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The determination of inorganic anions in uranium ore concentrates (UOCs) is useful to nuclear forensics for establishing the provenance of sample materials. In this collaborative study, quantitation of inorganic anions was carried out on three UOC reference materials from the National Research Council Canada: UCLO-1 (https://doi.org/10.4224/crm.2020.uclo-1), UCHI-1 (https://doi.org/10.4224/crm.2020.uchi-1), and UPER-1 (https://doi.org/10.4224/crm.2020.uper-1). The analytes were extracted into water and characterized by ion chromatography with combined standard uncertainties (uc) between 1.6 and 11%. The highest contributor to uc was homogeneity. Sulfate was the most abundant anion (2000–12,000 mg/kg SO42−). Other anions were in the 15–500 mg/kg range.

Stable hydrogen, carbon, nitrogen, oxygen and sulfur (HCNOS) isotope compositions expressed as isotope-delta values are typically reported relative to international standards such as Vienna Standard Mean Ocean Water (VSMOW), Vienna Peedee belemnite (VPDB) or Vienna Cañon Diablo Troilite (VCDT). These international standards are chosen by convention and the calibration methods used to realise them in practice undergo occasional changes. To ensure longevity and reusability of published data, a comprehensive description of (1) analytical procedure, (2) traceability, (3) data processing, and (4) uncertainty evaluation is required. Following earlier International Union of Pure and Applied Chemistry documents on terminology and notations, this paper proposes minimum requirements for publishing HCNOS stable-isotope delta results. Each of the requirements are presented with illustrative examples.

Stable carbon isotope ratio measurements are used to investigate the provenance of vanillin. In this study, a variety of commercial vanillin samples and vanilla products were analyzed to provide a frame of reference for the variability of carbon isotope delta values in various vanillin samples, with the results ranging from −20.6 to −36.7‰ relative to the Vienna Peedee Belemnite (VPDB). We present information on the development of two synthetic vanillin reference materials, VANA-1 and VANB-1, prepared in 0.75 g units in glass vials, to be used for the calibration of carbon isotope delta measurements of vanillin and other easily combustible organic materials. Characterization of 40 vials each of VANA-1 and VANB-1 was performed by three laboratories over several measurement sequences. The certified carbon isotope delta values are −31.30 ± 0.06‰ (VANA-1) and −25.85 ± 0.05‰ (VANB-1). These uncertainties, for the 95% confidence level, include considerations for measurement uncertainty, coherence of the reference materials used for calibration, batch homogeneity, and stability during storage and transportation. The results are traceable to the VPDB through a set of nine reference materials (IAEA-CH-6, USGS65, IAEA-600, NBS22, USGS61, IAEA-603, IAEA-610, IAEA-611, and IAEA-612). For up to date certified values, users should refer to doi.org/10.4224/crm.2022.vana-1 and doi.org/10.4224/crm.2022.vanb-1.

Trace impurity patterns are important nuclear forensic signatures in uranium ore concentrates (UOCs) and Certified Reference Materials (CRMs) are used to validate the analysis methods employed by end users. Herein, we discuss the certification campaign for three new UOC CRMs from the National Research Council Canada: UCLO-1 (https://doi.org/10.4224/crm.2020.uclo-1), UCHI-1 (https://doi.org/10.4224/crm.2020.uchi-1), and UPER-1 (https://doi.org/10.4224/crm.2020.uper-1). This study involved 15 laboratories from 10 countries, using sector-field and (triple) quadrupole inductively-coupled plasma mass spectrometry to analyze 64 trace element impurities. We discuss the importance of the acids used for sample digestion, difficulties analyzing in a high uranium matrix, and data combination and uncertainty evaluation for this large dataset.

Ciguatoxins (CTXs) and gambierones are ladder-shaped polyethers associated with ciguatera poisoning and Gambierdiscus spp. Several of these compounds contain carbonyl or hemiketal groups, which have the potential to exchange with (18)O-labeled water under acidic conditions. The effects of solvent composition and acid on the rate of exchange and on the stability of the labels at various pH values were assessed to optimize the incorporation of (18)O into Caribbean ciguatoxin-1 and -2 (C-CTX1/2), gambierone, and 44-methylgambierone. LC–HRMS results showed that (18)O-labeling occurred at the hydroxy group of the hemiketal at C-56 in C-CTX1/2, and at the hydroxy group of the hemiketal at C-4 and the ketone at C-40 in gambierones. Labeling occurred very rapidly (complete in

Main text The CCQM Isotope Ratio Working Group (IRWG) determined that an additional key comparison of carbon isotope delta measurements was required to capture the progress of this field. Vials containing 0.25 mg of vanillin were prepared at NRC, and evaluated for bottle-to-bottle homogeneity prior to distribution to the eight participating institutes. Participants were able to choose any suitable method and reference materials for carbon isotope delta measurements, and report a carbon isotope delta value and the associated uncertainty, and analysis details. To determine the key comparison reference value (KCRV) and its associated uncertainty, the NRC in collaboration with the NIST, developed a multivariate Bayesian random laboratory effects model, which also incorporates the uncertainty due to bottle-to-bottle homogeneity and any correlations between the reported results that arise due to the use of common reference materials. The KCRV for this study was determined to be -25.833 ‰ relative to the VPDB, with associated uncertainty of 0.028 ‰, and expanded uncertainty of 0.056 ‰ (k=2). All the results reported by the participants in this study were considered equivalent to the KCRV. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

In this study, data from thirteen laboratories from around the world are presented for a successful certification of uranium isotope ratios in uranium ore concentrate (UOC) certified reference materials from the National Research Council Canada. Different mass spectrometric measurement principles (including SF-ICP-MS, quadruple ICP-MS, TIMS, MC-ICP-MS, SIMS and AMS) and measurement procedures were employed. In general, data from all sources exhibit good consistency with TIMS and MC-ICP-MS showing superior performance. The three candidate UOC CRMs (UCLO-1, UCHI-1 and UPER-1) have natural uranium isotope ratios with certified values of 0.5304(7) × 10⁻⁴, 0.5475(2) × 10⁻⁴ and 0.5361(4) × 10⁻⁴ for n(²³⁴U)/n(²³⁸U) and 0.007 2563(13), 0.007 2563(10) and 0.007 2542(11) for n(²³⁵U)/n(²³⁸U), respectively, with expanded uncertainty (k = 2) applicable to the last digit of the value given in the parentheses. Information values for n(²³⁶U)/n(²³⁸U) in these three CRMs, measured by AMS, are also provided: 10 × 10⁻¹², 200 × 10⁻¹² and 22 × 10⁻¹². The uncertainties of the proposed certified values of uranium isotope ratios in UOC CRMs are superior to available reference materials, and the values of n(²³⁴U)/n(²³⁸U) and n(²³⁶U)/n(²³⁸U) show significant variation among the three CRMs.

In this study we demonstrate that the method of standard additions can provide unreliable results in chemical analysis when the linear calibration model is forced to fit the data. A well designed standard addition experiment can still yield results biased by 10% when the analyst relies only on the linear model. Recently, the Joint Committee for Guides in Metrology (GUM-6) has emphasized the need to address the uncertainty inherent to the choice of measurement models and here we show how model averaging can provide a practical way to account for model uncertainty in the method of standard additions.

By convention, carbon isotope ratios are expressed relative to VPDB defined by the calcite standard NBS19 in the 1980s. [See T. Coplen, Pure Appl. Chem. 1994, 66, 273–276.] To improve the realization of the VPDB scale, a second fixed point (lithium carbonate, LSVEC) was introduced in 2006 [T. Coplen et al. Anal. Chem. 2006, 78, 2439–2441], which is now known to be isotopically unstable. [Assonov, S. Rapid Commun. Mass Spectrom., 2018, 32, 827–830.] With the high-quality reference materials made available in 2020, it is now possible to realize the VPDB scale with high confidence. [Assonov, S. et al. Rapid Commun. Mass Spectrom., 2020, 34, e8867; Assonov, S. Rapid Commun. Mass Spectrom. 2021, 35, e9014; Qi, H. et al. Rapid Commun. Mass Spectrosc. 2021, 35, e9006.] Here, we report the analysis of 25 reference materials using isotope ratio combustion mass spectrometry, show the discontinuity between the values measured against the new IAEA reference materials and the values currently assigned to these reference materials on the VPDB2006, and provide a link bringing these materials onto the new VPDB2020.

Following the reviews of atomic-weight determinations and other cognate data in 2015, 2017, 2019 and 2021, the IUPAC (International Union of Pure and Applied Chemistry) Commission on Isotopic Abundances and Atomic Weights (CIAAW) reports changes of standard atomic weights. The symbol A r°(E) was selected for standard atomic weight of an element to distinguish it from the atomic weight of an element E in a specific substance P, designated A r(E, P). The CIAAW has changed the values of the standard atomic weights of five elements based on recent determinations of terrestrial isotopic abundances: Ar (argon): from 39.948 ± 0.001 to [39.792, 39.963] Hf (hafnium): from 178.49 ± 0.02 to 178.486 ± 0.006 Ir (iridium): from 192.217 ± 0.003 to 192.217 ± 0.002 Pb (lead): from 207.2 ± 0.1 to [206.14, 207.94] Yb (ytterbium): from 173.054 ± 0.005 to 173.045 ± 0.010 The standard atomic weight of argon and lead have changed to an interval to reflect that the natural variation in isotopic composition exceeds the measurement uncertainty of A r(Ar) and A r(Pb) in a specific substance. The standard atomic weights and/or the uncertainties of fourteen elements have been changed based on the Atomic Mass Evaluations 2016 and 2020 accomplished under the auspices of the International Union of Pure and Applied Physics (IUPAP). A r° of Ho, Tb, Tm and Y were changed in 2017 and again updated in 2021: Al (aluminium), 2017: from 26.981 5385 ± 0.000 0007 to 26.981 5384 ± 0.000 0003 Au (gold), 2017: from 196.966 569 ± 0.000 005 to 196.966 570 ± 0.000 004 Co (cobalt), 2017: from 58.933 194 ± 0.000 004 to 58.933 194 ± 0.000 003 F (fluorine), 2021: from 18.998 403 163 ± 0.000 000 006 to 18.998 403 162 ± 0.000 000 005 (Ho (holmium), 2017: from 164.930 33 ± 0.000 02 to 164.930 328 ± 0.000 007) Ho (holmium), 2021: from 164.930 328 ± 0.000 007 to 164.930 329 ± 0.000 005 Mn (manganese), 2017: from 54.938 044 ± 0.000 003 to 54.938 043 ± 0.000 002 Nb (niobium), 2017: from 92.906 37 ± 0.000 02 to 92.906 37 ± 0.000 01 Pa (protactinium), 2017: from 231.035 88 ± 0.000 02 to 231.035 88 ± 0.000 01 Pr (praseodymium), 2017: from 140.907 66 ± 0.000 02 to 140.907 66 ± 0.000 01 Rh (rhodium), 2017: from 102.905 50 ± 0.000 02 to 102.905 49 ± 0.000 02 Sc (scandium), 2021: from 44.955 908 ± 0.000 005 to 44.955 907 ± 0.000 004 (Tb (terbium), 2017: from 158.925 35 ± 0.000 02 to 158.925 354 ± 0.000 008) Tb (terbium), 2021: from 158.925 354 ± 0.000 008 to 158.925 354 ± 0.000 007 (Tm (thulium), 2017: from 168.934 22 ± 0.000 02 to 168.934 218 ± 0.000 006) Tm (thulium), 2021: from 168.934 218 ± 0.000 006 to 168.934 219 ± 0.000 005 (Y (yttrium), 2017: from 88.905 84 ± 0.000 02 to 88.905 84 ± 0.000 01) Y (yttrium), 2021: from 88.905 84 ± 0.000 01 to 88.905 838 ± 0.000 002

Many calculations for science or trade require the evaluation and propagation of measurement uncertainty. Although relative atomic masses (standard atomic weights) of elements in normal terrestrial materials and chemicals are widely used in science, the uncertainties associated with these values are not well understood. In this technical report, guidelines for the use of standard atomic weights are given. This use involves the derivation of a value and a standard uncertainty from a standard atomic weight, which is explained in accordance with the requirements of the Guide to the Expression of Uncertainty in Measurement. Both the use of standard atomic weights with the law of propagation of uncertainty and the Monte Carlo method are described. Furthermore, methods are provided for calculating uncertainties of relative molecular masses of substances and their mixtures. Methods are also outlined to compute material-specific atomic weights whose associated uncertainty may be smaller than the uncertainty associated with the standard atomic weights.

Measurements of zirconium isotopes provide insights into the formation of planetary bodies, dating nuclear explosions, or maintenance of nuclear reactors. Although many comparative measurements for the isotopic composition of zirconium have been performed using mass spectrometry, there is a lack of zirconium isotopic reference materials and only a single calibrated measurement has been reported to date by total evaporation thermal ionization mass spectrometry (TE-TIMS). In this study, we report an independent measurement of full zirconium isotopic composition in a new zirconium isotopic reference material by multicollector inductively coupled plasma MS using the regression method and two independent certified isotopic reference materials, NIST SRM 984 Rb and NIST SRM 987 Sr. Our results agree well with the recent TE-TIMS measurements and suggest a revision of the standard atomic weight of zirconium.

This study was undertaken to quantitatively explore the effect of temperature on the degradation of cannabinoids in dried cannabis flower. A total of 14 cannabinoids were monitored using liquid chromatography and tandem mass spectrometry in temperature environments from − 20 to + 40 °C lasting up to 1 year. We find that a network of first-order degradation reactions is well-suited to model the observed changes for all cannabinoids. While most studies focus on high-temperature effects on the cannabinoids, this study provides high-precision quantitative assessment of room temperature kinetics with applications to shelf-life predictions and age estimates of cannabis products., Part of ABCs 20th Anniversary Topical Collection

Challenges frequently faced during the analysis of selenomethionine in complex matrices such as food and environmental samples include the lack of SI-traceable primary standards as well as difficulties associated with complex sample preparation methods resulting in potentially biased measurement results. In an effort to overcome these challenges, the National Research Council Canada has prepared two selenomethionine reference materials: a high-purity powder of natural isotopic abundance (SENS-1), and a solution of selenium-82 labelled selenomethionine (SEES-1). The purity of SENS-1, 0.961 ± 0.007 g g−1 (k = 2), was established through quantitative nuclear magnetic resonance spectroscopy combined with data from inductively-coupled plasma mass spectrometry for total selenium content and the HPLC analysis of selenium-containing impurities. With the chemical purity of SENS-1 established, it was then used as the primary standard for reverse isotope dilution analysis, where the concentration of selenomethionine in SEES-1 was determined to be 1556 ± 60 μg g−1 (k = 2).

Main text This pilot study was conducted in parallel to the key comparison CCQM-K167. Vials containing 0.25 mg of vanillin were prepared at NRC and distributed to four participating institutes. Institutes could choose any suitable reference materials and methodology to perform carbon isotope delta measurements. Participants reported analysis details, and a carbon isotope delta value and associated uncertainty for the vanillin sample. Each of the carbon isotope delta results of vanillin were compared to the KCRV established from CCQM-K167, and metrological compatibility to the KCRV was determined. Three expert laboratories participated in this study, and their reported results serve as a benchmark to compare the performance of all other participants to these world-class institutes. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM.

VITA-1 and VITB-1 are low- and elevated level CRMs, respectively, which were certified for minerals and vitamin contents by National Research Council Canada. The proportions of key ingredients are the same in each formula, and they were prepared in such a way that VITB-1 has twice the amount of minerals and vitamins as VITA-1. The availability of these two matrix-matched CRMs, with different concentrations for all analytes, will not only assist in the validation of procedures and the development of methods for the determination of respective analytes in multivitamins or samples of a similar matrices, but also will be useful for calibration purposes (for the values that are certified). Tablets were individually packaged in trilaminate foil pouches and values presented in the certificate of analysis are expressed on a “as is” basis, with no need for the determination of moisture content on a separate test portion. In addition, certified/reference values are provided per single tablet (mass fraction expressed as both mg/kg and µg/tablet), eliminating the need of a homogenization step prior to analysis. Homogeneity and stability were assessed and included in the final expanded uncertainties of the certified values. Quantity value assignment for both VITA-1 and VITB-1 was based on the use of at least two independent methods, using data generated at NRC and data from external collaborators for confirmation purposes. As a result of this campaign, value assignment was possible for a total of 39 analytes: 24 trace elements and 15 vitamins.

In 2019, the world celebrated the International Year of the Periodic Table of Chemical Elements (IYPT2019) and the IUPAC centenary. This happy coincidence offered a unique opportunity to reflect on the value and work that is carried out by IUPAC in a range of activities, including chemistry awareness, appreciation, and education. Although IUPAC curates the Periodic Table and oversees regular additions and changes, this icon of science belongs to the world. With this in mind, we wanted to create an opportunity for students and the general public to participate in this global celebration. The objective was to create an online global competition centered on the Periodic Table and IUPAC to raise awareness of the importance of chemistry in our daily lives, the richness of the chemical elements, and the key role of IUPAC in promoting chemistry worldwide. The Periodic Table Challenge was the result of this effort.

Particle size measurements of cellulose nanocrystals (CNCs) are challenging due to their broad size distribution, irregular shape and propensity to agglomerate. Particle size is one of the key parameters that must be measured for quality control purposes and to differentiate materials with different properties. We report the results of an interlaboratory comparison (ILC) which examined atomic force microscopy (AFM) data acquisition and data analysis protocols. Samples of CNCs deposited on poly-L-lysine coated mica were prepared in the pilot laboratory and sent to 10 participating laboratories including academic, government and industrial organizations with varying levels of experience with imaging CNCs. The participant data sets indicated that the central location, width and asymmetry varied considerably for both length and height distributions. To deal with this variability we used a skew normal distribution to model the data from each laboratory and to obtain the consensus distribution that describes the CNC particle size. The skew normal distribution has 3 parameters: a central location (mean), distribution width (standard deviation) and asymmetry (shape) factor. This approach gave consensus distributions with mean, standard deviation and asymmetry factor of 94.9 nm, 37.3 nm and 6.0 for length and 3.4 nm, 1.2 nm and 2.8 for height, respectively. The use of multiple probes and/or deterioration of the probe with increased use are significant contributing factors to the variability in mean length between laboratories. There is less variability in height across participating laboratories and tests of applied imaging force indicate that it is possible to image without significant compression of the CNCs. The number of CNCs necessary to obtain a reliable data set depends on the probes and operating conditions, but with careful control of various parameters analysis of 250 and 300 CNCs should provide consistent data sets for height and length, respectively for one sample. Comparison of AFM with transmission electron microscopy (TEM) data obtained in the same ILC demonstrated excellent agreement between measured lengths for the 2 methods. By contrast AFM height was approximately one half the TEM width, a result that indicates the presence of a significant number of laterally agglomerated particles, consistent with literature data.

The processes of planetary accretion or formation of the Earth and other celestial objects can be studied by using the ¹⁸²Hf-¹⁸²W chronometer which requires precise measurements of tungsten isotope ratios. Many comparative measurements for the isotopic composition of tungsten have been performed using either thermal ionization mass spectrometry (TIMS) or multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Yet, calibrated measurements of tungsten isotope ratios, and, in turn, isotopic abundances and atomic weight, are still lacking. In this study, we report the first independent measurements of all tungsten isotope ratios in five commercial tungsten reagents, including the new NRC candidate isotopic reference material WOLF-1 by MC-ICP-MS with use of the-state-of-the-art optimized regression mass bias correction model and NIST SRM 989 isotopic rhenium as calibrator.

Background: Among the regulated mycotoxins that contaminate global food supplies, ochratoxin A is particularly harmful as a nephrotoxin and suspected carcinogen. Objective: To support global measurement comparability, certified calibration solutions for ochratoxin A and [13C6]-ochratoxin A (OTAN-1 and OTAL-1, respectively) as well as a mycotoxin-contaminated rye flour certified reference material (CRM) known as MYCO-1 were developed. Methods: Quantitative proton NMR was used along with maleic acid as an external standard traceable to the Système international (SI) to measure the concentration of ochratoxin A and [13C6]-ochratoxin A for the calibration solutions. OTAN-1 and OTAL-1 were then used as a pair in double isotope dilution MS to certify the mass fraction of ochratoxin A in MYCO-1. The natural ochratoxin A CRM served as the primary standard for traceable quantitation, while the synthetic [13C6]-ochratoxin A CRM served as the internal standard. Results: The certified mass fraction of ochratoxin A or [13C6]-ochratoxin A in the two mycotoxin calibration solution standards was established to be 11.03 ± 0.32 µg/g (k = 2) for OTAN-1 and 4.89 ± 0.18 µg/g (k = 2) for OTAL-1. The mass fraction of ochratoxin A in the rye flour standard MYCO-1 was certified at 4.05 ± 0.88 µg/kg (k = 2). Conclusions: These CRMs will support regulatory testing as they can be used in the method development, validation, calibration, and QC analysis of ochratoxin A. Highlights: This report highlights the methods used to certify OTAN-1, OTAL-1, and MYCO-1 as well as the challenges associated with producing such materials, which can be applied to a wide variety of other CRMs.

We would like to invite you to participate in the Analytical Challenge, a series of puzzles to entertain and challenge our readers. This special feature of “Analytical and Bioanalytical Chemistry” has established itself as a truly unique quiz series, with a new scientific puzzle published every three months. Readers can access the complete collection of published problems with their solutions on the ABC homepage at http:// www.springer.com/abc. Test your knowledge and tease your wits in diverse areas of analytical and bioanalytical chemistry by viewing this collection. In the present challenge, isotope deltas is the topic. And please note that there is a prize to be won (a Springer book of your choice up to a value of €100).

The periodic table of elements should be celebrated not only for the order it brings, but also for the fascinating stories underlying this icon of science, suggests Juris Meija.

A model for errors-in-variables regression is described that can be used to overcome the challenge posed by mutually inconsistent calibration data. The model and its implementation are illustrated in applications to the measurement of the amount fraction of oxygen in nitrogen from key comparison CCQM-K53, and of carbon isotope delta values in steroids from human urine. These two examples clearly demonstrate that inconsistencies in measurement results can be addressed similarly to how laboratory effects are often invoked to deal with mutually inconsistent results from interlaboratory studies involving scalar measurands. Bayesian versions of errors-in-variables regression, fitted via Markov Chain Monte Carlo sampling, are employed, which yield estimates of the key comparison reference function in one example, and of the analysis function in the other. The fitting procedures also characterize the uncertainty associated with these functions, while quantifying and propagating the ‘excess’ dispersion that was unrecognized in the uncertainty budgets for the individual measurements, and that therefore is missing from the reported uncertainties. We regard this ‘excess’ dispersion as an expression of dark uncertainty, which we take into account in the context of calibrations that involve regression models. In one variant of the model the estimate of dark uncertainty is the same for all the participants in the comparison, while in another variant different amounts of dark uncertainty are assigned to different participants. We compare these models with the conventional errors-in-variables model underlying the procedure that ISO 6143 recommends for building analysis functions. Applications of this procedure are often preceded by the selection of a subset of the measurement results deemed to be mutually consistent, while the more discrepant ones are set aside. This new model is more inclusive than the conventional model, in that it easily accommodates measurement results that are mutually inconsistent. It produces results that take into account contributions from all apparent sources of uncertainty, regardless of whether these sources are already understood and their contributions have been included in the reported uncertainties, or still require investigation after they will have been detected and quantified.

In this study, we report independent measurements of all stable isotope ratios of gadolinium. Our study employs multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) with National Research Council Canada (NRC) HALF-1 isotopic hafnium standard as a primary calibrator and surveys four commercial gadolinium materials, including a NRC candidate isotopic reference material, GADS-1. The isotopic composition of gadolinium is determined using the regression model without reliance on conventional normalizing isotope ratios or mass-dependent isotope ratio correction models. In this work, all gadolinium isotope ratios were obtained from ¹⁶⁰Gd/¹⁵⁸Gd which, in turn, was measured from hafnium ¹⁷⁸Hf/¹⁷⁷Hf either directly or indirectly through ¹⁶⁷Er/¹⁶⁶Er. The latter approach was used for the final determination of gadolinium isotopic composition, as it provides smaller combined uncertainty. We report high-precision measurements of the isotopic composition of gadolinium, which support a revised standard atomic weight. Isotope amount ratios of R₁₅₂/₁₅₈ = 0.008 20(2) ₖ₌₁, R₁₅₄/₁₅₈ = 0.087 98(12) ₖ₌₁, R₁₅₅/₁₅₈= 0.596 81(63) ₖ₌₁, R₁₅₆/₁₅₈ = 0.825 08(57) ₖ₌₁, R₁₅₇/₁₅₈ = 0.630 60(22) ₖ₌₁, and R₁₆₀/₁₅₈ = 0.879 10(60) ₖ₌₁, and the atomic weight of A ᵣ(Gd) = 157.2502(6) ₖ₌₁ were obtained for gadolinium in GADS-1.

An international comparison study on the accurate determination of the molar mass M(Si) of silicon artificially enriched in 28Si (x(28Si) > 0.9999 mol mol−1) has been completed. The measurements were part of the high level CCQM-P160 pilot study assessing the ability of National Metrology Institutes (NMIs) and Designated Institutes (DIs) to make such measurements at the lowest possible levels of measurement uncertainty and to identify possible difficulties when measuring this kind of sample. This study supports the molar mass measurements critical to disseminating the silicon route to realizing the new definitions for the kilogram and the mole. Measurements were also made by one external research institute and an external company. The different institutes were free to choose their experimental (mass spectrometric) set-ups and equipment, thereby enabling also the comparison of different techniques. The investigated material was a chemically pure, polycrystalline silicon material. The subsequent modified single crystalline secondary product of this material was intended for the production of silicon which was used for two additional spheres in the context of the redetermination of the Avogadro constant NA, required for the revision of the International System of Units (SI) via fundamental constants which came into force from May 2019. The CCQM pilot study was organized by Physikalisch-Technische Bundesanstalt (PTB). Aqueous silicon solutions were shipped to all participating institutions. The data analysis as well as the uncertainty modelling and calculation of the results was predefined. The participants were provided with an uncertainty budget as a GUM Workbench® file as well as a free software license for the duration of the comparison. The agreement of the values of the molar mass (M(Si) = 27.976 942 577 g mol−1) was excellent with ten out of 11 results reported within the range of relative uncertainty of 1 × 10−8 required for the revision of the SI.

Solution to trifluoroacetic acid NMR challenge.

This study was undertaken to quantitatively explore the effect of temperature on the degradation of cannabinoids in dried cannabis flower. A total of 14 cannabinoids were monitored using liquid chromatography and tandem mass spectrometry in temperature environments from - 20 to + 40

Isotope ratios offer countless applications but almost as a rule precision measurements are required. Making use of such measurements involves comparison of the results between the laboratories which, in turn, requires international primary standards. Much less appreciated is the role of data analysis and measurement models. This presentation will feature a variety of examples of stable isotope ratio measurements, including light and heavy elements with examples from the redefinition of the kilogram, lead-lead dating, and carbon isotope delta reference scales, showing that choices on how we interpret and model our measurements can affect the traceability and comparability of isotope ratio measurements. The challenge is therefore for the analysts to recognize data analysis practices as a natural part of the measurement.

Particle size is a key parameter that must be measured to ensure reproducible production of cellulose nanocrystals (CNCs) and to achieve reliable performance metrics for specific CNC applications. Nevertheless, size measurements for CNCs are challenging due to their broad size distribution, irregular rod-shaped particles, and propensity to aggregate and agglomerate. We report an interlaboratory comparison (ILC) that tests transmission electron microscopy (TEM) protocols for image acquisition and analysis. Samples of CNCs were prepared on TEM grids in a single laboratory, and detailed data acquisition and analysis protocols were provided to participants. CNCs were imaged and the size of individual particles was analyzed in 10 participating laboratories that represent a cross section of academic, industrial, and government laboratories with varying levels of experience with imaging CNCs. The data for each laboratory were fit to a skew normal distribution that accommodates the variability in central location and distribution width and asymmetries for the various datasets. Consensus values were obtained by modeling the variation between laboratories using a skew normal distribution. This approach gave consensus distributions with values for mean, standard deviation, and shape factor of 95.8, 38.2, and 6.3 nm for length and 7.7, 2.2, and 2.9 nm for width, respectively. Comparison of the degree of overlap between distributions for individual laboratories indicates that differences in imaging resolution contribute to the variation in measured widths. We conclude that the selection of individual CNCs for analysis and the variability in CNC agglomeration and staining are the main factors that lead to variations in measured length and width between laboratories.

The purity value assignment of metrologically traceable peptide reference standards requires specialized primary methods. Conventionally, amino acid analysis by isotope dilution tandem mass spectrometry (LC-MS/MS) following peptide hydrolysis is employed as a reference method. By contrast, quantitative nuclear magnetic resonance (qNMR) spectroscopy allows for quantitation of intact peptides, thus eliminating potential bias due to hydrolysis. Both methods are susceptible to interference from related peptide impurities, which need to be accurately measured and accounted for. The mass balance approach has also been employed for peptide purity measurements, whereby the purity is defined by the sum of the mass fraction of all impurities identified. Ideally, results from these three orthogonal methods can be combined for final purity assignment of peptide reference standards. Here we report a novel strategy for correcting both LC-MS/MS and 1H-qNMR results for related peptide impurities and combining results from both methods using a Bayesian statistical approach using mass balance results as prior knowledge. The mass balance method relied on a validated 19F-qNMR method to measure the trifluoroacetic acid (TFA) counter-ion, considered an impurity in this case at nearly 25% by mass. Using a candidate certified reference material (CRM) for angiotensin II, excellent agreement was achieved with the three methods. The final purity value assignment of the candidate CRM was 691 ± 9 mg/g (k = 2).

Despite its widespread applications in geology, all osmium isotope ratio measurements are either uncalibrated or rely on the veracity of the uncalibrated 1937 Nier values by adopting them as normalizing constants typically in conjunction with an exponential mass bias correction model. In this study, isotope ratios of osmium were determined in six commercial osmium materials, including the DROsS standard and a new NRC isotopic osmium reference material OSIS-1, by MC-ICPMS. We use a previously optimized and validated regression mass bias correction model to correct instrumental isotope fractionation effects which does not rely either on Nier’s values or on a strictly mass-dependent behavior of the isotopes. Deviations from mass-dependent fractionation (mass independent fractionation) were observed for osmium isotopes in MC-ICPMS with the most dramatic effect occurring for 187Os, wherein, on average, close to half-percent bias in the isotope ratio 187Os/188Os was observed as a result of imposing Russell’s law.

International audience; Certification of trace metals in seawater certified reference materials (CRMs) NASS-7 and CASS-6 is described. At the National Research Council Canada (NRC), column separation was performed to remove the seawater matrix prior to the determination of Cd, Cr, Cu, Fe, Pb, Mn, Mo, Ni, U, V, and Zn, whereas As was directly measured in 10-fold diluted seawater samples, and B was directly measured in 200-fold diluted seawater samples. High-resolution inductively coupled plasma mass spectrometry (HR-ICPMS) was used for elemental analyses, with double isotope dilution for the accurate determination of B, Cd, Cr, Cu, Fe, Pb, Mo, Ni, U, and Zn in seawater NASS-7 and CASS-6, and standard addition calibration for As, Co, Mn, and V. In addition, all analytes were measured using standard addition calibration with triple quadrupole (QQQ)-ICPMS to provide a second set of data at NRC. Expert laboratories worldwide were invited to contribute data to the certification of trace metals in NASS-7 and CASS-6. Various analytical methods were employed by participants including column separation, co-precipitation, and simple dilution coupled to ICPMS detection or flow injection analysis coupled to chemiluminescence detection, with use of double isotope dilution calibration, matrix matching external calibration, and standard addition calibration. Results presented in this study show that majority of laboratories have demonstrated their measurement capabilities for the accurate determination of trace metals in seawater. As a result of this comparison, certified/reference values and associated uncertainties were assigned for 14 elements in seawater CRMs NASS-7 and CASS-6, suitable for the validation of methods used for seawater analysis.

We would like to invite you to participate in the Analytical Challenge, a series of puzzles to entertain and challenge our readers. This special feature of “Analytical and Bioanalytical Chemistry” has established itself as a truly unique quiz series, with a new scientific puzzle published every three months. Readers can access the complete collection of published problems with their solutions on the ABC homepage at http://www.springer.com/abc. Test your knowledge and tease your wits in diverse areas of analytical and bioanalytical chemistry by viewing this collection. In the present challenge, NMR spectra is the topic. And please note that there is a prize to be won (a Springer book of your choice up to a value of €100). Please read on...

Main text The CCQM-K148.a comparison was coordinated by the BIPM on behalf of the CCQM Organic Analysis Working Group for NMIs and DIs which provide measurement services in organic analysis under the CIPM MRA. It was undertaken as a "Track A" comparison within the OAWG strategic plan. CCQM-K148.a demonstrates capabilities for assigning the mass fraction content of a solid organic compound having moderate molecular complexity, where the compound has a molar mass in the range (75 - 500) g/mol and is non-polar (pKow < −2), when present as the primary organic component in a neat organic solid and where the mass fraction content of the primary component in the material is in excess of 950 mg/g. Participants were required to report the mass fraction of Bisphenol A present in one supplied unit of the comparison material. Participants using a mass balance method for the assignment were also required to report their assignments of the impurity components present in the material. Methods used by the seventeen participating NMIs or DIs were predominantly based on either stand-alone mass balance (summation of impurities) or qNMR approaches, or the combination of data obtained using both methods. The results obtained using thermal methods based on freezing-point depression methods were also reported by a limited number of participants. There was excellent agreement between assignments obtained using all three approaches to assign the BPA content. The assignment of the values for the mass fraction content of BPA consistent with the KCRV was achieved by most of the comparison participants with an associated relative standard uncertainty in the assigned value in the range (0.1 - 0.5)%. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Isotopic internal standards are widely employed for accurate quantitation in chemical and clinical analysis. Although this type of internal standardization – also referred to as isotope dilution mass spectrometry (IDMS) – has calibration curves that are inherently nonlinear, most analysts fit linear model to calibration data and use R2 as a metric to decide whether the calibration curves are reasonably linear. We show that this approximation can lead to significant errors even in cases when R2 > 0.99. We present a simulation approach – available as supplementary Excel spreadsheet – able to predict the IDMS calibration curves and estimate the errors that are introduced by the linear simplification. The simulation does not require experimental input and was validated using examples to cover cases of large, intermediate, and unnoticeable nonlinear calibration curves. This spreadsheet can be a valuable tool to plan IDMS experiments and to assess if a linear model is fit for purpose.

The concept of the relative sensitivity factors required for the correction of the measured ion beam ratios in pin-cell glow discharge mass spectrometry is examined in detail. We propose a data-driven model for predicting the relative response factors, which relies on a non-linear least squares adjustment and analyte/matrix interchangeability phenomena. The model provides a self-consistent set of response factors for any analyte/matrix combination of any element that appears as either an analyte or matrix in at least one known response factor.

Methods based on species specific isotope dilution were developed for the accurate and SI traceable determination of arsenobetaine (AsBet) and methylmercury (MeHg) in prawn and cuttlefish tissues by LC-MS/MS and SPME GC-ICPMS. Quantitation of AsBet and MeHg were achieved by using a 13C-enriched AsBet spike (NRC CRM CBET-1) and an enriched spike of Me198Hg (NRC CRM EMMS-1), respectively, wherein analyte mass fractions in enriched spikes were determined by reverse isotope dilution using natural abundance AsBet and MeHg primary standards. Purity of these primary standards were characterized by quantitative 1H-NMR with the use of NIST SRM 350b benzoic acid as a primary calibrator, ensuring the final measurement results traceable to SI. Validation of employed methods of ID LC-MS/MS and ID SPME GC-ICPMS was demonstrated by analysis of several biological CRMs (DORM-4, TORT-3, DOLT-5, BCR-627 and BCR-463) with satisfying results. The developed methods were applied for the determination of AsBet and MeHg in two new certified reference materials (CRMs) prawn (PRON-1) and cuttlefish (SQID-1) produced jointly by Thailand Institute of Scientific and Technological Research (TISTR) and National Research Council Canada (NRC). With additional measurements of AsBet using LC-ICPMS with standard additions calibration and external calibration at NRC and TISTR, respectively, certified values of 1.206 ± 0.058 and 13.96 ± 0.54 mg kg−1 for AsBet as As (expanded uncertainty, k = 2) were obtained for the new CRMs PRON-1 and SQID-1, respectively. The reference value of 0.324 ± 0.028 mg kg−1 as Hg (expanded uncertainty, k = 2) for MeHg was obtained for the SQID-1 based on the results obtained by ID SPME GC-ICPMS method only, whereas MeHg in PRON-1 was found to be < 0.015 mg kg−1. It was found that AsBet comprised 69.7% and 99.0% of total As in the prawn and cuttlefish, respectively, whereas MeHg comprised 94.5% of total Hg in cuttlefish.

Microcystins are cyclic heptapeptides from cyanobacteria that are potent inhibitors of protein phosphatases and are toxic to animals and humans. At present, more than 250 microcystin variants are known, with variants reported for all seven peptide moieties. While d-glutamic acid (d-Glu) is highly-conserved at position-6 of microcystins, there has been only one report of a cyanobacterium (Anabaena) producing microcystins containing l-Glu at the variable 2- and 4-positions. Liquid chromatography–mass spectrometry analyses of extracts from Planktothrix prolifica NIVA-CYA 544 led to the tentative identification of two new Glu-containing microcystins, [d-Asp3]MC-ER (12) and [d-Asp3]MC-EE (13). Structure determination was aided by thiol derivatization of the Mdha7-moiety and esterification of the carboxylic acid groups, while 15N-labeling of the culture and isotopic profile analysis assisted the determination of the number of nitrogen atoms present and the elemental composition of molecular and product-ions. The major microcystin analog in the extracts was [d-Asp3]MC-RR (1). A microcystin with an unprecedented high-molecular-mass (2116 Da) was also detected and tentatively identified as a sulfide-linked conjugate of [d-Asp3]MC-RR (15) by LC–HRMS/MS and sulfide oxidation, together with its sulfoxide (16) produced via autoxidation. Low levels of [d-Asp3]MC-RW (14), [d-Asp3]MC-LR (4), [d-Asp3,Mser7]MC-RR (11), [d-Asp3]MC-RY (17), [d-Asp3]MC-RF (18), [d-Asp3]MC-RR–glutathione conjugate (19), and [d-Asp3]MC-RCit (20), the first reported microcystin containing citrulline, were also identified in the extract, and an oxidized derivative of [d-Asp3]MC-RR and the cysteine conjugate of 1 were partially characterized.

In this study, we report the first independent measurements of lutetium isotopic composition using multi-collector ICPMS in four commercial lutetium materials, including a new NRC candidate lutetium isotopic reference material, LUIS-1. The regression model was used to correct for the instrumental isotopic fractionation (mass bias) using NIST SRM 989 isotopic rhenium as the primary calibrator. The regression model is based on a short 15-min measurement sessions at varying ICP plasma power. Isotope ratio of R176/175 = 0.026553(11)k = 1, corresponding isotopic abundances of x176 = 0.025866(11)k = 1, x175 = 0.974134(11)k = 1, and an atomic weight of Ar(Lu) = 174.966693(13)k = 1 were obtained for lutetium in LUIS-1. Uncertainty estimation was performed using a mixture of modeling approaches in accordance with the JCGM 100:2008 “Guide to the Expression of Uncertainty in Measurement” and its Supplement 1. The relative contribution of the rhenium primary standard to the combined uncertainty of 176Lu/175Lu isotope ratio was 15%.

Despite the numerous important applications of hafnium isotopes in geological science, and the advances in multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS), hafnium still lacks calibrated measurements of its isotope ratios and, in turn, isotopic abundances and atomic weight. In this study, we determined the isotopic composition of hafnium in four commercial hafnium reagents, including a commonly used hafnium standard (JMC-475) and a NRC candidate isotopic reference material (HALF-1) by MC-ICPMS. The state-of-the-art regression model with NIST SRM 989 isotopic rhenium as calibrator was used to correct instrumental isotopic fractionation without reliance on other hafnium standards, normalizing isotope ratios, or exponential mass-bias fractionation model.

A high-precision exact-matching quadruple isotope dilution method (ID4MS) was employed for the quantitation of nitrate in an air-dried spinach powder Certified Reference Material (CRM). The analyte was extracted in hot water following addition of 15NO[Formula: see text] internal standard. The blend was then treated with sulfamic acid to remove nitrite and with triethyloxonium tetrafluoroborate to promote aqueous conversion of nitrate into volatile EtONO2. The derivative was analyzed by headspace GC-MS with 3-min elution time. The method performance was validated with a series of tests which demonstrated adequate selectivity and ruggedness. This method supported the development of novel SPIN-1 CRM giving a modest contribution to its uncertainty (uchar = 0.85%). With respect to previous attempts, the SPIN-1 was proven stable, homogeneous (uhom = 0.44%), and suitable for spinach monitoring under EU regulations. On dried basis, the nitrate content of SPIN-1 was found to be 22.53 ± 0.43 mg/g (Uc = 1.9%, k = 2). The material was also used in an inter-laboratory study where four laboratories employed a total of ten measurement methods. Graphical Abstract SPIN-1 Certified Reference Material for nitrate in spinach powder.

The determination of isotope ratios of lead finds many important applications in earth and planetary sciences. In this study, we report the first independent and fully calibrated absolute isotope ratio measurements of a common lead since the seminal work by the NIST in the 1960s, which has provided the widely used standards SRM 981 and SRM 982. This work employs MC-ICPMS for the absolute isotope ratio measurements, which were calibrated using two independent methods: the full gravimetric isotope mixture method based on the use of all four near-pure lead isotopes (the first application of this primary method to lead) and the regression method with NIST SRM 997 thallium isotopic standard as the primary calibrator. Both calibration methods provide results consistent to a few parts in 104, which were used to characterize isotope ratios of lead in an NRC candidate reference material, high-purity common lead HIPB-1.