Determination of ten organic acids by low pressure liquid chromatography

Summary Organic acids, such as lactic, malic and citric acids, are involved in primary metabolism of all living organisms. Their presence in food products contributes to the flavour and their equilibrium with inorganic cations defines to a large extent the acidity of the food preparations. A resin cation-exchanger device, normally used for separating amino-acids, can be adapted for characterizing 10 organic acids: formic, propionic, fumaric, succinic, lactic, malic tartaric, citric, and oxalic. Two monitoring systems were used, one of them based on specific iron III salt coloration with hydroxy-acids.     

Robust interface on ENR-50/TiO2 nanohybrid material based sol-gel technique: Insights into synthesis,characterization and applications in optical

In this work, the sol–gel technique was used to prepare a new organic–inorganic hybrid from Epoxidized Natural Rubber (ENR-50) and Titanium dioxide (TiO₂) by blending different content of titania precursors (10, 30, and 50 wt%) with an ENR-50 matrix. A wide range of analyses was conducted to understand the nature of this hybrid and also to evaluate its potential uses in applications required high refractive index such as micro optical and optoelectronic devices. Results indicated that the ring-opening reaction of epoxide groups in ENR-50 increased with the increase of titania content in the hybrid resulting a strong bonding between titania and ENR-50 through TiOC bond, which was observed in FTIR spectrum at 1027–1028 cm⁻¹. It is also observed a slight decrease in the intensity of the amorphous peak along with a new crystalline peak appeared at 2θ = 23 and 27° due to the crystalline nature of titania. The hybrids showed three thermal degradation steps in the range of temperature 76 to 769 °C due to the existence of the Ti moieties with the mixture of polymer chains, which in turn shifted the T_g at 24.3, 26.9 and 28.1 °C for the hybrid at 10, 30, and 50 wt% TiO₂ compared to the T_g of ENR-50 at −18.4 °C respectively. The morphology of the ENR-50 showed clear changes during of the synthesis of ENR-50/TiO₂ hybrids, these changes were proven by SEM, TEM, and AFM analyses. Uv–Vis results showed that the higher wavelength peak at 293 nm has shifted to 296, 298 and 300 nm for the hybrid at 10, 30, and 50 wt% TiO₂ respectively due to the strong interaction between titania precursors and ENR-50 matrix. Furthermore, the hybrids showed good optical transparency in the visible light range.     

Quantitative studies on furfural and organic acid formation during hydrothermal,acidic and alkaline degradation ofD-xylose

Summary Chromatographic analysis of the degradation ofD-xylose either in plain water or aqueous sulfuric acid at temperatures ranging from 180 – 220°C gave up to 50 mol% of furfural. Activation energies did not differ significantly between reactions in plain water (E _a =119.4 kJ/mol), 0.001M H₂SO₄ (E _a =120.6 kJ/mol), 0.01M H₂SO₄ (E _a =130.8 kJ/mol), and 0.1M H₂SO₄ (E _a =120.7 kJ/mol). However, under alkaline conditions the activation energy was only 63.7 kJ/mol, indicating a different reaction mechanism. Isotachophoretic analyses revealed the formation of pyruvic, formic, glycolic, lactic, and acetic acid. While the relative yields of these acids ranged from 0.8 to 7% under hydrothermal and acidic conditions, 10 – 23% were obtained in alkaline degradation.

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Quantitative Studien zur Bildung von Furfural und organischen Säuren während des hydrothermalen, sauren und alkalischen Abbaues vonD-Xylose

Zusammenfassung Die chromatographische Analyse des Abbaues vonD-Xylose in reinem Wasser und Schwefelsäure bei Temperaturen von 180 – 220°C ergab die Bildung von bis zu 50 mol% Furfural. In bezug auf die Aktivierungsenergie zeigten sich keine signifikanten Unterschiede zwischen dem Abbau vonD-Xylose in reinem Wasser (E _a =119.4 kJ/mol), 0.001M H₂SO₄ (E _a =120.6 kJ/mol), 0.01M H₂SO₄ (E _a =130.8 kJ/mol), and 0.1M H₂SO₄ (E _a =120.7 kJ/mol). Unter alkalischen Bedingungen hingegen betrug die Aktivierungsenergie nur 63.7 kJ/mol. Dies weist auf einen unterschiedlichen Reaktionsmechanismus hin. Ferner konnte mittels Isotachophorese die Bildung von Brenztraubensäure, Ameisensäure, Glycolsäure, Milchsäure und Essigsäure nachgewiesen werden. Während sich die relativen Ausbeuten in Wasser und Schwefelsäure zwischen 0.8 und 7% bewegten, betrugen sie unter alkalischen Bedingungen 10 bis 23%.

     

累托石/聚丙烯插层纳米复合材料的制备与性能

采用熔融共混法制备了有机改性累托石 (OREC)粘土 均聚聚丙烯 (PP)纳米复合材料 ,以X 射线衍射分析 (XRD)及透射电子显微镜分析 (TEM)观察了复合材料的相貌结构 ,研究了复合材料的力学性能及热性能 .结果表明 ,OREC在添加份数较少时可与均聚聚丙烯熔融插层形成插层型聚丙烯纳米复合材料 ,该复合材料与纯PP相比 ,具有较高的拉伸强度、断裂伸长率及冲击强度 .在有机粘土添加 2 %时 ,复合材料的拉伸强度、断裂伸长率、冲击强度最高 ,与纯PP相比 ,2 %添加量的聚丙烯纳米复合材料拉伸强度提高 6 5 7% ,断裂伸长率提高 2 89 3% ,冲击强度提高 14 1% ,10 %失重率时对应的热分解温度提高 50K .     

速差动力学分析及其应用进展

速差动力学分析是不经分离同时或连续测定混合物中性质密切相关的多组份的重要方法。本文综述了该法在１９８９－１９９２年间国内外新进展，尤着重其在有机，生物混合物中多组份分析的应用及新的计算方法，化学计量学的引入。引用最新文献６７篇。     

六次甲基四碲富瓦烯二碘盐的合成、晶体结构及其某些固态物性

在两相混合溶液中电解合成了HMTTeF·I_2盐的单晶。晶体属P2_1/n空间群,独立区里有一个HMTTeF分子,离子化发生在分子中的一个碲原子孤电子对上。粉末压片常温电导率为4.1×10~(-5)Scm~(-1)。喇曼光谱测定与电导率及X射线分析结果相符。     

Electroabsorption study of metal-to-ligand charge transfer in an organic complex of iridium (III)

The dipole moment and polarizability changes have been determined from electroabsorption (EA) spectroscopy of solid films of fac tris(2-(phenyl)pyridinato,N,C^2′)iridium (III) [Ir(ppy)₃]. The maximum changes in the dipole moment |Δμ|_S=(5.0±0.5) D/f (f is the local field correction factor: 1.3–1.7) accompany ground state to the lowest singlet, and |Δμ|_T=(1.7±0.5) D/f ground state to the lowest triplet metal-to-ligand charge transfer (MLCT) excited states formation, while the average polarizability change ų/f² follows from the fitting procedure throughout the visible absorption spectrum range. The experimental values of |Δμ| as well as energy positions of the MLCT states correlate with the literature results of time-dependent density functional theory.     

Time-resolved ultraviolet laser-induced breakdown spectroscopy for organic material analysis

Ultraviolet pulses (266 nm) delivered by a quadrupled Nd:YAG laser were used to analyze organic samples with laser-induced breakdown spectroscopy (LIBS). We present characteristics of the spectra obtained from organic samples with special attentions on the emissions of organic elements, O and N, and molecular bonds CN. The choice of these atomic or molecular species is justified on one hand, by the importance of these species to specify organic or biological materials; and on the other hand by the possible interferences with ambient air when laser ablation takes place in the atmosphere. Time-resolved LIBS was used to determine the time-evolution of line intensity emitted from these species. We demonstrate different kinetic behaviors corresponding to different origins of emitters: native atomic or molecular species directly vaporized from the sample or those generated through dissociation or recombination due to interaction between laser-induced plasma and air molecules. Our results show the ability of time-resolved UV-LIBS for detection and identification of native atomic or molecular species from an organic sample.     

“双一流”背景下高等农业院校有机化学基础课程教学新模式的构建及实践

The crop science of Sichuan Agricultural University is an authorized first-class discipline. As the strategic supporting department for innovative talent cultivation in agriculture and forestry major, we are facing a long-term challenge in reforming the teaching mode for basic course-organic chemistry and cultivating talented students with solid basic knowledge and strong sense of innovation. Herein a thorough survey was performing to establish the executable teaching programs for this course during the "Double-First Class Universities Plan" period. A multidimensional teaching resource library for organic chemistry course was also constructed. The new classroom teaching mode "Interest cultivation-Creative thought development-Autonomous and Cooperative learning", along with a stepwise practice teaching mode "Foundation skills-Integrated application-Innovative trial" was proposed and practiced among thirty-five majors including agriculture, forestry and veterinary, to improve the quality for innovative talent cultivation and support our first-class discipline construction. This research could probably serve as a reference for congeneric agricultural university.