A thin-layer spectroelectrochemical study of 3,3′,5,5′-tetramethylbenzidine at SnO2:F film optically transparent electrode

The electrooxidation of 3,3′, 5,5′-tetramethylbenzidine (TMB) is dependent on the pH value of Britton-Robinson (B-R) buffer solution. In this work, the electrooxidation behavior of TMB was investigated with a SnO2:F film optically transparent thin-layer spectroelectrochemical cell. TMB underwent one two-electron electrooxidation process in the pH range from 2.0 to < 4.0, and two successive one-electron electrooxidation processes in the pH range from 4.0 to < 7.0 in the B-R buffer solution. At pH 6.5, the electrooxidative product of TMB generated a subsequent chemical reaction to yield an azo compound. Several spectroelectrochemical techniques, such as thin-layer cyclic voltammetry, thin-layer cyclic voltabsorptometry, thin-layer potential-controlled electrolysis absorptometry, thin-layer single-potential-step chronoabsorptometry, thin-layer double-potential-step chronoabsorptometry, thin-layer single-potential-step open-circuit relaxation chronoabsorptometry, were applied to this investigation. The formal potential E^0′ and the electron transfer number corresponding to the electrooxidation of TMB in B-R buffer solution, and the reaction rate constant of the subsequent chemical reaction were determined.     

A thin-layer spectroelectrochemical study of 3,3′,5,5′-tetramethylbenzidine at SnO2:F film optically transparent electrode

Science China Chemistry - The electrooxidation of 3,3′, 5,5′-tetramethylbenzidine (TMB) is dependent on the pH value of Britton-Robinson (B-R) buffer solution. In this work, the...     

光透薄层光谱电化学法研究紫脲酸铵电还原过程

采用金网橱光透薄层电解池, 配合紫外可见光谱技术现场监测了有机染料紫脲酸铵的电还原过程。用光透薄层光谱电化学方法测定了紫脲酸铵在pH5.0醋酸盐缓冲溶液中的式电极电位和电子转移数。薄层循环伏安法和薄层光谱电化学法研究表明, 紫脲酸铵在金网栅电极上的还原为双电子转移不可逆过程, pH<8时, 还原产物双巴比士亚胺进一步分解为尿咪和巴比士酸。用双电位跃-计时吸收谱法研究了双巴比士亚胺在不同pH缓冲溶液中的分解动力学过程, 测定了拟-级反应动力学常数。     

乙醇在钯电极上的电氧化机理

利用循环伏安与现场傅里叶变换红外(FTIR)光谱对乙醇在Pd电极上的电氧化机理进行了研究. 循环伏安测量表明, 乙醇在Pd上氧化的性能受pH值与乙醇浓度的影响. 当溶液pH>11.0时, Pd对乙醇才具有催化性能, 而且乙醇在Pd上氧化的性能随着pH值和乙醇浓度的增加而提高. 现场红外光谱电化学测量结果证明, 乙醇在不同pH 溶液中的氧化反应机理和产物不同. 当溶液pH>13.0 时, 产物只有乙酸盐, 说明乙醇仅发生部分氧化, 乙醇中的C—C键没有断裂. 当溶液pH≤13.0时, 尽管乙醇在Pd电极上的氧化活性受到抑制, 却发生完全氧化而产生二氧化碳, 说明乙醇的C—C键在低碱环境中容易断裂, 最后乙醇被完全氧化. 实验中没有检测到CO, 表明该反应途径是一个非毒化过程.     

MAP-H2O2-HRP伏安酶联免疫分析测定南方菜豆花叶病毒

提出间氨基酚(MAP)-H₂O₂-辣根过氧化物酶(HRP)伏安酶联免疫分析新体系,并用于南方菜豆花叶病毒(SBMV)的测定.以线性扫描二阶导数伏安法检测HRP催化H₂O₂氧化MAP的产物,用于游离HRP及SBMV的测定,灵敏度均高于经典的ELISA显色光度法.本法对HRP测定的线性范围为1.0×10^-8～1.0×10^-6g/L,检测限为3.8×10^-9g/L;对SBMV测定的线性范围为4.0～5000ng/mL,检测限为4.0ng/mL.用所建立的方法测定病毒感染病叶澄清液的最高稀释比为1∶1.5×10⁵,并与现行的ELISA显色光度法进行对照,二者相关性很好.     

Direct Electrochemistry of Hemoglobin Immobilized in Sodium Alginate Film on the Ionic Liquid [BMIM]PF6 Modified Carbon Paste Electrode

In recent years the direct electron transfer of redox protein on electrode surface has attracted great attentions1. Different kind of modified electrode and various supporting films for immobilization of proteins had been proposed. But most of them are ba…     

槲皮素在聚谷氨酸修饰玻碳电极上的伏安行为及检测

制备了聚谷氨酸修饰玻碳电极,通过循环伏安法和差分脉冲伏安法研究了槲皮素在该修饰电极上的电化学行为。在pH 5.00的B-R缓冲液中,槲皮素在修饰电极上于0.28 V(vs Ag/AgCl)电位处产生一个灵敏的DPV阳极氧化峰,氧化峰电流与槲皮素的浓度在1.0×10-8～5×10-5 mol/L的范围内呈良好的线性关系,最低检测限为4.0×10-9 mol/L。实验表明,聚谷氨酸修饰电极可提高槲皮素的检测灵敏度,该电极用于芦丁水解产物中槲皮素的检测,回收率为103.4%～104.5%。     

Electrochemical behavior of valsartan and its determination in capsules

Electrochemical behavior of valsartan has been carried out in Britton-Robinson (B-R) buffer solution at pH 7.0 at the mercury film electrode (MFE) by cyclic, linear sweep, differential-pulse and square-wave voltammetry. The property of valsartan adsorption at the MFE using accumulation potential of +0.10 V was observed. The effects of experimental parameters on electrochemical process at the MFE were discussed. Differential-pulse adsorptive stripping and square-wave adsorptive stripping voltammetry for the valsartan determination were proposed, linearity was found in the range of 6.0 x 10(-8) to 4.0 x 10(-6)mol/L. The detection limits were 2.93 x 10(-9) and 3.27 x 10(-9)mol/L, respectively. The proposed methods were also applied to the commercial valsartan with good recoveries.     

Differential pulse voltammetric enzyme-linked immunoassay for the determination of Helicobacter pylori specific immunoglobulin G (IgG) antibody

A differential pulse voltammetric enzyme-linked immunoassay for the determination of helicobacter pylori (H. pylori) specific IgG antibody in human serum has been developed. The method is based on coupling the oxidation reaction of 3,3',5,5'-tetramethylbenzidine (TMB)-H(2)O(2) that is catalysed by horseradish peroxidase-IgG(HRP-IgG) conjugate with the electro-reduction of the enzymatic product to measure the activity of HRP-IgG. The latter reaction exhibits a sensitive differential pulse voltammetric response at 0.1 V (versus Ag AgCl ) in pH 4.0 acetate buffer solution. So, the H. pylori specific IgG antibody could be detected. The detection limit of present method for H. pylori specific IgG antibody was 1.0 units ml(-1), which was about seven times lower than that obtained by traditional spectrophotometric ELISA procedure.     

去甲肾上腺素电极过程的圆二色谱电化学研究

现场圆二色薄层光谱电化学研究去甲肾上腺素的电化学氧化还原过程 .研究表明去甲肾上腺素 ( pH =7.0磷酸缓冲溶液中 )在玻碳电极上经历了不可逆的电化学氧化 ,且遵从后行化学反应 (EC)机理 ,去甲肾上腺素醌和去甲肾上腺素红的再还原遵从简单电子转移 (E)机理 .由双对数法获得去甲肾上腺素电化学氧化的式电位为E10’=0 .2 0V ,电子转移系数和电子转移数之积为αn =0 .38,标准复相电极反应常数k10 =1 .2× 1 0 -4 cm·s-1.去甲肾上腺素醌和去甲肾上腺素红的电化学还原反应参数分别为E2 0’=0 .2 5V ,αn =0 .37,k2 0 =4.4× 1 0 -5 cm·s-1和E3 0’=- 0 .2 5V ,αn =0 .33,k3 0 =1 .1× 1 0 -4 cm·s-1.     

3,3',5,5'-四甲基联苯胺-H2O2-辣根过氧化物酶伏安酶联免疫分析法测定人血清免疫球蛋白E

近年来,电化学免疫分析法由于成功地将免疫反应的高选择性和电化学测定的高灵敏度相结合而越来越受到人们的重视[1]．酶联电化学免疫分析法的测定灵敏度与放射免疫法相近而又不必使用放射性同位素[2],充分显示了该法在临床检验中的优越性和发展前景．本文利用HRP催化TMB－H2O2的反应,以金电极为工作电极,用示差脉冲伏安法检测酶催化产物,建立了TMB－H2O2－HRP酶联免疫示差脉冲伏安分析体系,并成功地用于人血清IgE的测定。实验表明,本法较ELISA显色光度测定法的灵敏度高4倍,且具有更宽的线性范围,样品溶液基体对测定不产…     

镍纳米粒子修饰碳糊电极直接电催化鸟嘌呤的研究

将镍纳米粒子与石蜡、石墨按照一定比例混合制备镍纳米粒子修饰碳糊电极,采用循环伏安法(CV)对修饰碳糊电极进行电化学表征,在0.1 mol/L B-R缓冲溶液(pH4.5)中研究了鸟嘌呤在该修饰电极上的电化学行为。结果表明,与裸碳糊电极相比,以掺杂法制备的镍纳米粒子修饰电极能够明显降低鸟嘌呤的过电位,增大其氧化电流,很好地催化氧化鸟嘌呤。在优化的实验条件下,鸟嘌呤在该修饰电极上的氧化峰电流与其浓度在1.0×10-5~5.0×10-4mol/L范围内呈良好的线性关系,检出限(3σ)为7.5×10-6mol/L。     

电镀铂/金的金电极上As(Ⅲ)电化学行为的电化学石英晶体微天平研究

采用电化学石英晶体微天平(EQCM)技术研究了Britton-Robinson(B-R,pH=1.8～11.2)缓冲溶液和H2SO4介质中电镀铂淦的金电极上As(Ⅲ)的循环伏安行为.通过实时监测EQCM频率等参数的变化过程并利用预电沉积As(O)放大电极响应信号,考察了两电极上As.(O)的电沉积、AsⅢ皿和AsⅤ助组...     

Spectroelectrochemical and Voltammetric Studies of L‐DOPA

The electrooxidation of L -dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L -dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E⁰=228 mV, the apparent electron-transfer number of the electrooxidation reaction αn=0.376 (R=0.99, SD=0.26), the standard electrochemical rate constant k⁰=(3.93±0.12)×10⁻4 cm s⁻¹ (SD=1.02×10⁻²), and the formation equilibrium constant of the following chemical reaction k_c=(5.38±0.34)×10⁻¹ s⁻¹ (SD=1.02×10⁻²) were also obtained.     

抗坏血酸在聚槲皮素修饰电极上的电化学行为

采用电聚合方法制备了一种新的聚槲皮素(PQu)修饰电极,并用循环伏安法研究了该电极的电化学行为。在pH=4.0的B-R缓冲溶液中有一对准可逆的氧化还原峰,实验表明聚槲皮素电极过程是2电子2质子的可逆反应。该膜对抗坏血酸有良好的电催化作用,氧化峰电流与抗坏血酸浓度在4.76×10-6~1.0×10-4mol/L范围内呈良好的线性关系,检出限达1.5×10-6mol/L。尿酸不干扰抗坏血酸的测定。     

Bidimensional chronoabsorptometric study of electropolymerisation of 4,4′-bis(2-methylbutylthio)-2,2′-bithiophene

Bidimensional chronoabsorptometry is a novel spectroelectrochemical technique that monitors simultaneously three different signals: current and absorbance both normal to the electrode plane and parallel to this plane during a time in which a fixed potential is imposed. This technique is applied in the visible range to the study of the electropolymerisation of 4,4^′-bis(2-methylbutylthio)- 2,2^′-bithiophene (MBTBT). Experiments are performed in a spectroelectrochemical cell under finite diffusion conditions (thin layer cell) with the aim of interpreting the processes taking place both at the electrode surface and in the adjacent solution during the potentiostatic electrogeneration and deposition of the polymer. Correlations are drawn out among the trends of the oligomers concentration in solution, the polymer electrodeposition and charging, and the current flow, on the time scales of the different steps of the process.     

Preconcentration and voltammetric determination of palladium (II) at sodium humate modified carbon paste electrodes

A chemically modified carbon paste electrode was prepared by incorporating appropriate amounts of sodium humate(NaA). Palladium(II) was selectively accumulated in a solution of Britton-Robinson(B-R) buffer (pH 2.8) onto the electrode surface in open circuit mode. The subsequent electrochemical measurement was carried out by cyclic voltammetry (CV) and linear sweep anodic stripping voltammetry (LSASV) in a supporting electrolyte of 1.0 M HCl. The obtained oxidation currents (I_pa1 and L_pa2) were proportional to the Pd(II) concentration in the range of 4.7 × 10^–6 - 9.4 × 10^–8 M. The developed method was applied to the quantitative determination of palladium in real samples.     

A study of the electron transfer and oxygen binding reactions of myoglobin

Quasi-reversible electron transfer kinetics are reported for sperm whale myoglobin reacting at tin-doped indium oxide electrodes. This reaction was studied by three different electrochemical methods; cyclic voltammetry (CV), single potential step chronoabsorptometry (SPS/CA) and derivative cyclic voltabsorptometry (DCVA). Kinetic parameters were determined from experiments which followed the purification of the protein, the pretreatment of the electrode surface and the removal of dioxygen from the sample solution. A formal heterogeneous electron transfer rate constant, k^0'. of 2.6 (±0.5) × 10⁻⁵ cm s⁻¹ and a transfer coefficient, α, of 0.48 (±0.05) were obtained using SPS/CA. These results are shown to correlate well with those obtained using a second spectroelectrochemical method, DCVA. Anodic and cathodic responses for the heterogeneous electron transfer of myoglobin can be observed using cyclic voltammetry, but these responses are not as reproducible as those that are obtained using the optical methods described here. The advantages of these optical methods over those of cyclic voltammetry are clear from this study.     

Time-derivative cyclic voltabsorptometry for voltammetric characterization of catechin film on a carbon-paste electrode: one voltammogram becomes four

Using (+)-catechin electrodeposited on a carbon-paste electrode as a model system, we have demonstrated the usefulness of the time-derivative cyclic voltabsorptometry for voltammetric characterization of the deposited films, in the case when not only the deposited species but also the same ones in free solution participated in redox processes. A long-optical-path thin-layer cell was used for the voltabsorptometric measurements. The potential-dependent absorption signals were monitored for catechin at 252 and 279 nm in B-R buffer electrolytes with pH = 1.8. The combination of voltabsorptometry with voltammetry enabled one measured cyclic voltammogram to become four, which were attributed to catechin and its oxidized state, in free solution or in deposited state, respectively. The surface coverage of the electrode was evaluated from the cyclic voltammograms obtained for the deposited catechin, which decreased with the increasing scan rate. Also, the deposited species was found to make a major contribution to the total voltammetric current, especially at higher scan rates.     

利培酮的电化学行为及应用研究

采用循环伏安法、线性扫描伏安法、常规脉冲伏安法和恒电位电解法等电化学手段, 详细研究了利培酮在pH 7.07～10.32 B-R缓冲溶液和0.2 mol•L^－1 NaOH溶液中的电化学行为. 研究表明: 在pH 7.07～10.07 B-R缓冲溶液中, 利培酮产生的P₁波为催化氢波. 在pH＝10.32 B-R缓冲溶液中, 利培酮可以产生P₂和P₃两个波. 其中, P₂波为不可逆的单电子还原波, P₃波可以分裂成两个波P_3a和P_3b. P_3a波为P₂波的进一步单电子还原, 而P_3b波则属于催化氢波. 在0.2 mol•L^－1 NaOH溶液中, 利培酮产生的P₄波是一个两电子的不可逆还原波. 另外, 根据P₁波的一阶导数峰电流与利培酮浓度在1.6×10^－5～2.0×10^－6 mol•L^－1 (r＝0.9950)间的线性关系, 建立了利培酮片剂中利培酮含量的测定新方法. 新方法的检出限为1.0×10^－6 mol•L^－1, 回收率在105%～102%之间, 相对标准偏差为0.84%.