MOOCs offer solutions to traditional constraints faced in chemistry experimental teaching,such as limited lab space,insufficient equipment,and rigid scheduling,However,challenges like underutilization,reluctance from students,and faculty unfamiliarity can undermine these efforts.To address these issues,the National Demonstration Center for Experimental Chemistry and Chemical Engineering Education(Beijing University of Chemical Technology)has explored how to effectively use MOOCs to enhance teaching quality.The team has established an extensive array of online experimental teaching resources,implemented a synergistic blended learning model,and developed both a faculty skill enhancement program and a comprehensive system for tracking and feedback on teaching quality.These initiatives have significantly improved educational effects.

C20H40Cl2CuKO10, triclinic, P1‾$P\overline{1}$ (no. 2), a = 9.0148(5) Å, b = 9.3066(5) Å, c = 17.7296(10) Å, α = 78.383(2)°$78.383(2){}^{\circ}$, β = 88.488(2)°$88.488(2){}^{\circ}$, γ = 72.982(2)°$72.982(2){}^{\circ}$, V = 1392.35(13) Å3, Z = 2, Rgt(F) = 0.0781, wRref(F2) = 0.2089, T = 170(2) K.

Hindered phenolic antioxidants have been extensively recognized and applied to boost the heat resistance and oxidative aging performance of poly-(propylene) (PP) composites. Low-molecular-weight antioxidants are easy to volatilize, migrate, and be extracted from PP or PP-based products, which can directly reduce the antithermal oxidative aging effect of PP and its composites, and it can contaminate food or drugs under its packaging. The design of an efficient and durable antioxidant with antimigration performance has drawn the attention of researchers. Currently, three main approaches are explored: (I) enhancement of molecular weight, that is, high molecular weight of antioxidants can stimulate the structure stability and the resistance toward migration; (II) inorganic immobilization, which involves immobilizing the antioxidants on inorganic substrate to enhance the dispersion and the antimigration performance; and (III) intercalation-mediated assembly, which involved intercalating low-molecular-weight antioxidants into the interlayer region of a layered host to boost antimigration performance based on the host-guest interaction.

A magnetic solid phase extraction method based on magnetic covalent organic frameworks (TpBD@Fe3 O4 ; 2,4,6-triformylphloroglucinol (Tp) and benzidine (BD)) combined with high performance liquid chromatography has been developed to detect the sulfonamides including sulfadiazine, sulfamerazine, sulfamethazine, and sulfamethoxazole in milk and meat. TpBD@Fe3 O4 were synthesized at room temperature under mild reaction conditions with a simple and rapid operation. The TpBD@Fe3 O4 exhibited higher extraction efficiency because of the π-π and electrostatic interactions between the benzene ring structure of the TpBD and the sulfonamide molecules. The extraction conditions including the dosage of adsorbents, the type and dosage of eluent, the elution time, and the pH of the sample solution were fully optimized. The detection results showed good linearity over a wide range (50-5 × 104 ng/mL) and low detection limits (3.39-5.77 ng/mL) for the sulfonamide targets. The practicability of this magnetic solidphase extraction-high-performance liquid chromatography method was further evaluated by analyzing milk and meat samples, with recoveries of the targets of 71.6-110.8% in milk and 71.9-109.7% in pork. The successful detection of sulfonamides residues has demonstrated the TpBD@Fe3 O4 excellent practical potential for analyzing pharmaceutical residues in animal-derived foods.

Laboratory safety is an important part in the process of chemistry laboratory teaching, and it is also one of the key tasks of every school at all levels.A five-in-one laboratory safety mechanism, including laboratory technology lecture, laboratory safety and environmental protection class, safety explanation and demonstration in the process of experimental project implementation, emergency evacuation drill in laboratory accidents and laboratory fire drill, has been gradually formed after many years of teaching and exploration at the Experimental Teaching Center of Chemistry, Beijing University of Chemical Engineering.These measures greatly improve the safety awareness of students in the lab class, ensure the experiment proceeded in safely and stably, and ensure a good order of campus teaching effectively.This paper analyzes the above "five-in-one" chemistry laboratory safety education teaching mode, hoping to explore how to ensure the safety of chemistry laboratory teaching with all colleagues.

国家标准中采用冷溶剂指示剂滴定法测定油脂酸价,具有实验仪器简单、试剂易得、操作方便的优点.将国家标准方法转化为探究性实验教学内容,有利于激发学生学习兴趣,提高自主学习能力,但是该方法直接应用在实验教学中存在一定的不足之处,因此进行了相应的改进,包括采用常见的常量滴定管代替微量滴定管,降低滴定剂浓度,利用更安全的环己烷作溶剂,通过临近滴定终点前加入去离子水的方式提高滴定终点的稳定性等.在教学实践中采用以学生为主体,以问题为导向的教学模式,培养学生知识整合和综合应用的能力,促进素质型、创新型人才培养.

有益微量元素在人体的正常生命机能和各种新陈代谢中都发挥着重要的作用,同时有害重金属含量过高会对人体产生负面的影响.指甲是微量元素代谢的途径之一,因此分析指甲中元素的含量具有重要意义.本文首先建立了指甲中元素含量测定方法,采用微波消解法对指甲样品进行前处理,再使用ICP-MS测定V、Cr、Mn、Fe、Co、Cu、Zn、As、Se、Mo、Ag、Cd、Hg和Pb元素的含量,实验结果表明该方法的准确度和精密度良好.然后对同一地区100份不同个体的指甲进行了测定,结果表明指甲中有些元素的含量受性别影响,也跟环境和饮食有关.

为实现在新型冠状病毒肺炎疫情防控期间"停课不停教,停课不停学",以化学类本科专业课程"分离科学与技术"为例,构建了基于企业微信平台和在线教育综合平台的"双平台"线上教学策略,探索了线上教学中体现"以学生为中心"教育理念的教学方法.

目的 建立固相萃取-高效液相色谱法测定鸡蛋中氟虫腈农药及其主要的代谢物氟虫腈砜、氟虫腈亚砜、氟甲腈的分析方法.方法 选用含1％甲酸的乙腈溶液(V:V)为提取溶剂,用石墨化碳黑/氨基固相萃取小柱萃取净化,用乙腈作洗脱剂,并在以甲醇-水(67:33,V:V))为流动相的条件下进行高效液相色谱检测.结果 该方法的线性范围为0.3～10.0μg/g,4种目标物的检测限均在0.05～0.10μg/g之间.通过对实际鸡蛋样品加标检测,得到加标回收率在80.9％～115.8％之间,相对标准偏差均小于6.2％.结论 该方法精密度较高、稳定性良好、操作简便,可用于鸡蛋样品中氟虫腈及其3种代谢物的测定.

In this paper,the poly(amidoamine) dendrimer modified silica was used to immobilize aminoacylase by glutaraldehyde as crosslinking agent.The influence of different generation of PAMAM,glutaraldehyde concentration,reaction time and temperature on enzymatic activity of the immobilized enzyme were evaluated.The enzymatic properties of the immobilized enzyme were also evaluated.The results showed that the immobilization efficiency increased with the generation of PAMAM increasing,and the immobilized enzyme remained high activity.

PAMAM dendrimer modified silica was prepared for trypsin immobilization.The generation of PAMAM and the immobilization conditions were investigated.The results showed that the 3.0 G PAMAM dendrimer modified silica would provide high immobilization yields and enzymatic activity and it was employed for trypsin immobilization.The optimum temperature and pH of the immobilized enzyme were 60℃ and 9.0,respectively.The Km value for casein was 7.76 mg/mL.Compared with free enzyme,the immobilized enzyme has better thermo-stability,and it also features good storage stability and reusability.

The microwave assisted preparation of PMAM dentrimers modified silica was presented in the paper.The adsorption of BSA on modified silica was studied in details.The preparation processes were characterized by elementary analysis and FTIR. The results showed that the amide group in the surface of silica by the microwave assisted technique was the same as the traditional method but the preparation time was shorten from 24 hrs to 40 mins.This indicated that the microwave assisted technique can be used as a efficient preparation method for the silica modification by dendrimers.The adsorption capacity to BSA was found larger than that of bare silica and the capacities were increased with the increase of the generation of dendrimers.

Microwave irradiation was introduced into the preparation of an open tubular capillary electrochromatographic(OT-CEC) column with immobilized teicoplanin as chiral stationary phase.The change of electroosmotic flow(EOF) was measured by varying the pH values of the mobile phase.It indicated that teicoplanin immobilized capillary decreased EOF effectively.To evaluate the electrochromatographic performance of the prepared capillaries,the enantiomer separation of several chiral amino acids and aromatic racemates was investigated.Baseline separation of the enantiomers could be achieved by the column.The reproducibilities were also evaluated by D,L-Tryptophan with satisfactory results.

The effects of various activations including HCl activation at room temperature, H2SO4 activation at room temperature, anodic H2SO4 activation, cathodic H3SO4 activation, H2SO4 activation at elevated temperature of 65℃, and H2SO4-CrO3 activation on the uniformity and wear resistance of coloring films of stainless steel were investigated. The potential-time curves of the coloring films on the stainless steel were determined. The relationship between the potential-time curve parameters tb and tc and their influence on the quality of the coloring films on the stainless steel were also explored. It was found that the activation was able to speed the coloring process and helped the formation of bright, uniform, and wear-resistant coloring films. At the same time, the coloring rate of the stainless steel increased with increasing temperature, and anode electrolysis activation was superior to cathode electrolysis activation. Moreover, HCl and H2SO4 with the same concentration had the same activation effect, and the optimal activation was realized by anode electrolesis in 10% H2SO4. In addition, the potential-time curve parameters tb and tc could be used to express the activation effect and the readiness of coloring.

The effects of additives on chemical coloring of stainless steel are investigated in this paper.The results show that the colors of coloring film on the stainless steel at the same potential difference is basically consistent,but the colors move to long wave length direction as the three kinds additive dosages increase;ZnSO4 stabilizes the coloring potential,which not only makes the coloring potential easy to be recorded,but also makes the colors easy to be controled and reappeared;MnSO4 not only plays acceleration role,but also can increase the brightness of the coloring films;and(NH4)6Mo7O24·4H2O can not only enhance the brightness but also reinforce the wearability of the coloring films.

The structure,preparation,mensuration and application of polyiodides were summarized.Resin-polyiodides were prepared by fluidized bed method,solid and liquid polyiodides were prepared by direct reaction method.Means of mensuration of polyiodides are various and X-ray diffraction,Raman and far-IR spectroscopy are primary methods for the characterization of polyiodides.Polyiodides have important applications in the bactericidal and electric fields.

T818B pour point depressant was synthesized by esterification and polymerization,the pour point depression and the depressing mechanism were also discussed in the paper.The results showed that the T818B depressant has excellent depressing effects on naphthenic lube oil when containing 3～5 g/kg the additive,and almost has no effects on waxy lube oil.The depressing mechanism of T818B pour point depressant is that the dibehenyl fumarate-vinyl acetate copolymer changes the directions of the crystallization of the naphthenic lube oil,which makes it difficult to mass into three-dimensional net structure,and so the pour point is depressed.

The method of determining methyl naphthalenes by HPLC was established and the experiment parameters of UV detector wave length,mobile phase and the concentration etc.was determined in this paper.The results show that it is feasible to analyze α-methyl naphthalene and β-methyl naphthalene in the mixture of methyl naphthalenes by HPLC.