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The direct electron transfer reaction of glucose oxidase (GOx) at a bare silver electrode is verified. The electron transfer number n = 2, electron transfer coefficient α = 0.45 and rate constant of the electrochemical reaction Ks = 0.1 s−1 are obtained. This communication presents a multimolecular adsorption model to explain the properties of the direct electron reaction between GOx and bare silver electrodes. The residual valence force may be an important factor to ensure a direct electron transfer reaction on the bare electrode. On the basis of the experimental fact that only biologically active GOx exhibits electrochemical activity in solution, a facile analytical method for analyzing the active GOx concentration is developed. The results determined correspond very well to that of a spectrometric method. 相似文献
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An extremely sensitive stripping voltammetric procedure for determination of ultratrace titanium is reported. The method is based on the interfacial preconcentration of titanium-cupferron complex onto the hanging mercury drop electrode, followed by catalytic reduction of the adsorbed complex for the presence of cupferron. The peak currents are directly proportional to titanium in the ranges of 0.06-1.0 ng/ml and 1.0-30.0 ng/ml. Moreover, the character of stripping current has also been studied with various polarographic methods. Such coupling of catalytic and adsorptive collection processes holds great promise for the development of an ultrasensitive voltammetric procedure for other metals. 相似文献
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聚中性红膜修饰电极的电化学特性及其电催化性能 总被引:35,自引:5,他引:35
研究了中性红在玻碳电极表面电聚合成膜的方法和条件,对膜内电荷传输过程和电化学特性分别用循环伏安技术和电位阶跃暂态技术进行了初步探讨。该膜对维生素C和亚硝酸盐有较强的电催化作用,催化电流与底物浓度在很宽的范围内呈线性关系,可用于实际样品的分析。 相似文献
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The anodic voltammetric behavior of methotrexate was studied at glassy carbon electrode in acetate buffer (pH = 3.6) solution using cyclic, square-wave voltammetric and chronocoulometric techniques. The oxidation of methotrexate is an irreversible diffusion-controlled process. The oxidation mechanism was proposed and discussed in this work. The dependence of the current on pH, the concentration and nature of buffer, and instrumental parameters were investigated to optimize the experimental conditions for the determination of methotrexate. It was found that in the range of 8.0 × 10−7–2.0 × 10−5 mol/L, the currents measured by square-wave voltammetry presented a good linear property as a function of the concentrations of methotrexate. In addition, validation parameters, such as reproducibility, sensitivity and recovery were evaluated as well. The proposed method was also successfully applied for the determination of methotrexate in diluted human urine with good satisfactory. 相似文献
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A simple and sensitive voltammetric sensor for esculetin, based on electrochemically reduced graphene oxide film modified glassy carbon electrode, was reported for the quantitative determination of esculetin in the Chinese traditional herbal drug Viola yedoensis Makino. Electrochemical impedance spectroscopy and scanning electron microscopy were employed to study the characteristic of the graphene oxide film. The electrochemical behavior of esculetin on this sensor was investigated in pH 3.0 phosphate buffer solution by cyclic voltammetry. Significant advantages were achieved by the excellent conductivity and the high surface‐to‐volume ratio of electrochemically reduced graphene oxide. A calibration plot of oxidation peak currents versus esculetin concentrations was linear in the range of 4.0 ξ 10‐8 mol L‐1 to 5.0 ξ 10‐6 mol L‐1 with a detection limit of 2.0 ξ 10‐8 mol L‐1. The practical application of the present sensor was demonstrated by determining the concentration of esculetin in real sample with no interference. 相似文献
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In this paper, we study the global exponential stability in Lagrange sense for a class of Cohen–Grossberg neural networks with time-varying delays and finite distributed delays. Based on the Lyapunov stability theory, several global exponential attractive sets in which all trajectories converge are obtained. We analyze three different types of activation functions which include both bounded and unbounded activation functions. These results can also be applied to analyze monostable as well as multistable and more extensive neural networks due to making no assumptions on the number of equilibria. Meanwhile, the results obtained in this paper are more general and challenging than that of the existing references. Finally, one example is given and analyzed to verify our results. 相似文献
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Hu K Qu K Li Y Ding C Wang X Zhang J Ye B Zhang S 《Journal of separation science》2008,31(13):2430-2433
Calixarenes are macrocyclic oligomers having the shape of a conical vase. Their inner cavity can accommodate various guest molecules, i. e. form supramolecules. Thus, calixarenes can be employed to manipulate selectivity in separation sciences. The essential step of separation is the interaction between calixarene and analytes. Therefore, in the present work, the retention mechanisms of benzenediol and naphthol positional isomers on a calix[4]arene column were investigated. The optimized supramolecular structures showed that there exist hydrogen bonding and pi-pi interactions for benzenediol, and for naphthol the pi-pi interactions dominate. Thermodynamic results from quantum chemistry calculations using DFT-B3LYP/STO-3G** basis set were consistent with the retention behaviors of benzenediol and naphthol positional isomers on the calix[4]arene column. This work will provide theoretical support for the design of new calixarene stationary phases. 相似文献
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Kai Hu Junwei Liu Chao Tang Caijuan Wang Ajuan Yu Fuyong Wen Wenjie Zhao Baoxian Ye Yangjie Wu Shusheng Zhang 《Journal of separation science》2012,35(2):239-247
A new para‐tert‐butylcalix[4]arene column containing thiadiazole functional groups was prepared and used for the separation of polycyclic aromatic hydrocarbons, phenolic compounds, aromatic amines, benzoic acid and its derivatives by high‐performance liquid chromatography (HPLC). The effect of organic modifier content in the mobile phase on retention and selectivity of these compounds were investigated. The results indicate that the stationary phase behaves like reversed‐phase packing. However, hydrogen bonding, π–π and inclusion interactions seem to be involved in the separation process. The column has been successfully employed for the analysis of clenbuterol in pork and pig casing; the limit of detection and the limit of quantitation for this method by HPLC‐UV detection was 0.03 and 0.097 μg/mL, respectively; the method is demonstrated to be suitable and a competitive alternative analytical method for the determination of clenbuterol. 相似文献
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Ying Xu Fei Wang Le Wang Fangyuan Zhao Baocheng Yang Baoxian Ye 《Journal of Solid State Electrochemistry》2012,16(4):1473-1480
A novel voltammetric sensor, based on single-walled carbon nanotubes (SWNT) dispersed in Nafion and modified glassy carbon
electrode (GCE), was fabricated and used to determine the trace amounts of dihydromyricetin (DMY). The electrochemical behavior
of DMY at this sensor was investigated in 0.1 mol L−1 sulfuric acid solutions + 0.1 mol L−1 NaCl by cyclic voltammetry and squarewave voltammetry. Compared with bare GCE, the electrode presented an excellent response
of DMY through an adsorption-controlled quasi-reversible process. Under the optimum conditions, the response peak currents
were linear relationship with the DMY concentrations in the range of 1.0 × 10−7–1.0 × 10−5 mol L−1 with a detection limit of 9 × 10−8 mol L−1. Based on this voltammetric sensor, a simple and sensitive electroanalytical method for DMY was proposed and applied to quantitative
determination of DMY in Ampelopsis grossedentata samples. In addition, the oxidation mechanism was proposed and discussed, which could be a reference for the pharmacological
action of DMY in clinical study. 相似文献