pKamide, which is the same as that for the saturated complex, showed that Gly-Gly-His has the lowest pKamide values among the 27 tripeptides. Visible spectroscopy indicated the formation of metal-ligand dimers for tripeptides His-His-Gly and His-His-Glu, but not for His-His-His, and the formation of multiple ligand bis compexes CuL2 and Cu(HL)2 for tripeptides (Glu/Gly)-His-(Glu/Gly) and His-(Glu/Gly)-(Glu/Gly), respectively.

Herein, we study the effect of interfacial design, specifically the orientation of a DNA probe strand, the length of the diluent and the type of target (DNA vs. microRNA), on the electrochemical response from methylene blue (MB) at low-density DNA films. The probe DNA interfaces are formed from mixed self-assembled monolayers of single-stranded DNA (ss-DNA) and a hydroxyl terminated alkanethiol diluents on gold surfaces. Variation in the current from the DNA–MB complex after hybridization with complementary and single adenine–cytosine mismatch DNA target is shown to depend on whether the 3′ or 5′ end is tethered to the electrode and the length of the diluent (6-mercapto-1-hexanol vs. 9-mercapto-1-nonanol). The sensors show better mismatch discrimination of single base pairs when both the duplexes are tethered from the 5′ end to the electrode and with a longer-chain (9-mercapto-1-nonanol) diluent. Of particular note is our demonstration that the DNA/microRNA duplex exhibits greater single adenine–cytosine mismatch discrimination when compared to the corresponding DNA/DNA duplex. This study contributes to the development of selective DNA and microRNA biosensors.

We report pK(a) values with measurement uncertainties for all labile protons of the 27 tri-peptides prepared from the amino acids glutamic acid (E), glycine (G) and histidine (H). Each tri-peptide (GGG, GGE, GGH, …, HHH) was subjected to alkali titration and pK(a) values were calculated from triplicate potentiometric titrations data using HyperQuad 2008 software. A generalized multiplicative analysis of variance (GEMANOVA) of pK(a) values for the most acidic proton gave the optimum model having two terms, an interaction between the end amino acids plus an isolated main effect of the central amino acid.

Data analysis is central to understanding phenomena in host–guest chemistry. We describe here recent developments in this field starting with the revelation that the popular Job plot method is inappropriate for most problems in host–guest chemistry and that the focus should instead be on systematically fitting data and testing all reasonable binding models. We then discuss approaches for estimating uncertainties in binding studies using case studies and simulations to highlight key issues. Related to this is the need for ready access to data and transparency in the methodology or software used, and we demonstrate an example a webportal (supramolecular.org) that aims to address this issue. We conclude with a list of best-practice protocols for data analysis in supramolecular chemistry that could easily be translated to other related problems in chemistry including measuring rate constants or drug IC50 values.

Risk of a false decision on conformity of a multicomponent material or object due to measurement uncertainty is discussed. Even if conformity assessment for each component of a material sample is successful, the total probability of a false decision (total consumer's risk or producer's risk) concerning the sample as a whole might still be significant. A model of the total probability of such false decisions is formulated based on the law (theorem) of total probability. It is shown that the total risk can be evaluated as a combination of the particular risks of conformity assessment of sample components. For a more complicated task, i.e. for a larger number of components of a sample under control, the total risk is greater. As a case study, the total probability of false conforming (total consumer's risk) is evaluated for customs control of completely denatured alcohols, where conformity assessment is performed by comparison of chemical analytical test results with the regulatory limits.

An accurate method for the measurement of carbon isotope ratios of steroids in human urine has been developed at the National Measurement Institute, Australia (NMIA) for the certification of a freeze-dried human urine reference material (CRM NMIA MX005). The method measures δ13C values by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis following hydrolysis, solvent extraction and high performance liquid chromatography (HPLC) purification. Reference δ13C values for testosterone metabolites etiocholanolone, androsterone, and endogenous reference compounds (ERCs) 11β-hydroxyandrosterone and pregnanediol were determined, as well as information δ13C values for testosterone, epitestosterone, 11-oxoetiocholanolone, and a range of differences (Δ13C) between testosterone metabolites and ERCs. The measurement uncertainty was rigorously evaluated with expanded uncertainties for the reference δ13C values between 1.1 and 1.6 ‰ at the 95% coverage level. Copyright © 2012 John Wiley & Sons, Ltd.