多巴胺在聚亚甲基蓝/石墨烯修饰电极上的电化学行为研究

利用电聚合方法在石墨烯修饰的玻碳电极表面制备了聚亚甲基蓝/石墨烯修饰电极(PMB/GH/GCE)。采用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了多巴胺(DA)和抗坏血酸(AA)在该修饰电极上的电化学行为。在pH 6.9的磷酸盐缓冲溶液中,DA和AA分别在0.208 V和-0.108 V处产生灵敏的氧化峰,与其在聚亚甲基蓝和石墨烯单层修饰电极上的电化学行为相比,两者的峰电流明显增加,峰电位差达316 mV。研究表明,电聚合方法使亚甲基蓝牢固地非共价修饰到石墨烯上,并产生协同增效作用,较好地提高了电极的灵敏度和分子识别性能,有利于在大量AA存在下实现对DA的选择性测定。在1.00×10-3mol/L AA的存在下,DA的差分脉冲伏安法峰电流与其浓度在1.00×10-7～5.00×10-3mol/L范围内呈良好的线性关系,检出限达1.00×10-8mol/L。将该方法用于盐酸多巴胺注射液的测定,结果满意。     

Electrocatalytic Oxidation of Dopamine at a Nanocuprous Oxide‐Methylene Blue Composite Glassy Carbon Electrode

Cuprous oxide nanowhisker was prepared by using cetyltrimethyl ammonium bromide (CATB) as soft template, and was characterized by XRD and TEM methods. The electrochemical properties of nano‐Cu₂O and nano‐Cu₂O‐methylene blue (MB) modified electrode were studied. The experimental results indicate that nano‐Cu₂O shows a couple of redox peaks corresponding to the redox of Cu(II)/Cu(I), the peak currents are linear to the scan rates which demonstrate that the electrochemical response of Cu₂O is surface‐controlled. The composite nano‐Cu₂O‐Nafion‐MB modified electrode shows a trend of decrease of peak currents corresponding to the Cu (II)/Cu (I). However, the electrocatalytic ability of nano‐Cu₂O‐MB composite film to dopamine increases dramatically. At this composite electrode, dopamine shows a couple of quasireversible redox peaks with a peak separation of 106 mV, the peak current increases about 8 times and the oxidation peak potential decreases about 200 mV as compared to that at bare glassy carbon electrode. The peak currents change linearly with concentration of dopamine from 1×10^?7 to 3.2×10^?4 mol/L, the detection limit is 4.6×10^?8 mol/L. The composite electrode can effectively eliminate the interference of ascorbic acid and has better stability and excellent reproducibility.     

溴酚蓝修饰玻碳电极测维生素C中抗坏血酸含量

使用溴酚蓝修饰的玻碳电极,以快速循环伏安法测定维生素C片剂中抗坏血酸含量并优化实验条件.结果表明,溴酚蓝(BPB)修饰玻碳电极用于抗坏血酸含量的分析,有良好的稳定性和抗干扰能力.在0.0050~0.1500 g.L-1浓度范围内,峰电流与浓度呈良好的线性关系,R=-0.9991,检出限为0.0010 g.L-1,结果令人满意.     

烟酰胺腺嘌呤二核苷酸的聚亚甲基蓝/单壁碳纳米管修饰电极差分脉冲伏安法检测

研究了聚亚甲基蓝/单壁碳纳米管修饰电极的制备、电化学性质,采用差分脉冲伏安法成功应用于烟酰胺腺嘌呤二核苷酸(NADH)的测定.在实验条件下,该修饰电极对NADH氧化具有很好的电催化作用,NADH浓度在2.0～500靘oL/L范围内与峰电流呈良好的线性关系,检出限为0.6 靘ol/L,结果令人满意.     

抗坏血酸在多壁碳纳米管修饰玻碳电极上的催化氧化

多壁碳纳米管;抗坏血酸;修饰电极;电催化;伏安法     

基于溶胶-凝胶普鲁士蓝膜修饰玻碳电极电催化氧化测定水果中抗坏血酸

制备了一种溶胶-凝胶普鲁士蓝膜修饰玻碳电极,研究了抗坏血酸在该电极上的电催化氧化作用,建立了测定抗坏血酸的方法。在磷酸缓冲溶液(pH 5.0)中,在2.5×10-5-3.2×10-3mol.L-1范围内,抗坏血酸的浓度与氧化峰电流呈线性关系,相关系数为0.999 5,检出限为7×10-6mol.L-1。该修饰电极具有制备简单、灵敏度高、响应速度快、稳定性和重现性好等特点。方法已用于水果中抗坏血酸的测定,所得结果与药典法测得结果一致。     

聚伊文思蓝修饰电极对多巴胺和抗坏血酸的电分离及同时测定

研究多巴胺(DA)和抗坏血酸(AA)在聚伊文思蓝(Evans Blue)修饰电极上的伏安行为,建立差示脉冲伏安测定法.在pH4.5磷酸盐缓冲液中,聚伊文思蓝修饰电极对DA和AA有显著的增敏和电分离作用.DA和AA氧化峰电流与浓度分别在1.0×10-6~3.0×10-5mol/L和5.0×10-6~1.05×10-4mol/L范围内呈良好的线性关系,检测限分别为2.5×10-7mol/L和3.0×10-7mol/L.当DA与AA共存时,由该修饰电极检测的二者氧化峰电位差达184 mV,故可同时测定DA和AA,并有效消除其它组分对DA测定的干扰,已用于实际样品中DA和AA含量的测定,结果令人满意.     

曲克芦丁在羧基化单壁碳纳米管修饰电极上的电化学氧化

研制了羧基化单壁碳纳米管修饰玻碳电极( SWCNTs - COOH/GCE).用交流阻抗谱法(EIS)和扫描电镜( SEM)研究了电极膜性能,应用循环伏安法(CV)考察了曲克芦丁在修饰电极上的电化学行为.结果表明,SWCNTs - COOH修饰电极对曲克芦丁的氧化有良好的电催化活性,其氧化反应为单电子单质子过程,结合恒...     

Electrocatalytic Oxidation of Estrogenic Phenolic Compounds at a Nickel‐Modified Glassy Carbon Electrode

This paper demonstrates for the first time, successful electrocatalytic oxidation of electroactive estrogenic phenolic compounds (EPCs) at a nickel‐modified glassy carbon electrode (Ni‐GCE). The electrode was evaluated in terms of electrocatalytic activity, sensitivity, linear dynamic range, limit of detection, and response stability. In comparison to bare glassy carbon electrode, current amplification was observed for EPCs at Ni‐GCE, for example, for a 40 µM estrone at Ni‐GCE was amplified by a factor of 1224. The Ni‐GCE gave good figures of merit with no evidence of electrode fouling. As an example, the limit of detection (S/N=3) for 17β‐estradiol was 100 nM and the response precision (n=5) was 3.4 %.     

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.     

Methylene Blue/Multiwall Carbon Nanotube Modified Electrode for the Amperometric Determination of Hydrogen Peroxide

A novel amperometric sensor based on the incorporation of multiwalled carbon nanotubes (MWCNT) into a poly(methylene blue) (PMB) film immobilized on carbon composite electrodes is described. Cyclic voltammetry indicated that at a surface covered by a MWCNT/PMB layer the cathodic reduction of hydrogen peroxide is facilitated and occurs already at 0.0 V versus SCE. The effect of the order of deposition of PMB and MWCNT, as well as its loading, on electrochemical behaviour was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The influence of the various immobilised platforms on the electrocatalytic performance towards hydrogen peroxide was also examined.     

Determination of Rutin by a Graphene-Modified Glassy Carbon Electrode

A reduced graphene oxide-modified glassy carbon electrode for sensitive detection of rutin is reported. The modified electrode was obtained by one-step electrochemical reduction of graphene oxide on the bare glassy carbon electrode. In the presence of graphene, an enhanced electrochemical response for rutin appeared with a pair of well-defined anodic and cathodic peaks in pH 3.0 phosphate buffer. Under the optimized conditions, the anodic peak currents exhibited a linear relationship with rutin concentration from 0.1 to 2.0 µM with a detection limit of 23.2 nM. The modified electrode was employed to the analysis of tablets (with satisfactory recovery of 19.96 mg/per tablet) and Flos Sophorae. The graphene-modified electrode exhibited high sensitivity, good stability, and selectivity for the determination of rutin.     

巯基化合物在铁氰化铟薄膜修饰玻碳电极上的电催化氧化及其液相色谱安培测定

在酸性介质中，铁氰化铟薄膜修饰玻碳电极（ＩｎＨＣＦ／ＧＣ）大大催化了巯基化合物的氧化。比较了不同制备方法所得修饰电极的稳定性。全氟代磺酸Ｎａｆｉｏｎ涂敷于修饰电极表面增强了其在流动体系中的稳定性。液相色谱分离检测了半胱氨酸、还原型谷胱甘肽和Ｎ－乙酰半胱氨酸。线性范围达２个数量级。检测限为１．７ｎｇ、１０．０ｎｇ和６．０ｎｇ。     

Radical Cation of Pyrazine-di-N-oxide as a Mediator in Electrocatalytic Oxidation of Organic Compounds

The mechanism of oxidation of cyclohexanol, methanol, diethyl ether, triethyl orthoformate, and cyclohexane in the presence of a mediator—electrochemically generated radical cation of pyrazine-di-N-oxide (PyrDNO)—is studied on glassy carbon and platinum in a 0.1 M LiClO₄ solution in acetonitrile employing cyclic voltammetry, ESR electrolysis, and gas chromatography. Effect of temperature, additives of acid and water, oxygen, and the nature of the substrate and solvent on the shape of cyclic voltammograms and intensity of ESR signal of PyrDNO is examined. ESR spectra for radical cations and anions of PyrDNO with g factors equal to, respectively, 2.0090 and 2.0031 are recorded. A mechanism for the overall two-electron catalytic oxidation of an organic substance, which involves a stage in which it complexes with the radical cation of PyrDNO, is suggested.     

Voltammetric Determination of Folic Acid Using Adsorption of Methylene Blue onto Electrodeposited of Reduced Graphene Oxide Film Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of folic acid by adsorbing methylene blue onto electrodeposited reduced graphene oxide film modified glassy carbon electrode (MB/ERGO/GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The surface morphology of the MB/ERGO/GCE modified electrode was characterized using scanning electron microscopy, displays that both MB and ERGO distributed homogeneously on the surface of GCE. The MB/ERGO/GCE modified electrode shows more favorable electron transfer kinetics for potassium ferricyanide and potassium ferrocyanide probe molecules, which are important electroactive compounds, compared with bare GCE, MB/GCE, and ERGO/GCE. The electrochemical behaviors of folic acid at MB/ERGO/GCE were investigated by cyclic voltammetry, suggesting that the modified electrode exhibited excellent electrocatalytic activity towards folic acid compared with other electrodes. Under physiological condition, the MB/ERGO/GCE modified electrode showed a linear voltammetric response from 4.0 μM to 167 μM for folic acid, and with the detection limit of 0.5 μM (S/N=3). The stability, reproducibility and anti‐interference ability of the modified electrode were examined. The developed method has been successfully applied to determination of FA in tablets with a satisfactory recovery from 96 % to 100 %. The work demonstrated that the electroactive MB adsorbing onto graphene modified electrode showed an enhanced electron transfer property and a high resolution capacity to FA.     

对乙酰氨基酚在多壁碳纳米管修饰电极上的电化学行为

制备了多壁碳纳米管修饰玻碳电极,研究了对乙酰氨基酚在多壁碳纳米管修饰电极上的循环伏安行为,并建立了测定对乙酰氨基酚含量的电化学分析方法。在pH为6.89的磷酸盐缓冲液中,多壁碳纳米管修饰电极对对乙酰氨基酚有明显的电催化作用,其氧化峰电流与对乙酰氨基酚浓度在1.0×10-6～1.0×10-4mol·L-1范围内呈良好的线性关系,检测限为2.0×10-7mol·L-1。     

Simultaneous Determination of Dopamine and Uric Acid by Electrocatalytic Oxidation on a Carbon Paste Electrode Using Pyrogallol Red as a Mediator

A sensitive and selective electrochemical method for the simultaneous determination of dopamine (DA) and uric acid (UA) was developed using a pyrogallol red modified carbon paste electrode. Under the optimized conditions, the peak current was linearly dependent on 1.0–700.0 μmol L^?1 DA and 50.0–1000.0 μmol L^?1 UA. The detection limits for DA and UA were 0.78 μmol L^?1 and 35 μmol L^?1, respectively. Finally, this method was also examined for the determination of DA and uric acid in real samples such as drugs and urine.     

Electrocatalytic Oxidation of Paracetamol on Ni and NiCu Alloy Modified Glassy Carbon Electrode

In this study we investigated the electrocatalytic oxidation of anti‐inflammatory drug (paracetamol) on Nickel and Nickel–copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in alkaline solution. These electrodes prepared by galvanostatic method and different electrochemical techniques such as cyclic voltammetry and chronoamperometry were used to track the oxidation process and its kinetics. From Voltammetric studies we concluded that in the presence of drugs the anodic peak current of low valences Nickel species increased, followed by a decrease in the corresponding cathodic current peak. This indicates that drugs were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron's equation, the values of α and k_s for the immobilized redox species were determined. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of paracetamol was found in agreement with the values obtained from CV measurements.     

甲氧苄啶在多壁碳纳米管-Nafion修饰电极上的电催化氧化及电分析方法

用循环伏安法(CV),计时库仑法(CC),计时电流法(CA),线性扫描伏安法(LSV)及电流-时间曲线研究了甲氧苄啶(trimethoprim, TMP)在碳纳米管-Nafion修饰电极(MWCNTs-Nafion/GCE)上的电化学行为,电化学动力学性质以及电分析方法.结果表明,TMP在GCE上有一个极弱的氧化峰,而在MWCNTs-Nafion/GCE上出现一个敏锐的氧化峰,表明MWCNTs-Nafion/GCE对TMP电化学氧化具有良好的催化作用.在扫描速度为10～800 mV/s时其氧化峰电流与扫描速度平方根(v1/2)呈良好线性关系,表明TMP在MWCNTs-Nafion/GCE上的伏安行为是受扩散控制的电化学过程.TMP在MWCNTs-Nafion/GCE上氧化峰电流与浓度在5.0×10-6～1.0×10-3 mol/L范围内呈良好线性关系;检出限为6.6×10-7 mol/L;RSD在0.75%～1 69%之间;加标回收率在98.1%～101.1%之间.本方法简便快捷,测定结果令人满意,可用于TMP的电化学定量测定.     

用多壁碳纳米管修饰玻碳电极为工作电极循环伏安法测定辛硫磷

将多壁碳纳米管(MWCNT′s)置于硝酸-硫酸(1+1)溶液中回流6 h使之净化及功能化。取MWCNT′s 5 mg置于超纯水10 mL中经超声振荡20 min制得其悬浮液,取悬浮液10μL滴加在玻碳电极(GCE)表面,经自然干燥后即得用MWCNT′s修饰的玻碳电极(MWCNT′s/GCE)。基于此修饰电极对辛硫磷的催化还原反应,提出了蔬菜中辛硫磷的循环伏安测定法,在pH 4的乙酸盐支持电解质溶液中,在电位0.78 V(对SCE)处可见明显的还原峰,且其峰电流值与辛硫磷浓度在5.0×10-8~1.0×10-6mol.L-1之间呈线性关系。应用此法分析了两件蔬菜样品,并以此试样为基体加入标准溶液对方法进行回收及精密度试验,测得其回收率的平均值和相对标准偏差(n=5)分别依次为100.3%,96.5%及3.7%,3.2%。