高效液相色谱-三重四极杆质谱法测定面粉中7种荧光增白剂

建立了高效液相色谱-三重四极杆质谱(HPLC-MS/MS)测定面粉中7种荧光增白剂(FWAs)的分析方法。在样品中加入30 mL乙酸乙酯,超声提取10 min,离心后在40℃下氮吹浓缩,用乙腈定容后,上机检测。选用Phenomenex Kinetex C18色谱柱(100 mm×2.1 mm,2.6μm)分离,以0.1%(v/v)甲酸-乙腈和水为流动相进行梯度洗脱,采用电喷雾离子(ESI)源,在正离子、多反应监测(MRM)模式下进行扫描,外标法定量。7种荧光增白剂在各自范围内线性关系良好,相关系数均大于0.99,检出限(S/N=3)为0.50~2.65μg/kg,定量限(S/N=10)为1.60~8.80μg/kg;在3个添加水平下的平均加标回收率为64.8%~117.5%,相对标准偏差(n=6)为0.9%~14.4%。该方法操作简单、回收率高、精密度好,适于面粉中7种荧光增白剂的测定。     

Three-dimensional porous silicon-MWNT heterostructure with superior lithium storage performance

A novel three-dimensional porous Si-MWNT heterostructure was designed to meet the demand of high-capacity and long-life lithium storage. This material presented a stable capacity above 1000 mAh g(-1) for nearly 200 cycles, which benefited from its highly porous structure combined with robust MWNT connections that accommodated the host volume change and improved the electric conductivity.     

基于Mask RCNN的桥梁裂缝检测方法设计及研究北大核心CSCD

裂缝是桥梁道路上常见的一种病害,针对其检测准确率有待提高的问题,提出了基于Mask RCNN(region-based convolutional neural networks)的桥梁裂缝检测算法,设计了语义增强模块(semantic enhancement module,SEM),将该模块与特征金字塔网络(feature pyramid network,FPN)相结合,通过特征融合Add计算得到新的多尺度特征图feature maps。针对裂缝形态复杂多样存在识别困难的问题,将裂缝做了两类划分进行检测,并制定了两种策略进行对比实验。实验结果表明:该文中改进的方法可以得到更好的检测结果,检测准确率Accuracy可达99.8%,平均检测精度(mean average precision,mAP)提高了12.6%。     

A crosslinking hydrogel binder for high-sulfur content S@pPAN cathode in rechargeable lithium batteries

High-energy density lithium-sulfur(Li-S)batteries have received intensive attention as promising energy storage system.Among diverse sulfur-based cathodes,sulfu...     

Intercalation of lithium ions into bulk and powder highly oriented pyrolytic graphite

The electrochemical reactions of highly oriented pyrolytic graphite (HOPG) bulk and powder electrodes in 1 M LiPF₆ 1:1 EC/DMC solution were investigated and the results show that the intercalation reaction of lithium ion into HOPG electrode occurs only at the edge plane and SEI formation reaction on the basal plane is negligible in comparison with that on the edge plane. The active surface area of HOPG powder electrode could be deduced by comparing the peak area (consumed charge for SEI formation) at potential of 0.5 V on voltammograms with that of bulk HOPG edge electrode. The diffusion coefficients of lithium ion in HOPG bulk layers and in HOPG powder was for the first time measured by use of electrochemical impedance spectra and potential step chronamperameter methods. It was found that the diffusion coefficients of lithium in HOPG were in the range of 10⁻¹¹-10⁻¹² cm² s⁻¹ for the lithium-HOPG intercalation compounds at potentials from 0.2 (vs. Li/Li⁺) to 0.02 V, decreasing with the increase of lithium intercalation degree. A good agreement was obtained between the results from bulk and powder HOPG electrodes by electrochemical impedance spectra method.     

高效液相色谱-串联质谱法检测乳制品中10种氨基糖苷类抗生素残留

建立了乳制品中链霉素、双氢链霉素、新霉素、卡那霉素、妥布霉素、庆大霉素、安普霉素、潮霉素B、巴龙霉素、阿米卡星等10种氨基糖苷类抗生素(aminoglycosides, AGs)残留的高效液相色谱-串联质谱(HPLC-MS/MS)检测方法。乳制品提取液经亲水-亲脂平衡(hydrophilic- lipophilic balance, HLB)柱净化后,采用反相离子对高效液相色谱分离,电喷雾串联四极杆质谱检测。对样品前处理条件、液相色谱流动相以及质谱条件进行了优化。结果表明: 10种AGs在20～1000 μg/L范围内定量离子的峰面积和样品的质量浓度之间有很好的线性关系;在乳制品中的加标回收率为71.2%～101.7%,相对标准偏差为3.4%～13.8%。该方法简便、灵敏、准确,可用于乳制品中多种AGs残留的同时检测。     

DDQ/TFA： an Efficient Nonmetallic Reagent System for the Oxidative Coupling to Construct Phenanthrene Rings

A mild synthetic method of a series of phenanthrenes with different substituents on the phenanthrene ring is described.The method involves intramolecular oxidative coupling with 2,3-dichloro-5,6-dicyanobenzoquinone （DDQ）/trifluoroacetic acid（TFA） as oxidant to produce phenanthrenes in high yields and is fit for large-scale preparation.Furthermore,DDQ can be regenerated by a simple oxidation.The present approach solves a key step for the synthesis of polycyclic structures related to an alkaloid tylophorine.     

高效液相色谱-荧光检测法测定食品接触材料塑料制品中荧光增白剂

建立了同时测定食品接触材料塑料制品(食品包装袋)中荧光增白剂的高效液相色谱-荧光检测法。样品用20 mL三氯甲烷作提取剂,超声提取30 min,提取温度为40 ℃,用高效液相色谱进行定性定量分析。采用Eclipse XDB-C18(250 mm×4.6 mm, 5 μm)为分析柱,以5 mmol/L乙酸铵溶液和乙腈为流动相,梯度洗脱,荧光激发波长为350 nm,发射波长为430 nm。结果显示,4种荧光增白剂4,4′-双［2-(邻氰苯基)乙烯基］苯(1,4-bis(4-cyanostyryl)benzene, C.I. 199)、1,4-双(2-苯并恶唑)萘(1,4-bis (2-benzoxazolyl)naphthalene, C.I. 367)、4,4′-双(2-甲氧苯乙烯基)联苯(4,4′-bis(2-methoxystyryl)biphenyl, C.I. 378)和2,5-双(5-叔丁基-2-苯并恶唑基)噻吩(2,5-thiophenediylbis (5-tert-butyl-1,3-benzoxazole), C.I. 184)可以较好地分离;检出限(S/N=3)分别为0.3、0.1、0.05、0.14 mg/L,定量限(S/N=10)分别为1.0、0.4、0.2、0.5 mg/L,回收率范围为78.9%～101.1%,相对标准偏差小于10%,线性关系良好。该法简便、结果准确、灵敏度高,能够满足进出口食品包装材料塑料制品中荧光增白剂的日常检测。     

用于镁硫电池的原位生长NiS的泡沫镍正极集流体

采用原位生长NiS的泡沫镍NiS@Ni(NNF)和铜箔分别作为硫@微孔碳(S@MC)正极材料的集流体, 0.4 mol/L(PhMgCl)₂-AlCl₃+1.0 mol/L LiCl “二代镁锂混合”作为电解液, 测试了镁硫电池恒电流和不同倍率下的充放电性能, 分析了2种不同的集流体在涂覆相同正极材料下对镁硫电池性能影响的原因. 研究发现, 采用铜箔集流体的镁硫电池循环后正极极片上观察到明显的裂缝, 镁负极表面有分布不均匀的附着物, 硫含量略高. 采用NNF为集流体时, 由于泡沫镍具有缓冲硫正极体积变化的孔道结构, 正极极片能基本保持原本的形貌; 特别是在NNF上原位生长的NiS可电催化加速多硫化物中间体的转化, 减少多硫化物的生成并减缓其穿梭, 不干扰镁负极上发生的电化学反应, 使镁负极极片表面更为均匀, 明显改善了镁硫电池的循环稳定性和倍率性能.