Square Wave‐Anodic Stripping Voltammetric Determination of Copper at a Bismuth Film/Glassy Carbon Electrode Using 3‐[(2‐Mercapto‐Vinyl)‐Hydrazono]‐ 1,3‐Dihydro‐Indol‐2‐One

This study reports a highly sensitive electrochemical sensor based on Bi film modified glassy carbon electrode (BiF/GCE) for total determination and speciation trace concentrations of copper(II) ions in environmental water samples. Square wave‐adsorptive anodic stripping voltammetric (SW‐ASV) experiment was performed for monitoring selective accumulation of copper(II) with reagent 3‐[(2‐mercapto‐vinyl)‐hydrazono]‐1,3‐dihydro‐indol‐2‐one (MHDI) at pH 9–10. The mechanism of the electrode reaction of Cu²⁺‐MHDI complex was safely assigned. The sensor exhibited a wide linear range (3.22×10⁻⁹–2.0×10⁻⁷ mol L⁻¹) with lower limits of detection (LOD) and quantitation (LOQ) of 9.6×1⁻¹⁰ and 3.22×10⁻⁹ mol L⁻¹, respectively (R²=0.9993). The proposed sensor exhibited interference from active metal ions e. g. Cd, Hg. The performance of the proposed method was compared successfully with most of the reported methods and comparable efficiencies were obtained. The analytical utility of the proposed SW‐ASV method has been successfully validated for trace analysis of copper(II) in environmental water samples. The method offers a precise, accurate approach with good reproducibility, robustness, ruggedness, and cost effectiveness.     

当前疫情下分析化学教学的一点思考

2019年底爆发的新型冠状病毒肺炎席卷了整个中国,在分析化学教学中如何能结合这一热点问题启发学生多方位思考、多角度理解分析化学的一些关键知识点(如3S+2A)并能激发后续学习兴趣,结合在当前肺炎疫情下线上教学的广泛使用,作者对这些相关内容做了一些思考,并在教学过程中进行了尝试。     

The latest research progress on the prevention of storage pests by natural products: Species,mechanisms, and sources of inspiration

The quality of grains is influenced by storage pests, which are not only spoilers of stored grain, but also vectors of human and animal diseases. Chemical pesticides play an essential role in the cultivation and storage of cereals, however, due to the low degradability and residual toxicity of synthetic pesticides on the environment and non-target organisms, as well as the increasing resistance of target organisms to them, consideration should be given to the development of alternative pest control agents. Compounds isolated from natural sources have emerged as preferred targets for the development of novel insecticidal agents because of their eco-friendliness, safety, and effectiveness. In this review, we primarily focus on the natural product (NPs) control of storage pests. The effective monomer components of NPs and their anti-insect mechanisms were discussed, and natural sources of inspiration and models for insect repellents are described. This review aimed to provide guidelines for the exploitation and utilization of green and efficient natural insecticides.     

Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

Anti-pathogens constituents and novel ergosterol derivatives with the broad-spectrum germicidal substances from earthworm, Pheretima aspergillum

Antimicrobial activity-guided isolation found a series of new compounds from Pheretima aspergillum. Novel structures were elucidated by NMR spectroscopic and HRMS analyses, whereas their absolute configurations were established by ORD and CD spectrometer. The further evaluation for antipathogens activities showed that broad-spectrum germicidal effects of novel ergosterol derivatives for compound II and III. Our data provide antimicrobial mechanistic insights by molecular docking.     

Preparation of Novel 1,2,3-Triazoles and a Comparative Study Involving Two Recent Methods for 1,2,3-Triazole Synthesis

Abstract

The syntheses of three novel 1,2,3-triazoles and a comparative study involving two recent methods of 1,2,3-triazole synthesis by diazo group transfers to enaminones, 5,7-dinitro-3-diazo-isatine and mesyl azide, are described. It was observed that the former is the more general and promising method for the synthesis of any 1,2,3-triazole but, when both methods work the mesyl azide one generally gives better yields.     

Techno-functional properties of edible insect proteins and effects of processing

Insects represent a rich source of protein and a more sustainable alternative to conventional animal sources. Insect proteins are diverse in amino acid composition, structure, and physicochemical and functional properties. Processing treatments cause changes in properties of insect proteins and protein-enriched fractions of varying purity, affecting their techno-functional properties and the possible application range. This review discusses recent findings on the effect of processing techniques on the techno-functionality of insect protein fractions including solubility, foaming, emulsifying, and gelling properties. It is demonstrated that a treatment type and its intensity alter physicochemical and functional properties to different degrees. The review also shows the potential for the production of insect-derived food ingredients with tailored functional properties using the diversity of available processing methods.     

新型高温超导复合导体的磁场仿真与实验分析

针对兆伏安级容量的超导变压器,通过绕组初步设计,考虑导体的电流密度、载流量和交流损耗,提出面向大容量超导变压器应用的新型超导复合导体结构,介绍了含内外超导层的新型高温超导复合导体的结构。引入电流矢量T和磁矢量势A的方法,考虑临界电流密度J_c和磁场B的关系,建立了导体不对称三维数值载流模型,计算分析了不同结构参数对导体临界电流的影响规律。通过绕制的新型高温超导复合导体短样,在液氮环境下对其自场临界电流进行了测量,计算结果和实验结果基本吻合,验证了模型的合理性。     

Sonochemical application reduces monosaccharide levels and improves cryoprotective effect of Jerusalem artichoke extract on Leuconostoc mesenteroides WiKim33 during freeze-drying

Lactic acid bacteria (LAB) are being used for probiotic and starter cultures to prevent global damage to microbial cells. To retain the benefits of LAB in the commercially used powdered form, highly efficient cryoprotective agents are required during the manufacturing process. This study suggests a novel cryoprotective agent derived from Jerusalem artichoke (JA; Helianthus tuberous L.) and describes the mechanism of cryoprotective effect improvement by sonication treatment. The cryoprotective effect of JA extract was verified by examining the viability of Leuconostoc mesenteroides WiKim33 after freeze-drying (FD). Sonication of JA extract improved the cryoprotective effect. Sonication reduced fructose and glucose contents, which increased the induction of critical damage during FD by 15.84% and 46.81%, respectively. The cryoprotective effects of JA and sonication-treated JA extracts were determined using the viable cell count of Leu. mesenteroides WiKim33. Immediately after FD and storage for 24 weeks, the viability of Leu. mesenteroides WiKim33 with JA extract was 82.8% and 76.3%, respectively, while that of the sonication-treated JA extract was 95.2% and 88.8%, respectively. Our results show that reduction in specific monosaccharides was correlated with improved cryoprotective effect. This study adopted sonication as a novel treatment for improving the cryoprotective effect and verified its efficiency.     

Study of a Mn–Cr/TiO2 mixed oxide nanocatalyst prepared via an inorganic precursor complex for high-temperature water–gas shift reaction

The influence of three preparation methods on the properties and reaction performances of a titania-supported Mn–Cr bimetallic nanocatalyst for high-temperature water–gas shift reaction has been studied. Impregnation, co-precipitation and thermal decomposition of the [Mn(H₂O)₆]₃[Cr(NCS)₆]₂·H₂O/TiO₂ precursor as an inorganic precursor complex were utilized for the preparation of the Mn–Cr/TiO₂ catalysts. The calcined catalyst and the precursor that were used for its preparation were characterized by powder X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller specific surface area measurements, thermal gravimetric analysis, differential scanning calorimetry and Fourier transform–infrared spectroscopy. The high-temperature water–gas shift activity was appraised in the temperature range from 280 to 420 °C. The results showed that thermal decomposition of inorganic precursor complexes is more advantageous than impregnation and co-precipitation methods for the preparation of Mn–Cr/TiO₂ catalysts for high-temperature water–gas shift reaction.