二茂铁甲基季铵盐对异烟肼的电催化氧化及其电分析方法研究

研究了铂电极上二茂铁甲基季铵盐电催化氧化异烟肼的电化学行为,并且对异烟肼药物的电分析方法进行了研究。实验结果发现,二茂铁甲基季铵盐对异烟肼的电化学氧化具有很好的催化作用。当二茂铁甲基季铵盐浓度一定时,催化氧化峰电流与异烟肼浓度在5×10-5~6×10-4mol/L的浓度范围有良好的线性关系(r=0.9984),运用方波伏安法测定了异烟肼样品含量,与紫外分光光度法所得结果进行比较,相对标准偏差在0.5%以内,标准加入的回收率在98.0%~101.0%之间。     

铂电极上二茂铁甲基季铵盐电催化氧化异烟肼的电化学及其动力学性质研究

在0.1 mol·L-1Na2SO4水溶液中,二茂铁甲基季铵盐对异烟肼的电化学氧化具有很好的催化作用。运用循环伏安法研究了二茂铁甲基季铵盐和异烟肼的浓度、扫描速率分别对该电催化氧化体系的影响,同时运用循环伏安法和计时电流法探讨了该电催化氧化反应体系的电化学动力学规律,由电化学动力学测定并计算出了该催化体系的电子转移系数α、反应级数、催化反应速率常数k值。     

Study on Electrocatalytic Oxidation of L‐Cysteine at Glassy Carbon Electrode by (FcM)TMA and Its Electrochemical Kinetics

The electrocatalytic oxidation of L ‐cysteine by (ferrocenylmethyl)trimethylammonium at a glassy carbon electrode in 0.1 M Na₂SO₄ aqueous solution has been studied. The rate constant for the catalytic reaction was evaluated as (4.28±0.05)×10³ M^?1 s^?1 by chronoamperometry. Experimental conditions, which maximize the current efficiency of the electrocatalytic oxidation, such as pH value and the concentration of the catalyst, were also investigated. The experimental results of electrocatalytic kinetics of L ‐cysteine oxidation on GCE in the presence of (ferrocenylmethyl)trimethylammonium obviously support the reaction mechanism proposed and the rate determining step assumed in scheme described in this work.     

硫脲在10-甲基吩噻嗪修饰碳糊电极上的电催化氧化及电分析方法研究

研究了硫脲(Thiourea,Tu)在10-甲基吩噻嗪修饰碳糊电极(MPT/CPE)上的电催化氧化行为.结果表明,Tu在裸碳糊电极(CPE)上的直接电化学氧化过程十分迟缓,MPT/CPE对Tu的电化学氧化具有良好的催化作用.用计时电流法(CA)测定了Tu在MPT/CPE上的电极过程动力学参数,测得电荷传递系数α=0.61,电催化氧化反应的速率常数k=(1.96±0.10)×104(mol/L)-1·s-1.用方渡伏安法(SWV)测得催化氧化峰电流与Tu浓度在1.0×10-6～8.0×10-3mol/L范围内呈良好的线性关系,线性回归方程为,Ips(μA)=10.836c(10-3mol/L)+5.326,R=0.9984,检出限为2.2×10-7mol/L(S/N=3).方法可用于Tu的电化学法测定.     

聚L-赖氨酸修饰电极对去甲肾上腺素的电催化氧化

研究了L 赖氨酸在玻碳电极上电化学聚合的条件及修饰电极的电化学特性,发现该聚合膜对去甲肾上腺素(NE)的电氧化有显著的催化作用,在磷酸盐缓冲溶液(pH7)中,恒电位-0.2V富集2.0min后,用方波溶出伏安法对NE进行了测定,线性范围为1.0×10-8～5.0×10-4mol L,检出限(信噪比=3)为8 2×10-10mol L。对1.0×10-7mol LNE平行测定8次相对标准偏差为2 4%。     

化学修饰电极的研究及其分析应用

化学修饰电极的出现推动了电化学的发展,是现代电分析化学领域中一个重要的研究方向。本文较详细地评述了化学修饰电极的制备方法及其电分析应用,对其未来发展作了展望。     

聚亚甲基蓝修饰金电极对抗坏血酸电催化氧化及其电分析方法研究

研究了亚甲基蓝(methylene blue,MB)聚合物膜修饰金电极(PMB/Au)的制备及其性质,通过电化学阻抗谱图对PMB/Au进行了表征,并对抗坏血酸(ascorbic acid,AA)在PMB/Au上的电化学行为进行了研究。结果表明,PMB/Au对AA的氧化具有良好的电催化作用,使AA的过电位降低约200 mV,氧化峰电流明显增大。测得AA在PMB/Au上的电荷转移系数为0.70,催化反应速率常数为5.99×103mol-1.L.s-1。用方波伏安法(Square Wave Voltammetry,SWV)测得氧化峰电流与AA浓度在2.0×10-5~6.0×10-3mol/L范围内呈良好线性关系,检出限为1.0×10-5mol/L。将PMB/Au应用于Vc片剂和Vc注射液中AA的测定。     

甲苯胺蓝修饰电极的电化学性质及对抗坏血酸的测定

研究了甲苯胺蓝(TB)聚合膜修饰金电极的制备及其电化学性质,并用于抗坏血酸(AA)的测定。在pH 6.5的磷酸盐缓冲溶液中,AA在甲苯胺蓝修饰金电极上产生一灵敏的氧化峰,峰电流与AA的浓度在3.9×10-5~1.0×10-2mol/L范围内呈良好的线性关系,检出限为1.3×10-5mol/L。该电极重现性良好,已用于实际样品中AA的测定。     

Modified platinum electrode with phytic acid and single-walled carbon nanotube: Application to the selective determination of dopamine in the presence of ascorbic and uric acids

A platinum (Pt) electrode modified by single-walled carbon nanotubes (SWNTs) and phytic acid (PA) was investigated by voltammetric methods in buffer solution. The PA-SWNTs/Pt-modified electrode demonstrated substantial enhancements in electrochemical sensitivity and selectivity towards dopamine (DA) in the presence of L-ascorbic acid (AA) and uric acid (UA). The PA-SWNTs films promoted the electron transfer reaction of DA, while the PA film, acting as a negatively charged linker, combined with the positively charged DA to induced DA accumulation in the film at pH under 7.4. However, the PA film restrained the electrochemical response of the negatively charged AA due to the electrostatic repulsion. The anodic peak potentials of DA, AA and UA could be separated by electrochemical techniques, and the interferences from AA and UA were effectively eliminated in the DA determination. Linear calibration plots were obtained in the DA concentration range of 0.2-10 μM and the detection limit of the DA oxidation current was determined to be 0.08 μM at a signal-to-noise ratio of 3. The results indicated that the modified electrode can be used to determine DA without interference from AA and UA, while ensuring good sensitivity, selectivity, and reproducibility.     

亚硫酸盐在乙酰二茂铁修饰碳糊电极上的电催化氧化及其电化学动力学性质研究

研究了亚硫酸盐在乙酰二茂铁(AFc)修饰碳糊电极(AFc/CPE)上的电催化行为。研究结果表明,其在裸碳糊电极(CPE)上的行为比亚硫酸盐在AFc/CPE上的氧化峰电流增加约3倍,氧化峰电位负移360 mV,表明AFc/CPE对亚硫酸盐的电化学氧化具有良好的催化作用。用循环伏安法、计时电流法测定了亚硫酸盐在AFc/CPE上的电极过程动力学参数,测得电荷传递系数α为0.70,电催化氧化反应速率常数k为(4.91±0.05)×104(mol/L)-1.s-1。催化氧化峰电流与亚硫酸盐在5.0×10-4~1.1×10-2mol/L浓度范围内呈良好的线性关系,线性回归方程为Ipa(μA)=1.345 7.956c(10-3mol/L),R=0.9988,检出限为2.0×10-5mol/L。可用于亚硫酸盐的电化学定量测定方法。     

苦参碱在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电分析方法

研究了苦参碱(Matrine, MT) 在多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电化学行为. 与GCE相比, MT在MWCNT/GCE上峰电位负移120 mV, 峰电流增大约2.5倍, 表明MWCNT/GCE对MT的电化学氧化具有良好的催化作用. 同时测定并计算了MT在MWCNT/GCE上的电极过程动力学参数: 电子转移系数α、电极反应速率常数ks、扩散系数D. 运用差分脉冲伏安法对苦参碱样品含量进行测定, 相对标准偏差为0.12%～2.9%, 加标回收率为98.4%～99.0%. 该方法可用于MT的电化学定量测定.     

聚对氨基酚修饰电极的制备及其对尿酸的催化氧化作用

采用循环伏安法制备了聚对氨基酚薄膜修饰玻碳电极, 研究了尿酸在该修饰电极上的电化学行为, 建立了循环伏安法测定尿酸的新方法. 研究发现: 在pH 5.6的磷酸盐缓冲溶液中, 以0.1 mol/L KCl作支持电解质, 聚对氨基酚修饰电极对尿酸存在灵敏的氧化作用, 应用循环伏安法对尿酸进行定量分析, 线性范围为1.0×10-6～4.0×10-5 mol/L, 检出限为8×10-7 mol/L. 对2.0×10-5 mol/L尿酸平行测定5次, 相对标准偏差为4.0%.     

Electrochemical oxidation of cisatracurium on carbon paste electrode and its analytical applications

The electrochemical oxidation of cisatracurium was investigated by cyclic voltammetry and differential pulse voltammetry at a carbon paste electrode and the experimental parameters have been optimized in order to obtain the optimum analytical signal. A differential pulse voltammetric method with carbon paste electrode is described for the determination of cisatracurium with detection limit of 0.38 μg/ml and quantitation limit of 1.26 μg/ml. The proposed method was applied to determine the content of cisatracurium in human urine and human serum, obtaining accurate and precise results.     

Electrocatalytic oxidation of aliphatic diols on platinum and gold Part I: Effects of chain length and isomeric position

The electrochemical reactivity of propanediol, butanediol, pentanediol, hexanediol and heptanediol, on polycrystalline platinum and gold electrodes, was studied in acid and alkaline media. The effect of the number of carbon atoms, i.e. the chain length, was observed. The apparent energies of activation were evaluated systematically and discussed in relation to the molecular structure of the different diols. In the case of the butanediol isomers, an effect of the alcohol group positions on the activation energy and reaction mechanisms was clearly shown.     

A new method for electrocatalytic oxidation of ascorbic acid at the Cu(II) zeolite-modified electrode

A new method is developed for the catalytic oxidation of ascorbic acid at graphite zeolite-modified electrode, doped with copper(II) (Cu²⁺A/ZCME). Copper(II) exchanged in zeolite type A acts as catalyst to oxidize ascorbic acid. The modified electrode lowered the overpotential of the reaction by ∼400 mV. First, the electrochemical behavior of copper(II), incorporated in the zeolite type A modified electrode, was studied. The results illustrate that diffusion can control the copper(II)/copper(0) redox process at the Cu²⁺A/ZCME. Then, the behavior of electrocatalytic oxidation reaction for ascorbic acid was researched. The electrode was employed to study electrocatalytic oxidation of ascorbic acid, using cyclic voltammetry and chronoamperometry as diagnostic techniques. The diffusion coefficient of ascorbic acid was equal to 1.028 × 10⁻⁵ cm² s⁻¹. A linear calibration graph was obtained over the ascorbic acid with a concentration range of 0.003-6.00 mmol L⁻¹. The detection limit (DL) of ascorbic acid was estimated as 2.76 × 10⁻⁷ mol L⁻¹. The relative standard deviations of 10 replicate measurements (performed on a single electrode at several ascorbic acid concentrations between 3.0 and 200 μmol L⁻¹) were measured between 1.0 and 2.4%.     

溶胶-凝胶-钴-邻菲啰啉修饰电极对一氧化氮的电催化氧化及其测定

报道了溶胶 凝胶 钴 邻菲口罗啉膜修饰电极的制备方法及其在一氧化氮(NO)检测中的应用,采用循环伏安法(CV)研究修饰电极的电化学特性,差示脉冲伏安法(DPV)对NO进行检测。该修饰电极对NO的电化学氧化具有很好的催化作用,使其氧化电位负移了210mV,氧化峰电流与NO浓度在5.6×10-8～2.8×10-5mol/L范围内呈良好的线性关系,相关系数r=0.999,检测限为1.4×10-8mol/L,且生物体内常见的干扰物质如抗坏血酸、NO2-和儿茶酚胺类神经递质的代谢物等不干扰测定。     

Electrochemical behavior of dopamine at a quercetin-SAM-modified gold electrode and analytical application

A stable quercetin–thioglycolic acid-modified gold electrode (Qu–TCA/Au) was prepared as a self-assembled monolayer (SAM) and its electrochemical behavior was investigated by electrochemical methods. In 0.05-M phosphate buffer solution (pH 7.0) quercetin exhibits quasi-reversible signals at the Qu–TCA/Au electrode. The stability of the quercetin-modified gold electrode is very good. The quercetin self-assembled monolayer is an effective mediator for the oxidation of dopamine, which was investigated by cyclic voltammetry and differential pulse voltammetry. Ascorbic acid does not interfere with determination of dopamine at an electrode modified with a mixture of quercetin–thioglycolic acid and quercetin–11-mercaptoundecanoic acid. This modification allows dopamine to be determined in the presence of ascorbic acid in the range from 3×10^–5 to 3×10^–4 M. The detection limit is 1×10^–6 M. Scanning electrochemical microscopy (SECM) was employed to study the electrochemical performances of the modified gold electrode indicating different feedback modes at differently modified surfaces.     

Voltammetric study of the behaviour of N-acetyl-p-aminophenol in aqueous solutions at a platinum electrode

The electrochemical oxidation of N-acetyl-p-aminophenol (PAR) was investigated at a Pt electrode with the application of cyclic (CV) and differential pulse (DPV) voltammetry methods. An effect of scan rate, substrate concentration and pH on electrode reactions was determined. The parameters of substrate electro-oxidation, i.e. heterogeneous rate constant, charge transfer coefficient, and diffusion coefficient, were calculated. Our investigation's results prove the exchange of two electrons and one proton in the first step, followed by a chemical reaction. PAR electro-oxidation occurs according to an EC mechanism.     

Asymmetric oxidation of sulfides catalyzed by chiral (salen)Mn(III) complexes with a pyrrolidine backbone

Catalytic properties of a series of chiral (pyrrolidine salen)Mn(III) complexes for asymmetric oxidation of aryl methyl sulfides were evaluated. Moderate activity, good chemical selectivity and low enantioselectivity were attained with iodosylbenzene as a terminal oxidant. Enantioselectivity of sulfide oxidation was affected slightly by polar solvent and the sulfoxidation carried out in THF for thioanisole and in CH₃CO₂Et for electron‐deficient sulfides gave better enatioselctivities. The addition of the donor ligand PPNO (4‐phenylpyridine N‐oxide) or MNO (trimethylamine N‐oxide) only has a minor positive effect on the enantioselectivity. Also explored was the steric effect of the N_aza‐substituent in the backbone of (pyrrolidine salen)Mn(III) complexes on the enantioselectivity of sulfide oxidation. The sulfides' access pathway is discussed based on the catalytic results. Copyright © 2006 John Wiley & Sons, Ltd.