Convolutive Cyclic Voltammetry,Chronoamperometry and Chronopotentiometry Studies of C6Me6-isocloso-ruthenaborane Complex in Non-aqueous Medium at a Glassy Carbon Electrode

Electroreduction of the C₆Me₆‐isocloso‐ruthenaborane complex {(C₆Me₆)‐isocloso‐1‐RuB₁₀H₁₀} has been investigated using cyclic voltammetry, convolutive voltammetry, chronoamperometry and chronopotentiometry techniques at a glassy carbon electrode in 0.1 mol·L⁻¹ tetrabutyl ammonium perchlorate dissolved in methylene chloride. The investigated complex has been reduced via the consumption of two sequential electrons leading to the formation of monoanion and dianion, respectively. The electrode reaction pathway and the electrochemical parameters of the investigated system were determined. The extracted electrochemical parameters were verified via digital simulation treatments. Diffusion coefficient and heterogeneous electron transfer kinetics of the {(C₆Me₆)‐isocloso‐1‐RuB₁₀H₁₀} complex at low temperature were studied and discussed.     

双嘧达莫在玻碳电极上的阳极伏安法研究

用直流伏安法(DCV),微分脉冲伏安法(DPV)和循环伏安法(CV)在玻碳电极(GCE)上研究了双嘧达莫(DPM)在不同介质中的阳极伏安行为,发现在0.01mol/LCHl溶液中于0.62V(vs.Ag/AgCl)右左生产一个阳极氧化峰,其峰高与浓度的线性方程分别为r=0.0004 0.17C(0.05~1.0mg/L)和y=0.052 0.22C(0.5~10mg/L). 在此体中大多数金属离子和20多种有机生代物质不干扰测定,采用该方法可不经分离,直接测定药物制剂和尿样吕DPM的含量,同时对DPM的电极反反应机理进行了探讨.     

阴极溶出伏安法测定异烟肼的研究

报道了吸附阴极溶出伏安法测定异烟肼。探讨了电极反应机理。在０．０１ｍｇｏｌ／Ｌ硼砂底液中，峰电位为－１．４０Ｖ。峰电流与异烟肼浓度在４．０＊１０＾－７－１．５＊１０＾－５ｍｏｌ／Ｌ范围内呈良好的线性关系，相关系为０．９９１３。该方法用于异烟肼片剂的测定，获得满意结果。     

化学修饰电极循环伏安法的数值模拟

用ＣＮ法对化学修饰电极（ＣＭＥ）的循环伏安法（ＣＶ）进行了数值模拟。建立了ＣＭＥ的有限扩散理论模型,引入了活度系数比、扩散系数校正因子及动力学参数等。模拟的普鲁士兰（ＰＢ）修饰电极与文献相符很好。     

Determination of Phosphate by Cathodic Stripping Voltammetry at a Glassy Carbon Electrode

Abstract

The oxidation of Fe(II) in the presence of phosphate results in a film of a sparingly soluble Fe(III) phosphate salt on a glassy carbon electrode. The reaction is used as the preconcentration step in a cathodic stripping method for phosphate. The recommended procedure yields working curves which are linear over single orders-of-magnitude down to 0.1 ppm, With a 40-minute preconcentration time, 40 ppb phosphate can be detected. The method is free of interference by chloride and sulfate.     

Cyclic Lipopeptide Antibiotic Daptomycin Electrochemical Oxidation at a Glassy Carbon Electrode

Daptomycin was the first approved drug from a new class of antimicrobials, the cyclic lipopeptides, and presents a broad spectrum of activity against a wide range of gram‐positive bacteria. The daptomycin redox behaviour, by cyclic, differential pulse and square wave voltammetry, in a wide pH range, at a glassy carbon electrode, was investigated. The daptomycin oxidation was a two‐step irreversible diffusion‐controlled process and the diffusion coefficient D_DPT = 2.32 × 10⁻⁵ cm² s⁻¹, was calculated. A detection limit LOD = 0.32 μM, was obtained. For the first time daptomycin, in fetal bovine serum biological fluid, using DP voltammetry, was determined.     

耦联酶催化反应电化学体系的表面循环伏安行为的数字模拟

采用数字模拟法对耦联酶催化反应体系的表面循环伏安行为进行了研究,讨论了介体氧化还原动力学、酶催化动力学及介体催化酶动力学等参数对循环伏安图的影响,并用实验进行了验证。     

Ultra-Sensitive Anodic Stripping Voltammetry for the Determination of Xanthine at a Glassy Carbon Electrode

An electrochemical anodic stripping procedure for ultra-trace assay of xanthine in Cu²⁺ solution at a glassy carbon electrode (GCE) is described. Cyclic voltammetry was used to characterize the nature of the process taking place at the GCE. The anodic stripping response in the presence of Cu²⁺, at 150mV (peak I) and 600mV (peak II), is evaluated with respect to various experimental and instrumental conditions. Voltammetric studies show that the mechanism of the overall reaction is similar to that of the oxidation of purine derivatives at a pyrolytic graphite electrode. It is found that the copper metal deposited onto the GCE was oxidized to Cu⁺ at around –180mV vs. Ag/AgCl and the generated Cu⁺ reacted with xanthine to accumulate on the GCE as an insoluble compound. The Cu⁺-xanthine compound accumulated on the GCE was redissolved by the oxidation of Cu⁺ to Cu²⁺ at ca. 150mV, and the concentration of xanthine in the vicinity of the GCE increased. The results enabled us to use the measurement of the oxidation peak current as the basis of a simple, accurate and rapid method of determining xanthine within a concentration range of 19.9 to 166nM for peak (I) and 0.24 to 17.2µM for peak (II). Promising results were obtained for xanthine determination by using an external mixing step prior to stripping measurements, which yielded a detection limit of 0.138µgL^–1 (9.1×10^–10M) xanthine. The effect of some interferences (e.g. purine compounds, amino acids and some metal ions) was considered.     

浓碱溶液中生成高铁酸盐的玻碳电极循环伏安法表征(英文)

用玻碳电极研究了与Fe(Ⅵ)／Fe(Ⅲ)电对氧化还原有关的循环伏安曲线.所研究的体系是13mol·L-1NaOH中浓度范围分别为0.015～0.06mol·L-1的Na2FeO4和0.01～0.025mol·L-1的NaFeO2溶液。另一类研究体系是胶体石墨分别与固体K2FeO4、固体KFeO2组成的混合物,将这些混合物粘附于玻碳电极表面后在13mol·L-1KOH中进行循环伏安曲线的测定。结果证明了峰电位在0.7～1.0V的阳极电流峰与峰电位在0.15～0.2V(均相对于13mol·L-1NaOH或13mol·L-1KOH溶液中的Hg／HgO参比电极)的阴极电流峰,分别与高铁酸盐的生成与还原相对应。确定了将高铁酸盐的阳极生成电流峰与阳极析氧电流峰区别开来的条件。     

Voltammetry of the Erythromycin-Modified Glassy Carbon Electrode and Interaction With Dna

ABSTRACT

The chemically modified electrode (CME) which was constructed by covalently attaching Erythromycin (ERM) to a glassy carbon (GC) surface was investigated in Tris-HCl buffer (pH=6.0) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In the potential range -0.5 to +0.4V, CME yields a pair of stable redox waves. It is the carbonyl group of the ERM molecule immobilized on the GC surface that behaves as a two-electron redox process involving one proton. The interaction of CME with DNA was also studied by DPV. The CME shows the same interaction with DNA as that in the solution. And the interactive model between ERM and DNA was proved by fluorescence in aqueous solutions.     

Simultaneous Determination of Lipophilic Vitamin Esters Using Square-wave Voltammetry at the Glassy Carbon Electrode

Simple and rapid voltammetric method for simultaneous determination of all-trans-retinyl acetate (RAc) or all-trans-retinyl palmitate (RPa) and α-tocopheryl acetate (α-TOAc) has been proposed. The respective method was based on the anodic oxidation of the compounds of interest by square-wave voltammetry in acetone with 0.1 mol L⁻¹ LiClO₄ at the glassy carbon electrode. The procedure was also beneficial with respect to simple dissolution of sample directly in the supporting electrolyte. The all-trans-retinyl acetate could be quantified in two linear ranges (3.1–140 μmol L⁻¹ and 140–400 μmol L⁻¹) and α-tocopheryl acetate in linear range 5.3–400 μmol L⁻¹ with detection limits of 0.9 μmol L⁻¹ RAc (or 0.8 μmol L⁻¹ RPa) and of 1.6 μmol L⁻¹ α-TOAc. Selected commercial cosmetic products were analysed achieving satisfactory recoveries.     

Differential Pulse Voltammetric Determination of L-Cysteine After Cyclic Voltammetry in Presence of Catechol with Glassy Carbon Electrode

An electrochemical method of determination of cysteine has been developed in the solution containing catechol as the indicator. Nucleophilic addition of the thiol species to the electrogenerated o-quinone results in the formation of o-quinone-cysteine adducts that easily accumulate use at the surface of the electrode in the acidic solution. Therefore, the use of cyclic voltammetry leads to the amplification of the o-quinone-cysteine adduct's reductive current. As cyclic voltammetry was performed prior to differential pulse voltammetry, the peak of o-quinone-cysteine could be separated preferentially from o-quinone in the differential pulse voltammogram and the selectivity of the method has been assessed with no interference from ascorbic acid, glycine, L-tyrosine, or L-lysine. The magnitude of o-quinone-cysteine peak is proportional to the concentration of cysteine, and thus it can be exploited to determine cysteine within the injection. The results were consistent with those obtained by means of HPLC analysis.     

钴氢氧化物修饰玻碳电极的镀膜/循环伏安法制备及其电化学行为

采用一种新方法镀膜 /循环伏安法成功制备了钴氢氧化物修饰玻碳电极 .考察了影响钴氢氧化物膜电催化活性的因素 ,确定最佳富集时间为 2min ,最佳活性单元浓度为 9 90× 10 -4mol·L-1.讨论了成膜过程及机理 .膜氧化峰电流 (i0pa)与扫描速率 (v <0 60V·s-1)成正比 ,具有表面吸附反应特征 ,表面覆盖量约相当于 0 5个单层的氧化还原活性物质 .制得的钴氢氧化物膜修饰电极具有相当的稳定性 ,并对H2 O2 氧化表现出较高的电催化活性 .线性回归方程为 :Δipa( μA) =-2 10 3 6+2 3 72 0× 10 4CH2 O2 (mol·L-1) (R =0 9990 ,n =18) ,线性范围为 :1 43× 10 -5～ 1 80× 10 -2 mol·L-1,检出限为 :9 5 9× 10 -6mol·L-1( 3S/k) .     

Cyclic Voltammetry Determination of Epinephrine with a Nano—gold Modified Glassy Carbon Electrode in the Presence of High Concentration Ascorbic Acid

As we know, there are usually some problems in electrochemical analysis with bare electrode to detect neurotransmitters. One is low electron transfer rate and the other is interfering compounds, such as ascorbic acid. So some kinds of modified electrodes have been successfully employed to promote the efficiency of electrochemical analysis1-4, such as Nafion modified electrode5,6 and SAM modified electrode7. They can attract positively-charged neurotransmitters while repulse negatively-cha…     

循环伏安和现场FTIR反射光谱研究甲醛在金电极上的氧化

The electro-oxidation of formaldehyde on a gold electrode in a gold electrode in a solution containing 0.1mol •L -1 Na2CO3＋0. 1mol•L - 1NaHCO3＋0. 1 mol•L - 1 HCHO was investigated by cyclic voltammetry and in -situ FTIR spetroscopy . The experimental results demonstrated that the oxidation of formaldehyde at different potential range connected with different surface species of gold. At lower potentials, the main product of formaldehyde oxidation was HCOO-, and at higher potentials, the products HCOO- and CO2 were detected simultaneously. From the results, a possible reaction mechanism was proposed.     

Investigation of Electrochemical Properties of Xanthine,Adenine and Thymine on a Glassy Carbon Electrode by Voltammetry

In this paper for investigation of electrochemical properties of nitrogenous bases by voltammetry xanthine (Xa), adenine (A) and thymine (T) with constant-current potential sweep with differentiation were used. The electrochemical behavior of Xa, A and T on the surface of a glassy carbon electrode were investigated. The conditions of registration of their joint detecting in the solution were defined. It is demonstrated that the oxidation peak currents of Xa, A and T increased linearly with their concentration in the range of 4.0 10^-8 - 1 10^-4 mol/dm³ for Xa, 3.0 10^-7 – 1.0 10^-4 mol/dm³ for A, and 1.0 10^-5 – 1.1 10^-3 mol/dm³ for T with correlation coefficients of 0.996, 0.996 and 0.999, respectively.     

Electrochemical Behavior of Thalidomide at a Glassy Carbon Electrode

Thalidomide is an oral drug marketed in the 1950s as a sedative and an anti‐emetic during pregnancy that was removed from the market when its teratogenic side effects appeared in new born children due to inadequate tests to assess the drug's safety. Recent studies evaluating the use of thalidomide in cancer and HIV diseases have sparked renewed interest. The electrochemical behavior of thalidomide on a glassy carbon electrode has been investigated using cyclic, differential and square‐wave voltammetry in aqueous media at different pHs. The oxidation mechanism of thalidomide is an irreversible, adsorption‐controlled process, pH dependent up to values close to the pK_a and occurs in two consecutive charge transfer reactions. A mechanism of oxidation of thalidomide involving one electron and one proton to produce a cation radical, which reacts with water and yields a final hydroxylated product is proposed. The reduction of thalidomide is also a pH dependent, irreversible process and occurs in a single step, with the same number of electrons and protons transferred. The reduction mechanism involves the protonation of the nitrogen that bridges the two cyclic groups, and the product of the protonation reaction causes irreversible dissociation. Both thalidomide and the non electroactive oxidation and reduction products are strongly adsorbed on the glassy carbon electrode surface.     

Electrochemical Oxidation of Sulfasalazine at a Glassy Carbon Electrode

Sulfasalazine (SSZ) is a pharmaceutical compound used for the treatment of rheumatoid arthritis. The electrochemical oxidation of SSZ at a glassy carbon electrode was studied by cyclic, differential pulse and square wave voltammetry in a wide pH range. For electrolytes with pH<11.0, the oxidation is an irreversible, diffusion‐control, pH‐dependent process that involves the transfer of one electron and one proton from the hydroxyl group of the salicylic moiety. For pH>11.0 the oxidation is pH‐independent, and a pK_a≈11 was determined. The formation of a quinone‐like oxidation product that undergoes two electrons and two protons reversible redox reaction was observed. Also, UV‐vis spectra of SSZ were recorded as a function of supporting electrolytes pH. An electrochemical oxidation mechanism was proposed.     

Discrimination of Beers by Cyclic Voltammetry Using a Single Carbon Screen-printed Electrode

A fast, simple and costless methodology without sample pre-treatment is proposed for the discrimination of beers. It is based on cyclic voltammetry (CV) using commercial carbon screen-printed electrodes (SPCE) and includes a correction of the signals measured with different SPCE units. Data are submitted to partial least squares discriminant analysis (PLS−DA) and support vector machine discriminant analysis (SVM−DA), which allow a reasonable classification of the beers. Also, CV data from beers can be used to predict their alcoholic degree by partial least squares (PLS) and artificial neural networks (ANN). In general, non-linear methods provide better results than linear ones.     

电化学法修饰玻璃碳电极及其铜的阳极溶出伏安法测定

在邻苯二酚－甲醛－ＮａＯＨ介质中，于－０．１￣＋１．５Ｖ（ｖｓ，ＳＣＥ）扫描范围内用循环伏安法制作修饰玻璃碳电极。电极可用于水中痕量铜的测定，其灵敏度比未修饰的玻璃碳电极提高３５倍以上，定量下限为０．１ｎｇ／ｍｌ。