维生素B_6在石墨烯/纳米Cu_2O复合修饰电极上的电化学氧化

本文采用HNO3+H2SO4混酸氧化石墨烯之后,掺杂自制的粒径均一的纳米Cu2O,构建了石墨烯/纳米Cu2O复合修饰电极,并研究了维生素B6在该修饰电极上的电化学行为。结果表明,与裸玻碳电极以及单一材料修饰的电极相比,由于复合修饰电极充分发挥了石墨烯和纳米Cu2O的协同作用,从而对维生素B6的电化学氧化有显著的电催化作用。在优化实验条件下,该方法测定维生素B6的线性检测范围为5.0×10-8~1.5×10-4 mol/L,检出限为2.1×10-8 mol/L。该方法可快速、高灵敏测定药物中维生素B6。     

镍离子注入修饰电极上米托蒽醌与DNA相互作用的电化学研究

研究了在镍离子注入修饰电极和0.05mol/LTris-0.5mol/LNaCl缓冲溶液(pH=7.1)中,米托蒽醌(MX)与DNA作用的电化学.在37℃恒温1.5h条件下,MX与DNA形成一种非电活性的结合物,使MX峰电流降低,其结合比n(MX):n(DNA)=2:1,结合常数为1.61×10¹²,电子转移系数为0.41,电极反应速率常数0.33s^-1.加入DNA后,MX峰电流降低,据此,可以测定DNA.     

Electrochemical Studies of Pirarubicin and Its Interaction with DNA at a Co／GC Ion Implantation Modified Electrode

IntroductionIon implantation is a new material surfacemodification technique.It has been also applied tostudying the electrochemical behaviors of organicdrugs and biological materials as well as their de-terminations. This method offers good stability,reproductivity and catalytic activity[1] .Pirarubicin( THP) is an active highly effective and new antitu-moral anthracycline antibiotic,which has gainedwidespread clinical use in the chemotherapeutictreatment of a variety of human cancers.The d…     

Electrochemical Detection of 2‐Naphthol at a Glassy Carbon Electrode Modified with Tosflex Film

In this study, a Tosflex (a perfluoro‐anion‐exchange membrane) modified glassy carbon electrode has been used to detect 2‐naphthalenol (2‐naphthol) in aqueous solutions in order to demonstrate the electroanalytical application of Tosflex. 2‐naphthol polymerizes upon electrochemical oxidation at a glassy carbon electrode; however, the current related to this oxidation is too small for analytical purpose at low concentration level. A Tosflex polymer modified glassy carbon electrode (TFGCE) was found of having capability to improve the detection limit because 2‐naphthol molecules deprotonated in basic solutions to form 2‐naphtholate anions that were accumulated to TFGCE by the anion‐exchange characteristic of Tosflex. The accumulated 2‐naphtholate anions were determined with the following differential pulse voltammetry. With 3 minutes accumulation at +0.05 V, the dependence of oxidation current versus concentration was linear from 8×10^?7 M to 1×10^?5 M with a regression coefficient of 0.999 and a detection limit of 2×10^?7 M. Unlike many other anion‐exchange polymer modified electrodes, the TFGCE is stable at highly basic condition.     

A Polypyrrole‐Imprinted Electrochemical Sensor Based on Nano‐SnO2/Multiwalled Carbon Nanotubes Film Modified Carbon Electrode for the Determination of Oleanolic Acid

A sensitive molecularly imprinted electrochemical sensor with specific recognition ability for oleanolic acid was synthesized by modification of multiwalled carbon nanotubes (MWNTs) decorated with tin oxide nanoparticles (nano‐SnO₂/MWNTs) and polypyrrole‐imprinted polymer on a carbon electrode. The morphology and electrochemical performance of the imprinted sensor were investigated by using scanning electron microscope (SEM), X‐ray diffraction (XRD), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometric i–t curve. The results showed that the imprinted sensor displayed excellent selectivity toward oleanolic acid. A linear relationship between the response currents and oleanolic acid concentrations ranging from 5.0×10^?8 g/L to 2.0×10^?5 g/L was obtained for the imprinted sensor. The limit of detection (LOD) of the imprinted sensor toward oleanolic acid was calculated as 8.6×10^?9 g/L at a signal to noise ratio (S/N) of 3. This imprinted sensor was successfully applied to the determination of oleanolic acid in Acitinidia deliciosa root samples.     

Electrocatalytic Oxidation of Dopamine at Sol‐Gel Carbon Composite Electrode Chemically Modified with Copper Hexacyanoferrate

An organic‐inorganic composite electrode was prepared by the sol‐gel method. For this purpose the carbon composite electrode (CCE) was modified with copper hexacyanoferrate (CuHCF). The CuHCF‐CCE was prepared by two methods. In one method CCE was prepared in one step and in another method the electrode was prepared in a two‐step process. The electrochemical behavior of the CuHCF modified electrode was studied by cyclic voltammetry; the modified electrode shows a pair of peaks with a surface‐confined characteristic in a 0.1 M phosphate buffer (pH 7) with K⁺ cation, as a supporting electrolyte. The CuHCF‐CCE showed electrocatalytic activity toward oxidation of Dopamine (DA). The kinetics of the catalytic reaction was investigated by using chronoamperometry. The average value of the rate constant for catalytic reaction and the diffusion coefficient were calculated. At a 0.85 V potential under hydrodynamic conditions (stirred solution), the oxidation current is proportional to the dopamine concentration, and the calibration plot was linear over the concentration range of 5‐85 μM.     

Biomimetic Sensor for Dobutamine Employing Nano‐ TiO2/Nafion/Carbon Nanoparticles Modified Electrode

A novel voltammetric biosensor based on nano‐TiO₂/nafion/carbon nanoparticles modified glassy carbon electrode (TiO₂/N/CNP/GCE) was developed for the determination of dobutamine (DBA). Characterization of the surface morphology and property of TiO₂/N/CNP layer was carried out by the scanning electron microscopy and atomic force microscopy. The electrochemical performance of the modified electrode was investigated by means of the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy techniques. Effective experimental variables, such as the scan rate, pH of the supporting electrolyte, drop size of the casted modifier suspension and accumulation conditions of DBA on the surface of TiO₂/N/CNP/GCE were optimized. Under the optimized conditions, a significant electrochemical improvement was observed toward the electro‐oxidation of DBA on the surface of TiO₂/N/CNP/GCE compared to the bare GCE. Under the optimized conditions, a wide linear dynamic range (6 nM–1 µM) with a low detection limit of 2 nM for DBA was resulted. The prepared modified electrode shows high sensitivity, stability and good reproducibility in the determination of DBA concentrations. Satisfactory results were obtained for DBA analysis in the pharmaceutical and clinical preparations using TiO₂/N/CNP/GCE.     

Electrochemical Behavior and Determination of L‐Tyrosine at Single‐walled Carbon Nanotubes Modified Glassy Carbon Electrode

Based on single‐walled carbon nanotubes (SWCNTs) modified glassy carbon electrode (GCE/SWCNTs), a novel method was presented for the determination of L ‐tyrosine. The GCE/SWCNTs exhibited remarkable catalytic and enhanced effects on the oxidation of L ‐tyrosine. In 0.10 mol/L citric acid‐sodium citrate buffer solution, the oxidation potential of L ‐tyrosine shifted negatively from +1.23 V at bare GCE to +0.76 V at GCE/SWCNTs. Under the optimized experimental conditions, the linear range of the modified electrode to the concentration of L ‐tyrosine was 5.0×10^?6–2.0×10^?5 mol/L (R₁=0.9952) and 2.7×10^?5–2.6×10^?4 mol/L (R₂=0.9998) with a detection limit of 9.3×10^?8 mol/L. The kinetic parameters such as α (charge transfer coefficient) and D (diffusion coefficient) were evaluated to be 0.66, 9.82×10^?5 cm² s^?1, respectively. And the electrochemical mechanism of L ‐tyrosine was also discussed.     

Electrochemical Sensor Based on Oxidation of 2,8‐Dihydroxyadenine to Monitor DNA Damage in Calf Thymus DNA

A novel and reliable direct electrochemical method has been established to monitor DNA damage in acid hydrolyzed calf thymus DNA, based on the determination of 2,8‐dihydroxyadenine (2,8‐DHA). A single‐wall carbon nanotubes (SWCNT) modified edge plane pyrolytic graphite electrode (EPPGE) has been used as a sensor to monitor the DNA damage. 2,8‐DHA the main in vivo adenine oxidation product undergoes oxidation at ～395 mV at SWCNT modified EPPGE using square wave voltammetry (SWV). The sensor exhibits potent and persistent electron‐mediating behavior. A well‐defined oxidation peak for the oxidation of 2,8‐DHA was observed at modified electrode with lowering of peak potential and increase in peak current as compared to bare EPPGE. At optimal experimental conditions, the catalytic oxidative peak current was responsive with the 2,8‐DHA concentrations ranging from 0.05 nM to 100 nM. The detection limit was 3.8×10^?11 M and limit of quantification was 1.27×10^?10 M. The modified electrode exhibited high stability and reproducibility.     

Electrocatalytic Oxidation of 2‐Thiouracil and 2‐Thiobarbituric Acid at a Carbon‐Paste Electrode Modified with Cobalt Phthalocyanine

Voltammetric behavior of two mercaptopyrimidine derivatives (2‐thiouracil and 2‐thiobarbituric acid) has been studied by cyclic voltammetry at a cobalt phthalocyanine (CoPc)‐modified carbon‐paste electrode. The results of voltammetric determinations showed that the CoPc in the matrix of modified electrode acts as catalyst for electrooxidation of these thiols (RSH), lowering the overpotential of the reaction and significantly increasing the sensitivity for detection of thiols in neutral conditions. The results of voltammetric and polarization measurements in solutions with various pHs were used for prediction of the mechanism of electrocatalytic oxidation at the surface of modified electrode. These results showed that at the modified electrode, electrochemical oxidation of thiolate anion (RS^?) is the rate‐determining step. It was found that the modified electrode exhibits good selectivity for catalytic oxidation of mercaptopyrimidines over other biologically important mercaptans such as cysteine, glutathione and thioglycolic acid. The results demonstrate that the peak current for thiol oxidation has a linear variation with the concentration in the range of 1×10^?2–1×10^?5 M. This system can be used for sensitive and selective voltammetric detection of mercaptopyrimidine derivatives.     

Preparation and Electrochemical Behaviour of Silver Pentacyanonitrosylferrate Film Modified Glassy Carbon Electrode and Its Electrocatalytic Oxidation to L‐cysteine

A glassy carbon (GC) electrode modified with silver pentacyanonitrosylferrate (AgPCNF) film as a redox mediator was fabricated. Cyclic voltammetry was used to study the redox property of AgPCNF modified electrode. The modified electrode showed a well‐defined redox couple due to [Ag^IFe^III/II(CN)₅NO]^1‐/2‐system. The effects of scan rates, supporting electrolytes and solution pHs were studied on the electrochemical behavior of the modified electrode. The feasibility of using the AgPCNF modified electrode to measure L ‐cysteine was investigated. It showed an excellent electrocatalytic activity towards the oxidation of L ‐cysteine and the anodic currents were proportional to the L ‐cysteine concentration in the range of 0.1 μM to 20 μM, the linear regression equation is I_pa(μA) = ‐68.58 ‐ 5.78C_{L ‐cysteine} (μM), with a correlation coefficient 0.998 for N = 23. The detection limit was down to 3.5 × 10^‐8 M (three times the ratio of signal to noise).     

Electrocatalytic Oxidation and Determination of Nitrite at Multi‐walled Carbon Nanotubes Modified Carbon Ceramic Electrode

In the present work, the electrochemical oxidation of nitrite on carbon ceramic electrode (CCE) modified with multi‐walled carbon nanotubes (MWCNTs) was investigated. The modified electrode exhibited catalytic activity toward the electrooxidation of nitrite. Experimental parameters such as solution pH, scan rate, concentration of nitrite and nanotubes amount were studied. It was shown nitrite can be determined by differential pulse voltammetry (DPV) and hydrodynamic amperometry (HA) using the modified electrode. Under the optimized conditions the calibration plots are linear in the concentration ranges of 15‐220 and 50‐3000 μM with limit of detections of 4.74 and 35.8 μM for DPV and HA, respectively. The modified electrode was successfully applied for analysis of nitrite in spinach sample. The results were favorbly compared to those obtained by UV‐Visible spectrophotometric method. The results of the analysis suggest that the proposed method has promise for the routine determination of nitrite in the examined products.     

Nanobiocomposite Modified Carbon‐Ceramic Electrode Based on Nano‐TiO2‐Plant Tissue and Its Application for Electrocatalytic Oxidation of Dopamine

A new modified carbon‐ceramic electrode was prepared by incorporating TiO₂ nanoparticle into sol‐gel network by accompanying apple tissue. A mixture of fine graphite powder with 15 wt% of TiO₂ nanoparticle was used for the preparation of the carbon matrix and finally modification with a known amount weighted of apple tissue. The apple tissue containing polyphenol oxidase enzyme acts as molecular recognition element. The electrocatalytic oxidation of dopamine was investigated on the surface of the nanobiocomposite modified carbon‐ceramic electrode using cyclic voltammetry, chronoamperometry and amperometry techniques. Effect of pH, scan rate, TiO₂ percentage on the response of modified electrode was studied. The prepared modified electrode presented a linear range for dopamine from 5.0×10^?6 to 1.2×10^?3 M in buffered solutions with pH 7.4 by amperometry. The detection limit was 3.41×10^?6 M dopamine. The response of the modified carbon‐ceramic electrode and unmodified carbon‐ceramic electrode was compared.     

Hemin Modified SnO2 Films on ITO‐PET with Enhanced Activity for Electrochemical Sensing

We present a simple and efficient method for the preparation of hemin‐modified SnO₂ films on low cost, flexible, conducting ITO‐PET substrates to enable the development of a sensitive electrochemical sensor for the determination of H₂O₂. Using a hydrothermal processing method meant that the SnO₂ films can be prepared at low temperatures, compatible with the PET substrate. The properties of the electrodes enable a high hemin loading to be achieved in a stable and functional way, allowing the direct reduction and oxidation of the immobilized hemin and maintaining its high electrocatalytic activity in the reduction of H₂O₂ on the surface. The results showed a sensitive response linearly proportional to the concentration of H₂O₂ in the range 1.5 to 90 μM.     

纳米PbO2修饰电极电催化氧化性能的研究

利用旋转圆盘电极对纳米PbO2修饰电极的电催化氧化性能进行了初步的研究．实验表明由于电极表面PbO2晶粒呈纳米结构，使纳米PbO2修饰电极表面具有大的比表面积，高的表面活性中心，良好的导电性及宏观隧道效应，使得纳米PbO2修饰电极对苯酚有很好的氧化催化性能，用安培法测定了多种有机物在纳米PbO2修饰电极上的电流响应，实验表明，纳米PbO2修饰电极可以作为分析传感器用于有机化合物的测定中.     

Ni/ZSM‐5 Zeolite Modified Carbon Paste Electrode as an Efficient Electrode for Electrocatalytic Oxidation of Formaldehyde

In this study, we prepared a modified carbon paste electrode consisting of Nickel entrapped in synthesized ZSM‐5 zeolite (Ni/ZMCPE). Then Ni(II) ions were incorporated to electrode by immersion of modified electrode in 1 M Ni(II) ion solution. Cyclic voltammetry and chronoamperometry experiments were used for electrochemical study of this modified electrode; a good redox behavior of Ni(OH)₂/NiOOH couple at the surface of electrode can be observed, the excellent capability of this modified electrode for catalytic oxidation of formaldehyde was demonstrated during the anodic potential sweep in alkaline solution. The amount of transfer coefficient (α), surface coverage (Γ*) of the redox species and catalytic chemical reaction rate constant (k) for formaldehyde were evaluated. Thus, it can be a candidate as an anode for fuel cell application.     

Studies on Electrochemical Behavior of Bleomycin and Its Interaction with DNA at a Co／GC Ion Implantation Modified Electrode

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Nano‐Gold Modified Genosensor for Direct Detection of DNA Hybridization

In this paper, nano‐gold modified carbon paste electrode (NGMCPE) was employed to develop an electrochemical DNA hybridization biosensor. The proposed sensor was made up by immobilization of 15‐mer single stranded oligonucleotide probe for detection of target DNA. Hybridization detection relies on the alternation in guanine oxidation signal following hybridization of the probe with complementary genomic DNA. The guanine oxidation was monitored using differential pulse voltammetry (DPV). Different factors such as activation potential, activation time and probe immobilization conditions were optimized. The selectivity of the sensor was investigated by non‐complementary oligonucleotides. Diagnostic performance of the biosensor was described and the detection limit was found 1.9 × 10^?13 M at the NGMCPE surface. All of the investigations were performed in both CPE and NGMCPE and finally their results were compared.     

氨甲蝶呤在Co/GC离子注入修饰电极上电化学行为及其应用研究

氨甲蝶呤在0.1mol/LHAc-NaAc(pH=4.96)缓冲溶液中,用Co/GC离子注入修饰电极进行伏安测定,得到一良好的还原峰,峰电位为-0.95V(vs.SCE).峰电流Ip与氨甲蝶呤的浓度在2.2×10^-7～8.8×10^-6mol/L范围内呈线性关系。检出限为1.1×10^-8mol/L.建立了测定氨甲蝶呤的新方法,可用于实际样品的测定,回收率在98.9%～106.2%之间。用线性扫描和循环伏安法研究了体系的电化学行为及电极反应机理。实验表明,氨甲蝶呤的还原为不可逆吸附过程,并伴随两个电子和两个氢离子参与电极反应。用俄歇电子能谱(AES)和X射线光电子能谱(XPS)等表面分析技术对Co离子注入修饰电极的表面元素组成及深度分布等进行测定,表明Co离子确被注入到玻碳表面。扫速对催化效率的影响实验证明体系存在催化作用。     

New Determination Scheme of p‐Aminophenol by MnO2 Modified Electrode Coupled with Flow Injection Analysis

New determination scheme of p‐aminophenol by using MnO₂ as a preoxidant is demonstrated in this work. In the flow injection system, the p‐aminophenol is oxidized to quinoneimine by MnO₂ at up‐stream, which can be detected at a suitable reductive potential. After optimization, the linear range of PAP is started from 1 μM to 30 μM (R²=0.999), the estimated detection limit (S/N=3) is 0.28 μM. Two real samples are studied and excellent recoveries are achieved by using standard addition method.