Direct Electrooxidation of Ascorbic Acid at the Nanocrystaline Graphite‐like Pyrolytic Carbon Film Electrode

Pyrolytic carbon films (PCFs) were prepared by chemical vapor deposition (CVD) at different deposition temperatures. As an example of using PCF electrode in electroanalysis, the direct electrooxidation of ascorbic acid (AA) at the PCF electrode was investigated and compared with common carbon‐based electrodes such as glassy carbon (GC), edge plane pyrolytic graphite (EPPG), and basal plane pyrolytic graphite (BPPG) electrodes. It was found that the PCF electrodes prepared under deposition temperatures higher than 1050 °C showed a higher sensitivity and lower overpotential compared to the other carbon electrodes. The electrode was successfully applied for determination of AA in real samples.     

Direct Oxidation of Ascorbic Acid at an Edge Plane Pyrolytic Graphite Electrode: A Comparison of the Electroanalytical Response with Other Carbon Electrodes

The direct electrochemical oxidation of ascorbic acid at an edge plane pyrolytic graphite electrode (EPPG) is investigated and compared with other common carbon‐based electrodes, specifically glassy carbon, boron doped diamond and basal plane pyrolytic graphite. It is found that the EPPG electrode shows a significantly higher degree of electrochemical reversibility than the other electrode substrates giving rise to an analytically optimized limit of detection and sensitivity of 7.1×10^?5 M and 0.065 A M^?1 respectively.     

Electrochemical Characterization of a Pyrolytic Carbon Film Electrode and the Effect of Anodization

A pyrolytic carbon (PC) film electrode was fabricated by the chemical vapor deposition (CVD) method. This report deals with the preparation, characterization and electrochemical behavior of this carbon film. Cyclic voltammetry, linear sweep voltammetry, Raman spectroscopy and scanning electron microscopy were employed to characterize the electrode. Low background current and capacitance were observed and the rate of charge transfer for Fe(CN) redox couple was determined via cyclic voltammetry. Also the effect of the anodic activation on the electrochemical activity was evaluated and characterized with respect to the sequence of voltage applied to the electrode. The excellent electrochemical activity and low background current are the reasons why this electrode is attractive for electroanalysis measurements with lower detection limit.     

Voltammetric Determination of 5‐Aminoquinoline at Carbon Film Electrode and Carbon and Gold Screen Printed Electrodes – A Comparative Study

Aminoquinolines are widely used as antimalarial drugs and thus there is an ever increasing demand for their determination. In this paper, non‐traditional carbon film electrode developed in our laboratory (CFE) with easily replaceable carbon film was used for the determination of 5‐aminoquinoline (5‐AQ) and compared with well‐established commercially available carbon screen printed electrode (CSPE) and gold screen printed electrode (AuSPE). Electrochemical behavior of 5‐AQ was characterized by cyclic and differential pulse voltammetry. Differences in electrochemical behavior of 5‐AQ at different electrodes were evaluated. Determination of 5‐AQ was carried out by differential pulse, square wave, and direct current voltammetry. Practical applicability of the method was verified by direct determination of 5‐AQ in model samples of drinking and river water. Achieved limits of quantitation were in submicromolar concentrations. It was found out that novel CFE in terms of overall performance is in most aspects superior to routinely used commercially available CSPE and AuSPE.     

Cyclic Voltammetric Studies of a Pyrolytic Carbon Film Electrode and the Effect of Laser Irradiation

The effects of laser irradiation with a small N₂ laser on the reactivation of a pyrolytic carbon (PC) film electrode were investigated. Cyclic voltammetry, Raman spectroscopy and scanning electron microscopy (SEM) were used to characterize the electrode. The electrode response decayed during the solution exposure but could be restored to a good performance via this reactivation method. It was found that the effect of laser to promote electron transfer was desorption the physisorbed impurities to exposure more active sites on the surface. Also, the electrochemical results were compared to the results of organic solvent washing and anodization.     

Electroanalytical Determination of Vancomycin at a Graphene‐modified Electrode: Comparison of Electrochemical Property between Graphene,Carbon Nanotube,and Carbon Black

Carbon nanotube, graphene and carbon black, as electrode modifiers, were compared and evaluated for the electrochemical determination of vancomycin. Among them, the best results were obtained at the graphene‐modified electrode. Additions of vancomycin using square wave voltammetry at the graphene‐modified electrode showed a linear range from 0.70 μM to 50 μM and a detection limit of 0.20 μM was obtained. To control the correct dose of vancomycin and reduce its side effects, its accurate determination in blood plasma is very important. Therefore, the method was applied for the vancomycin determination in spiked human plasma samples and satisfactory recoveries were observed. The developed method exhibited fast analysis, high sensitivity, good repeatability and freedom from other interfering species.     

Synthesis of Sub‐nanometer Porous Carbon Film for Energy Storage

Carbon‐based supercapacitors are a kind of supercapacitors with very promising applications because of their low cost, good stability and adjustable properties. Simple and rapid syntheses of carbon materials with a high surface area and narrow pore size distribution are of great significance to practical applications of carbon‐based supercapacitors. Here we report a new strategy to synthesize sub‐nanometer porous carbon films (Snp‐CF) via a condensation reaction under mild conditions. Carbon films exhibit a narrow pore size distribution (6.6 Å) and high surface area (508 m² g^?1) after annealing at 700 °C. Snp‐CF‐700 displays a good specific capacity and excellent cycle performance (130 F g^?1 after 5000 cycles, 118 % of initial 110 F g^?1).     

碳薄膜电极材料在电分析化学中的应用

由于具有一系列的优点,碳材料被广泛地应用于电分析化学。新型碳电极材料的开发及其性质研究对电分析化学的发展起着重要的推动作用。最近文献报道了一些制备新型碳薄膜电极材料的方法,因为制备方法不同,这些碳薄膜材料的电化学性质如电位窗、稳定性、导电性也显著不同。人们对电位窗宽、背景电流低、稳定性高、表面不易被电极产物钝化的碳薄膜电极材料的研究非常活跃。本文综述了采用不同方法制备的一些碳薄膜电极材料如硼掺杂的金刚石薄膜、无定形碳和纳米晶体碳薄膜材料等在电分析化学中应用。     

Electroanalytical Sensor Based on Unmodified Screen‐Printed Carbon Electrode for the Determination of Levo‐Thyroxine

The electrochemical behaviour of thyroxine (T₄) is analysed using the disposable screen‐printed carbon electrode (SPCE) in the neutral phosphate buffer solution with cyclic voltammetric technique. The Differential Pulse Voltammetry and Chronoamperometry were employed for sensing of T₄. The lowest detection limit of 3 nM was obtained from the differential pulse voltammetric method without preconditioning. The Density Functional Theoretical study of T₄ was performed to elucidate the mechanism of oxidation. The analysis of the commercial pharmaceutical samples indicates the validity of the proposed method.     

Thiol‐Functionalized Silica Thin Film Modified Electrode in Determination of Mercury Ions in Natural Water

The use of a thin thiol‐functionalized silica film modified glassy carbon electrode in the determination of Hg(II) ions in a natural water sample is described. A typical measurement involves two successive steps: a glassy carbon electrode coated with a thin mesoporous silica film containing 10% of mercaptopropyl groups, according to the MPTMS/TEOS ratio in the starting sol‐gel, was first immersed into the accumulation medium for 15 min, then removed, and finally transferred into a detection solution containing KCl 1.0 mol L^?1 where detection was performed by anodic stripping voltammetry. In this medium the previously accumulated Hg²⁺ species complexed by the thiol groups in an open circuit preconcentration step is then directly reduced at ?0.6 V during 60 s prior to be quantified by a differential pulse anodic scan from ?0.6 to 0.3 V (vs. Ag/AgCl). A stripping peak appeared at about ?0.01 V, which is directly proportional to the quantity of the analyte previously accumulated into the film. The best results were obtained under the following conditions: 100 mV pulse amplitude and 10 mV s^?1 scan rate in 1.0 mol L^?1 KCl solution pH 2.0. Using such parameters a linear dynamic range from 1.00 to 10.0×10^?8 mol L^?1 Hg(II) was observed with a limit of detection of 4.3 nmol L^?1 for an accumulation time of 15 min. Hg(II) spiked in a natural water sample was determined between 97.0 and 101.4% mean recovery at 10^?8 mol L^?1 level. The results indicate that this electrode is sensitive and selective for the Hg(II)determination.     

Electroanalytical Application of Carbon Based Electrodes to the Pharmaceuticals

Abstract

Carbon and its derivatives, as the high performance material, occupy a special place in electrochemistry due to its ‐in many ways‐ extreme properties. Recent trends and advances in the electrochemistry of carbon‐based electrodes are reviewed. The varieties of carbon‐based electrodes, their basic physicochemical properties and some characteristics are surveyed. Special attention is paid to the possibilities of carbon‐based electrodes in electroanalytical investigation in pharmaceutical dosage forms and biological samples using modern electrochemical techniques. This review includes a summary of the rules that must be considered for drug analysis from its dosage forms and biological samples using carbon‐based electrodes. The present review is the first comprehensive report on the heterogeneous and homogeneous carbon electrodes, and an addition to many excellent reviews on carbon electrodes in the literature. This review summarizes some of the recent developments and applications of carbon‐based electrodes for drug compounds in their dosage forms and in biological samples in the period from 1996 till 2006. Also some further selected designs (screen‐printed; carbon nanotubes, etc.) and applications have been discussed.     

Over‐Oxidized Poly (Phenol Red) Film Modified Glassy Carbon Electrode for Anodic Stripping Voltammetric Determination of Ultra‐Trace Antimony (III)

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over‐oxidized poly(phenol red) modified glassy carbon electrode (PPhRed_ox/GCE) in 0.1 mol L^‐1 HCl medium. The formation of both poly(phenol red) and over‐oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRed_ox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRed_ox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 ‐ 1.218 μg L⁻¹ and 3.40 – 18.26 μg L⁻¹ with a detection limit of 0.0075 μg L⁻¹. The proposed over‐oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE‐EnviroMAT™ EP−L‐2).     

嵌入式超薄碳膜电极的伏安行为及其应用

以镍铬合金为基体,在其表面嵌入碳膜或碳纳米管,制备了超薄碳膜电极,并用于酚磺乙胺(ETA)的测定。超薄碳膜电极对ETA有良好的电催化作用和增敏作用,与玻碳电极相比,氧化峰电位负移120mV,还原峰电位正移160mV,电流响应明显增大。在最优条件下,ETA浓度在5×10-7 ~9×10-6 mol/L和9×10-6~6×10-5 mol/L之间与其氧化峰电流呈良好的线性关系,相关系数分别为0. 9967和0. 9979。该电极制备简便,价格低廉,用于酚磺乙胺的测定结果令人满意。     

碳糊电极阳极吸附伏安法测定氧氟沙星

碳糊电极阳极吸附伏安法测定氧氟沙星;氧氟沙星; 阳极吸附伏安法; 碳糊电极     

Immobilization of Enzymes on the Nano‐Au Film Modified Glassy Carbon Electrode for the Determination of Hydrogen Peroxide and Glucose

A new enzyme‐based amperometric biosensor for hydrogen peroxide was developed relying on the efficient immobilization of horseradish peroxidase (HRP) to a nano‐scaled particulate gold (nano‐Au) film modified glassy carbon electrode (GC). The nano‐Au film was obtained by a chitosan film which was first formed on the surface of GC. The high affinity of chitosan for nano‐Au associated with its amino groups resulted in the formation of nano‐Au film on the surface of GC. The film formed served as an intermediator to retain high efficient and stable immobilization of the enzyme. H₂O₂ was detected using hydroquinone as an electron mediator to transfer electrons between the electrode and HRP. The HRP immobilized on nano‐Au film maintained excellent electrocatalytical activity to the reduction of H₂O₂. The experimental parameters such as the operating potential of the working electrode, mediator concentration and pH of background electrolyte were optimized for best analytical performance of amperometry. The linear range of detection for H₂O₂ is from 6.1×10^?6 to 1.8×10^?3 mol L^?1 with a detection limit of 6.1 μmol L^?1 based on signal/noise=3. The proposed HRP enzyme sensor has the features of high sensitivity (0.25 Almol^?1cm^?2), fast response time (t_90%≤10 s) and a long‐term stability (>1 month). As an extension, glucose oxidase (GOD) was chemically bound to HRP‐modified electrode. A GOD/HRP bienzyme‐modified electrode formed in this way can be applied to the determination of glucose with satisfactory performance.     

Tellurium Film Electrodes Deposited on Carbon and Mesoporous Carbon Screen‐printed Substrates for Anodic Stripping Voltammetric Determination of Copper

The performance of screen‐printed electrodes modified in situ with tellurium film for the anodic stripping voltammetric (ASV) determination of Cu(II) is reported. It was found that two types of screen‐printed substrates, namely carbon and mesoporous carbon, were optimal for this application. The selected in situ tellurium film modified electrodes were applied for the square wave ASV determination of copper at μg L⁻¹ concentration levels. Well‐defined and reproducible Cu oxidation stripping peaks were produced at a potential more negative than the anodic dissolution of tellurium. The highest sensitivity of Cu determination was achieved in 0.05 M HCl containing 50 μg L⁻¹ Te(IV) after 300 s of accumulation at −0.5 V. Using the optimized procedure, a linear range from 2 to 35 μg L⁻¹ of Cu(II) was obtained with a detection limit of 0.5 μg L⁻¹ Cu(II) (S/N=3) for 300 s of deposition time. Both sensors, carbon TeF‐SPE and mesoporous carbon TeF‐SPE, were successfully applied for the quantification of Cu in a certified reference surface water sample.     

嵌入式超薄碳糊膜电极伏安法同时测定黄嘌呤和次黄嘌呤

以镍铬合金为基体制备了嵌入式超薄碳糊膜电极,研究了黄嘌呤(Xa)和次黄嘌呤(Hxa)在该电极上的电化学行为。该电极对Xa和Hxa具有良好的电化学催化特性。两峰电位相差320mV。其氧化峰电流与Xa和Hxa的浓度在5.0×10-8～8.0×10-5mol/L和7.0×10-8～7.0×10-5mol/L范围内呈良好线性关系;检出限为2.0×10-10mol/L。电极制备简单,有良好的灵敏度、选择性和稳定性。该方法可用于人尿中Xa和Hxa的同时测定。     

乙胺丁醇在玻碳电极上的阳极伏安行为及其测定

对乙胺丁醇（EMB）在玻碳电极上的阳极伏安行为进行了研究，发现在0.039mol/L Na2HPO4溶液中于1.04V(vs,Ag/AgCl)左右产生一个与EMB浓度3-1000mg/L呈良好的线性关系的阳极氧化峰；大多数金属离子和药剂辅料及生化有机物质不干扰测定。方法用于药剂和加标人尿中EMB的测定，获得满意结果。     

氟嗪酸在碳纳米管修饰电极上的电化学行为及含量的测定

在玻碳电极上制备了多壁碳纳米管/Nafion(MWNTs-Nafion)膜,用交流阻抗谱(EIS)、循环伏安法(CV)、线性扫描伏安法(LSV)研究了氟嗪酸在该膜上的电化学行为。与裸玻碳电极相比,这种纳米结构膜修饰的电极对氟嗪酸的电化学氧化显现出极好的促进作用,氟嗪酸的氧化峰电流明显增强,在修饰电极上于 0.97 V处产生了1个灵敏氧化峰。LSV测定氟嗪酸的线性范围为1.0×10-8～1.0×10-6mol/L和1.0×10-6～2.0×10-5mol/L,开路富集400 s后,检出限为8.0×10-9mol/L(3倍信噪比),方法可用于人尿中氟嗪酸的实时测定。     

Electrochemical Investigations of the Anticancer Drug Idarubicin Using Multiwalled Carbon Nanotubes Modified Glassy Carbon and Pyrolytic Graphite Electrodes

The effect of surface modifications on the electrochemical behavior of the anticancer drug idarubicin was studied at multiwalled carbon nanotubes modified glassy carbon and edge plane pyrolytic graphite electrodes. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The modified electrodes were constructed for the determination of idarubicin using adsorptive stripping differential pulse voltammetry. The experimental parameters such as supporting electrolyte, pH, accumulation time and potential, amount of carbon nanotubes for the sensitive assay of idarubicin were studied as details. Under the optimized conditions, idarubicin gave a linear response in the range 9.36×10^?8–1.87×10^?6 M for modified glassy carbon and 9.36×10^?8–9.36×10^?7 M for modified edge plane pyrolytic graphite electrodes. The detection limits were found as 1.87×10^?8 M and 3.75×10^?8 M based on modified glassy carbon and edge plane pyrolytic graphite electrodes, respectively. Interfering species such as ascorbic acid, dopamine, and aspirin showed no interference with the selective determination of idarubicin. The analyzing method was fully validated and successfully applied for the determination of idarubicin in its pharmaceutical dosage form. The possible oxidation mechanism of idarubicin was also discussed. The results revealed that the modified electrodes showed an obvious electrocatalytic activity toward the oxidation of idarubicin by a remarkable enhancement in the current response compared with bare electrodes.