Confirmation of ethanol administration in racing greyhounds by LC-MS-MS.

Ethanol is a prohibited substance in professional animal racing as its administration causes physiological effects such as depression of the central nervous system. Regulation of potential doping agents, including those that inhibit performance, is critical to ensure integrity and animal welfare in greyhound racing, but the detection of ethanol is complicated by dietary and/or environmental exposure. In response, a reliable analytical method capable of detecting recent ethanol administration in greyhound urine samples was validated and implemented. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) was used to investigate the variation in urinary ethanol metabolites; ethyl-ß-D glucuronide (EG; γ ¯ EG $$ {\overline{\gamma}}_{\mathrm{EG}} $$ = 1.0 µg/ml, s EG $$ {s}_{\mathrm{EG}} $$ = 3.3 µg/ml) and ethyl sulfate (ES; γ ¯ ES $$ {\overline{\gamma}}_{\mathrm{ES}} $$ = 0.9 µg/ml, s ES $$ {s}_{\mathrm{ES}} $$ = 1.9 µg/ml) levels from a reference population of 202 racing greyhounds. These were compared to urine samples collected following administration of ethanol to one male and one female greyhound. Results were used to establish a threshold within the national rules of greyhound racing: γ ¯ EG $$ {\overline{\gamma}}_{\mathrm{EG}} $$ and γ ¯ ES $$ {\overline{\gamma}}_{\mathrm{ES}} $$ > 20 µg/ml in urine are defensible criteria to confirm ethanol administration to greyhounds. Case studies of competition samples are provided to demonstrate the forensic translation of this work.

Chemical data evaluation: general considerations and approaches for IUPAC projects and the chemistry community (IUPAC Technical Report).

The International Union of Pure and Applied Chemistry (IUPAC) has a long tradition of supporting the compilation of chemical data and their evaluation through direct projects, nomenclature and terminology work, and partnerships with international scientific bodies, government agencies and other organizations. The IUPAC Interdivisional Subcommittee on Critical Evaluation of Data (ISCED) has been established to provide guidance on issues related to the evaluation of chemical data. In this first report we define the general principles of the evaluation of scientific data and describe best practices and approaches to data evaluation in chemistry.

Machine Learning Color Feature Analysis of a High Throughput Nanoparticle Conjugate Sensing Assay.

Plasmonic nanoparticles are finding applications within the single molecule sensing field in a "dimer" format, where interaction of the target with hairpin DNA causes a decrease in the interparticle distance, leading to a localized surface plasmon resonance shift. While this shift may be detected using spectroscopy, achieving statistical relevance requires the measurement of thousands of nanoparticle dimers and the timescales required for spectroscopic analysis are incompatible with point-of-care devices. However, using dark-field imaging of the dimer structures, simultaneous digital analysis of the plasmonic resonance shift after target interaction of thousands of dimer structures may be achieved in minutes. The main challenge of this digital analysis on the single-molecule scale was the occurrence of false signals caused by non-specifically bound clusters of nanoparticles. This effect may be reduced by digitally separating dimers from other nanoconjugate types. Variation in image intensity was observed to have a discernible impact on the color analysis of the nanoconjugate constructs and thus the accuracy of the digital separation. Color spaces wherein intensity may be uncoupled from the color information (hue, saturation, and value (HSV) and luminance, a* vector, and b* vector (LAB) were contrasted to a color space which cannot uncouple intensity (RGB) to train a classifier algorithm. Each classifier algorithm was validated to determine which color space produced the most accurate digital separation of the nanoconjugate types. The LAB-based learning classifier demonstrated the highest accuracy for digitally separating nanoparticles. Using this classifier, nanoparticle conjugates were monitored for their plasmonic color shift after interaction with a synthetic RNA target, resulting in a platform with a highly accurate yes/no response with a true positive rate of 88% and a true negative rate of 100%. The sensor response of tested single stranded RNA (ssRNA) samples was well above control responses for target concentrations in the range of 10 aM-1 pM.

Interlaboratory comparison of the intensity of drinking water odor and taste by two-way ordinal analysis of variation without replication.

A case study of ordinal data from human organoleptic examination (sensory analysis) of drinking water obtained in an interlaboratory comparison of 49 ecological laboratories is described. The recently developed two-way ordinal analysis of variation (ORDANOVA) is applied for the first time for the treatment of responses on the intensity of chlorine and sulfurous odor of water at 20 and 60 °C, which is classified into the six categories from 'imperceptible' to 'very strong'. The one-way ORDANOVA is used for the analysis of the 'salty taste' intensity of the water. A decomposition of the total variation of the ordinal data and simulation of the multinomial distribution of the data-relative frequencies in different categories allowed the determination of the statistical significance of the difference between laboratories in classifying chlorine or sulfurous odor intensity by categories, while the effect of temperature was not significant. No statistical difference was found between laboratories on salty taste intensity. The capabilities of experts to identify different categories of the intensity of the odor and taste are also evaluated. A comparison of the results obtained with ORDANOVA and ANOVA showed that ORDANOVA is a more useful and reliable tool for understanding categorical data such as the intensity of drinking water odor and taste.

Siderophore-Assisted Dissolution of Iron(III) Hydroxide Oxides from Iron-Rich Fossil Matrices.

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 of a false decision on conformity of an alloy due to measurement uncertainty and correlation of test results.

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.

Risk of a false decision on conformity of an environmental compartment due to measurement uncertainty of concentrations of two or more pollutants.

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.

Redox Recycling Amplification Using an Interdigitated Microelectrode Array for Ionic Liquid-Based Oxygen Sensors.

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.

Dual Signaling DNA Electrochemistry: An Approach To Understand DNA Interfaces.

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.

Ionic Liquid Microstrips Impregnated with Magnetic Nanostirrers for Sensitive Gas Sensors.

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.

Risk of false decision on conformity of a multicomponent material when test results of the components' content are correlated.

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.

Modelling an electrochemically roughened porous platinum electrode for water oxidation.

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.

Nucleic-acid recognition interfaces: how the greater ability of RNA duplexes to bend towards the surface influences electrochemical sensor performance.

The influence of RNA versus DNA on the performance of electrochemical biosensors where redox-labelled nucleic acid duplexes bend towards the electrode surface has been assessed. Faster electron transfer was observed for duplexes containing RNA, suggesting duplexes with RNA are more flexible. These data are of particular importance for microRNA biosensors.

Investigating the interfacial properties of electrochemically roughened platinum electrodes for neural stimulation.

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.

Experiences with a researcher-centric ELN.

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.

Gas chromatography with parallel hard and soft ionization mass spectrometry.

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 (r(2) =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.

Factors influencing total carbon dioxide concentrations in plasma of thoroughbred and standardbred racehorses.

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.

Formation constants of copper(II) complexes with tripeptides containing Glu, Gly, and His: potentiometric measurements and modeling by generalized multiplicative analysis of variance.

We report a systematic study of the effects of types and positions of amino acid residues of tripeptides on the formation constants logß, 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. logß 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 logß values of the saturated, most protonated, monoprotonated, logß(CuL) - logß(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.

Measurement of stable isotope ratios in methylamphetamine: a link to its precursor source.

The illicit drug methylamphetamine is often prepared from the precursor ephedrine or pseudoephedrine, which in turn are obtained by three processes: extraction from the Ephedra plant ("natural"), via fermentation of sugars ("semi-synthetic"), and by a "fully synthetic" route from propiophenone. We report the first method to differentiate between the three industrial routes used to produce the precursors ephedrine and pseudoephedrine by measurement of stable isotope ratios of nitrogen (δ(15)N), hydrogen (δ(2)H), and carbon (δ(13)C). Analysis of 782 samples of seized methylamphetamine allowed classification into three groups using k-means clustering or the expectation-maximization algorithm applied to a Gaussian mixture model. By preparation of 30 samples of ephedrine by the "fully synthetic" industrial process and measuring their δ(15)N, δ(2)H, and δ(13)C values, we observed that (15)N becomes significantly depleted compared to the methylamine starting material. Conversion of ten ephedrine samples to methylamphetamine showed that this depletion is maintained in the final drug product, of which the δ(15)N, δ(13)C, and δ(2)H values were distinct from those of ephedrine and methylamphetamine samples of a semi-synthetic (fermentation pathway) origin. Combining modeling analysis with the new experiments and published information on the values of δ(2)H gave a definitive assignment of the three model groups, and equations to obtain probabilities for the precursor origin of any new sample. A simple rule of thumb is also presented. Making an assignment using delta values is particularly useful when no other chemical profiling information is available.