Preparation of Copper Chromite by Vaccum Freezing Drying Method and Its Catalytic Activity for Sulfuric Acid Decomposition

Iodine sulfur (IS) process is one of the most promising routes for massive and CO₂‐free hydrogen production. Among the three reactions IS process composed, decomposition of sulfuric acid is the most energy intensive step and has to be conducted in the presence of catalyst. In this work, copper chromite (CuCr₂O₄) was prepared, characterized, and used as the catalyst for sulfuric acid decomposition reaction. The co‐precipitation preparation method of CuCr₂O₄ which featured in vacuum freezing drying (VFD), was applied, and the main factors which influence the structure of CuCr₂O₄ such as pH values of the co‐precipitation solution and calcination temperature were investigated. Results showed that pH value affected the size of copper chromite granule, when pH was between 7 and 8, the size of prepared CuCr₂O₄ was in nanometer scale. Calcination temperature influenced the purity of the crystal. The samples were characterized by XRD, TEM and BET. The catalytic activity of CuCr₂O₄ prepared by VFD was evaluated and compared with CuCr₂O₄ prepared by usual co‐precipitation method and Pt/Al₂O₃. Results showed that the activity of CuCr₂O₄ was close to that of Pt catalyst, but apparently higher than that of CuCr₂O₄ prepared by usual method. In addition, it presents good stability in the 70 h test. Therefore, it was promising to be used in the sulfuric acid decomposition step of IS process.     

Determination of Nitrite by a Modified Electrode of Poly(1-Naphthylamine) Film Doped with Dawson-Type Heteropolyanions

 The voltammetric behavior of the electrode modified with poly(1-naphthylamine) film doped with α-P₂W₁₈ heteropolyanions was investigated. The concentration of the modifier, the acidity of the medium and the scan range of potential had obvious effects on the electrochemical characteristics of the electrode. The electrocatalytical characteristics of the film electrode were studied by cyclic voltammetry and other methods. It is suggested that the electrocatalytic reaction of nitrite is controlled by its diffusion. The applicability of the electrode was assessed by the determination of nitrite in waste-water. Determination limit for nitrite was 5 × 10⁻⁷ mol.L⁻¹. Received August 23, 1999. Revision January 2, 2001     

阿托品选择电极的研制和应用

报道了一种阿托品选择性电极的研制和应用，该电极是将对阿托品敏感的聚氯乙烯膜涂敷于ｐＨ玻璃电极球部表面而制成。在０．１０ｍｏｌ／Ｌ，磷酸盐冲浓度（ｐＨ４．０）中，所制电极对阿托品的Ｎｅｒｎｓｔ响应线性范围为１．７０×１０＾－５～２．００×１０＾－２ｍｏｌ／Ｌ阿托品，响应斜率为５５．８ｍＶ，电极响应时间小于４５ｓ，使用寿命大于６个月，而且具有制作简单，使用方便的特点，已将该电极应用于硫酸阿托品制剂中测     

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.     

Regioselective synthesis of pentathiepines fused with pyrrole, thiophene, or indole rings

Pentathiepines fused with pyrrole, thiophene, or indole rings were obtained by reactions of the corresponding heterocycles or their tetrahydro derivatives with a prepared mixture of sulfur monochloride and DABCO. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2002–2005, November, 2006.     

降低聚氯乙烯膜黄连素选择性电极检出限的新方法

PVC药物选择性电极的检出限主要是由膜中活性物质的溶解和内参比溶液中被测离子在膜中的迁移所决定的。为了减少这两种不利因素的影响 ,采用内参比为含可乐定的氯化钠溶液的可乐定选择性电极测定黄连素。测定的线性范围为 1.0× 10 - 4～ 1.0× 10 - 8mol L ,平均斜率为 5 8.6mV decade ;检出下限为 2 .5×10 - 9mol L ,比已报道的检出下限要低 2～ 3个数量级。电极的选择性明显提高 ,选择性系数的测定更加可靠真实 ,并获得良好的重现性和稳定性。以标准加入法测定回收率 ,结果令人满意。     

Electrochemical behavior of some triazine derivatives at glassy carbon electrode in non-aqueous media

Electroreduction of 4-amino-6-methyl-3-thio-1,2,4-triazine-5-one (I), 6-methyl-3-thio-1,2,4-triazine-5-one (II), and 2,4-dimethoxy-6-methyl-1,3,5-triazine (III) in dimethylformamide was investigated. Electrochemical techniques including differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry, and coulometry were employed to study the mechanism of the electrode process. From the analysis of the voltammetric and spectroscopic experiments a mechanism was proposed for the electroreduction of thio-triazine and triazine compounds. Compounds I and II having thiol groups exhibited similar redox behavior. Both compounds displayed two cathodic peaks, whereas the third compound (III), with no thiol group, showed only one cathodic peak in the same potential range as the second peak of compounds I and II.The results of this study show that in the former wave, the one electron reduction of thiol led to a dimer (disulfide) species and in the latter, the triazine ring was reduced in a two-electron process. The effects of various physical and electrochemical parameters were studied and the electrochemical behavior of the monomers was reported as a function of these parameters. A completely irreversible behavior was observed from cyclic voltammograms obtained under different conditions. Furthermore, in this study some numerical constants, such as diffusion constant, transfer coefficient, and rate constant of coupled chemical reaction were determined.     

Eliminating the Interference of Ascorbic Acid and Uric Acid to the Amperometric Glucose Biosensor by Cation Exchangers Membrane and Size Exclusion Membrane

The characteristics of a multiuse planar amperometric biosensor modified with Nafion and/or polyion membrane were investigated. A new enzyme immobilization process was proposed, in which the polyvinyl alcohol bearing a styrylpyridinium (SbQ)/glucose oxidase composite was treated with glutaraldehyde vapor prior to the photocrosslinking reaction. The resulting planar enzyme electrode remains active for at least 150 days. Compared with poly‐L ‐lysine/poly (4‐stryenesulfonate) polyion complex membrane the Nafion membrane showed marked effect to reduce the electrochemical response of the modified planar enzyme electrode to the biological interferents, such as ascorbic acid and uric acid. Furthermore, Nafion membrane can effective restricting the oxidized anionic interferent to adhear on its surface, thereby the fouling of the electrode was avoided.     

Differential Pulse Anodic Stripping Voltammetric Determination of Lead with Heparin Modified Electrode

Introduction Overall exposure to lead is of public health concern because of several hazardous effects that may occur to human beings. Lead poisoning may provoke irritability, anorexia, malaise and headache. Intoxication progress may lead to attacks of abdominal pain until coma and death.1 The determination of trace lead in variety of en-vironmental samples is of great importance since lead is recognized as a cumulative poison to animals and hu-mans. There is a constant demand for improved an…