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Objective: To establish a method for the simultaneous determination of 6 benzodiazepine sedatives residue in aquatic products by high performance liquid chromatography-triple quadrupole mass spectrometry., Methods: The samples were extracted with acetonitrile and purified by C_(18 )solid phase extraction column. The sample solution was separated by Waters ACQUITY UPLC BEH C_(18 )column(2.1 mm×50 mm, 1.7 μm) using 0.1% formic acid and methanol as mobile phase for gradient elution, determined in multiple reaction monitoring mode and quantified by internal standard method., Results: Six benzodiazepine sedatives had a good linear relationship in the range of 1.0-50.0 μg/L with r>0.9990, the limits of detection and limits of quantification were 0.3 and 1.0 μg/kg. Average recoveries for the analytes at 3 spiked levels ranged from 74.2%-108.0% with relative standard deviations of 1.1%-6.7%(n=6)., Conclusion: The method is simple, rapid, sensitive and accurate, which is suitable for simultaneous determination of 6 benzodiazepine sedatives residue in aquatic products.

Aqueous solutions of magnesium chloride (MgCl 2 (aq)) are often used to test advances in the theory of electrolyte solutions because they are considered an ideal strong 2:1 electrolyte. However, there is evidence that some ion association occurs in these solutions, even at low concentrations. Even a small ion-pairing constant can have a significant impact on the chemical speciation of ions, so it is important to determine whether ion pairing actually occurs. In this study, MgCl 2 (aq) with concentrations ranging from 1 to 35% was studied using three methods: X-ray scattering (XRS) with the Shanghai Synchrotron Radiation Facility (SSRF) and silver-anode laboratory sources, Raman spectroscopy, and molecular dynamics (MD) simulations with the COMPASS-II and Madrid force fields. XRS results were analyzed in the framework of PDF theory to obtain the reduced structure function F ( Q ) and the reduced pair distribution function G ( r ). The F ( Q ) values from synchrotron radiation and laboratory sources both showed that the tetrahedral hydrogen bonds in bulk water were destroyed with the increased MgCl 2 concentration. The results of G ( r ) indicated that the main peaks centered at 2.05 and 2.80 Å can be ascribed to the interactions of Mg-O and O-O, respectively. The peak at 3.10 Å is attributed to the combined effect of O-O and Cl-O. By comparing the structural information on MgCl 2 solution obtained from the two light sources, it was found that both SSRF and silver-anode laboratory sources can reflect the above-mentioned structural information on MgCl 2 solution. The radial distribution function (RDF) obtained from MD simulations of MgCl 2 solutions assigned the peaks at 2.0, 2.8, and 3.2 Å to the Mg-O, O-O, and Cl-O interatomic pairs, respectively. The decrease in the O-O coordination number confirms that the hydrogen-bonding network of water is disrupted by increasing MgCl 2 observed by X-ray scattering. The proportion of Mg-Cl contact ion pairs gradually increases with MgCl 2 concentration as does the coordination number. Raman spectroscopy results show that the bond type changes from double donor double acceptor (DDAA) to single donor-single acceptor (DA) with increasing concentration, providing explicit details of the hydrogen-bond evolution in the aqueous solution.

The BIMEVOXes are among the best oxide ion conductors at low and intermediate temperatures. Their high conductivity is associated with local defect structure. In this work, the local structures of two BIMEVOX compositions, Bi 2 V 0.9 Ge 0.1 O 5.45 and Bi 2 V 0.95 Sn 0.05 O 5.475 , are examined using total neutron and X-ray scattering methods, with both compositions exhibiting the ordered α-phase at 25 °C and the disordered γ-phase at 700 °C. While the diffraction data for the α-phase do not allow for the polar ( C 2) and nonpolar ( C 2/ m ) structures to be readily distinguished, measurements of dielectric permittivity suggest the α-phase is weakly ferroelectric in character, consistent with calculations of spontaneous polarization based on a combination of density functional calculations and machine learning methodology. Reverse Monte Carlo (RMC) analysis of total scattering data reveals Ge preferentially adopts tetrahedral geometry at both temperatures, while Sn is found to predominantly adopt octahedral coordination in the α-phase and tetrahedral coordination in the γ-phase. In all cases, V polyhedra are found to consist of tetrahedral, pentacoordinate, and octahedral geometries, as also predicted by the crystallographic analysis and confirmed by 51 V solid state NMR spectroscopy. Although similar long-range structures are observed at room temperature, the oxide ion vacancy distributions were found to be quite different between the two studied compositions, with a nonrandom deficiency in vacancy pairs in the second-nearest shell along the ⟨100⟩ tetragonal direction for BIGEVOX10, compared with a long-distance (>8.0 Å) ordering of equatorial vacancies for BISNVOX05. This is attributed to the differences in the preferred coordination geometries of the substituent cations in the two systems. Impedance spectroscopy measurements reveal both compositions show high conductivity in the order of 10 -1 S cm -1 at 600 °C., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Grain size can have significant effects on the properties of electroceramics for dielectric, piezoelectric, and ferroelectric applications. Here, we systematically investigate the effect of grain size on the structure and properties of Mn-modified 0.67BiFeO 3 -0.33BaTiO 3 ceramics, an important lead-free piezoelectric ceramic that exhibits both a high piezoelectric coefficient and a high Curie point. Ceramics with average grain sizes ranging from 0.46 to 6.85 μm were prepared using conventional and spark plasma sintering. It was found that the morphotropic phase boundary compositions are composed of two polar structures, rhombohedral and tetragonal, with DC poling inducing an increase in the fraction of the rhombohedral phase. All ceramics show relaxor behavior and their freezing temperature moves to higher temperatures with increasing grain size, although their Burns temperature is independent of grain size. In fine-grained ceramics, which show pronounced relaxor behavior, significant grain size dependency is seen in dielectric, piezoelectric, and ferroelectric properties, which is attributed to the presence of single ferroelectric domains and high concentrations of polar nanoregions. In coarse-grained ceramics, a critical grain size of 2.83 μm yields the highest dielectric permittivity at room temperature, with the piezoelectric coefficient plateauing at this grain size, which can be attributed to the contribution of both polar nanoregions and high domain wall density.

Ferroelectric domain walls (DWs) are important nanoscale interfaces between two domains. It is widely accepted that ferroelectric domain walls work idly at terahertz (THz) frequencies, consequently discouraging efforts to engineer the domain walls to create new applications that utilize THz radiation. However, the present work clearly demonstrates the activity of domain walls at THz frequencies in a lead-free Aurivillius phase ferroelectric ceramic, Ca 0.99 Rb 0.005 Ce 0.005 Bi 2 Nb 2 O 9 , examined using THz-time-domain spectroscopy (THz-TDS). The dynamics of domain walls are different at kHz and THz frequencies. At low frequencies, domain walls work as a group to increase dielectric permittivity. At THz frequencies, the defective nature of domain walls serves to lower the overall dielectric permittivity. This is evidenced by higher dielectric permittivity in the THz band after poling, reflecting decreased domain wall density. An elastic vibrational model has also been used to verify that a single frustrated dipole in a domain wall represents a weaker contribution to the permittivity than its counterpart within a domain. The work represents a fundamental breakthrough in understanding the dielectric contributions of domain walls at THz frequencies. It also demonstrates that THz probing can be used to read domain wall dielectric switching.

In this study, saxitoxin (STX) immunoaffinity column (IAC) solid phase extraction (SPE) technology was used to extract and purify STX in bivalve aquatic products. By optimizing the conditions of sample pretreatment, the method of detecting STX in bivalve aquatic products had been established by high performance liquid chromatograph-tandem mass spectrometry (LC-MS/MS) based on the cleanup of SPE with immunoaffinity interaction mechanism. The phosphate buffer solution (PBS) was used to extract STX in bivalves. The sample was separated on a TSK-GEL Amide column (2.0 mm × 250 mm, 5 µm) with water contained 2 mM ammonium formate-50 mM formic acid and 95% acetonitrile contained 2 mM ammonium formate-50 mM formic acid as mobile phase by gradient elution. STX had a good linearity in the range of 2.468 μg/kg to 246.8 μg/kg with the correlation coefficient of r greater than 0.999. The detection of limit (0.1 μg/kg) was more sensitive, two orders of magnitude better than previous report (20 μg/kg) in bivalve aquatic products. The recovery ranged from 79.3% to 102.9%. The method has a good selectivity with eliminating matrix effect thoroughly, no need for matrix matching, thus it can satisfy the requirements of trace STX detection in bivalve aquatic products., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Nanomaterials play a significant role in adsorption treatment of dye wastewater, but irreversible aggregation of nanoparticles poses a significant problem. In this work, nanomesoporous zinc-doped silicate (NMSZ) was prepared by an in situ method. To prevent agglomeration, NMSZ was covalently bonded to graphene oxide (GO) sheets to form a nano-silica/zinc/graphene oxide composite (GO-NMSZ), aimed at removal of cationic dye methylene blue (MB). For comparison, undoped mesoporous silica (MS) was also synthesized and modified to obtain a silica/graphene oxide composite (GO-MS). The materials were characterized by powder XRD, SEM, FTIR spectroscopy, TEM, nitrogen sorption, and X-ray photoelectron spectroscopy (XPS). Preservation of the oxygen-containing groups of GO in the composites led to higher adsorption capacities. The best GO-NMSZ composite exhibited an enhanced adsorption capacity of 100.4 mg g -1 for MB compared to those of undoped GO-MS (80.1 mg g -1 ) and nongrafted NMSZ (55.7 mg g -1 ). The nonselective character of GO-NMSZ is demonstrated by effective adsorption of anionic dye Congo red (127.4 mg g -1 ) and neutral dye isatin (289.0 mg g -1 ). The adsorption kinetics, adsorption isotherms, and a thermodynamic study suggested that MB adsorption occurs by chemisorption and is endothermic in nature., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objectives: To investigate an unusual outbreak of tetrodotoxin poisoning in Leizhou, southeast China, a case series analysis was conducted to identify the source of illness., Methods: A total of 22 individuals experienced symptoms of poisoning, including tongue numbness, dizziness, nausea and limb numbness and weakness. Two toxic species, Amoya caninus and Yongeichthys nebulosus, were morphologically identified from the batches of gobies consumed by the patients. Tetrodotoxin levels in the blood and Goby fish samples were detected using liquid chromatography-tandem mass spectrometry., Results: The tetrodotoxin levels in the remaining cooked Goby fish were determined to be 2090.12 µg/kg. For Amoya caninus, the toxicity levels were 1858.29 µg/kg in the muscle and 1997.19 µg/kg in the viscera and for Yongeichthys nebulosus, they were 2783.00 µg/kg in the muscle and 2966.21 µg/kg in the viscera., Conclusion: This outbreak demonstrates an underestimation of the risk of Goby fish poisoning. Furthermore, the relationships among the toxic species, climates and marine algae present should be clarified in the future.