ION-EXCHANGE RESIN–CATALYZED SYNTHESIS OF POLYOXYMETHYLENE DIMETHYL ETHERS: A PRACTICAL AND ENVIRONMENTALLY FRIENDLY WAY TO DIESEL ADDITIVE

Polyoxymethylene dimethyl ethers (PODE_n) were synthesized via the reaction between dimethoxymethane (DMM) and trioxymethylene catalyzed by CT175, a macroporous strongly acidic cation-exchange resin. The influences of reaction conditions such as catalyst types, reaction temperature, time, pressure, catalyst dosage, and mass ratio of DMM to trioxymethylene were also investigated. Under the optimized conditions of m(dimethoxymethane):m(trioxymethylene) = 2.5:1, CT175 (7.5 wt.%), 90°C, 0.5 h, and 1.5 MPa, the conversion of trioxymethylene and the selectivity to PODE_3-8 was obtained as high as 89.0% and 64.2%, respectively. Moreover, the resin catalyst can be reused up to 20 times without obvious change in its activity. The 100% atom efficiency, green reaction process, mild reaction conditions, as well as easy workup make the protocol advantageous and acceptable.     

Syntheses, Crystal Structures and Photophysical Properties of a Series of LnIII (Ln?=?Sm, Tb, Pr) Coordination Polymers

Four new lanthanide(Ш) coordination polymers, [Ln(p-aminobenzoate)₂(DMF)(HCOO) (H₂O)]_n (Ln = Sm 1, Tb 2, Pr 3) and {[Pr(2,5-dcp)(CH₃COO)(H₂O)]·1.5H₂O}_n (4) (DMF = N,N-dimethylformamide, 2,5-dcp = pyridine-2,5-dicarboxylate), have been synthesized by hydrothermal method. The structures are determined by the single-crystal X-ray diffraction. The four polymers all crystallize in the monoclinic space group P2₁/n. Polymers 1 and 2 are isostructural; both Sm^III ion of polymer 1 and Tb^III ion of polymer 2 are eight-coordinate. Although polymer 3 possesses the same asymmetric unit as polymers 1 and 2, the three are not isomorphous. The Pr^III ions in polymers 3 and 4 are nine-coordinate. In polymers 1, 2 and 3 the neighboring units are bridged by formyloxy and extend into infinite chains, which are connected by hydrogen bonds to form a hydrogen bond network. However, polymer 4 is bridged by pyridine-2,5-dicarboxylate and acetates to form an infinite 3D network. At room temperature, the IR, UV–Vis–NIR and emission spectra of the four polymers were measured and analyzed. The four polymers emit in the visible or NIR region. The luminescent properties are discussed.     

二极管阵列-超高效液相色谱法同时测定食品中5种添加剂的含量

目的建立二极管阵列-超高效液相色谱法同时测定食品中苯甲酸、山梨酸、安赛蜜、糖精钠及脱氢乙酸的分析方法。方法样品采取优化的前处理方法,纯水超声提取,高速离心后准确量取清亮液体经0.22μm滤膜过滤,5种添加剂通过乙腈-磷酸二氢钾洗脱体系与甲醇-乙酸铵洗脱体系的比对分析实验,同时采用二极管阵列检测器和保留时间对待测组分进行双重定性鉴别,采取外标法定量。结果 5种成分采用2种洗脱体系均能得到良好的检测结果,在0.001～0.10 mg/m L范围内,有良好的线性关系(r≥0.9999)。CFAPA-175酱油中山梨酸的检测及PTC T118果汁中苯甲酸的检测2个能力验证,采用乙腈和磷酸二氢钾洗脱体系均取得满意结果。结论乙腈-磷酸二氢钾洗脱体系有较好的分离效果,运行时间短,方法操作简单、快速、准确,绿色环保,可应用于批量样品中5种添加剂的检测。     

2017~2019年昆明市市售食用鱼中几种违禁药物分析

目的 了解2017~2019年昆明市市售食用鱼中违禁药物残留状况。方法 2017~2019年随机采集市售食用鱼142份, 按照《国家食品污染和有害因素风险监测工作手册》检测违禁药物残留, 几种违禁药物都不得检出。结果 142件样品中违禁药物添加检出62件, 检出率39.4%(56件)。孔雀石绿和隐形孔雀石绿, 硝基呋喃代谢物, 喹乙醇及其代谢物检出率分别为2.8%(4件), 28.2%(40件), 8.4%(12件), 检出率最高的是硝基呋喃代谢物。违禁药物检出率最高的是鳝鱼, 其次是泥鳅。结论 昆明市市售食用鱼存在不同程度的违禁药物使用情况, 建议相关部门加大监管力度。     

食品包装瓶用PET树脂乙醛含量测定结果的影响因素研究

目的探究氮气、水分、粉碎时间、粒径对食品包装瓶用聚对苯二甲酸乙二醇酯(PET)树脂粒子中残留乙醛含量测定结果的影响。方法根据SH/T 1817-2017《瓶用聚对苯二甲酸乙二醇酯(PET)树脂中残留乙醛含量的测定顶空气相色谱法》,采用控制变量法,考察氮气吹扫顶空瓶、样品含水量、粉碎时间、粒径对瓶用PET树脂粒子乙醛含量测试结果的影响。结果经过氮气保护的测试结果高于未经氮气保护的测试结果;含5、10、15μL蒸馏水试样的测试结果高于干燥样品的测试结果,且含水量越大测试结果越大;粉碎时间对测试结果的影响不明显(P=95%);粒径越小测试结果越大。结论测试食品包装瓶用PET树脂粒子乙醛含量时,样品须用氮气保护且保持干燥状态,以获得准确的测试结果。建议SH/T 1817-2017中对于试样粒径的要求进一步细化,以提高测试方法的统一性。     

Self-assembled ionic liquid synthesis of nitrogen-doped mesoporous TiO2 for visible-light-responsive hydrogen production

Nitrogen-doped mesoporous TiO₂ has been synthesized by a simple solvent evaporation-induced self-assembly method using a nitrogen-containing ionic liquid concurrently as a nitrogen source and mesoporous template. After being evaporated and subsequently calcined at various temperatures (300–900 °C), the synthesized samples were thoroughly characterized by X-ray diffraction (XRD), Raman, small-angle X-ray scattering patterns (SAXS), N₂ adsorption-desorption isotherms, X-ray photoelectron (XPS) and UV–Vis diffuse reflectance (UV–Vis DR) spectroscopies. The obtained results suggest that the calcination temperature greatly influences the crystallization of TiO₂, formation of mesoporous structure, specific surface area and N-doping amounts. Among the fabricated photocatalysts, the samples calcined at 600 °C exhibit superior photocatalytic performance for hydrogen production in water/methanol solution under visible light illumination if compared to other synthesized samples and commercial TiO₂ (Degussa P25). The finding is possibly due to the synergy of more N-doping amounts on the well-defined mesoporous TiO₂ with highly anatase crystal phase and moderate surface area in the catalysts.     

Use of flexible micro-temperature sensor to determine temperature in situ and to simulate a proton exchange membrane fuel cell

In this work, a micro-temperature sensor on a 40 μm flexible stainless-steel substrate was fabricated using micro-electro-mechanical systems (MEMS). Embedding a micro-temperature sensor in a proton exchange membrane fuel cell (PEMFC) to monitor temperature will not damage the sensor during the experimental process. This investigation is the first to develop a micro-temperature sensor that can be placed anywhere between the membrane electrode assembly (MEA) and the flow-channel plate inside a PEMFC. The simulated temperature is consistent with the experimentally determined temperature. The performance curve is also consistent with experimental results, revealing the accuracy of the simulation and the effectiveness of monitoring temperature inside a PEMFC.     

2019年云南市售大米真菌毒素污染水平及风险评估

目的 检测云南省市售大米中16种真菌毒素污染水平,评估其食用安全风险.方法 采用高效液相色谱-串联质谱法(high performance liquid chromatography-tandem mass spectrometry,HPLC-MS/MS)对大米中的真菌毒素进行检测分析,并对检测结果进行食用安全性评估....     

Fast determination of royal jelly freshness by a chromogenic reaction

Royal jelly is one of the most important products of honeybees. Given its role in development of bee brood into fertile individuals of the royal caste it is also used in health products for human consumption. Royal jelly spoils and loses its health-promoting properties depending on storage duration and conditions. To ensure product quality before selling, it is therefore necessary to assess royal jelly freshness. Many indexes of freshness have been suggested, but they all lack reliability or require complex and time-consuming analyses. Here we describe a method to detect royal jelly freshness based on a chromogenic reaction between royal jelly and HCl. We demonstrate that analyses based on color parameters allow for the discrimination of royal jelly samples based on the duration of their storage. Color parameters of royal jelly stored at -18 and 4 °C for 28 d remained comparable to that of fresh samples, which supports the reliability of the method. The method of freshness determination described is practical, cheap, and fast and can thus be used in real-time when trading royal jelly. PRACTICAL APPLICATION: The method developed can be used to assess royal jelly freshness. It is practical, cheap, and fast and can thus be used in real-time when trading royal jelly.     

超高效液相色谱-串联质谱法测定食品中脱氧雪腐镰刀菌烯醇的方法优化

目的 优化超高效液相色谱-串联质谱法测定食品中脱氧雪腐镰刀菌烯醇含量的分析方法。方法 样品经粉碎匀质后, 采用70%乙腈-甲酸水溶液涡旋浸泡提取, 普瑞邦亲和柱净化, 以乙腈-0.05%氨水作为流动相, Waters BEH C18柱(2.1 mm×100 mm, 1.7 μm)进行色谱分离, 超高效液相色谱-串联质谱的多反应监测(multiple reaction monitoring, MRM)模式进行测定, 内标法定量。结果 脱氧雪腐镰刀菌烯醇在5.0~150.0 μg/L范围内具有良好的线性关系(r2=0.9995), 添加回收率为93.4%~101.6%, 相对标准偏差为1.41%~3.54%, 质控样检测值在参考值允许范围内(569±60) μg/kg, 具有较好的重现性和准确度。结论 本研究提升了脱氧雪腐镰刀菌烯醇的检测能力, 该方法准确、可靠、便捷, 可满足实验要求。