抗坏血酸在壳聚糖-碳纳米管-二茂铁复合修饰玻碳电极上的电化学行为

制备了壳聚糖-碳纳米管修饰玻碳电极(CHIT-MWCNTs/GCE)、二茂铁修饰玻碳电极(Fc/GCE)两种修饰玻碳电极,结果表明,制备的修饰玻碳电极对抗坏血酸(AA)的氧化有明显电催化作用。用CHIT-MWCNTs/GCE、Fc/GCE两种电极来检测水中AA浓度,利用循环伏安CV曲线分析电流和电位的变化得到AA在修饰玻碳电极上的电化学行为。结果表明,p H=5.97,磷酸缓冲溶液(PBS)浓度为50 mmol/L的支持电解质溶液下,制备的修饰玻碳电极有效检测AA的浓度范围为0.1~10 mmol/L,检出限为0.01 mmol/L。扫描速度与峰电流呈良好的线性相关关系y=-0.080 31X-1.994 53,r=-0.99,表明该反应机理受吸附控制。     

氨基-β-环糊精-单壁碳纳米管-二茂铁修饰电极对抗坏血酸的电化学行为研究

合成制备了氨基-β-环糊精(NH2-β-CD),然后通过主客体反应将NH2-β-CD与二茂铁(Fc)形成稳定的包合物,再与单壁碳纳米管(SWCNTs)复合后得到NH2-β-CD/Fc/SWCNTs复合膜修饰电极。通过循环伏安法研究该修饰电极对抗坏血酸(AA)的电催化行为。结果表明,在pH7.0的磷酸盐缓冲溶液(PBS)中,电位范围在-0.2～0.6V内,峰电流的变化值与抗坏血酸的浓度在1×10-5～1×10-3mol/L范围内成良好的线性关系,检出限为3.6×10-7mol/L。当用于模拟样品的测定,加标回收率为98.3%～100.8%,效果良好。     

对氨基苯酚在玻碳电极上的电化学行为研究及测定

研究了对氨基苯酚 (PAP)在玻碳电极上的电化学行为。对氨基苯酚在玻碳电极上能够发生可逆的氧化还原反应 ,其单扫和多扫循环伏安图保持一致 ,在电极上的反应是扩散控制的过程。用示差脉冲伏安法对其测定条件进行了优化 ,在最佳测定pH 8.4的Tris缓冲溶液中 ,PAP的浓度与峰电流在 1.0× 10 -7～ 1.0× 10 -4mol/L范围内呈线性关系。对电极氧化还原机理进行了讨论     

抗坏血酸在dsDNA修饰玻碳电极上的电催化氧化

制备了双链和单链DNA修饰的玻碳电极,并且比较了抗坏血酸在裸电极和DNA修饰电极上的电催化性能,同时研究了扫描速度、pH对抗坏血酸在双链DNA修饰电极上的氧化性能的影响,计算了电子转移系数。     

胡椒碱在碳纳米管修饰下的电化学行为

用微分脉冲阴极伏安法研究了胡椒碱的电化学行为,用碳纳米管修饰玻碳电极作工作电极,在pH2.0的磷酸盐缓冲溶液中,胡椒碱在0.98V左右产生一个氧化峰,在最优化条件下,胡椒碱的浓度在5mg/L～50mg/L范围内与峰高呈较好的线性关系。方法简便易行、灵敏、准确。     

2,6-二甲基苯酚在玻碳电极上的电化学行为研究

研究了2,6-二甲基苯酚在玻碳电极上的电化学行为。通过线性扫描伏安法研究了支持电解质、溶液pH和扫描速度对2,6-二甲基苯酚测定的影响。并采用示差脉冲伏安法研究了氧化峰电流与2,6-二甲基苯酚浓度之间的关系,结果显示峰电流与2,6-二甲基苯酚的浓度在7.0×10^-5～2.0×10^-2 mol/L之间有良好的线性关系。同时玻碳电极对2,6-二甲基苯酚的测定具有较好的重现性和稳定性。     

色氨酸在多壁碳纳米管-Nafion修饰玻碳电极上的电化学行为及测定

采用滴涂法制备了多壁碳纳米管-Nafion修饰玻碳电极(MWCNTs-Nafion/GCE),基于此修饰电极,建立了发酵液中色氨酸的电化学检测方法。结果表明:在pH 4.0的磷酸盐缓冲溶液中,色氨酸在MWCNTs-Nafion/GCE电极上有良好的响应,氧化峰电势为1.01 V,在5×10-7-2×10-4mol/L范围内,色氨酸氧化峰电流与其浓度呈良好的线性关系,线性方程为:Ip(10-6 A)=2.432×104 C(mol/L)+3.1452,R2为0.9973,检测限为2.7×10-8mol/L(S/N=3),回收率在98.3%~104.3%之间,相对标准偏差≤3.0%。该方法操作简单、结果稳定、选择性和灵敏度良好。     

聚溴酚蓝/壳聚糖修饰玻碳电极对抗坏血酸的电催化氧化作用

在玻碳电极表面滴涂一层壳聚糖膜,吸附富集聚溴酚蓝介体,使其固定在电极表面,制备了聚溴酚蓝/壳聚糖玻碳修饰电极,研究了抗坏血酸在修饰电极上的电化学行为.实验结果表明,修饰电极对抗坏血酸具有良好的电催化氧化性能,在4.0×10-6-1.0×10-3mol/L范围内,抗坏血酸浓度与其循环伏安扫描峰电流呈良好的线性关系,相关系数为0.999 3,检测限1.2×10-6mol/L.该法测定药物中抗坏血酸的含量,结果满意.     

碳纳米管修饰电极测定对乙酰氨基酚和抗坏血酸的研究

本文的研究结果表明,碳纳米管修饰电极加快对乙酰氨基酚和抗坏血酸的电化学氧化。相比裸玻碳电极,碳纳米管修饰电极使PA的氧化峰负移113mV,电流增大3倍;AA的氧化电位负移126mV,电流增大4倍,且使PA和AA的氧化电位差达到344mV,PA和AA的氧化峰不再重叠,能够同时测定。PA和AA的检出限分别达到1.01×10-6mol.L-1和2.46×10-5mol.L-1。方法应用于药品的测定,结果满意。     

柠檬酸/多壁碳纳米管修饰电极电化学检测多巴胺和抗坏血酸

通过柠檬酸与多壁碳纳米管复合修饰玻碳电极得到新型电化学传感器,采用循环伏安法研究多巴胺和抗坏血酸电化学行为,并讨论了pH值、缓冲溶液、浓度和扫描速度等对多巴胺和抗坏血酸的影响。结果表明,在pH=6.80的磷酸盐(PBS)缓冲溶液中,修饰电极对多巴胺和抗坏血酸均有良好的电催化作用。多巴胺和抗坏血酸峰电流在浓度分别为1.00×10~(-6)~5.00×10~(-3)和1.00×10~(-4)~5.00×10~(-2) mol/L的范围内呈现良好的线性关系。柠檬酸/多壁碳纳米管(CA/MWNT)电极易制备,可望用于盐酸多巴胺注射液和维生素C药片的测定。     

用聚甲苯胺蓝修饰的玻碳电极同时测定多巴胺和抗坏血酸

研究了聚甲苯胺蓝修饰的玻碳电极的制备及其对多巴胺和抗坏血酸的电催化作用.由于多巴胺和抗坏血酸在该修饰电极的氧化还原电位相差约0.190 V(vs SCE),在同一溶液中,两者无需分离可以分别检出而互不干扰.其可检测的线性范围分别为4～1.8 mmol/L和2.0～ 3.2 mmol/L,检测下限分别为1.4 μmol/L和0.8μmol/L.     

Stearic acid modified glassy carbon electrode for electrochemical sensing of parathion and methyl parathion

Stearic acid modified glassy carbon electrode for the sensing of parathion and methyl parathion was fabricated. The electrochemical responses for parathion and methyl parathion were investigated by cyclic voltammetry, differential pulse voltammetry and amperometry. The results on stearic acid modified electrode and bare glassy carbon electrode were compared. Higher sensing current was obtained on stearic acid modified glassy carbon electrode. Analytical characteristics of the sensor such as sensitivity, linear dynamic range, lower detection limit and response time were evaluated.     

Selective determination of dopamine in the presence of ascorbic acid using ferrocenyl-tethered PAMAM dendrimers modified glassy carbon electrode

Determination of dopamine (DA) in the absence and presence of ascorbic acid (AA) by ferrocenyl-tethered PAMAM G3 dendrimers (Fc-D) modified glassy carbon electrode (GCE) was reported. The modified electrode was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Factors influencing the detection processes were optimized and kinetic parameters were calculated. The sensor exhibited excellent catalytic activities for the oxidation–reduction reactions of DA and eliminated the interference of AA. Under optimal condition, the linear range of 1 × 10⁻⁵–1.5 × 10⁻³ mol L⁻¹ and the detection limit of 4.7 × 10⁻⁶ mol L⁻¹ was obtained. This study provides a new idea for the determination of DA in the presence of AA.     

Enhancement of electrochemiluminesence of lucigenin by ascorbic acid at single-wall carbon nanotube film-modified glassy carbon electrode

The electrochemiluminescent behavior of lucigenin on a single-wall carbon nanotube/DMF film-modified glassy carbon electrode was studied in this paper. Comparing with the bare glassy carbon electrode, the electrochemiluminescent of lucigenin at modified electrode is more stable and without tedious procedure for clean-up the surface of modified electrode. It has been found that ascorbic acid could enhance the electrochemiluminescent intensity of lucigenin greatly at this modified electrode. Based on which, a new sensitive and simple electrochemiluminescent method for determination of ascorbic acid could be developed. The condition for the determination of ascorbic acid was optimized. Under the optimized condition, the enhanced electrochemiluminescent intensity versus ascorbic acid concentration was linear in the range of 1.0 × 10⁻⁸ to 4.0 × 10⁻⁶ mol/L with a detection limit of 2.0 × 10⁻¹⁰ mol/L, and the relative standard derivation for 1.0 × 10⁻⁷ mol/L ascorbic acid was 3.8% (n = 8). The possible mechanism was also discussed.     

Voltammetric studies of a novel bicopper complex modified glassy carbon electrode for the simultaneous determination of dopamine and ascorbic acid

A novel modified glassy carbon electrode (GCE) with a binuclear copper complex was fabricated using a cyclic voltammetric method in phosphate buffer solution. This modified electrode shows very efficient electrocatalytic activity for anodic oxidation of both dopamine (DA) and ascorbic acid (AA) via substantial decrease in anodic overpotentials for both compounds. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using this modified electrode show two well-resolved anodic waves for the oxidation of DA and AA in mixed solution, which makes it possible for simultaneous determination of both compounds. Linear analytical curves were obtained in the ranges 2.0–120.0 μM and 5.0–160.0 μM for DA and AA concentrations by using DPV methods, respectively. The detection limits were 1.4 × 10⁻⁶ M of DA and 2.8 × 10⁻⁶ M of AA. This electrode was used for AA and DA determinations in medicine and foodstuff samples with satisfactory results.     

Direct electrochemical behavior of cytochrome c on DNA modified glassy carbon electrode and its application to nitric oxide biosensor

Cytochrome c/DNA modified electrode was achieved by coating calf thymus DNA onto the surface of glassy carbon electrode firstly, then immobilizing cytochrome c on it by multi-cyclic voltammetric method and characterized by the electrochemical impedance. The electrochemical behavior of cytochrome c on DNA modified electrode was explored and showed a quasi-reversible electrochemical redox behavior with a formal potential of 0.045 ± 0.010 V (versus Ag/AgCl) in 0.10 M, pH 5.0, acetate buffer solution. The peak currents were linearly with the scan rate in the range of 20-200 mV/s. Cytochrome c/DNA modified electrode exhibited elegant catalytic activity for the electrochemical reduction of NO. The catalytic current is linear to the nitric oxide concentration in the range of 6.0 × 10⁻⁷ to 8.0 × 10⁻⁶ M and the detection limit was 1.0 × 10⁻⁷ M (three times the ratio of signal to noise, S/N = 3).     

Electrocatalytic hydrazine oxidation on quinizarine modified glassy carbon electrode

The electrocatalytic oxidation of hydrazine has been studied on glassy carbon modified by electrodeposition of quinizarine, using cyclic voltammetry and chronoamperometry techniques. It has been shown that the oxidation of hydrazine to nitrogen occurs at a potential where oxidation is not observed at the bare glassy carbon electrode. The apparent charge transfer rate constant and transfer coefficient for electron transfer between the electrode surface and immobilized quinizarine were calculated as 4.44 s⁻¹ and 0.66, respectively. The heterogenous rate constant for oxidation of hydrazine at the quinizarine modified electrode surface was also determined and found to be about 4.83 × 10³ M⁻¹ s⁻¹. The diffusion coefficient of hydrazine was also estimated as 1.1 × 10⁻⁶ cm² s⁻¹ for the experimental conditions, using chronoamperometry.     

The electrochemical oxidation of aqueous phenol at a glassy carbon electrode

The electrooxidation of phenol is of interest as a model compound for the treatment of aqueous organic wastes. The effect of voltage, concentration and temperature on the electrochemical oxidation of acidic dilute aqueous solutions of phenol was studied. Electrolysis was carried out by recirculating phenol solutions through a flow-by electrochemical reactor employing a reticulated glassy carbon anode. Concentrations of phenol and some breakdown products were monitored using HPLC analysis. Increased voltage was found to shift the product distribution to favour more oxidized products but also to increase electrode corrosion and decrease current efficiency. Higher phenol concentrations (over the range of 5-20 mmol/L) showed a shift in product distribution to favour less oxidized, mostly insoluble products. Elevated temperatures (about 50°C and higher) showed a marked ability to reduce electrode passivation and increase the phenol oxidation rate.