Determination of ammonia based on the electro-oxidation of hydroquinone in dimethylformamide or in the room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

The results detail a novel methodology for the electrochemical determination of ammonia based on its interaction with hydroquinone in DMF. It has been shown that ammonia reversibly removes protons from the hydroquinone molecules, thus facilitating the oxidative process with the emergence of a new wave at less positive potentials. The analytical utility of the proposed methodology has been examined with a linear range from 10 to 95 ppm and corresponding limit-of-detection of 4.2 ppm achievable. Finally, the response of hydroquinone in the presence of ammonia has been examined in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide, [EMIM][N(Tf)₂]. Analogous voltammetric waveshapes to that observed in DMF were obtained, thereby confirming the viability of the method in either DMF or [EMIM][N(Tf)₂] as solvent.     

4种喹诺酮类药物滤纸基质室温光法研究

提出了以滤纸为基质的环丙沙星、氟罗沙星、洛美沙星和氧氟沙星4种喹诺酮类药物的滤纸基质室温光(PS-RTP)分析的新方法. 方法取样量少(1.5 μL).其线性动力学范围依次为0.11～55.2、0.35～211、2.10～526 、1.03～411(ng/斑点);灵敏度高,其检出限分别为0.082、0.070、0.080、0.123(ng/ 斑点);标准回收率在97.70%～102.2%之间.相对标准偏差RSD＜1.8%.     

离子液体反应介质中3-羟基丙酸甲酯加氢反应研究

以室温离子液体[Bmim]PF6作为反应介质,研究了四羰基钴钾K[Co(CO)4]催化3-羟基丙酸甲酯(3-HPM)加氢制1,3-丙二醇(1,3-PDO)的反应,并对反应条件进行了优化.同有机溶剂作为反应介质相比,该体系具有更高的选择性和更好的催化活性,并且产物经水萃取便可实现催化体系的回收利用.在反应温度165℃、氢气压力10.5 MPa、反应时间10 h、咪唑为促进剂的较佳反应条件下,3-HPM的转化率可达99.4%,1,3-PDO的收率可达82.9%,催化剂重复使用3次,1,3-PDO的收率不低于70%.并根据实验结果,提出了可能的催化反应机理.     

新型室温酯化法接枝聚合物改性SiO_2纳米微粒

提出了一种在室温、大气环境等温和条件下通过酯化反应将端羧基聚合物链接枝到纳米SiO2微球表面从而制备有机/无机复合纳米微粒的新方法.该方法通过以下两个步骤得以实现,即第一,用3-环氧丙基三甲氧基硅烷对纳米SiO2微球表面进行改性处理,接着将引入到纳米SiO2表面的环氧基团转化为烷羟基基团;第二,通过引入到纳米SiO2微球表面的烷羟基与聚合物中的端羧基在室温下发生酯化反应,从而将聚合物接枝到纳米SiO2表面制得复合微球.利用XPS、FTIR、TEM和TGA等测试手段对纳米SiO2的改性过程以及聚合物接枝后得到的复合微球进行了表征.研究结果表明,该室温酯化接枝方法具有较高的接枝率,接枝到无机纳米微粒表面的聚合物占复合微球质量的55wt%～70wt%;接枝聚合物后,纳米SiO2微球的粒径从40nm增加到64～75nm,从而得到了以SiO2为核、以聚合物为壳的有机-无机复合微球.     

常温直接沉淀法制备ZnO纳米棒

在常温下, 以PEG-400(聚乙二醇400)为表面活性剂, 采用直接沉淀法合成了ZnO纳米棒. 产物用XRD, TEM, SAED和 HRTEM等进行了表征. 结果表明, 所得ZnO为一维的纳米棒, 属于六方纤维矿的单晶结构. ZnO纳米棒的直径在20~40 nm之间, 长度在300~800 nm范围. (0001)面为ZnO纳米棒的生长方向. 讨论了ZnO相的生成和ZnO纳米棒的形成机理以及PEG-400在其形成过程中的作用.     

室温离子液体在分离分析中的应用

室温离子液体是指室温或接近室温下全部由离子组成的有机液体物质,具有不挥发,不易燃,溶解范围大,对空气和热稳定等特点,作为一种“可设计”型的环境相对友好溶剂,已被成功应用于分离分析领域中。本文重点综述了离子液体近年来在毛细管电泳、液相色谱及气相色谱中的应用进展,也对离子液体在质谱和光谱中的应用作了介绍。     

Synthesis of multi-hydroxyl and sulfonyl dual-functionalized room temperature ionic liquids

Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1,3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts and corresponding acidic room temperature ionic liquids have been synthesized. The hydroxyl groups of the synthesized substances were confirmed by the 1H NMR measurement. These zwitterionic salts and ionic liquids may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte).     

Polypyrrole-Fe2O3 nanohybrid materials for electrochemical storage

We report on the synthesis and electrochemical characterization of nanohybrid polypyrrole (PPy) (PPy/Fe₂O₃) materials for electrochemical storage applications. We have shown that the incorporation of nanoparticles inside the PPy notably increases the charge storage capability in comparison to the “pure” conducting polymer. Incorporation of large anions, i.e., paratoluenesulfonate, allows a further improvement in the capacity. These charge storage modifications have been attributed to the morphology of the composite in which the particle sizes and the specific surface area are modified with the incorporation of nanoparticles. High capacity and stability have been obtained in PC/NEt₄BF₄ (at 20 mV/s), i.e., 47 mAh/g, with only a 3% charge loss after one thousand cyles. The kinetics of charge–discharge is also improved by the hybrid nanocomposite morphology modifications, which increase the rate of insertion–expulsion of counter anions in the bulk of the film. A room temperature ionic liquid such as imidazolium trifluoromethanesulfonimide seems to be a promising electrolyte because it further increases the capacity up to 53 mAh/g with a high stability during charge–discharge processes.     

Room Temperature Ionic Liquid Carbon Nanotube Paste Electrodes: Overcoming Large Capacitive Currents Using Rotating Disk Electrodes

The voltammetric response of graphite or carbon nanotube paste electrodes, which incorporate the room temperature ionic liquid, N‐butyl‐N‐methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide or [C₄mpyrr][NTf₂], (RTIL‐CNTPE and RTIL‐CPE respectively) as the binder, towards anionic, cationic and neutral redox probes is examined and compared to conventional paste electrodes which use mineral oil as the binder. The RTIL paste electrodes are found to suffer from very large background currents due to capacitive charging. This is exacerbated further when CNTs are combined with RTILs in the paste. The large charging currents obscure any Faradaic processes of interest, especially at low analyte concentrations. By employing steady state voltammetry at a rotating disk electrode made of the RTIL pastes this problem can be overcome. This allows the electroanalytical properties of these interesting electrode substrates, which combine the attractive properties of CNTs with RTILs to be further explored and developed.     

Electrochemical Determination of Ascorbic Acid in Room Temperature Ionic Liquid BPPF6 Modified Carbon Paste Electrode

A room temperature ionic liquid N‐butylpyridinium hexafluorophosphate (BPPF₆) was used as a binder to make an ionic liquid modified carbon paste electrode (IL‐CPE), which showed good characteristics such as simple preparation procedure, fast electrochemical response and good conductivity. The electrochemical oxidation of ascorbic acid (AA) on the new IL‐CPE was carefully studied. The oxidation peak potential of AA on the IL‐CPE appeared at 109 mV (vs. SCE), which was about 338 mV decrease of the overpotential compared to that obtained on the traditional carbon paste electrode (CPE) and the oxidation peak current was increased for about four times. The electrochemical parameters of AA on the IL‐CPE were calculated with the charge transfer coefficient (α) and the electrode reaction rate constant (k_s) as 0.87 and 0.800 s^?1, respectively. Based on the relationship of the oxidation peak current and the concentration of AA a sensitive analytical method was established with cyclic voltammetry. The linear range for AA determination was in the range from 1.0×10^?5 to 3.0×10^?3 mol/L with the linear regression equation as I_p (μA)=?2.52–0.064C (μmol/L) (n=13, γ=0.9942) and the detection limit was calculated as 8.0×10^?6 mol/L (3σ). The proposed method was free of the interferences of coexisting substances such as dopamine (DA) and amino acids etc., and successfully applied to the vitamin C tablets determination.