多菌灵在玻碳电极上的伏安行为及其应用

应用循环伏安法、微分脉冲伏安法对多菌灵在破碳电极上的电化学行为及其测定进行了研究。在ｐＨ＝９．０的２ｍｏｌ／Ｌ ＮＨ３－ＮＨ４Ｃｌ底液中，对其进行循环伏安扫描，发现于０．６１Ｖ（ｖｓ．Ａｇ／ＡｇＣｌ）产生一灵敏的氧化峰。微分脉冲伏安法殉菌灵的检测限为４×１０＾－８ｍｏｌ／Ｌ。多菌灵的浓度在５．０×１０＾－７￣１．０×１０＾－５ｍｏｌ／Ｌ间与微分脉冲伏安峰电流呈线性关系（ｒ＝０．９９４２）。对于１×     

对硫磷在单壁碳纳米管/金-四氧化三铁纳米粒子复合材料修饰电极上的电化学响应及其测定

制备了单壁碳纳米管/金-四氧化三铁纳米粒子复合材料修饰玻碳电极,用循环伏安法研究了对硫磷在该电极上的电化学行为。该电极对对硫磷具有较好的富集和催化特性,在优化条件下,对硫磷的浓度与其峰电流在2.0×10-9～1.0×10-6 mol/L范围内呈线性关系,其检出限为1.0×10-9 mol/L。对1.0×10-7 mol/L的对硫磷溶液平行测定9次的RSD为3.9%(n=9)。用该电极对不同蔬菜样品中的对硫磷进行测定,平均回收率在96.0%～105.5%之间,相对标准偏差在3.3%～3.9%之间。     

Electrochemistry and voltammetric determination of colchicine using an acetylene black-dihexadecyl hydrogen phosphate composite film modified glassy carbon electrode

The electrochemical behavior of colchicine at an acetylene black-dihexadecyl hydrogen phosphate (denoted as AB-DHP) composite film coated glassy carbon electrode (GCE) was investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Compared with the poor electrochemical signal at the unmodified GCE, the electrochemical response of colchicine at the AB-DHP film modified GCE was greatly improved, as confirmed from the significant peak current enhancement. The remarkable peak current enhancement indicates that the AB-DHP modified GCE has great potential in the sensitive determination of colchicine. Thus, all the experimental conditions, which influence the electrochemical response of colchicine, were studied and the optimum conditions were achieved. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range of 1.0 x 10(-7) approximately 4.0 x 10(-5) mol/L, was developed for the determination of colchicine. The detection limit of colchicine was also examined and a low value of 4.0 x 10(-8) mol/L for 4-min accumulation was obtained (S/N=3). This electrode was successfully applied to detect colchicine in human urine samples.     

Voltammetric determination of tyrosine based on an L-serine polymer film electrode

A novel film electrode for the voltammetric determination of tyrosine has been constructed based on electropolymerization of L-serine on a glassy carbon electrode. Voltammetric behaviour of tyrosine on the poly-L-serine film electrode was investigated with cyclic voltammetry and linear sweep voltammetry, and electrochemical parameters were calculated from chronocoulometry. In optimal conditions, the oxidation peak current of tyrosine on the poly-L-serine film electrode was enhanced greatly. A sensitive oxidation peak at 0.90 V was employed to determine tyrosine. A linearity between the oxidation peak current and the tyrosine concentration was obtained in the range of 3.0 x 10(-7) to 1.0 x 10(-4) mol L(-1) with a detection limit of 1.0 x 10(-7)mol L(-1). The practical application of the film electrode in the determination of tyrosine in a commercial amino acid oral solution demonstrated that it has good selectivity and high sensitivity.     

基于聚谷氨酸修饰玻碳电极的甲基对硫磷电化学传感器

制备了一种简单的聚谷氨酸修饰玻碳电极的用于检测甲基对硫磷的电化学传感器。 并应用循环伏安法研究了甲基对硫磷在该修饰电极上的氧化还原行为;甲基对硫磷的浓度检测采用差分脉冲伏安法,结果表明,甲基对硫磷在5.0×10-7～7.5×10-4 mol/L浓度范围与响应电流有良好的线性关系。 甲基对硫磷检测限（S/N=3）可达1.0×10-9 mol/L。 该法制备的传感器有望应用于实际样品中的甲基对硫磷的检测。     

Cathodic adsorptive stripping square-wave voltammetric determination of nifedipine drug in bulk,pharmaceutical formulation and human serum

Nifedipine is a calcium-channel antagonist drug used in the management of angina pectoris and hypertension through inhibition of calcium influx. A fully validated sensitive cathodic adsorptive stripping square-wave voltammetry procedure was optimized for the determination of the drug at trace levels. The procedure was based on the reduction of the nitrophenyl group after the interfacial accumulation of the drug onto a hanging mercury drop electrode in Britton-Robinson buffer of pH 11.0. The optimal conditions of the procedure were found to be: accumulation potential=-0.9 V vs. Ag/AgCl/KCl(s)), accumulation time=30 s, scan increment=10 mV, pulse amplitude=50 mV and frequency=120 Hz. Under these conditions, a well-defined peak was obtained; its peak current showed a linear dependence on drug concentration in the range of 2x10(-9)-2x10(-7) mol L(-1) bulk nifedipine. The mean recoveries based on eight replicate measurements for 1x10(-8) and 5x10(-8) mol L(-1) bulk nifedipine solutions were 98.46+/-0.86% and 98.23+/-0.92%, respectively. A detection limit of 3.42x10(-10) mol L(-1) bulk nifedipine was achieved. The procedure was successfully applied for assay of the drug in tablets and spiked human serum with mean recoveries of 101.95+/-1.42% and 98.70+/-0.63%, respectively. The limit of detection of the drug in spiked human serum was found to be 3.90x10(-10) mol L(-1).     

Voltammetric determination of niclosamide at a glassy carbon electrode

A very sensitive and selective procedure was developed for the determination of niclosamide based on square-wave voltammetry at a glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical reduction of niclosamide at a glassy carbon electrode. Niclosamide was first irreversibly reduced from NO2 to NHOH at -0.659 V in aqueous buffer solution of pH 8.5. Reversible and well defined peaks at -0.164 V and -0.195 V (vs. Ag/AgCl) were obtained that are responsible for two electron peaks between NHOH and NO. Following optimisation of the voltammetric parameters, pH and reproducibility, a linear calibration curve over the range 5 x 10(-8)-1 x 10(-6) mol dm(-3) was achieved. The detection limit was found to be 2.05 x 10(-8) mol dm(-3) niclosamide. For eight successive determinations of 5 x 10(-7) mol dm(-3) niclosamide, a relative standard deviation of 2.4% was obtained. This voltammetric method was applied to the direct determination of niclosamide in tablets. The results of the analysis suggest that the proposed method has promise for the routine determination of niclosamide in the products examined.     

Simultaneous electrochemical determination of xanthine and uric acid at a nanoparticle film electrode

A sensitive electrochemical method was developed for simultaneous determination of uric acid (UA) and xanthine (XA) at a glassy carbon electrode modified with multi-wall carbon nanotubes (MWNTs) film. The oxidation peak currents of UA and XA were increased at the MWNTs film electrode significantly. The experimental parameters, which influence the peak currents of UA and XA, such as the amount of MWNTs on the glassy carbon electrode, the pH of the solution, accumulation time, and scan rate, were optimized. Under optimum conditions, the peak currents were linear to the concentration of UA over the wide range from 1 x 10(-7) mol L(-1) to 1 x 10(-4) mol L(-1) and to that of XA over the wide range from 2 x 10(-8) mol L(-1) to 2 x 10(-5) mol L(-1). The interferences studies showed that the MWNTs-modified electrode exhibited excellent selectivity in the presence of ascorbic acid, dopamine, and hypoxanthine. The proposed procedure was successfully applied to detect UA and XA in human serum without any preliminary treatment.     

Covalent modification of glassy carbon electrodes with glycine for voltammetric separation of dopamine and ascorbic acid

Glycine was covalently grafted on to a glassy carbon electrode (GCE) by amine cation radical formation in electrooxidation of the amino-containing compound. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry proved the immobilization of glycine on the GCE. The modified electrode reduced the overpotentials of dopamine (DA) and ascorbic acid (AA) by approximately 0.15 V and 0.23 V, respectively, and resolved the overlapping voltammetric response of DA and AA into two well-defined voltammetric peaks in cyclic voltammetry (CV) or differential pulse voltammetry (DPV), unlike the unmodified GCE; this can be used for the simultaneous determination of these species in a mixture. The differential pulse peak current was linearly dependent on DA and AA concentration in the range 5 x 10(-6)-8 x 10(-4) mol L(-1) and 6 x 10(-5)-4 x 10(-3) mol L(-1), with correlation coefficients of 0.996 and 0.994, respectively. The detection limits (3delta) for DA and AA were 1.8 x 10(-6) mol L(-1) and 2.1 x 10(-5) mol L(-1), respectively. The modified electrode is very sensitive, selective and stable, and has been applied to the determination of DA and AA simultaneously in samples with satisfactory results.     

2,4,6-tri(3,5-Dimethylpyrazoyl)-1,3,5-triazine modified carbon paste electrode for trace Cobalt(II) determination by differential pulse anodic stripping voltammetry

A differential pulse anodic stripping voltammetry was developed for the sensitive and selective determination of Co(II) at 2,4,6-tri(3,5-dimethylpyrazoyl)-1,3,5-triazine modified carbon paste electrode in 0.1 mol l(-1) NH(4)Cl solution (pH 4.95). The oxidation peak of Co(II) was observed at 0.03 V(vs. Ag/AgCl) by scanning the potential in a positive direction. The analysis procedure consisted of an open circuit accumulation step in stirred sample solution. This was followed by medium exchange to a clean solution and subsequently an anodic potential scan was effect to obtain the voltammetric peak. The current was proportional to the concentration of the Co(II) ion in a range of 1x10(-8)-1x10(-6) mol l(-1) for 3 min accumulation and in the range of 1x10(-9)-1x10(-8) mol l(-1) for 5 min accumulation; most of metal ions do not interfere with the determination. The developed method was applied to Co(II) determination in potable water.     

Electrochemical behavior of thiamine on a self-assembled gold electrode and its square-wave voltammetric determination in pharmaceutical preparations.

The electrochemical behavior of thiamine on a self-assembled electrode of L-cysteine (Cys/SAM/Au) has been investigated and Cys/SAM/Au can be used to detect thiamine using square-wave voltammetry (SWV). At pH 11.40 Britton-Robinson buffer, thiamine exhibits a well-defined anodic peak on Cys/SAM/Au. Under the optimized conditions, the anodic peak current of SWV was linear with the content of thiamine in the range of 1.1 x 10(-8) - 2.2 x 10(-6) mol/L; the detection limit was 5.5 x 10(-9) mol/L. The method was successfully applied to the determination of thiamine in pharmaceutical preparations.     

层层自组装纳米金与乙酰胆碱酯酶电化学生物传感器检测有机磷农药

采用层层自组装技术制备了快速检测有机磷农药的生物传感器,利用带正电荷的高分子聚电解质聚二烯丙基二甲基氯化铵(PDDA)将乙酰胆碱酯酶(AChE)和金纳米粒子(AuNPs)通过静电力逐层固定到玻碳电极(GCE)表面,并采用交流阻抗和微分脉冲伏安法研究了此生物传感器的电化学行为。由于金纳米粒子优异的电催化性能和良好的生物相容性,使固定化的乙酰胆碱酯酶对其底物具有更高的亲和力和更快的响应速度。实验结果表明:修饰金纳米粒子后,传感器的氧化电流明显增大,在4.6×10-5～5.3×10-3mol/L范围内,固定化酶的抑制率与甲基对硫磷浓度的对数成正比,检出限为7.6×10-6mol/L。该生物传感器具有制备方法简便、成本低、灵敏度高等优点,已成功用于蔬菜样品中甲基对硫磷含量的测定。     

Adsorptive and electrochemical behaviors of estradiol valerate at a mercury electrode

It was found that estradiol valerate could be adsorbed at a mercury electrode under open circuit. The adsorptive and electrochemical behaviors of estradiol valerate on a static mercury electrode were investigated by cyclic voltammetry, linear scan voltammetry and chronocoulometry. Based on this, a sensitive and selective adsorptive stripping square-wave voltammetric method was developed for the determination of estradiol valerate based on the optimization of solution conditions and electrochemical parameters. It was found that in a Britton-Robinson buffer solution containing 18% alcohol (pH 9.5), estradiol valerate gave a sensitive reductive peak at potential -1.29 V (vs. SCE) and the peak current was linear with the concentration of estradiol valerate in the range 2.0 x 10(-8)-2.5 x 10(-6) mol L-1. The detection limit was 1.1 x 10(-8) mol L-1. The interference of some common steroid estrogens was examined and it was found that they did not interfere in the determination of estradiol valerate in the present system.     

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%。     

Covalent modification of glassy carbon electrodes with beta-alanine for voltammetric separation of dopamine and ascorbic acid.

beta-Alanine was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation process of the amino-containing compound. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) proved the immobilization of beta-alanine monolayer on GCE. The electrode shows strong electrocatalytic functions to dopamine (DA) and ascorbic acid (AA), reducing the overpotentials by 0.20 V and 0.23 V, respectively. Due to its different catalytic effects toward DA and AA, the modified electrode resolved the overlapping voltammetric responses of DA and AA into two well-defined voltammetric peaks by CV or differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly related to DA and AA concentrations in the ranges of 4.0 x 10(-6)-5.0 x 10(-4) mol/L and 2.0 x 10(-5)-6.0 x 10(-3) mol/L with correlation coefficients of 0.997 and 0.995, respectively. The detection limits (3 sigma) for DA and AA were 2.4 x 10(-6) mol/L and 1.2 x 10(-5) mol/L, respectively. The electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of DA and AA simultaneously in samples with satisfactory results.     

Determination of the pesticide Chlorpyrifos by cathodic adsorptive stripping voltammetry

The adsorption behavior and differential pulse cathodic adsorptive stripping voltammetry of the pesticide Chlorpyrifos (CP) were investigated at the hanging mercury drop electrode (HMDE). The pesticide was accumulated at the HMDE and a well-defined stripping peak was obtained at –1.2 V vs Ag/AgCl electrode at pH 7.50. A voltammetric procedure was developed for the trace determination of Chlorpyrifos using differential pulse cathodic adsorptive stripping voltammetry (DP-CASV). The optimum working conditions for the determination of the compound were established. The peak current was linear over the concentration range 9.90 × 10^–8– 5.96 × 10^–7 mol/L of Chlorpyrifos. The influence of diverse ions and some other pesticides was investigated. The analysis of Chlorpyrifos in commercial formulations and treated waste water was carried out satisfactorily     

阿奇霉素在多壁碳纳米管修饰电极上的电化学行为及其测定

运用循环伏安法与线性扫描伏安法研究了阿奇霉素在多壁碳纳米管修饰玻碳电极上的电化学行为,建立了一种直接测定阿奇霉素的电化学分析方法。结果表明,与裸玻碳电极相比,多壁碳纳米管修饰电极能显著提高阿奇霉素的氧化峰电流,阿奇霉素的电极过程完全不可逆,存在典型的吸附特性。在优化的实验条件下,氧化峰电流与阿奇霉素浓度在3.0×10-7～2.5×10-5 mol/L和2.5×10-5～5.0×10-4 mol/L范围内呈现良好的线性关系,检出限为1.0×10-7 mol/L。     

石墨烯/铂纳米粒子杂化膜测定肾上腺素

利用循环伏安法制备了石墨烯/铂纳米粒子杂化膜修饰电极,并利用该修饰电极研究了肾上腺素（EP）的电化学行为,建立了测定肾上腺素的电化学方法。 分别利用扫描电子显微镜（SEM）和循环伏安法对电极表面的形貌和电化学性能进行了表征。 试验优化了修饰电极制备过程中影响电极性能的条件和EP的测定条件。 试验结果表明,石墨烯/铂纳米粒子修饰电极对肾上腺素有明显的电催化作用。 在pH=5.0的柠檬酸 磷酸氢二钠缓冲溶液中,EP的氧化峰电流与其浓度在4.4×10-8~2.2×10-6 mol/L的范围内呈良好的线性关系。 线性方程为ipa(10 μA)=0.0753c(mol/L)+3.7653×10-5,r=0.9989,检出限为2.2×10-9 mol/L（S/N=3）。 修饰电极表具有良好的重现性,可用于实际样品的测定。     

Carbon paste electrode for trace zirconium(IV) determination by adsorption voltammetry.

A very sensitive and selective procedure was developed for trace measurement of zirconium based on the cathodic adsorptive stripping voltammetry of the zirconium-alizarin red S(ARS) complex at a carbon paste electrode (CPE). The 2nd-order derivative linear scan voltammograms of the zirconium-ARS complex were recorded by a model JP-303 polarographic analyzer from 0.0 to -1.0 V (vs. SCE). Optimal analytical conditions were found to be: an acetic acid (0.1 mol l(-1))-potassium biphthalate (0.08 mol l(-1)) buffer solution (pH 4.8) containing 4.0 x 10-6 mol l(-1) ARS; accumulation potential, 0.0 V; accumulation time, 180 or 90 s; rest time, 10 s; scan rate, 250 mV s(-1). The results showed that the complex can be adsorbed on the surface of the CPE, yielding one peak at -0.51 V, corresponding to the reduction of ARS in the complex at the electrode. The detection limit was found to be 1.0 x 10(-10) mol l(-1) (S/N = 3) for 240 s accumulation. The linear range was 2.0 x 10(-10)-4.0 x 10(-7) mol l(-1). The developed method was applied to the determination of trace zirconium in the ore samples with satisfactory results.     

Covalent modification of glassy carbon electrode with aspartic acid for simultaneous determination of hydroquinone and catechol

Glassy carbon electrode (GCE) is covalently modified with aspartic acid (Asp). The modified electrode is used for the simultaneous electrochemical determination of hydroquinone (HQ) and catechol (CC) and shows an excellent electrocatalytical effect on the oxidation of HQ and CC by cyclic voltammetry (CV) in 0.1 mol/L acetate buffer solution (pH 4.5). In differential pulse voltammetric (DPV) measurements, the modified electrode could separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 101 mV though the bare electrode gave a single broad response. A successful elimination of the fouling effect by the oxidized product of HQ on the response of CC has been achieved at the modified electrode. The determination limit of HQ in the presence of 0.1 mmol/L CC was 9.0 x 10(-7) mol/L and the determination limit of CC in the presence of 0.1 mmol/L HQ was 5.0 x 10(-7) mol/L. The proposed method has been applied to the simultaneous determination of HQ and CC in a water sample with simplicity and high selectivity.