Main text The CCQM-K154.c comparison was coordinated by the the Bureau International des Poids et Mesures (BIPM) and the Chinese National Institute of Metrology (NIM) on behalf of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) for National Measurement Institutes (NMIs) and Designated Institutes (DIs) which provide measurement services in organic analysis under the 'Comité International des Poids et Mesures' Mutual Recognition Arrangement (CIPM MRA) and/or have participated in the BIPM's Mycotoxin Metrology Capacity Building and Knowledge Transfer (MMCBKT) project as part of its "Metrology for Safe Food and Feed in Developing Economies" Capacity Building Programme. Gravimetrically-prepared solutions having an assigned mass fraction of specified organic analytes are routinely used to calibrate measurement processes for the quantification of the same analytes in matrix samples. Appropriate assignments of the property value and associated uncertainty of calibration solutions thus underpin the traceability of routine analysis and are critical for accurate measurements. Evidence of successful participation in relevant international comparisons is needed to document calibration and measurement capability claims (CMCs) made by national metrology institutes and designated institutes. In total, nine NMIs/DIs participated in the Track C, Model II, Key Comparison CCQM-K154.c [Gravimetric preparation and value assignment of deoxynivalenol (DON) in acetonitrile (ACN)] for emerging areas of global interest and innovation. Participants were requested to gravimetrically prepare calibration solutions and value assign the mass fractions, expressed in mg/kg, of deoxynivalenol (DON) in the acetonitrile (ACN) solution. Study samples, with assigned values and associated uncertainties were prepared by the comparison participants and sent to the coordinating laboratory for comparison. The Key Comparison Reference Values (KCRVs), calculated from values measured by the coordinating laboratory based on calibrations obtained from independent gravimetrically prepared calibrant solutions, agreed with participants reported values, within their stated uncertainties. DON belongs to the large group of trichothecene mycotoxins. It is produced by certain fungi of the genus Fusarium that predominantly infect wheat, corn, oats, barley, rice, and other grains in the field or during storage. It was anticipated to provide a challenge representative for the gravimetrical preparation and value assignment of calibration solutions in the mass fraction range of 10 mg/kg to 100 mg/kg of mycotoxins with broadly similar structural characteristics. Ten participants of the MMCBKT programme were provided with a stock solution having a known DON mass fraction and expanded uncertainty to use to gravimetrically prepare and value assign a calibration solution. Three NMIs/DIs also participated using their own calibration solutions. The use of in-house solutions required an additional capacity to undertake a fit-for-purpose purity assessment. NIM was the only NMI participating using both the MMCBKT based and their own in-house assigned solutions in order to connect the two different groups. It was decided to propose separate KCRVs for each of the two ampoules provided by the participating NMIs/DIs based on the DON mass fraction. This allowed participants to demonstrate the efficacy of their implementation of the approaches used to gravimetrically prepare calibration solutions and to assess the DON mass fraction. The majority of the DON mass fraction KCRVs ( w KCRV ) for CCQM-K154.c spanned a mass fraction range of 9.88 mg/kg to 123.45 mg/kg. The relative expanded uncertainties U( w KCRV ) ranged from 2.8 % to 6.8 %. Inspection of the degree of equivalence plots for the DON mass fraction assignments in CCQM-K154.c indicated that there was an excellent agreement of results. 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).
Converting carbon dioxide (CO2) into value-added chemicals by CO2 reduction has been considered as a potential way to solve the current energy crisis and environmental problem. Among the methods of CO2 reduction, the electrochemical method has been widely used due to its mild reaction condition and high reaction efficiency. In the electrochemical reduction system, the CO2 electrocatalyst is the most important part. Although many CO2 electrocatalysts have been developed, efficient catalysts with high activity, selectivity and stability are still lacking. Copper sulfide compound, as a low-toxicity and emerging material, has broad prospects in the field of CO2 reduction due to its unique structural and electrochemical properties. Much progress has been achieved with copper sulfide nanocrystalline and the field is rapidly developing. This paper summarizes the preparation, recent progress in development, and factors affecting the electrocatalytic CO2 reduction performance with copper sulfide compound as a catalyst. Prospects for future development are also outlined, with the aim of using copper sulfide compound as a highly active and stable electrocatalyst for CO2 reduction.
In this study, a Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method was developed for simultaneous determination of 30 legacy and emerging per- and polyfluoroalkyl substances (PFASs) in fish by UHPLC-MS/MS.
The real active moiety of Fe-N-C single-atom catalysts (SACs) during the oxygen reduction reaction (ORR) depends on the applied potential. Here, we examine the ORR activity of various SAC active moieties (Fe-N4, Fe-(OH)N4, Fe-(O2)N4, and Fe-(OH2)N4) over a wide potential window ranging from -0.8 to 1.0 V (vs. SHE) using constant potential density functional theory calculations. We show that the ORR activity of the Fe-N4 moiety is hindered by the slow *OH protonation, while the Fe-(OH2)N4 (0.4 V ≤ U ≤ 1.0 V), *O2-assisted Fe-N4 (-0.6 V ≤ U ≤ 0.2 V), and Fe-(OH)N4 (U = -0.8 V) moieties dominate the ORR activity of the Fe-N-C catalysts at different potential windows. These oxygenated species modified the single-atom Fe sites and can promote *OH protonation by regulating the electron occupancy of the Fe 3dz2 (spin-up) and Fe 3dxz (spin-down) orbitals. Overall, our findings provide guidance for understanding the active moieties of SACs.
Abstract Atomically dispersed transition metal sites have been extensively studied for CO 2 electroreduction reaction (CO 2 RR) to CO due to their robust CO 2 activation ability. However, the strong hybridization between directionally localized d orbits and CO vastly limits CO desorption and thus the activities of atomically dispersed transition metal sites. In contrast, s‐block metal sites possess nondirectionally delocalized 3s orbits and hence weak CO adsorption ability, providing a promising way to solve the suffered CO desorption issue. Herein, we constructed atomically dispersed magnesium atoms embedded in graphitic carbon nitride (Mg‐C 3 N 4 ) through a facile heat treatment for CO 2 RR. Theoretical calculations show that the CO desorption on Mg sites is easier than that on Fe and Co sites. This theoretical prediction is demonstrated by experimental CO temperature program desorption and in situ attenuated total reflection infrared spectroscopy. As a result, Mg‐C 3 N 4 exhibits a high turnover frequency of ≈18 000 per hour in H‐cell and a large current density of −300 mA cm −2 in flow cell, under a high CO Faradaic efficiency ≥90 % in KHCO 3 electrolyte. This work sheds a new light on s‐block metal sites for efficient CO 2 RR to CO.
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