Determination of Phosphatidylcholine in Shrimp by High-Resolution Mass Spectrometry

The molecular species of phosphatidylcholine from freshwater sources (Macrobranchium nipponense and Macrobranchium rosenbergii) and marine sources (Euphausia superba and Penaeus chinesis) were characterized by high-resolution mass spectrometry. The tandem secondary mass spectrometry (MS/MS) fragmentation allowed for the identification of fatty acyl residues of phosphatidylcholine molecular species. (16:0–18:1)Phosphatidylcholine was the main phosphatidylcholine molecular species determined in all shrimp samples, especially in E. superba. Macrobranchium rosenbergii phosphatidylcholine was particularly rich in (16:0–20:5)phosphatidylcholine and (16:0–22:6)phosphatidylcholine. The proportion of the two molecular species was next to the phosphatidylcholine of E. superba. Therefore, M. rosenbergii appears to be a potential freshwater source for the supplementation of polyunsaturated fatty acids, particularly eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6). This approach may be used as an efficient method for the identification of natural phosphatidylcholine sources from the broad range of plant, animal, and marine origins.     

第32届中国化学奥林匹克初赛有机试题详解

利用框图全面归纳了第32届全国化学奥林匹克竞赛（初赛）有机试题的考点分布,并对考题进行了详细解析,以帮助致力于参加高中化学竞赛的考生取得优异成绩。     

同结构GdIIIMII(M=Cu，Ni，Co，Fe，Mn)配合物磁性理论研究

基于DFT-BS方法,在不同泛函方法和基组下计算[CuIIGdIII{pyCO(OEt)py C(OH)(OEt)py}3]2+及3d-Gd异金属配合物的磁耦合常数,结果表明,PBE0/TZVP(Gd为SARC-DKH-TZVP)水平可用于描述其磁学性质。顺磁中心CuII、GdIII与桥联配位氧原子间存在较强的轨道相互作用,其磁轨道主要由GdIII的4fz3、4fz(x2-y2)轨道、CuII的3dx2-y2轨道和桥联配位原子O的p轨道组成。顺磁中心CuII离子以自旋离域作用为主,GdIII离子以自旋极化作用为主,顺磁中心CuII自旋离域作用对桥联氧原子的影响大于顺磁中心GdIII的自旋极化作用。在同结构3d-Gd配合物中,随着MII离子未成对电子的增加,顺磁中心间自旋密度平方差越大,顺磁中心MII和GdIII之间的反铁磁性贡献越大,其磁耦合常数越小。     

Lithium Bonds in Lithium Batteries

Lithium bonds are analogous to hydrogen bonds and are therefore expected to exhibit similar characteristics and functions. Additionally, the metallic nature and large atomic radius of Li bestow the Li bond with special features. As one of the most important applications of the element, Li batteries afford emerging opportunities for the exploration of Li bond chemistry. Herein, the historical development and concept of the Li bond are reviewed, in addition to the application of Li bonds in Li batteries. In this way, a comprehensive understanding of the Li bond in Li batteries and an outlook on its future developments is presented.     

Electrocatalytically Active Fe‐(O‐C2)4 Single‐Atom Sites for Efficient Reduction of Nitrogen to Ammonia

Single‐atom catalysts have demonstrated their superiority over other types of catalysts for various reactions. However, the reported nitrogen reduction reaction single‐atom electrocatalysts for the nitrogen reduction reaction exclusively utilize metal–nitrogen or metal–carbon coordination configurations as catalytic active sites. Here, we report a Fe single‐atom electrocatalyst supported on low‐cost, nitrogen‐free lignocellulose‐derived carbon. The extended X‐ray absorption fine structure spectra confirm that Fe atoms are anchored to the support via the Fe‐(O‐C₂)₄ coordination configuration. Density functional theory calculations identify Fe‐(O‐C₂)₄ as the active site for the nitrogen reduction reaction. An electrode consisting of the electrocatalyst loaded on carbon cloth can afford a NH₃ yield rate and faradaic efficiency of 32.1 μg h^?1 mg_cat.^?1 (5350 μg h^?1 mg_Fe^?1) and 29.3 %, respectively. An exceptional NH₃ yield rate of 307.7 μg h^?1 mg_cat.^?1 (51 283 μg h^?1 mg_Fe^?1) with a near record faradaic efficiency of 51.0 % can be achieved with the electrocatalyst immobilized on a glassy carbon electrode.     

Enantioselective separation and dissipation of pydiflumetofen enantiomers in grape and soil by supercritical fluid chromatography–tandem mass spectrometry

Pydiflumetofen is registered in many countries and is widely used in crop production in the racemate form. However, the environmental behavior of the enantiomers has not been studied. An effective and sensitive chiral analytical method was first established for analyzing the pydiflumetofen enantiomers by supercritical fluid chromatography with tandem triple quadrupole mass spectrometry. The enantiomers could be separated and detected using the Chiralcel OD‐3 column in less than 3 min. The separation conditions were as follows: mobile phase, CO₂/methanol (80:20); flow rate, 1.0 mL/min; column temperature, 30°C, auto back‐pressure regulator pressure, 2000 psi with modified quick, easy, cheap, effective, rugged, and safe sample treatment method. The average recoveries of analytes from both matrices at three spiking levels were in the range of 84.1–103.0%. The limit of quantitation for each enantiomer was 0.005 mg/kg with a baseline resolution of approximately 1.64. The method was applied to monitor the enantioselective dissipation of pydiflumetofen in grape and soil. In grapes, (?)‐pydiflumetofen was degraded more rapidly than (+)‐pydiflumetofen. In soil, (+)‐pydiflumetofen was preferentially degraded. The data provided useful references for the risk assessment and rational use of pydiflumetofen in agriculture.     

顶空气相色谱法测定杏脯中二氧化硫

建立顶空气相色谱测定杏脯中二氧化硫残留的方法,探讨了气液体积比、加酸量、平衡温度和平衡时间对检测结果的影响。向450 mL顶空瓶内加入5 g样品、10 g石蜡、200 mL水及25 mL盐酸溶液,于75℃平衡20 min后放至室温,抽取0.5 mL顶空气体进行定性定量分析检测。该方法标准工作曲线线性相关系数r~2为0.992,检出限和定量限分别为0.1,1.0 mg/kg,测定结果的相对标准偏差为1.9%~3.2%(n=6),样品加标回收率为89.4%~94.3%。该法操作简便、快捷,灵敏度高,人为误差小,满足杏脯中二氧化硫残留的批量检测要求。     

Quantification of flupirtine maleate polymorphs using X-ray powder diffraction

Flupirtine maleate,a pharmaceutical compound for treating psychotic disease in clinics,has seven polymorphs.Form A,with better crystal stability and bioavailability,has been widely used as the pharmaceutical crystal form.Unfortunately,it is usually found in a polymorphic mixture with form B.In this study,pure crystal forms of A and B were prepared and characterized by X-ray powder diffraction (XRPD),Fourier transform infrared spectroscopy (FT-IR) and thermal analysis.An XRPD-based method for the quantitative determination of the amount of the flupirtine maleate polymorphs form A and form B was also established through a systematic optimization of instrumental parameters.The results of the analytical methodology validation showed that the XPRD method had a broad quantitative range of 0-100%(w/w),good linear relationship,with R²=0.999,excellent repeatability and precision and low limits of detection (LoD) of 0.15%(w/w) and quantification (LoQ) of 0.5%(w/w).The results also showed that the single-peak method was not as good as the whole pattern in reducing the influence of the preferred orientation,but this can be compensated for by a systematic optimization of instrumental parameters and validating the analytical methodology to reduce errors and obtain a good,repeatable,sensitive,and accurate method.This XRPD method can be used to analyze mixtures of flupirtine maleate polymorphs (forms A and B) quantitatively and control the quality of the bulk drug.     

Enhanced electrochemical performance of SnS nanoparticles/CNTs composite as anode material for sodium-ion battery

SnS/CNTs composite as anode for SIBs exhibits high reversible capacity, good cyclability as well as rate performance, which is superior to that of pure SnS. The enhanced electrochemical performance can be attributed to the adding of CNTs as a flexible and conductive structure supporter and the formation of SnS nanoparticles with small diameter.     

A Novel Method for the Detection of Chlorpyrifos by Combining Quantum Dot-labeled Molecularly Imprinted Polymer with Flow Cytometry

Uniform-sized fluorescent molecularly imprinted polymers were prepared by one-step swelling and suspension polymerization, while chlorpyrifos, methacrylic acid, ethylene glycol dimethacrylate, and oil-soluble CdSe/ZnS quantum dots were used as the carrier, template molecule, functional monomer, cross-linker, and fluorophor, respectively. The morphology, adsorption dynamics, binding ability, and selectivity of quantum dot-labeled molecularly imprinted polymers were evaluated. The dosage of quantum dots for labeling the molecularly imprinted polymers was optimized. The results showed that the optimized dose of quantum dots was 200?µL using a concentration of 8.0?µM. The microsphere size was approximately 10?µm with a honeycombed surface. The quantum dot-labeled molecularly imprinted polymers had an even brightness and a high selectivity. In the presence of different concentrations of chlorpyrifos, a decrease in the fluorescence intensity of the quantum dot-labeled molecularly imprinted polymer was clearly identified by flow cytometry. The whole detection process was accomplished within 2?h including pretreatment. This method was used for the determination of chlorpyrifos in tap water samples.