Preconcentration and voltammetric determination of trace myoglobin at a 6-mercaptopurine modified silver electrode

6-Mercaptopurine(6-MP) is covalently modified onto a silver electrode to construct a chemically modified electrode (CME). It exhibits the capability of selectively complexing myoglobin and can be applied as a selective biosensor for this compound. Myoglobin is accumulated onto the CME at 0.32 V (vs. SCE); after exchanging the medium it is determined by differential pulse stripping voltammetry. A cathodic stripping peak is obtained at 0.15 V (vs. SCE) by scanning the potential from 0.35 to –0.1 V. The peak currents are linearly proportional to the concentration of myoglobin in the range of 0.2 ～ 4 μg/mL with a relative standard deviation of 7.8%. The detection limit is about 0.1 μg/mL. The mechanism of the complexation is also discussed.     

痕量铅在草酸修饰电极上阳极溶出伏安的研究

本文对草酸修饰电极的制作、痕量铅在草酸修饰电极上的反应机理和电化学特性作了研究。采用阳极溶出伏安法,测定铅的灵敏度比玻碳电极提高7.5倍,在1.0～15.0ng·/mL铅浓度范围内溶出峰高与铅浓度呈良好的线性关系。连续测定12次变异系数为3.0％。利用草酸修饰电极对人尿中痕量铅进行了测定,结果良好。     

Studies on the voltammetric behaviour of a 2-mercaptoimidazole containing carbon paste electrode: determination of traces of silver

The voltammetric behaviour of a 2-mercaptoimidazole (2-MI) containing carbon paste electrode was studied. When mixed to carbon paste as an electrode modifier, 2-MI can be reduced at negative potentials (–1 V vs. SCE), but it does not give a response in the potential range where Ag(0) is oxidized to Ag(I). Silver could be accumulated from 0.1 mol l^–1 acetate buffer onto a 2-MI modified carbon paste electrode without a potential applied; after medium exchange, it was reduced at –1 V vs. SCE in 0.1 mol l^–1 acetate buffer solution and determined by differential pulse anodic stripping voltammetry. With suitable preconcentration times, the detection limit was 0.1 g l^–1; a linear relation between current and concentration was found to exist within a range of 0.5 to 1000 g l^–1. In the presence of EDTA, common metal ions have no or only little effect on the voltammetric determination of silver.     

生物分子电催化的研究(Ⅲ)——血红蛋白在甲酚固紫修饰碳糊电极上的电催化

血红蛋白是脊椎动物红细胞内的呼吸蛋白,但由于其电活性中心不容易暴露以及在电极表面强烈吸附造成电极的钝化,使得它在一般固体电极上的电子传递速率很慢,得不到有效的电流响应。有关血红蛋白在固体电极上的电化学行为的研究很少。众多的分析化学家都在积极寻求加速血红蛋白电子传递速度的途径,使蛋白质直接电化学分析成为可能。最近的研究表明,某些染料修饰电极可以促进血红蛋白的电极过程,从而获得有效的电流响     

Nafion‐Modified Glassy Carbon Electrode for Trace Determination of Indium

Abstract

A new method for determination of trace indium is proposed by the adsorption stripping voltammetry (ASV) using a Nafion‐modified glassy carbon electrode (NMGCE). This chemically modified electrode (CME) shows a better stability. A sensitive oxidation peak was observed, and the anodic peak potential is ca. ?0.548 V (vs. SCE). The influences of various experimental parameters on the current peak were completely studied. Under the optimized condition, the method has been applied to the determination of indium in water samples. There is a good linear relationship between the peak current (i_p) and indium(III) concentration in the range of 1.0×10^?9–1.0×10^?7 mol/l, and the limit of detection is 7.5×10^?10 mol/l.     

Voltammetric Determination of L‐Dopa Using a Carbon Nanotubes‐Nafion Modified Glassy Carbon Electrode

Abstract

A method for determination of L‐dopa by the adsorption stripping voltammetry (ASV) using a multiwalled carbon nanotubes (MWNTs)–Nafion modified glassy carbon electrode (GMGCE) was proposed. This chemically modified electrode (CME) shows a better stability. A sensitive oxidation peak was observed and the anodic peak potential is ca. 0.374V (vs. SCE). The influences of various experimental parameters on the current peak were completely studied. Under the optimized condition, the method has been applied to the determination of L‐dopa in samples. There is a good linear relationship between the peak current (i_p) and L‐dopa concentration in the range of 3.5×10^?7～1.5×10^?5 mol/L, with the limit of detection 5.0×10^?8 mol/L.     

Automated determination of molybdenum(VI) in seawater by means of constant-current reduction of the adsorbed 8-quinolinol complex in a computerized flow potentiometric stripping analyzer

Molybdenum(VI) in seawater is determined by means of potentiostatic adsorption of the 8-quinolinol complex onto a mercury film electrode at ?0.2 V vs. SCE and subsequent reduction of the complex by means of constant-current stripping in 5 M calcium chloride medium with a fully automated stripping analyzer. A single stripping peak at –0.42 V vs. SCE was obtained. The molybdenum(VI) concentration in reference seawater NASS-1, with a certified value of 11.5 ± 1.9 μg 1^?1, was found to be 8.9 ± 1.3 μg 1^?1 (n = 10).     

芦荟大黄素1.5阶微分阳极溶出伏安法测定及电化学性质研究

研究了芦荟大黄素在以 0 .1mol/LHAc (pH 2 .89)为支持电解质 ,玻碳电极为工作电极的吸附伏安行为 .结果表明芦荟大黄素存在一个准可逆的双电子转移过程 ,其峰电流Ip 和峰电位Ep 与溶液 pH值有关 .同时还建立了用 1.5阶微分阳极溶出伏安法测定含量的新方法 .在 - 0 .80V(vs.SCE)电位下富集 ,可得一灵敏的微分阳极溶出峰 ,峰电位Ep 为 - 0 .38V ,峰电流Ip 与芦荟大黄素的浓度在 2 .0× 10 - 7～ 8.0× 10 - 6 mol/L范围内成线性关系 ,最低检出限为 1.0× 10 - 7mol/L .该法用于含有芦荟大黄素体系的测定 ,具有简便、快速、准确等优点     

多壁碳纳米管修饰乙炔炭黑微电极测定碘

以多壁碳纳米管修饰乙炔炭黑微电极为工作电极,研究了碘离子在该修饰电极上的阳极溶出伏安特性。在0.1 mol/L KH2PO4 缓冲液(pH4.0)中,从200 mV以200 mV/s的速率正向扫描至1200 mV,碘离子在570 mV处出现一灵敏的阳极溶出峰。峰电流与碘离子的浓度在2.0×10-6～1.0×10-3 mol/L范围内呈良好的线性关系,检出限为8.0×10-7 mol/L。方法用于食盐中碘含量的测定,结果满意。     

Determination of palladium by adsorptive stripping voltammetry

 Adsorptive accumulation of the Pd(II) complex with dimethylglyoxime was evaluated for stripping voltammetry with respect to different parameters. The sensitivity of the method and the linearity between the peak current and the concentration of Pd(II) depends on the ionic strength, the electrode area, the preconcentration time, the transport rate to the electrode, and the potential scan rate. The most appropriate medium was 0.1 mol/L acetate buffer between pH 3.5 and 4. Using 2 min of preconcentration at a 2.6 mm² electrode and the differential pulse mode, a detection limit of 0.05 μg/L Pd was achieved for liquid samples and 50 ng/g for solid samples. Different aqueous and solid samples were analysed and the recovery from biological and inorganic materials investigated. Received: 29 February 1996/Revised: 29 July 1996/Accepted: 1 August 1996     

Voltammetric Determination of Folic Acid with a Multi-Walled Carbon Nanotube-Modified Gold Electrode

The voltammetric behavior of folic acid (FA) at a multi-walled carbon nanotube (MWNT) modified gold electrode has been investigated by cyclic voltammetry, chronoamperometry and chronocoulometry. The modified electrode exhibits a good promoting effect on the electrochemical reaction of FA. FA can generate a well-defined anodic peak at around 0.83 V (vs. SCE) in 0.1 M H₃PO₄–NaH₂PO₄ buffer solution of pH 2.5. The peak results from a 2-electron transfer of FA, and the standard potential of FA is estimated to be 0.79 V (vs. SCE). The parameters affecting the response of FA, such as solution pH, accumulation time, accumulation potential, and amount of MWNTs are optimized for the determination of FA. Under the optimum conditions, the peak current changes linearly with FA concentration in the range from 2.0 × 10⁻⁸ M to 1.0 × 10⁻⁶ M. This method has been applied to the determination of FA in drug tablets, and the recovery is 93.9–96.9%. In addition, the influence of some coexistent species is examined. When a Nafion layer is introduced on the gold electrode before deposition of MWNTs, the resulting composite electrode can give better response to FA. At the same time, the interference by some foreign species is suppressed to some extent.     

Electrode Modified with Langmuir–Blodgett (LB) Film of Calixarenes for Preconcentration and Stripping Analysis of Hg(II)

A new type of current sensor, Langmuir–Blodgett (LB) film of calixarene on the surface of glassy carbon electrode (GCE) was prepared for determination of mercury by anodic stripping voltammetry (ASV). An anodic stripping peak was obtained at 0.15 V (vs. SCE) by scanning the potential from ?0.6 to +0.6 V. Compared with a bare GCE, the LB film coated electrode greatly improves the sensitivity of measuring mercury ion. The fabricated electrode in a 0.1 M H₂SO₄+0.01 M HCl solution shows a linear voltammetric response in the range of 0.07–40 μg L^?1 and detection limit of 0.04 μg L^?1 (ca. 2×10^?10 M). The high sensitivity, selectivity, and stability of this LB film modified electrode demonstrates its practical application for a simple, rapid and economical determination of Hg²⁺ in a water sample.     

天青I修饰电极的电化学性质及对血红蛋白的电催化还原

天青I修饰电极在pH=5.5的HAc-NaAc缓冲溶液中,在0.3～-0.7V电位范围内表现出可逆的氧化还原行为,其表面式量电位E^0'=-0.21V,表观电极反应速率常数k_s'=0.69s^-1,该电极对血红蛋白的还原过程具有良好的催化作用。实验结果表明,由电沉积构成的修饰电极较吸附法制备的修饰电极具有更好的稳定性。     

甲苯胺蓝修饰石墨电极的电化学性质及对血红蛋白的电催化还原

本文将电子媒体甲苯胺蓝吸附在石墨电极上制备成修饰电极。在＋０．２～０．５Ｖ（ｖｓ．ＳＣＥ）范围内，吸附态的甲苯胺蓝呈现有两质子参与的可逆性两电子氧化还原行为，在ｐＨ５．５醋酸盐缓冲溶液中，其表面式量电位Ｅ＾０为－０．２２Ｖ，表观表面电子传递速率常数ｋ为１．１Ｓ＾－１，甲苯胺蓝修饰电极具有良好的稳定性，它能加速血红蛋白在固体电极上的电子传递，产生很好的电流响应。     

茜素修饰碳糊电极吸附伏安法测定痕量铜

报道了采用茜素修饰碳糊电极测定痕量铜的阳极溶出伏安法。在浓度为0 .1 mol/L 的 HAc- Na Ac缓冲溶液 (p H4.5)中 ,于 +0 .1 0 V处富集 ,- 0 .30 V还原后再进行阳极化扫描 ,于 - 0 .0 5V处获得一灵敏的铜的溶出峰 ,二次导数峰电流与铜浓度在 1 .6× 1 0 -9mol/L～ 4.7× 1 0 -7mol/L范围内呈线性关系 ,检出限达 8.0× 1 0 -10 mol/L。同时 ,对电极反应机理进行了讨论。方法应用于锌合金中铜的测定。     

甲基对硫磷在聚噻吩/纳米二氧化钛修饰玻碳电极上的电化学行为及其测定

用循环伏安法(CV)、线性扫描溶出伏安法(LSSV)研究了甲基对硫磷(MPT)在聚噻吩/纳米二氧化钛修饰玻碳电极(PTh-NTiO2/GCE)上的电化学行为.实验表明,该修饰电极能显著提高MPT的氧化还原峰电流,在B-R缓冲溶液(pH 5.72)中,于-0.662V( vs.SCE)处产生灵敏的不可逆还原峰,其峰电流与...     

Bucky-gel coated glassy carbon electrodes, for voltammetric detection of femtomolar leveled lead ions

Femtomolar (fM) leveled lead ions were electrochemically detected using a bucky-gel coated glassy carbon electrode and differential pulse anodic stripping voltammetry. The bucky-gel was composed of dithizone, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and multi-walled carbon nanotubes (MWCNTs). The fabrication of the bucky-gel coated electrode was optimized. The modified electrode was characterized with voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. After the accumulation of lead ions into the bucky-gel modified electrode at −1.2 V vs. saturated calomel electrode (SCE) for 5 min in a pH 4.4 sodium acetate-acetate acid buffer solution, differential pulse anodic stripping voltammograms of the accumulated lead show an anodic wave at −0.58 V. The anodic peak current is detectable for lead ions in the concentration range from 1.0 μM down to 500 fM. The detection limit is calculated to be 100 fM. The proposed method was successfully applied for the detection of lead ions in lake water.     

Determination of medecamycin by adsorptive stripping voltammetry with an activated electrode

The adsorptive and electrochemical behaviors of medecamycin were investigated on a glassy carbon electrode (GCE) pretreated by anodic oxidation at +1.8 V for 5 min in 0.025 mol l^–1 NH₃-NH₄Cl (pH 8.6) solution. An adsorptive stripping voltammetric method for the determination of medecamycin at the pretreated glassy carbon electrode has been developed. Medecamycin was accumulated in NH₃-NH₄Cl buffer (pH 9.0) at a potential of –0.7 V (vs. saturated calomel electrode (SCE)) for a certain time, and then determined by second-order differential anodic stripping voltammetry. The second-order differential anodic stripping peak current at +0.72 V was proportional to the concentration of medecamycin in the range 2.0 g ml^–1 to 50.0 g ml^–1. The detection limit (three times the signal-to-noise) was 1.0 g ml^–1 and the relative standard deviation of the results was 3.28% for eight successive determinations of 10.0 g ml^–1 medecamycin. This method has been applied to the direct determination of medecamycin in commercial tablets and spiked urine samples with satisfactory results.     

亚硒酸钠在L-半胱氨酸自组装类生物膜修饰电极上的电化学行为

利用L-半胱氨酸自组装膜修饰金电极(L-Cys,Au/SAMs), 在0.05mol/L H_2SO_4 底液中研究了 Na_2SeO_3 的电化学特性.在0.00～1.30 V (vs. SCE) 电位范围内对微量Na_2SeO_3进行循环伏安扫描,发现L-Cys, Au/SAMs修饰电极在峰电位0.89 V处有灵敏的Se的氧化溶出峰.通过比较裸金电极和修饰电极在Na_2SeO_3 溶液中的电化学特性发现,修饰电极通过巯基中的S与Na_2SeO_3发生氧化还原作用生成Se,且修饰电极对沉积在电极表面的Se的氧化过程具有催化作用.根据Na_2SeO_3在单分子膜上的电化学行为,提出了单分子膜中硫(Au-S)与Se(Ⅳ)作用生成Se的反应机理、Se电化学催化氧化机理及巯基化合物通过生成纳米硒生物吸收Se的类生物膜模型.     

Determination of cobalt by catalytic-adsorptive differential pulse voltammetry in the presence of 2-aminocyclopentene-1-dithiocarboxylic acid and nitrite

A novel method for the determination of cobalt(II) by stripping voltammetry is described. It involves an adsorptive accumulation of the cobalt(II)-2-aminocyclopentene-1-dithiocarboxylic acid complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the catalytic reduction current of the complex at –1.4 V at pH = 9 (vs. Ag/AgCl). The effects of various experimental parameters on the catalytic current were investigated. An accumulation time of 60 s results in a low experimental limit of detection of 0.1 ng/mL of Co(II), and 0.50 to 40.0 ng/mL of cobalt can be determined. The relative standard deviation at 0.50 ng/mL is 2.8%. Possible interferences from co-existing ions were also investigated. Received: 17 August 1998 / Revised: 16 November 1998 / Accepted: 20 November 1998