Electrochemical Determination of Hydrogen Peroxide Using a Glassy Carbon Electrode Modified with Three-Dimensional Copper Hydroxide Nanosupercages and Electrochemically Reduced Graphene Oxide

Three-dimensional copper hydroxide nanosupercages and electrochemically reduced graphene oxide were used to modify the glassy carbon electrode for the selective determination of hydrogen peroxide. The morphology and electrochemistry properties of copper hydroxide nanosupercage/electrochemically reduced graphene oxide/glassy carbon electrode were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectra, cyclic voltammetry, and electrochemical impedance spectroscopy. The resulting copper hydroxide nanosupercage/electrochemically reduced graphene oxide/glassy carbon electrode showed favorable performance for the electrocatalytic reduction of hydrogen peroxide. The amperometric current–time curve of the electrochemical sensor exhibited a wide linear range from 0.5 to 1030?µM with a limit of detection of 0.23?µM at a signal-to-noise ratio of three. Moreover, the sensor provided favorable selectivity, reproducibility, and stability and was used for the determination of H₂O₂ in tap water.     

纳米金修饰玻碳电极对鸟嘌呤的催化氧化

采用电化学沉积法制备了纳米金修饰玻碳电极,并用循环伏安法和电化学阻抗法进行了表征,以此建立了一种直接测定鸟嘌呤的电分析方法。在磷酸盐缓冲溶液(pH 6.0)中,研究了鸟嘌呤在纳米金修饰电极上的电化学行为,实验结果表明,纳米金修饰电极可以增强鸟嘌呤在电极表面的吸附,并加快鸟嘌呤在电极表面的电子传输,使其电化学信号明显增大,检测灵敏度大大提高,该修饰电极对鸟嘌呤表现出良好的电催化性能。在优化实验条件下对鸟嘌呤进行测定,方法的线性范围为8.0×10-7~6.0×10-5mol/L,检出限为1.0×10-8mol/L,在鸟嘌呤浓度为1.0×10-5mol/L时测得RSD(n=10)为2.5%。     

Comparative Study on Electroanalysis of Fenthion Using Silver Amalgam Film Electrode and Glassy Carbon Electrode Modified with Reduced Graphene Oxide

Oxidation and reduction processes of the insecticide fenthion was comparatively investigated at a reduced graphene oxide modified glassy carbon electrode (RGO‐GCE) and a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) using square wave stripping voltammetry (SWSV). The influence of pH and SW parameters was investigated. The linear concentration ranges were found to be 1 × 10⁻⁶ – 2 × 10⁻⁵ and 1 × 10⁻⁷ – 2 × 10⁻⁵ mol L⁻¹ for Hg(Ag)FE and RGO‐GCE, respectively. The detection and quantification limits were calculated as 1.3 × 10⁻⁷ and 4.5 × 10⁻⁷ mol L⁻¹ for Hg(Ag)FE and 7.6 × 10⁻⁹ and 2.5 × 10⁻⁸ mol L⁻¹ for RGO‐GCE. Both of the developed electroanalytical methods offer rapid and simple detection of fenthion and were used on spiked tap and river water and apple juice samples. Scanning electron microscopy was used for RGO‐GCE surface characterization.     

尿酸在石墨烯修饰玻碳电极上的电化学行为及测定

以抗坏血酸为还原剂,采用微波水热法化学还原氧化石墨烯合成了石墨烯纳米片,制备了石墨烯修饰的玻碳电极(RGO/GCE),并采用循环伏安法、计时电量法、交流阻抗法等电化学技术研究了尿酸在该修饰电极上的电化学行为及其影响因素。结果表明,在PBS缓冲溶液中,尿酸(UA)在石墨烯修饰电极上的电极反应是一个受扩散控制的不可逆氧化过程。电极反应的转移电子数n=2,有效面积A=0.182 cm2,扩散系数D=1.51×10-6 cm2.s-1。UA的氧化峰电流与其浓度在5.0×10-6～1.5×10-4 mol/L范围内呈良好线性,r=0.995 7。利用该RGO/GCE修饰电极可以快速准确地测定UA,检出限为2.7×10-7 mol/L,加标回收率为98%～100%。     

Electrochemical Determination of Carbofuran in Tomatoes by a Concanavalin A (Con A) Polydopamine (PDA)-Reduced Graphene Oxide (RGO)-Gold Nanoparticle (GNP) Glassy Carbon Electrode (GCE) with Immobilized Acetylcholinesterase (AChE)

A new biosensor method was developed to determine residual carbofuran in tomatoes in a rapid and convenient fashion based on immobilizing acetylcholinesterase (AChE) on an electrode modified by concanavalin A (Con A)/polydopamine (PDA)-reduced graphene oxide (RGO)-gold nanoparticle (GNP) nanocomposites. The specific binding between Con A and AChE was investigated by the Ellman method and cyclic voltammetry (CV). The synthesis of nanocomposites was monitored by ultraviolet-visible absorption spectroscopy, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The results showed that, due to the specific binding and good electrical conductivity, the biosensor had 2.2 times higher bioactivity, leading to high sensitivity with a low Michaelis constant of 0.10?mM. Parameters that affect the response of the biosensor, such as the pH, enzyme loading, ionic concentration, and inhibition time, were optimized. When used for the detection of carbofuran, this biosensor showed a wide range of applicability from 5?µg/kg to 40?µg/kg with a detection limit of 0.012?µg/kg. In addition, the biosensor demonstrated good recovery values of 101% and 90% for 10?µg/kg and 100?µg/kg of the analyte, good stability, high repeatability, and a rapid detection time of 20?min for carbofuran in tomatoes, which provides significant advantages for future analysis.     

Electrochemical Determination of Dopamine Using a Poly(3,4-Ethylenedioxythiophene)-Reduced Graphene Oxide-Modified Glassy Carbon Electrode

Poly(3,4-ethylenedioxythiophene) was deposited on a reduced graphene oxide-decorated glassy carbon electrode through an electrochemical polymerization. The resulting glassy carbon electrode-reduced graphene oxide-poly(3,4-ethylenedioxythiophene) electrode was applied as an electrochemical biosensor for the determination of dopamine in the presence of ascorbic acid and uric acid. The material deposited on glassy carbon electrode was investigated in terms of morphology and structural analysis. The comparison of electrochemical behavior of the glassy carbon electrode-reduced graphene oxide-poly(3,4-ethylenedioxythiophene) electrode with the glassy carbon electrode-graphene oxide, glassy carbon electrode-reduced graphene oxide, and glassy carbon electrode-poly(3,4-ethylenedioxythiophene) electrodes exhibited high electrocatalytic activity for dopamine detection. Electrochemical kinetic parameters of glassy carbon electrode-reduced graphene oxide-poly(3,4-ethylenedioxythiophene), including the charge transfer coefficient α (0.49) and electron transfer rate constant k_s (1.04), were determined and discussed. The glassy carbon electrode-reduced graphene oxide-poly(3,4-ethylenedioxythiophene) electrode was studied for the determination of dopamine by differential pulse voltammetry and exhibited a linear range from 19.6 to 122.8?µM with a sensitivity of 3.27?µA?µM^?1?cm^?2 and a detection limit of 1.92?µM. The developed biosensor exhibited good selectivity toward dopamine with high reproducibility and stability.     

Electrochemical Determination of Tannins Using Multiwall Carbon Nanotubes Modified Glassy Carbon Electrode

A novel chemically modified electrode is prepared on the basis of the attachment of multiwall carbon nanotubes (MWNTs) to the surface of a glassy carbon electrode (GCE) in the presence of a hydrophobic surfactant. The electrochemical behavior of tannins at the MWNTs-modified GCE is investigated. Tannins yield a well-defined oxidation at about 0.30 V (SCE) at the MWNTs-modified GCE. MWNT-film shows remarkable enhancement effect on the oxidation peak current of tannins. The experimental parameters are optimized, and a direct electrochemical method to detect tannins is proposed. The oxidation peak current is proportional to the concentration of tannins over the range from 4 × 10^–7 to 2 × 10^–4 M, and the detection limit is 1 × 10^–7 mol/l after 5 min of accumulation. The relative standard deviation of 6% for determination of 2 × 10^–6 mol/l tannins indicates excellent reproducibility. The analysis method is demonstrated by using tea and Chinese gall samples.     

纳米金修饰玻碳电极测定邻苯二酚

采用恒电位沉积方法将HAuCl4直接还原成纳米金并修饰于玻碳电极表面,制备了对邻苯二酚具有电催化氧化作用的纳米金修饰电极。邻苯二酚在该修饰电极上发生一可逆的氧化还原反应。在磷酸盐缓冲溶液(pH 7.5)中,当邻苯二酚的浓度为3.0×10-3mol.L-1时,与裸玻碳电极相比,其Epa负位移了170 mV,Epc正位移了50 mV,ΔE下降为60 mV,且峰电流显著增大,氧化峰电流与邻苯二酚浓度在5.0×10-6~4.2×10-3mol.L-1范围内呈线性关系,相关系数为0.997 6,检出限(3σ)为5.0×10-7mol.L-1。在浓度为5.0×10-4mol.L-1测得RSD(n=10)为2.9%,回收率在98.0%~101.0%之间。     

Electrochemical Detection of Alloxan on Reduced Graphene Oxide Modified Glassy Carbon Electrode

Alloxan is a toxic reagent that strongly induces the diabetes by destroying insulin‐producing β‐cells in the pancreas of living organisms. The reduction product of alloxan is dialuric acid, which is responsible for the intracellular generation of ROS to enhance the stress in living cells to cause kidney disease or diabetic nephropathy. Herein, we studied for the first time the electrochemical properties of alloxan on reduced graphene oxide modified glassy carbon electrode (rGO/GCE) in 0.1 M phosphate buffer solution (PBS) at pH 7. The obtained results were compared with graphene oxide modified GCE (GO/GCE) and bare GCE surfaces. The modified rGO/GCE showed well defined redox couple with 10 fold increase in both reduction as well as oxidation peak current for alloxan than that of GO/GCE and bare GCE. Differential pulse voltammetry (DPV) technique shows the linear increase in both oxidation and reduction peak current of alloxan in the range of 30 μM to 3 mM with LOD of 1.2 μM. An amperometric signal of alloxan is also increases with respect to each addition of 50 μM of alloxan on rGO/GCE at constant potential of ?0.05 V. The linear range of alloxan is observed between 50 μM to 750 μM (S/N=3). This kind of rGO/GCE surface is more suitable platform or sensor matrix for estimating unknown concentration of alloxan molecule in the real biological systems.     

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。     

多壁碳纳米管修饰玻碳电极测定乙炔雌二醇

多壁碳纳米管修饰玻碳电极测定乙炔雌二醇;多壁碳纳米管;乙炔雌二醇;化学修饰电极;电化学测定     

肉豆蔻酸-双层类脂膜修饰玻碳电极研究氯化血红素的电化学行为

报道了氯化血红素在肉豆蔻酸-双层类脂膜修饰玻碳电极上的电化学行为。在0.1~-0.7 V(vs.Ag/AgCl)电位范围内,扫描速率为40 mV/s时,氯化血红素在-0.4 V处产生很灵敏的还原峰电流。于pH7.50.01 mol/L KH2PO4-Na2HPO4底液中,该氧化峰电流与氯化血红素浓度在7.32×10-9~1.57×10-6mol/L范围内呈良好线性关系。该电极可作为检测氯化血红素的新型的高灵敏度电化学生物传感器。     

Electrochemical Study and Application on Shikonin at Poly(diallyldimethylammonium chloride) Functionalized Graphene Sheets Modified Glass Carbon Electrode

The electrochemical behaviors of shikonin at a poly(diallyldimethylammonium chloride) functionalized graphene sheets modified glass carbon electrode(PDDA-GS/GCE) have been investigated. Shikonin could exhibit a pair of well-defined redox peaks at the PDDA-GS/GCE located at 0.681 V(E_pa) and 0.662 V(E_pc)[vs. saturated calomel electrode(SCE)] in 0.1 mol/L phosphate buffer solution(pH=2.0) with a peak-to-peak separation of about 20 mV, revealing a fast electron-transfer process. Moreover, the current response was remarkably increased at PDDA-GS/GCE compared with that at the bare GCE. The electrochemical behaviors of shikonin at the modified electrode were investigated. And the results indicate that the reaction involves the transfer of two electrons, accompanied by two protons and the electrochemical process is a diffusional-controlled electrode process. The electrochemical parameters of shikonin at the modified electrode, the electron-transfer coefficient(α), the electron-transfer number(n) and the electrode reaction rate constant(k_s) were calculated to be as 0.53, 2.18 and 3.6 s^-1, respectively. Under the optimal conditions, the peak current of differential pulse voltammetry(DPV) increased linearly with the shikonin concentration in a range from 9.472×10^-8 mol/L to 3.789×10^-6 mol/L with a detection limit of 3.157×10^-8 mol/L. The linear regression equation was I_p=0.7366c+0.7855(R=0.9978; I_p: 10^-7 A, c: 10^-8 mol/L). In addition, the modified glass carbon electrode also exhibited good stability, selectivity and acceptable reproducibility that could be used for the sensitive, simple and rapid determination of shikonin in real samples. Therefore, the present work offers a new way to broaden the analytical application of graphene in pharmaceutical analysis.     

Highly Sensitive and Selective Voltammetric Sensor Fullerene Modified Glassy Carbon Electrode for Determination of Cefitizoxime in Solubilized System

The usefulness of fullerene modified glassy carbon electrode in mediating the reduction of cefitizoxime in solubilized system has been demonstrated. Due to the unique structure and extraordinary properties, fullerene shows higher catalytic efficiency towards cefitizoxime reduction. The kinetic parameters, electron transfer coefficient (α) and rate constant (K₀) across the modified electrode are 0.37 and 0.1081/s respectively. The proposed square‐wave voltammetric method is linear over the concentration range 1.2–10.3 µg/mL. The limit of detection (LOD) is found 0.27 ng/mL. High sensitivity and selectivity together with low detection limit of the electrode response make it suitable for the determination of cefitizoxime.     

钴/玻碳离子注入修饰电极伏安法测定呋喃妥因的研究

呋喃妥因 (NFT)在 0 .1mol/LHAc NaAc (pH 4 .0 )溶液中于钴 /玻碳 (Co/GC)离子注入修饰电极上产生一灵敏的伏安还原峰 ,峰电位为 - 0 .2 6V(vs.Ag/AgCl) ,峰电流与NFT浓度在 6 .0× 10 -8～ 5 .0× 10 -6mol/L范围内呈线性关系 (r =0 .9987) ,检出限为 1.0× 10 -8mol/L。用线性扫描伏安法和循环伏安法研究了NFT的伏安行为、吸附特性和电极反应机理。测定了电子转移数 (n =4 )、转移系数 (α =0 .5 8)和参与反应的质子数 (X =4 )等电化学参数。结果表明该电极过程为一具有吸附性的不可逆过程。该法用于片剂中NFT含量的测定 ,得到满意的结果。用标准加入法测得该法的回收率为 94 .0 %～ 98.5 %。     

盐酸伪麻黄碱在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电化学动力学性质

盐酸伪麻黄碱;碳纳米管修饰电极;电催化氧化;电化学动力学     

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.     

Electrochemical Detection of Steroid Hormones Using a Nickel‐Modified Glassy Carbon Electrode

This paper demonstrates the development of an analytical method for detecting steroid hormones by coupling HPLC to electrochemical detection, using a nickel‐modified glassy carbon electrode. The method was evaluated in terms of sensitivity, linear dynamic range, limit of detection, and response stability. The developed method exhibited good figures of merit for the steroid hormones studied with no evidence of electrode fouling. As an example, the limit of detection (S/N=3) for E3 was 0.10 µM and the response precision (n=5) was 0.6 %. The application of the method for the analysis of a real river water sample is demonstrated.     

Electrochemical Determination of 4-Nitrophenol Using a Single-Wall Carbon Nanotube Film-Coated Glassy Carbon Electrode

A single-wall carbon nanotubes (SWNT) film coated glassy carbon electrode (GCE) was fabricated for the direct determination of 4-nitrophenol (4-NP). The electrochemical behaviors of 4-NP at the SWNT-film coated GCE were examined. In 0.1M phosphate buffer with a pH of 5.0, 4-NP yields a very sensitive and well-defined reduction peak at the SWNT-modified GCE. It is found that the SWNT film exhibits obvious electrocatalytic activity towards the reduction of 4-NP since it not only increases the reduction peak current but also lowers the reduction overpotential. Based on this, an electrochemical method was proposed for the direct determination of 4-NP. The reduction peak current varies linearly with the concentration of 4-NP ranging from 1×10^–8 to 5×10^–6M, and the detection limit is 2.5×10^–9M after 3min of open-circuit accumulation. The relative standard deviation at 2×10^–7M 4-NP was about 6% (n=10), suggesting excellent reproducibility. This new method was successfully employed to determine 4-NP in several lake water samples.     

基于对氨基苯硼酸修饰磁性纳米粒子及丝网印刷技术测定糖化血红蛋白

制备了对氨基苯硼酸修饰的磁性纳米粒子,其与血液中的糖化血红蛋白(Hb A1c)结合,通过网状玻璃态碳(RVC)电极的磁性区域后,可实现与未糖基化的血红蛋白分离。通过壳聚糖(CS)、正硅酸乙酯(TEOS)和碳纳米管构成的溶胶-凝胶膜修饰丝网印刷电极对血红蛋白进行电化学检测,从而建立了一种用于检测糖化血红蛋白的新方法。在0.10 V电位下,丝网印刷电极的电量与Hb A1c和Hb的浓度有较好的线性关系,检出限分别为6 mg/m L和0.05 mg/m L。该方法电极制作简单,有较好的重现性和稳定性,且能有效排除抗坏血酸(AA)、尿酸(UA)等的干扰,已成功应用于实际样品中Hb A1c的检测。