克拉霉素的电化学反应机理研究与应用

应用线性扫描伏安法、循环伏安法、常规脉冲伏安法等电化学手段并结合紫外吸收光谱研究了药物克拉霉素(clarithromycin, CAM)在pH 1.8～9.2 Britton-Robinson缓冲溶液和0.05 mol•L^－1 NaOH溶液中的电化学行为. 在所研究的pH范围, CAM分别产生P₁, P₂, P₃, P₄四个还原波, 其中P₁, P₂, P₄三个波均为其药效活性基团C-9位羰基的还原所产生. 实验结果表明: 在pH 1.8～5.7的B-R缓冲溶液条件下所获得的P₁波为两电子不可逆弱吸附还原波; 在6.0＜pH＜9.2的B-R缓冲溶液中, CAM产生P₂和P₃两个波, 其中P₂为两电子不可逆还原波, P₃为催化氢波. 在0.05 mol• L^－1 NaOH溶液中, CAM产生的P₄波是一个单电子的不可逆吸附还原波. 根据P₄波的峰电流i_P与CAM浓度的线性关系, 建立了CAM含量测定的新方法.     

Studies on the polarographic behaviors of alizarin complexone and the adsorptive complex wave of thulium-alizarin complexone

In the 0.1M acetate buffer solution, at pH 5.9, alizarin complexone exhibits a reversible adsorptive prewave. On the surface of DME, the adsorption of alizarin complexone obeys Frumkin adsorption isotherm. In the same buffer solution, when the thulium was added, a sensitive adsorptive complex wave of thulium-alizarin complexone has been obtained by single-sweep polarograph. The composition of the complex and the mechanism of electrode processes were studied in detail.     

Electrochemical behaviour of organolead compounds: Part I. Triphenyl-lead acetate

The electrochemical behaviour of triphenyl-lead acetate in 50% (v/v) ethanol has been investigated using various electrochemical techniques including polarography, cyclic voltammetry and controlled potential coulometry. It has been found to give three/four polarographic waves. The first normal wave involves an one-electron irreversible reduction of triphenyl-lead ions giving triphenyl-lead free radicals which are strongly adsorbed at the DME giving rise to an adsorption prewave. The triphenyl-lead free radicals produced in the normal reduction step immediately react with mercury of the DME producing phenylmercury radicals and metallic lead. Wave II has been ascribed to the simultaneous reduction of triphenyl-lead free radicals and phenylmercury free radicals. The metallic lead produced in these processes undergoes oxidation at the electrode and “distorts” the “normal” adsorption prewave of step I. A mechanism of reduction is proposed and polarographic methods have been developed for determining triphenyl-lead compounds at ordinary level and down to submicromolar level.     

Electrochemical reduction of substituted pyrimidines in acetonitrile

Polarographic studies of several substituted pyrimidines were reinforced by the results from cyclic voltammetry, controlled-potential electrolysis, and spectrophotometric examination of electrolyzed solutions, as well as by the examination of model compounds. Pyrimidines substituted with non-reducible groups (amino, methyl) are reduced in a single, one-electron (1e), diffusion-controlled process, very similar to that for pyrimidine itself. Pyrimidine-4-carboxylic acid exhibits three reduction waves: a very drawn-out acid-reduction wave with unusual properties and at more negative potential, an adsorption prewave and a wave corresponding to the 1e reduction of the pyrimidine moiety, 2-Chloro-and 2-bromopyrimidine each exhibit two polarographic waves; the first, corresponding to irreversible scission of the carbon-halogen bond, has electrochemical properties quite different from those normally expected; the second is due to reduction of the electro-generated pyrimidine. Results are compared with those for the reduction of bromobutane, bromobenene, and 2-bromopyridine.     

Keggin型缺位磷钨杂多阴离子的电化学性质及电催化还原过氧化氢

循环伏安实验显示, 缺位磷钨杂多阴离子 的酸性水溶液在玻碳(GC)电极上有两对可逆的还原-氧化波. 第一对波的电荷迁移数为1.4, 有2个质子参与反应; 第二对波的电荷迁移数为1.0, 参加电极反应的质子数为1. 根据峰电流与电位扫描速率平方根的关系得到 在0.1 mol•L－1 NaOAc＋HOAc溶液中的扩散系数 Do为3.54×10－6 cm2•s－1. 交流伏安和交流阻抗实验表明, 的电极过程包含吸附和脱附步骤, 第一对波的电荷迁移阻抗较大, 第二对波的较小, 对应的交换电流密度i0分别为4.6×10－5和6.7×10－4 A•cm－2. 电极过程的可逆性及其缺位特性使它对H2O2的还原有显著的电催化作用, 因此有望用于有机物的氧化和降解. 同时, 还提出了一个相关的电催化机理.     

Voltammetric study of the electrochemical reduction of lucigenin in aqueous medium

The electrochemical reduction of lucigenin (bis-N-methylacridinium nitrate) in aqueous solution was studied by d.c. Tast polarography at a dropping mercury electrode, by cyclic voltammetry at an amalgamated gold electrode and at a hanging mercury drop electrode, and by microcoulometry. The effects of pH, lucigenin concentration and temperature were studied, and special methods were applied to study the suspected adsorption and catalytic (regeneration) currents. A spectrophotometric study is also reported. It was found that lucigenin is reduced in two separate one-electron steps. An adsorption prewave accompanies the first step, while the second, below pH 3.5, is catalytic, owing to the chemical regeneration of the intermediate reduction product at the electrode surface.     

依来铬红B的电还原

本文用普通极谱、脉冲极谱、循环伏安法研究了依来铬红B的电还原。随着pH不同,共可产生3个波(pH6.2—12.2)。总波高相当于—受扩散控制的不可逆2电子还原波;第一波和第三波分别为吸附前波和吸附后波。根据实验结果,提出—电还原机理。     

桑色素极谱行为的研究

研究了桑色素在pH=1～14的水溶液中的极谱行为. 于不同pH范翻内得列了四个还原波. 研究证实在pH<4条件下获得的P_1波为表面催化氢波. 其余三个波为不同形态桑色素的单电子吸附还原波, 并伴有随后化学反应过程. 测得在单分子层饱和吸附条件下, 每一个桑色素分子所占汞电极面积为1.36 nm.     

Electrochemical Oxidation of Rutin

An electrochemical investigation of rutin oxidation on a glassy carbon electrode was carried out using cyclic voltammetry, differential pulse voltammetry and square‐wave voltammetry over a wide pH interval. The electrochemical oxidation is a complex process, which proceeds in a cascade mechanism, related with the 4‐hydroxyl groups of the rutin molecule. The catechol 3′,4′‐dihydroxyl group is the first to be oxidized by a two‐electron – two‐proton reversible oxidation reaction, followed by an irreversible oxidation reaction due to the 5,7‐dihydroxyl group. Both mechanisms are pH dependent. An adsorption process is also observed and the oxidation products block the electrode surface.     

Electrochemical behaviour of some neuroleptics: Haloperidol and its derivatives

The electrochemical characteristics of Haloperidol and related compounds, representative neuroleptics of the butyrophenone family, have been investigated as a function of pH and concentration by direct-current, alternating-current and differential-pulse polarography and cyclic voltammetry at a hanging mercury drop electrode. A single cathodic wave representing an irreversible two-electron reduction is obtained, and its half-wave potential differs from that characteristic of aromatic ketone reduction. Adsorption processes disturb the wave behaviour and an adsorption prewave is observed at high concentrations. Quantitative measurements were successful in the concentration range 1 x 10(-4)-1 x 10(-6)M (0.4 mg/l.), the lower concentration representing the detection limit by differential-pulse polarography.     

Aqueous Electrochemistry of Anthraquinone and Its Correlation with the Dissolved States of a Cationic Surfactant

Cyclic voltammetry was employed to study the electrochemical behavior of anthraquinone (AQ) in aqueous solution at a glassy carbon electrode using the sodium salt of anthraquinone-2-sulphonic acid (AQS). The cyclic voltammograms show a reduction wave and a corresponding oxidation wave. The electrochemical reaction of AQ in aqueous solution involves a two electron transfer process followed by a coupled chemical reaction and exhibits strong pH dependence at low pH (<4). A satellite peak is also observed at the cathodic side of the reduction wave for the reduction of the sulfonate group of AQS. The electrochemical investigation was also carried out in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB). Similar redox behavior can be observed for the electrochemical reaction of AQS in the presence of CTAB solutions similar to the aqueous media. The electrochemical responses have been found to depend on the dissolved states of the surfactant. The current-potential behavior of AQS depends on the concentration of CTAB and micellization has a profound effect on the electrochemical behavior of AQ.     

Electrochemical reduction of camphorquinone in DMF in the presence of a proton donor

The electroreduction of camphorquinone in DMF, at mercury electrodes, was investigated by a variety of techniques. In DMF, in the absence of proton donor, camphorquinone exhibits two one-electron waves: the first, a one-electron reversible wave to be due to a reversible charge transfer without a coupled chemical reaction. After the first charge transfer, the semidione anion radical is reduced to the dianion. The irreversibility of the second wave derives from a fast irreversible protonation of the dianion. A wide variety of changes in behaviour is observed in the reduction of camphorquinone as increasing amounts of benzoic acid are added: a new two-electron irreversible wave appears at a potential less negative than the original wave. A proton donor to substrate ratio of 2 is required to completely suppress the two original waves. A mechanism for the electroreduction of camphorquinone is proposed and discussed on the basis that the prewave current is controlled by the diffusion of the undissociated acid species and that the undissociated acid, rather than the solvated proton, takes part in the protonation, prior to the charge transfer.     

Electrochemical Investigation of Metal-Free and Nickel-Containing Porphyrazines Carrying Eight Tosylaminoethylthia Groups

 In this study, the electrochemical properties of metal-free and nickel-containing porphyrazines with eight tosylaminoethylthia groups were investigated using cyclic voltammetry, double potential step chronoamperometry, double potential step chronocoulometry, and controlled potential coulometry. Cyclic voltammetry measurements showed that both compounds exhibit two quasi-reversible and an irreversible reduction waves. The first electron transfer reaction was followed by an irreversible chemical reaction, the second one by a reversible chemical reaction for both species. The electrode processes of metal-free and nickel-containing porphyrazines are diffusion controlled, but the double potential step chronocoulometry measurements indicated that the nickel porphyrazine is adsorbed at the electrode. However, a small adsorption current has no significant effect on the mass transport mechanism of the system. Diffusion coefficients of both compounds were determined by both cyclic voltammetric and chronocoulometric measurements. The diffusion coefficients of the reduced forms of the porphyrazines were found to be smaller than those of the neutral forms.     

Electrochemical behavior of zopiclone

The electrochemical properties of zopiclone, an anxiolytic and hypnotic drug, have been investigated by different techniques. The compound is reduced in two 2-electron steps in the pH range 0-12. The first step, which corresponds to the reduction of the pyrazine ring, is reversible in acidic and neutral solutions. Strong adsorption phenomena accompany the reduction process in acidic and neutral media. Zopiclone can be quantitatively measured over the entire pH range using DC polarography. However, the use of differential pulse and square-wave modes for quantitative measurements is more limited due to a slope modification in the current-concentration relationship. Adsorptive stripping voltammetry can be applied to the determination of low levels of the drug at pH 9, but only short deposition times may be used because large amounts of material accumulated under stirring conditions due to fast adsorption kinetics are rapidly released from the electrode surface. Detection limits are 1 x 10(-7)M and 2 x 10(-10)M for polarography and adsorptive stripping voltammetry, respectively. Only the first wave is of analytical interest for both techniques.     

金属富勒烯[Dy@C_(82)(I)]膜的电化学研究

研究并对比了金属富勒烯Dy @C82 的主要异构体Dy @C82 (I)固体膜在有机溶剂乙腈及水溶液中的电化学性质 .在乙腈溶液中 ,Dy @C82 (I)膜的电化学行为不同于其溶于有机溶剂中的电化学行为 ,前两个还原峰与其对应的再氧化峰之间存在大的分裂 .但是 ,经过还原及再氧化后的Dy @C82 (I)膜却存在一对对称性很好的氧化及再还原峰 .解释为经过还原后的Dy @C82 (I)膜的结构有利于进一步氧化 ,而不需要结构重排 ;在水溶液中 ,Dy @C82 (I)膜的电化学行为不同于其在乙腈溶液中 ,却类似于其有机溶液在Pt电极上的电化学行为 ,出现了对称性很好的三对还原峰及一对氧化峰 .在水溶液中 ,Dy @ C82 (I)的前三价负离子及一价正离子是稳定的 .利用紫外 -可见 -近红外 (UV Vis NIR)光谱及扫描电镜 (SEM)等技术对膜的性质及表面形貌等进行了表征     

Electrochemical behaviour of dicyanobis(2,2′-bipyridine) ruthenium(II) and dicyanobis(1,10-phenanthroline) ruthenium(II) complexes

The electrochemical behaviour of Ru(bipy)₂(CN)₂ and Ru(phen)₂(CN)₂ (bipy=2,2′-bipyridine; phen=1,10-phenanthroline) has been investigated in dimethylformamide. Both complexes exhibit one oxidation wave and three reduction waves. In the case of Ru(bipy)₂-(CN)₂ the anodic process and the first two cathodic processes involve one electron and are reversible in the time scale of polarographic and cyclic voltammetric experiments. The third reduction step is irreversible and has been attributed to the addition of three electrons to Ru(bipy)₂(CN)₂ followed by liberation of one or more ligands and reduction of liberated bipyridine. The features of the redox processes for the Ru(phen)₂(CN)₂ are similar to those found for the bipy complex except for the first reduction wave, which is complicated by adsorption phenomena. A qualitative MO discussion of the redox processes is also reported.     

Electrochemical Investigation of Metal-Free and Nickel-Containing Porphyrazines Carrying Eight Tosylaminoethylthia Groups

Summary.  In this study, the electrochemical properties of metal-free and nickel-containing porphyrazines with eight tosylaminoethylthia groups were investigated using cyclic voltammetry, double potential step chronoamperometry, double potential step chronocoulometry, and controlled potential coulometry. Cyclic voltammetry measurements showed that both compounds exhibit two quasi-reversible and an irreversible reduction waves. The first electron transfer reaction was followed by an irreversible chemical reaction, the second one by a reversible chemical reaction for both species. The electrode processes of metal-free and nickel-containing porphyrazines are diffusion controlled, but the double potential step chronocoulometry measurements indicated that the nickel porphyrazine is adsorbed at the electrode. However, a small adsorption current has no significant effect on the mass transport mechanism of the system. Diffusion coefficients of both compounds were determined by both cyclic voltammetric and chronocoulometric measurements. The diffusion coefficients of the reduced forms of the porphyrazines were found to be smaller than those of the neutral forms. Received October 29, 2001. Accepted (revised) December 17, 2001     

白杨素在汞电极上的电化学行为及其消除超氧阴离子自由基能力研究

The electrochemical behavior of chrysin in pH 2.0-9.0 Britton-Robinson （B-R） buffer solutions was studied by the means of linear sweep voltammetry and cyclic voltammetry at a static mercury drop electrode. In different pH range of B-R buffer solutions, chrysin could cause four reduction waves. In pH 2.0-5.8 B-R buffer solutions, wave P1 yielded by chrysin is a one-electron reduction wave, and wave P1 caused by further reduction of the products of wave P1 in pH〈3.0 B-R buffer solution is also a one-electron reduction wave. But in 3.0〈pH〈5.8 B-R buffer solution wave P1 was overlapped by the hydrogen wave. Between pH 5.8 and 9.0, chrysin could yield two reduction waves P2 and P3- The former is an irreversible adsorptive wave of ionized chrysin involving one electron and the latter is also an irreversible adsorptive wave of reduction intermediate radical of chrysin involving one electron and one proton. And a linear relationship between ip3 and the concentration of chrysin can be established from 1.0×10^-6 to 4.0×10^-5 mol·L^-1 （r=0.9924） with the detection limit of 5×10^-7 mol·L^-1. In addition, the antioxidant ability of chrysin was investigated by linear sweep voltammetry （LSV）. The determination result of IC50 of chrysin showed that chrysin is a good antioxidant.     

Electrochemical reduction of triorganohalo-silanes and -germanes

The electrochemical reduction of triorganohalo-silanes and -germanes in 1,2-dimethoxyethane has been investigated by polarography, cyclic voltammetry, controlled potential coulometry, and macroscale electrolysis. The reduction of the silicon compounds exhibits a single irreversible wave. The polarograms for the germanium compounds exhibit two irreversible waves. The second wave shifts to more anodic potentials with addition of phenol or acetic acid. Dimer (i.e. disilanes or digermanes) are the main product of macroscale electrolysis in aprotic solvent but the hydrides are the principal products in protic solution.The results are interpreted in terms of the coexistence of two separate processes. The first involves a one electron reduction followed by dimerization of the radical. At higher cathodic potential a two electron charge transfer step occurs to form an anion, which in aprotic solvents reacts with the starting halogeno compound to form dimer, and in protic solutions gives the hydride.     

Methods for potentiostatic evaluation of heterogeneous kinetic parameters in the presence of an irreversible following chemical reaction

A theoretical study of Brdi?ka's adsorption waves and of the corresponding i-E curves in cyclic voltammetry and E-t curves in chronopotentiometry is presented under the following conditions: (a) the electrochemical reaction 0+ne?R is reversible; (b) both the oxidized and the reduced forms are strongly adsorbed; (c) the adsorption is rapid; (d) allowance is made in the isotherm for interactions between the molecules (Frumkin type isotherm). One mathematical function and its derivative are sufficient to describe the results in the three cases. The equations derived account in particular for the following experimental characteristics: (1) the linear variation of the half-wave potential of the adsorption wave (or of the chronopotentiogram) and of the voltammetric peak potential with the concentration c; (2) the changes in the slope of the wave when c varies and the discontinuous increase of current which is observed for high concentrations; (3) the changes in peak width and the hysteresis phenomenon observed in cyclic voltammetry; (4) the S-shaped experimental chronopotentiograms; (5) the appearance of prewaves (or postwaves) in cases where both O and R are equally adsorbed; (6) the fact that prewaves or postwaves usually appear for large molecules. The results show that the appearance of a Brdi?ka prewave or postwave is often caused by energy effects arising from the interactions between adsorbed molecules, rather than by energy effects caused by interactions with the electrode surface.