Graphene Nanosheets Modified Glassy Carbon Electrode as a Highly Sensitive and Selective Voltammetric Sensor for Rutin

Graphene nanosheets modified glassy carbon electrode (GNs/GCE) was fabricated as voltammetric sensor for rutin with good sensitivity, selectivity and reproducibility. The sensor exhibits an adsorption‐controlled, reversible two‐proton and two electron transfer reaction for the oxidation of rutin with a peak‐to‐peak separation (ΔE_p) of 26 mV as revealed by cyclic voltammetry. Moreover, the redox peak current increased about 14 times than that on bare glassy carbon electrode (GCE). The linear response of the sensor is from 1×10^?7 to 1×10^?5 M with a detection limit of 2.1 × 10^?8 M (S/N = 3). The method was successfully applied to determine rutin in tablets with satisfied recovery.     

芦丁在玻碳电极上的阳极伏安行为及其测定

本文应用线性扫描伏安法，微分脉冲伏安和循环伏安法对芦丁在玻碳电极上的阳极伏安行为进行了研究。     

Differential Pulse Voltammetric Determination of L-Cysteine After Cyclic Voltammetry in Presence of Catechol with Glassy Carbon Electrode

An electrochemical method of determination of cysteine has been developed in the solution containing catechol as the indicator. Nucleophilic addition of the thiol species to the electrogenerated o-quinone results in the formation of o-quinone-cysteine adducts that easily accumulate use at the surface of the electrode in the acidic solution. Therefore, the use of cyclic voltammetry leads to the amplification of the o-quinone-cysteine adduct's reductive current. As cyclic voltammetry was performed prior to differential pulse voltammetry, the peak of o-quinone-cysteine could be separated preferentially from o-quinone in the differential pulse voltammogram and the selectivity of the method has been assessed with no interference from ascorbic acid, glycine, L-tyrosine, or L-lysine. The magnitude of o-quinone-cysteine peak is proportional to the concentration of cysteine, and thus it can be exploited to determine cysteine within the injection. The results were consistent with those obtained by means of HPLC analysis.     

Determination of Tetracycline at a UV‐Irradiated DNA Film Modified Glassy Carbon Electrode

In this study, interaction of tetracycline (TC) and DNA in the Britton? Robinson buffer solution (BR) was studied by cyclic voltammetry. The experimental results reveal that TC can bind strongly to DNA and the association constant and binding number between TC and DNA was obtained. Then DNA was immobilized on a glassy carbon electrode by UV‐irradiation. Through this process, water‐soluble DNA was converted into insoluble materials, and a stable DNA film was formed on the electrode. The electrochemical oxidation behavior of TC was studied at UV‐irradiated DNA film modified glassy carbon electrode (UV‐DNA‐GCE). The response of modified electrode was optimized with respect to pH, accumulation time, ionic strength, drug concentration and other variables. TC at the surface of modified electrode showed a linear dynamic range of 0.30–90.00 µM and a detection limit of 0.27 µM. To demonstrate the applicability of the modified electrode, it was used for the analysis of real samples such as pharmaceutical formulations and milk.     

Synergistic Effect of Graphene and Multiwalled Carbon Nanotubes on a Glassy Carbon Electrode for Simultaneous Determination of Uric Acid and Dopamine in the Presence of Ascorbic Acid

A poly(diallyldimethylammonium chloride)-graphene-multiwalled carbon nanotube modified glassy carbon electrode was fabricated and evaluated by cyclic voltammetry and differential pulse voltammetry. The modified electrode offered high sensitivity, selectivity, excellent long-term stability, and electrocatalytic activity for uric acid and dopamine. This sensor showed wide linear dynamic ranges of 5.0 to 350.0 µmol L^?1 for uric acid and 10.0 to 400.0 µmol L^?1 for dopamine in the presence of 500 µmol L^?1 ascorbic acid. The limits of detection were 0.13 for uric acid and 0.55 µmol L^?1 for dopamine. This functionalized electrode has potential application in bioanalysis and biomedicine.     

氧化石墨烯/铁氰化铈修饰玻碳电极同时测定扑热息痛和咖啡因

采用滴涂法和电沉积法制备了氧化石墨烯/铁氰化铈(CeFe(CN)6)纳米复合膜修饰玻碳电极。用扫描电镜对氧化石墨烯和氧化石墨烯/CeFe(CN)6纳米复合膜进行了表征。分别用循环伏安法和差分脉冲伏安法研究了扑热息痛和咖啡因在修饰电极上的电化学行为。结果表明,在0.1 mol/L醋酸盐缓冲溶液(pH5.0)中,扑热息痛和咖啡因在此修饰电极上具有良好的电化学行为,扑热息痛和咖啡因分别在1.0×10-7～6.0×10-5mol/L和1.0×10-6～1.3×10-4mol/L浓度范围内与电化学响应信号呈良好的线性关系,相关系数分别为0.990和0.992;信噪比为3时,扑热息痛和咖啡因检出限分别为5.0×10-8mol/L和5.2×10-7mol/L。将本方法用于人尿样品分析,回收率为96.1%～105.4%。     

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.     

Electrochemical Determination of Capsaicin and Silymarin Using a Glassy Carbon Electrode Modified by Gold Nanoparticle Decorated Multiwalled Carbon Nanotubes

The goal of this study was to develop a suitable electroanalytical method for the determination of primary compounds in the extracts of capsaicin and silymarin. For this purpose, a glassy carbon electrode immobilized with multiwalled carbon nanotubes decorated with gold nanoparticles was characterized by high resolution transmission electron microscopy and attenuated total reflectance infrared spectroscopy. The developed electrochemical sensor had a linear dynamic range from 0.15 to 35.0 µM. In addition, the limits of quantification for silymarin and capsaicin with the gold nanoparticle decorated multiwalled carbon nanotubes were 0.1564 and 0.2761 µg L^?1 with relative standard deviations (n = 3) of 1.65% and 2.09% and equivalent mass percentages of 93.33% and 62.02%, respectively. The methodology may be employed for the determination of capsaicin and silymarin in pharmaceutical and food products.     

泛昔洛韦在NaOH修饰玻碳电极上的伏安行为及测定

泛昔洛韦为一种新型抗病毒药[1],2-[2-(氨基-9H-嘌呤-9-基)乙基]-1,3-丙二醇二醋酸酯,其结构如右图所示,服药后可能使人的神经系统、消化系统等产生异常反应。有头晕、恶心、腹痛、消化不良等副作用,因此,有必要建立一种简便、快速、准确的分析方法测定药物制剂的含量,以进行药     

铜膜差分脉冲阳极溶出伏安法测定药物中铋的含量

研究了铜膜电极代替汞膜电极测定重金属铋的差分脉冲溶出伏安法。实验了同位镀膜法测定铋的条件。在最佳实验条件下,Bi3+浓度在5×10-8~2×10-5mol/L范围内,其溶出峰峰高与浓度呈线性关系,检出限达到1×10-8mol/L。测定了一些药物中铋的含量,结果准确。     

在抗坏血酸存在下用L-赖氨酸修饰玻碳电极测定多巴胺

采用电化学氧化法制备了L-广赖氮酸单分子层修饰玻碳电极,研究了多巴胺（DA）和抗坏血酸（AA）在该电极上的电化学行为。结果表明,L-广赖氨酸单分子层修饰玻碳电极不仅能改善多巴胺和抗坏血酸的电化学行为,而且能将多巴胺和抗坏血酸二者在裸电极上的完全重叠的单氧化峰分开成为两个完全独立的氧化峰,循环伏安（CV）图上峰间距为507mV,差分脉冲伏安（DPV）图上峰间距为460mV,由此可实现在AA的共存下对样品中的DA进行选择性测定。     

日落黄在乙炔黑-壳聚糖修饰玻碳电极上的电化学行为研究

将新型炭材料乙炔黑(AB)分散制备成AB-壳聚糖(CTS)复合膜修饰玻碳电极(GCE)。运用循环伏安法(CV)和微分脉冲伏安法(DPV)研究了着色剂日落黄在该修饰电极上的电化学行为。通过对支持电解质、修饰剂的用量、富集电位、富集时间进行优化,建立了一种快速、灵敏测定日落黄的电化学分析方法。方法的线性范围为5.0×10-8~1.0×10-5 mol/L,检出限(S/N=3)为9.0×10-9 mol/L。该修饰电极制作简单,稳定性、重现性良好,已成功应用于实际样品的检测。     

Studies of an Alkaline Activated Glassy Carbon Electrode on the Determination of Purines and DNA

Performance of glassy carbon electrode on the determination of purines and DNA was found to be improved dramatically by activating the GCE with a simple but effective electrochemical pretreatment. Characteristics such as lowering of oxidation potential, enhancement of peak current and elimination of fouling effect were found for the activated GCE. By flow injection analysis, good reproducibility with relative standard deviations of 0.59 and 2.01% (n = 11) and rather low detection limits of 0.6 + 0.1 and 3.0 ± 0.4 nM can be obtained for the analysis of guanine and adenine. Solutions of denatured calf thymus DNA were analyzed by differential pulse voltammetry with the activated GCE. Good agreement between the obtained results and the known values confirms the feasibility of the activated GCE for DNA analysis.     

碳纳米管化学修饰电极测定土壤沉积物中的铜

本文研究了在碳纳米管(CNT)修饰的玻碳电极上,用微分脉冲溶出伏安法(DPSV)对土壤沉积物中铜的测定方法,在1.0mol/L的HCl介质中,于-0.6V电位处富集240s,静置10s,在阳极扫描过程中,被富集于修饰电极表面的铜在约-0.25V电位处出现特定的溶出峰,据此实现铜离子的测定。该方法的线性范围为8.0×10-7～1.2×10-5mol/L,检出限为2.0×10-7mol/L,结果令人满意     

Polyfurfural-Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode for the Direct Determination of Nitrofurazone

An electrochemical sensor based on a polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode has been developed for the sensitive and rapid determination of nitrofurazone. The morphologies and properties of the sensor were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry (DPV). In pH 7.0 Britton–Robinson buffer solution, the as-prepared polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode shows excellent electrocatalytic performance for the electrochemical reduction of nitrofurazone, and the reduction peak current is about 9.45, 1.31, and 1.25 times higher than that of the bare glassy carbon electrode, polyfurfural modified glassy carbon electrode, and electrochemically reduced graphene oxide modified glassy carbon electrode, respectively. The DPV determination of nitrofurazone indicates that the linear range and detection limit of nitrofurazone are 1–50 and 0.25?µmol/dm³, respectively. In addition, this sensor exhibits high selectivity, reproducibility, stability, and also was successfully used to directly determine nitrofurazone in the commercial antibacterial lotion with comparative sensitivity to high-performance liquid chromatography, showing its promising application prospects.     

铜纳米粒子/聚丙烯酸/石墨烯纳米复合材料修饰玻碳电极检测水中的4-硝基苯酚

采用一种温和且简单的原位生长法将铜纳米粒子和石墨烯非共价键合,得到铜纳米粒子/聚丙烯酸/石墨烯(CuNPs/PAA/GR)纳米复合材料,对4-硝基苯酚(4-NP)表现出良好的电催化活性.用扫描电镜对此纳米复合材料的形貌进行了表征.以此材料修饰的玻碳电极受吸附控制,4-NP在该电极表面的反应机理为两电子转移过程,电子转移数n=2.3,修饰电极的有效面积为0.6275 cm2,是裸电极的2.22倍,电极吸附量Гs为1.6×10-11 mol/cm2,催化速率常数kcat的平均值为1.15×104 L/(mol/s).修饰电极的响应电流与4-NP的浓度在1 ～ 150 μmol/L范围内呈良好的线性关系,线性方程为:Ipa(μA)=-0.015C(μmol/L)-0.98,(R2 =0.9951),检出限为0.23 μmol/L(S/N=3).此传感器制备简单、灵敏性高、稳定性和重现性好.使用此传感器检测实际水样中4-NP的回收率为88.6％～ 100.7％,相对标准偏差为2.6％ ～5.9％.     

硫桥杯[4]芳烃衍生物膜修饰玻碳电极差分脉冲溶出伏安法测定铅

将硫桥杯[4]芳烃衍生物25,27-二(2-噻二唑基硫代乙氧基)-26,28-二甲氧基-5,11,17,23-四叔丁基硫桥杯[4]芳烃(TTCA)溶于二氯甲烷中,滴涂在玻碳电极表面,制得硫桥杯[4]芳烃修饰的玻碳电极。循环伏安当研究结果表明:将此修饰电极浸泡在1.0×10-6mol.L-1铅(Ⅱ)溶液中一段时间后转移至0.1 mol.L-1硝酸溶液中,以扫速100 mV.s-1在电位-0.8~-0.2 V范围内扫描所得的CV图上出现一对氧化还原峰。当此修饰电极在上述浓度的铅(Ⅱ)溶液中于-1.1 V富集300 s后用差分脉冲溶出伏安法检测时,铅(Ⅱ)在-0.516 V处出现一良好的氧化峰。铅(Ⅱ)浓度在2.0×10-7~2.0×10-5mol.L-1范围内与峰电流呈线性关系。其检出限(3S/N)为8.0×10-9mol.L-1。此法应用于水样中痕量铅的测定,测得回收率在95.0%~104.0%之间。     

嗪草酮在玻碳电极上的伏安行为及测定

用循环伏安法及微分脉冲阴极溶出伏安法,在玻碳电极(GCE)上研究了嗪草酮在不同底液中的伏安特性,发现在B-R(Britton-Robinson)电解质溶液(pH2)中于-0.524V(vs.SCE)左右产生1个尖锐的阴极还原峰。嗪草酮的浓度在1.0×10-6~1.0×10-4mol/L范围内与峰电流呈良好的线性关系(r=0.9987)。对其反应机理作了初步探讨。     

Rutin as an Electrochemical Mediator in the Determination of Captopril using a Graphite Paste Electrode

A simple, rapid and sensitive cyclic voltammetry method is described for the determination of the antihypertensive drug captopril in aqueous solution using a graphite paste electrode with rutin as mediator. The catalytic role of rutin in the oxidation of captopril was confirmed by the increase observed in anodic peak current at+0.44 V vs. SCE in the presence of the mediator. Anodic peak current varied linearly with the concentration of captopril in the dynamic range 0.2 to 1.0 mmol L^?1. The method exhibited a limit of detection of 89.4 μmol L^?1 and a reproducibility of 1 %, values that are comparable with those exhibited by other methodologies employing electrodes without any modification. The recovery rate for the determination of captopril in a pharmaceutical sample was good (91.21 %) suggesting that the described analytical technique would be effective in industrial applications whilst offering a number of advantages over published cyclic voltammetric methods.