Polyviologen Modified Glassy Carbon Electrode Employed for Anodic Stripping Voltammetric Determination of Mercury(II)

In this study, a polyviologen modified glassy carbon electrode (PVGCE) was used to detect Hg(II) in aqueous solutions containing significant amounts of chloride anions in order to demonstrate the electroanalytical application of the electropolymerized polyviologen. The polyviologen thin film was formed on the electrode surface by applying a constant potential of ?1.0 V in the pH 4.2 Britton–Robinson (BR) buffer solution that contains 0.1 wt% of viologen oligomers. The PVGCE was found capability to improve the detection limit of Hg(II) in the solutions with high concentration of chloride because Hg(II) forms negative complex ions HgCl that can be accumulated to PVGCE by the anion‐exchange characteristic of polyviologen. With 5 minutes accumulation at ?0.2 V, the adsorbed HgCl anions were reduced to Hg and deposited on the electrode surface, and were determined with the following anodic stripping differential pulse voltammetry (ASDPV). The dependence of anodic stripping current versus concentration was linear from 1 ppb (5 nM) to 100 ppb (0.5 μM) with a regression coefficient of 0.9959.     

有机磷农药在C16化学修饰电极上的伏安特性及分析应用

以C16作为修饰剂制备化学修饰电极,用于有机磷农药的伏安法测定.研究了支持电解液种类及酸度、修饰膜厚度、富集时间、扫描速度等因素对伏安曲线的影响,获得较为优化的测试条件.在0.1 mol/L柠檬酸缓冲液(pH 2.1)中,有机磷的浓度在4.0×10-7～2.0×10-5 mol/L范围内与还原峰电流呈良好线性关系(r=0.9989),检出限达8.0×10-8mol/L.多种金属离子和有机物质不干扰测定.该电极具有很好的重现性,在含1.2×10-5mol/L有机磷试液中连续测定10次,其RSD为1.2%.本法用于实际水样测定,结果满意.     

聚甲基红膜修饰电极的电化学性质及其对盐酸吡哆辛的伏安测定

制备了聚甲基红膜修饰电极 ( PMRE) ,采用循环伏安法、计时库仑法及交流阻抗法对该膜电极的电化学性质进行了初步研究。同时发现 ,聚甲基红膜修饰电极对盐酸吡哆辛 ( VB6 )有良好的伏安响应 ,在较低的扫速下 ,VB6 在该修饰电极上产生一对准可逆氧化还原峰。氧化峰电流与 VB6 浓度在 2× 1 0 - 7～ 1× 1 0 - 2 mol/L范围内有良好的线性关系 ,检测限可达 1× 1 0 - 7mol/L ,用于样品分析 ,取得了满意的结果     

聚乙烯吡咯烷酮修饰碳糊电极上酪氨酸的电化学研究及其测定

研究了酪氨酸在聚乙烯吡咯烷酮修饰碳糊电极的伏安行为,优化了测定条件,在此基础上建立了一种直接测定酪氨酸的电分析方法。氧化峰电流与酪氨酸的浓度在2×10-7～5×10-5mol·L-1之间有良好的线性关系,开路富集3min,检出限为1×10-7mol·L-1。用此方法测定了酒样和人尿中酪氨酸的含量,结果满意。     

聚苯基荧光酮修饰玻碳电极吸附溶出伏安法测定痕量汞

研究利用聚苯基荧光酮修饰玻碳电极测定痕量汞的溶出伏安法,在0.1 mol.L-1氨水-NH4Cl缓冲溶液中(pH 9.5),开路搅拌,Hg(Ⅱ)富集于修饰电极表面,通过介质交换至0.1mol.L-1盐酸溶液中,于-0.40 V还原后阳极化线性扫描,在0 V左右处获得一灵敏汞的溶出峰。其氧化峰电流与Hg(Ⅱ)浓度在9.0×10-8~8.0×10-7mol.L-1范围内呈线性关系,开路富集5 min,检出限达2.0×10-8mol.L-1。应用此方法于尿液中汞的测定,所得平均RSD值小于4.02%,回收率试验结果在98.4%~103.2%间。     

肾上腺素在多壁碳纳米管修饰金电极上的电化学行为及测定

报道了一种测定肾上腺素的化学修饰电极和电化学分析方法。与裸金电极相比,刚果红改性的多壁碳纳米管修饰金电极可显著提高肾上腺素的氧化峰电流。实验优化了底液、pH值、修饰剂量、富集电位和富集时间等条件,建立了一种直接测定肾上腺素的高灵敏的电化学分析方法。该方法测定肾上腺素的线性范围为4.0×10-7~2.0×10-4mol.L-1;富集30 s后的检出限为8.5×10-8mol.L-1;对2.0×10-5mol.L-1的肾上腺素平行测定10次的相对标准偏差为4.9%。此方法已成功用于盐酸肾上腺素注射液中含量的测定。     

Graphene-gold Nanoparticle Composite Film Modified Electrode for Determination of Trace Mercury in Environmental Water

The graphene-gold nanoparticles composite film modified glassy carbon electrode （EG- AuNPs/GCE） was prepared by one-step coelectrodeposition and employed for determination of trace mercury in environmental water with differential pulse stripping voltammetry. Such a nanostructured composite film combined with the advantages of gold nanoparticles and graphene, can greatly promote the electron-transfer process and increase accumulation abil-ity for Hg（Ⅱ）, leading to a remarkably improved sensitivity. The linear calibration curve ranged from 0.2 μg/L to 30 μg/L for Hg（Ⅱ） and the detection limit （S/N=3） was found to be 0.03 μg/L at a deposition time of 300 s. Moreover, the stablity of the as-prepared electrode and interferences from other substances were evaluated. The modified electrode was successfully applied to the direct detection of Hg（Ⅱ） in real water samples.     

碳纳米管复合物极的构筑及其对嘌呤衍生物的同时测定

以嵌入式超薄碳糊(IUCP)前驱膜为基体,构建了单壁碳纳米管复合聚天青Ⅰ修饰电极(SWNTs/AZ/IUCP/CME).以扫描电镜表征其表面形貌,循环伏安法和微分伏安法考察其在黄嘌呤(XA)和次黄嘌呤(HXA)中的响应情况.实验表明,电极对XA和HXA的电化学反应表现出良好的增敏作用,采用微分伏安法测得XA和HXA的氧...     

掺杂硒修饰碳糊电极伏安法测定对乙酰氨基酚

采用循环伏安法制备了掺杂硒修饰碳糊电极,用循环伏安法和差分脉冲伏安法研究了对乙酰氨基酚在掺杂硒修饰碳糊电极上的电化学行为,建立了掺杂硒修饰碳糊电极测定对乙酰氨基酚的电化学方法。在pH 4.6的0.1mol·L-1乙酸-乙酸钠缓冲溶液中,对乙酰氨基酚在+0.61V呈现一个灵敏的氧化峰。对乙酰氨基酚的浓度在6.0×10-7~1.5×10-4 mol·L-1范围内与其氧化峰电流呈线性关系,检出限(3s/k)为2.8×10-7 mol·L-1。方法用于药品中对乙酰氨基酚的测定,测定结果与药典法测定值相符,测定值的相对标准偏差(n=5)在2.1%~2.5%之间。     

双硫腙修饰固体银汞合金电极吸附伏安法测定痕量铅

制作了银汞合金电极,在其表面用双硫腙进行修饰,溶液中铅离子与电极表面的双硫腙发生螯合作用被富集。当电极电位在-0.20~-0.70V间进行阴极化扫描时,配合物中铅离子在电极表面被还原,于-0.40V左右形成灵敏的还原峰。选择了反应介质并优化了pH值、双硫腙用量、富集时间等实验参数。利用该修饰电极测定铅的线性范围为0.02~1.2mg/L,检出限为10μg/L。对0.6mg/L Pb2 溶液进行11次平行测定,相对标准偏差为4.1%。该法用于实际水样铅的测定,回收率为94.8%。     

Voltammetric Behavior and Determination of Tocopherol in Vegetable Oils at a Polypyrrole Modified Electrode

The voltammetric behavior of α‐tocopherol in the presence of vegetable oil is studied at a polypyrrole modified Pt electrode in a 1,2‐dichloroethane‐ethanol medium with cyclic voltammetry. Cyclic voltammogram of α‐tocopherol showed a well‐defined oxidation peak; the peak potential shifting toward less positive and a much higher peak current obtained at a polypyrrole modified electrode than that obtained at the unmodified Pt electrode. An electroanalytical method for the determination of α‐tocopherol based on its electrochemical oxidation at the polypyrrole modified Pt electrode is developed. Using differential pulse voltammetry, the peak currents were found to increase linearly with the α‐tocopherol concentration over the range of 5.0 to 300 μM, with a sensitivity of 5.38×10^?2 A L mol^?1 and the limit of detection of 1.5 μM (S/N=3), the detection time being about 90 s for each assay. The interference of other synthetic antioxidants such as TBHQ, BHA and BHT to the analysis of α‐tocopherol was investigated. The developed method is applied to the quantification of tocopherols in six vegetable oils, showing that the results are in good agreement with those by HPLC method.     

Cathodized Gold Nanoparticle‐Modified Graphite Pencil Electrode for Non‐Enzymatic Sensitive Voltammetric Detection of Glucose

A highly sensitive enzymeless electrochemical glucose sensor has been developed based on the simply prepared cathodized gold nanoparticle‐modified graphite pencil electrode (AuNP‐GPE). Cyclic voltammetry (CV) experiments show that AuNP‐GPE is able to oxidize glucose partially at low potential (around −0.27) whereas the bare GPE cannot oxidize glucose in the entire tested potential windows. Besides, fructose and sucrose cannot be oxidized at potential lower than +0.1 V at AuNP‐GPE. As a result, the glucose oxidation peak at around −0.27 V is suitable enough for selective detection of glucose in the presence of fructose and sucrose. Cathodization of AuNP‐GPE under optimum condition (‐1.0 V for 30 s) in the same glucose solution before voltammetric measurement enhanced glucose oxidation peak current around −0.27 V to achieve an efficient electrochemical sensor for glucose with a detection limit of 12 μM and dynamic range between 0.05 to 5.0 mM with a good linearity (R²= 0.999). Almost no interference effect was observed for sensing of glucose in the presence of ascorbic acid, alanine, phenylalanine, fructose, sucrose, and NaCl.     

Determination of Mercury by Anodic Stripping Voltammetry with a Gold Nanoparticle‐Modified Glassy Carbon Electrode

The aim of this work is the development of a procedure for the determination of aqueous Hg(II) by anodic stripping voltammetry at a gold nanoparticle‐modified glassy carbon electrode (AuNPs‐GCE). The signal of aqueous Hg(II) was measured in the square wave mode; the effect of potential scan parameters, deposition potential and deposition time on the analytical signal was examined. The supporting electrolyte was 0.06 M HCl. The repeatability, the linearity, the accuracy, the detection limit of the procedure and the interferences of other cations and of anions were evaluated. The performance of the AuNPs‐GCE was compared with those of a solid (SGE) and a film (FGE) gold electrode: the AuNPs‐GCE showed to provide lower detection limits and higher repeatability. The renewable surface permits to eliminate memory effects, to maintain a stable baseline and response, and to avoid frequent mechanical cleaning steps. The applicability of the AuNPs‐GCE for Hg(II) determination in drinking waters, sediments and pharmaceuticals was demonstrated.     

Voltammetric Determination of BHT Antioxidant at Gold Electrode in Biodiesel

The voltammetric determination of synthetic antioxidant 2,6‐di‐tert‐butyl‐4‐methylphenole (BHT) was studied using linear‐sweep voltammetry (LSV) and cyclic voltammetry (CV) with a gold electrode and performed in isopropanol media containing either 0.1 mol L^?1 H₂SO₄ or 0.1 mol L^?1 LiClO₄ as supporting electrolyte. The results obtained have revealed that the most reliable detection was acquired in acidic media (isopropanol–H₂SO₄) whereas the use of isopropanol? LiClO₄ solution exhibited poorer reproducibility due to possible passivation of the electrode. Real samples of biodiesel mixture were analyzed without any special sample treatment or separation and results were compared with those obtained by FTIR‐spectroscopy.     

Enhanced Oxidation of Aldohexose and Aldopentose on Hg Adatom‐Modified Au Electrode in Alkaline Aqueous Solution

The electrochemical behavior of aldohexose and aldopentose monosaccharides was examined on Hg adatom‐modified and bare Au electrodes in alkaline aqueous solution using cyclic voltammetry. For the bare Au electrode, the oxidation peak currents are dependent on hydroxyl group configuration on the monosaccharides. On the other hand, for the Hg adatom‐modified Au electrode, the actual oxidation peak currents were similar for all monosaccharides other than glucose. Dispersion of Hg adatoms on the Au surface led to diminishment of configurational differences between monosaccharides as well as enhancement of oxidation peak current.     

化学修饰电极富集石墨炉原子吸收法测定痕量金

本文提出用聚丙烯脒硫氰酸盐化学修饰石墨管内壁、电化学预富集石墨炉原予吸收测定Au的分析方法.分析灵敏度提高100倍.应用于矿石中痕量Au的测定,获得了满意的结果.     

Voltammetric Behavior of Semicarbazide at Graphene Modified Electrode and Application to Detection

Herein voltammetric behaviors of semicarbazide (SEM) are investigated by employing a graphene modified working electrode, which displays attractive electroanalytical properties. In the acetate buffer solution of pH 4.00, there is a well‐defined oxidative peak of SEM, attributing to the irreversible and adsorption‐controlled electrode reaction with 2 electrons participation. The values of apparent heterogeneous electron transfer rate constant k′_s with the redox are 0.0061 s^?1 and 0.0009 s^?1, respectively, for two scan rate section. After the experimental parameters, which influence the voltammetric responses of SEM, including supporting electrolyte, pH, accumulation time and accumulation potential, etc., are optimized, it is found that the anodic peak current of SEM is proportional to its concentration in the range of 4 ‐ 40 μmol/L with a detection limit of 1 μmol/L (S/N = 3). Then, an electrochemical method for detecting SEM quantitatively is developed successfully. The concentrations of SEM in fortified tap water samples are tested with satisfactory recovery, indicating that the novel method is strongly promising in the environmental monitoring application.     

Simultaneous Adsorptive Cathodic Stripping Voltammetric Determination of Nickel(II) and Cobalt(II) at an In Situ Bismuth‐Modified Gold Electrode

A study on the simultaneous determination of Ni(II) and Co(II) dimethylglyoximates (Ni‐DMG and Co‐DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth‐modified gold electrode (Bi‐AuE) is reported. The key operational parameters, such as Bi(III) concentration, accumulation potential and accumulation time were optimized and the morphology of the Bi‐microcrystals deposited on the Au‐electrode was studied. The Bi‐AuE allowed convenient analysis of trace concentrations of solely Ni(II) or of Ni(II) and Co(II) together, with cathodic stripping voltammograms characterized by well‐separated stripping peaks. The calculated limit of detection (LOD) was 40 ng L^?1 for Ni(II) alone, whereas the LOD was 98 ng L^?1 for Ni(II) and 58 ng L^?1 for Co(II), when both metal ions were measured together. The optimized method was finally applied to the analysis of certified spring water (NIST1640a) and of natural water sampled in the Lagoon of Venice. The results obtained with the Bi‐AuE were in satisfactory agreement with the certified values and with those provided by complementary techniques, i.e., ICP‐OES and ICP‐MS.     

Electrochemical Oxidation of Methionine Mediated by a Fullerene‐C60 Modified Gold Electrode

The usefulness of a C₆₀‐fullerene modified gold (Au) electrode in mediating the oxidation of methionine in the presence of potassium ions electrolyte has been demonstrated. During cyclic voltammetry, an oxidation peak of methionine appearing at +1.0 V vs. Ag/AgCl was observed. The oxidation current of methionine is enhanced by about 2 times using a C₆₀ modified gold electrode. The current enhancement is significantly dependent on pH, temperature and C₆₀ dosage. Calibration plot reveals linearity of up to 0.1 mM with a current sensitivity of close to 50 mA L mol^?1 and detection limit of 8.2×10^?6 M. The variation of scan rate study shows that the system undergoes diffusion‐controlled process. Diffusion coefficient and rate constant of methionine were determined using hydrodynamic method (rotating disk electrode) with values of 1.11×10^?5 cm² s^?1 and 0.0026 cm s^?1 respectively for unmodified electrode while the values of diffusion coefficient and rate constant of methionine using C₆₀ modified Au electrode are 5.7×10^?6 cm² s^?1 and 0.0021 cm s^?1 respectively.