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41.
43.
A renewable three-dimensional chemically modified carbon ceramic electrode containing Ru [(tpy)(bpy)Cl] PF6 was constructed by sol-gel technique. It exhibits an excellent electro-catalytic activity for oxidation of l-cysteine and glutathione at pH range 2-8. Cyclic voltammetry was employed to characterize the electrochemical behavior of the chemically modified electrode. The electrocatalytic behavior is further exploited as a sensitive detection scheme for l-cysteine and glutathione by hydrodynamic amperometry. Optimum pH value for detection is 2 for both l-cysteine and glutathione. The catalytic rate constants for l-cysteine and glutathione were determined, which were about 2.1×103 and 2.5×103 M−1 s−1, respectively. Under the optimized condition the calibration curves are linear in the concentration range 5-685 and 5-700 μM for l-cysteine and glutathione determination, respectively. The detection limit (S/N=3) and sensitivity is 1 μM, 5 nA/μM for l-cysteine and 1 μM, 7.8 nA/μM for glutathione. The relative standard deviation (RSD) for the amperogram's currents with five injections of l-cysteine or glutathione at concentration range of linear calibration is <1.5%. The advantages of this amperometric detector are: high sensitivity, good catalytic effect, short response time (t<3 s), remarkable long-term stability, simplicity of preparation and reproducibility of surface fouling (RSD for six successive polishing is 3.31%). This sensor can be used as a chromatographic detector for analysis of l-cysteine and glutathione. 相似文献
44.
《Electroanalysis》2003,15(9):787-796
The use of [Cu(bipy)2]Cl2?6H2O as a biomimetic catalyst in the construction of an amperometric sensor for dopamine determination is reported. The sensor was prepared modifying a glassy carbon electrode with a Nafion membrane doped with [Cu(bipy)2]Cl2?6H2O complex. The sensor presented a higher response in 0.25 mol L?1 phosphate buffer solution (pH 7.0), with an applied potential of ?50 mV (vs. SCE). In the optimized operational conditions, a linear response range between 35 and 240 μmol L?1, with a sensitivity of 2.02±0.07 nA l μmoL?1 cm?2 and detection limit of 8.0 μmol L?1 were typically observed for the sensor. The response time presented for this sensor was 0.5 s, presenting the same response for at least 40 successive measurements, with good repeatability (3.0%) expressed as relative standard deviation for n=6. The difference of the response between four sensor preparations was 4%. A detailed investigation about the sensor response for other sixteen phenolic compounds and interfering species were carried out. The sensor was applied in the determination of dopamine in pharmaceutical preparation with success. 相似文献
45.
利用循环伏安法制备了聚对氨基苯磺酸修饰电极, 研究了尿酸在该修饰电极上的电化学行为. 结果表明, 该电极对尿酸有较强的电催化作用, 并对抗坏血酸有较强的抗干扰能力. 在pH 5.6的乙酸盐缓冲溶液中, 用循环伏安法和差分脉冲伏安法在该电极上测定了尿酸, 其线性范围分别为1.0×10-5~2.0×10-4 mol/L和4.0×10-7~1.0×10-5 mol/L, 检出限分别为6.0×10-6 mol/L和1.0×10-7 mol/L. 已用于尿液中尿酸的测定. 相似文献
46.
用直径7 μm的碳纤维组合成超微圆盘电极,以聚苯胺修饰电级.以阶梯扫描法、循环伏安法、双阶跃计时电量法和交流阻抗法等,研究了Cd2+在该电极上的表面络合吸附特性和电极过程.在循环伏安图上出现两个还原峰,实验和理论都证明,由于电极表面的聚苯胺对Cd2+的特性吸附,形成电活性的表面吸附态络合物.因此,这种表面络合物首先被还原,形成峰电位-0.90 V处的表面络合吸附波,还原峰电位比Cd2+直接还原电位(-0.98 V)正移,循环反扫时,氧化波无峰形.根据实验数据推测了电极过程的反应机理,证实该还原波具有扩散和表面反应同时控制的表面络合吸附波的特性.理论计算与实验基本一致,并求得了表面吸附态配合物的形成常数、吸附量和表面络合反应的动力学参数.实验还证实,在峰电位-1.06 V 处的还原波,是Cd2+的表面吸附还原态诱导而产生的催化氢波. 相似文献
47.
Santiago MB Vélez MM Borrero S Díaz A Casillas CA Hofmann C Guadalupe AR Colón JL 《Electroanalysis》2006,18(6):559-572
We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10‐phenanthroline‐5,6‐dione)(2,2′‐bipyridine)ruthenium(II) ([Ru(phend)2bpy]2+) exchanged into the inorganic layered material zirconium phosphate (ZrP). X‐Ray powder diffraction showed that the interlayer distance of ZrP increases upon [Ru(phend)2bpy]2+ intercalation from 10.3 Å to 14.2 Å. The UV‐vis and IR spectroscopies results showed the characteristic peaks expected for [Ru(phend)2bpy]2+. The UV‐vis spectrophotometric results indicate that the [Ru(phend)2bpy]2+ concentration inside the ZrP layers increased as a function of the loading level. The exchanged [Ru(phend)2bpy]2+ exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°′=–38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis–Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers' yeast alcohol dehydrogenase. A calibration plot for ethanol is presented. 相似文献
48.
A study of the electrocatalytic oxidation of aspirin on a nickel hydroxide-modified nickel electrode
The electrocatalytic oxidation of aspirin has been investigated on a nickel oxide-modified nickel electrode in alkaline solution.
The process of oxidation and its kinetics have been investigated by using cyclic voltammetry, chronoamperometry, and electrochemical
impedance spectroscopy techniques and also steady-state polarization measurements. Voltammetric studies have indicated that
in the presence of aspirin, the anodic peak current of low-valence nickel species increases, followed by a decrease in the
corresponding cathodic current. This indicates that aspirin was oxidized on the redox mediator immobilized on the electrode
surface via an electrocatalytic mechanism. The rate constant of the catalytic oxidation of aspirin and the electron transfer
coefficient have been found to be 1.15×105 cm3 mol−1s−1 and 0.49, respectively. Impedance measurements show that aspirin is diffused into the bulk of the modifier film, and the
oxidation process of aspirin occurs in the bulk of nickel oxide film. It has been shown that by using this modified electrode,
aspirin can be determined with a detection limit of 4.8×10−5 and successfully applied for determination of aspirin in tablet. 相似文献
49.
50.