多壁碳纳米管修饰电极测定诺氟沙星

运用循环伏安法、线性扫描伏安法及示差脉冲伏安法等测试技术研究了诺氟沙星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诺氟沙星的电化学分析方法.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诺氟沙星的氧化峰电流.在优化的实验条件下,氧化峰电流与诺氟沙星浓度在1.0×10-7～1.0×10-6mol/L和1.0×10-6～2.5×10-5 moL/L范围呈现良好的线性关系,检出限为3.0×10-8mol/L对1.0×10-5mol/L诺氟沙星溶液平行测定10次的RSD为4.1%.测定了诺氟沙星胶囊中诺氟沙星的含量,结果满意.     

Electrochemical simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode

A novel method for simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode has been developed. The gold nanoparticles were directly electrodeposited onto the glassy carbon electrode via a constant potential −0.2 V (vs. SCE) for 60 s from 0.1 mol L⁻¹ KNO₃ containing 0.4 g L⁻¹ HAuCl₄. The resulting electrode (nano-Au/GCE) was characterized with scanning electron microscopy (SEM). The electrochemistry response of nitrophenol isomers at the nano-Au/GCE was studied. The result indicated that o-, m-, and p- nitrophenol are separated entirely at nano-Au/GCE, and a semi-derivative voltammetric technology was adopted to enhance the determination sensitivity. This modified electrode could be applied to direct simultaneous voltammetric determination of nitrophenol isomers in water samples without preseparation with higher sensitivity.     

多壁碳纳米管修饰电极测定水样中痕量镉

通过多壁碳纳米管修饰玻碳电极,建立了水样中痕量镉的线性扫描阳极溶出伏安分析法。优化了支持电解质及pH、修饰剂用量、富集电位及时间等测定条件,在pH 4.0的NaAc-HAc缓冲液中,-1.10 V富集5 min后,溶出峰电流与Cd2 浓度在2.0×10-8~5.0×10-5mol/L的范围内呈良好的线性关系,检测限为8.0×10-9mol/L。该法用于实际水样中痕量镉的测定,平均回收率在98.7%~105.0%之间,结果满意。     

Electrochemical determination of phloroglucinol using a carbon nanotube modified electrode enhanced by surfactant

A novel technique is utilized to detect trace amounts of phloroglucinol. In pH 5.0, 0.1 mol L⁻¹ HAc–NaAc buffer solution, phloroglucinol exhibited a stable and sensitive oxidation signal at a glassy carbon electrode modified with multi-wall carbon nanotube. By using the surfactant cetyl pyridinium chloride, the electrochemical response was greatly enhanced. The mechanism was systematically explored. In the range 9.0 × 10⁻⁷–3.0 × 10⁻⁴ mol L⁻¹, the oxidation peak currents of phloroglucinol have a linear relationship with concentration: the limit of detection was estimated to be 2.5 × 10⁻⁷ mol L⁻¹ (S/N = 3). The method was adopted to detect the content of phloroglucinol injection, and the recovery was from 97.5% to 103.0%.     

Hematoxylin multi-wall carbon nanotubes modified glassy carbon electrode for electrocatalytic oxidation of hydrazine

A new hydrazine sensor has been fabricated by immobilizing hematoxylin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotube (MWCNT). The adsorbed thin films of hematoxylin on the MWCNT modified GCE show one pair of peaks with surface confined characteristics. The hematoxylin MWCNT (HMWCNT) modified GCE shows highly catalytic activity toward hydrazine electro-oxidation. The results show that the peak potential of hydrazine at HMWCNT modified GCE surface shifted by about 167 and 255 mV toward negative values compared with that at an MWCNT and activated modified GCE surface, respectively. In addition, at HMWCNT modified electrode surface remarkably improvement the sensitivity of determination of hydrazine. The kinetic parameters, such as the electron transfer coefficient, α, and the standard heterogeneous rate constant, k⁰, for oxidation of hydrazine at the HMWCNT modified GCE were determined and also is shown that the heterogeneous rate constant, k′, is strongly potential dependent. The overall number of electron involved in the catalytic oxidation of hydrazine and the number of electrons involved in the rate-determining steps are 2 and 1, respectively. The amperometric detection of hydrazine is carried out at 220 mV in 0.1 M phosphate buffer solution (pH 7) with linear response range 2.0-122.8 μM hydrazine, detection limit of 0.68 μM and sensitivity of 0.0208 μA μM⁻¹. Finally the amperometric response for hydrazine determination is reproducible, fast and extremely stable, with no loss in sensitivity over a continual 400 s operation.     

Electrochemical determination of bromide at a multiwall carbon nanotubes-chitosan modified electrode

A multiwall carbon nanotubes (MWNTs)-chitosan modified glassy carbon electrode (GCE) exhibits attractive ability for highly sensitive cathodic stripping voltammetric measurements of bromide (Br⁻). In pH 1.8 H₂SO₄ solution, a substantial increase in the stripping peak current of Br⁻ (compared to bare GCE and chitosan modified GCE) is observed using MWNTs-chitosan modified electrode. Operational parameters were optimized and the electrochemical behaviors of Br⁻ were studied by different electrochemical methods. The kinetics parameters were measured, the number of electron transfer (n) was 1 and the transfer coefficient (α) is 0.17. A wide linear calibration range (3.6 × 10⁻⁷-1.4 × 10⁻⁵ g mL⁻¹) was achieved, with a detection limit of 9.6 × 10⁻⁸ g mL⁻¹. The mechanism of electrode reaction was fully discussed.     

Electrochemical oxidation of benzene at a glassy carbon electrode

Benzene oxidation in sulfuric acid at a glassy carbon electrode was investigated using voltammetric, chronoamperometric, and spectroscopic methods. The results are compared with those at a Pt electrode. Benzene was observed to be oxidized to benzoquinone presumably by active oxygen that was adsorbed on the GC electrode in the oxygen evolution region. It is concluded that oxidation at glassy carbon can produce benzoquinone or quinone-like compounds from an aqueous benzene solution. The applied potential for benzene oxidation should be less than 2.1 V vs RHE in order to prevent glassy carbon electrode damage by oxidation during long operation.     

Electrocatalytic oxidation of hydrazine at a Co(II) complex multi-wall carbon nanotube modified carbon paste electrode

The catalytic oxidation of hydrazine was investigated by a cobalt(II) bis (benzoylacetone) ethylenediimino multi wall carbon nanotube-modified carbon paste electrode (Co(II)BBAEDI-MWCNT-MCPE) as a highly sensitive electrochemical sensor. The effect of variables such as pH and modifier percent on cyclic voltammograms peak current was optimized. The modified electrode showed very efficient electrocatalytic activity for anodic oxidation of hydrazine in 0.1 M phosphate buffer solution (pH 7.0). Anodic peak potential of hydrazine oxidation at the surface of modified electrode shifts by about 500 mV toward negative values compared with that on the bare electrode. The diffusion coefficient and electron transfer coefficient of hydrazine were obtained using electrochemical approaches. The Co(II)BBAEDI-MWCNT-MCPE showed good reproducibility (RSD < 3.3%). The electrocatalytic current increased linearly with the hydrazine concentration in the range of 0.3–70.0 μM and detection limit was 0.1 μM. The effect of various interferences on the hydrazine peak current was studied. This method was applied to determine hydrazine in water samples.     

Electrochemical determination of bisphenol A at Mg-Al-CO3 layered double hydroxide modified glassy carbon electrode

The electrochemical behavior of bisphenol A (BPA) was investigated on Mg-Al layered double hydroxide (LDH) modified glassy carbon electrode (GCE) by cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and chronocoulometry (CC). The cyclic voltammogram of BPA on the modified electrode exhibited a well defined anodic peak at 0.454 V in 0.1 M pH 8.0 phosphate buffer solution (PBS). The experimental parameters were optimized and the kinetic parameters were investigated. The probable oxidation mechanism was proposed. Under the optimized conditions, the oxidation peak current was proportional to BPA concentration in the range from 1 × 10⁻⁸ to 1.05 × 10⁻⁶ M with the correlation coefficient of 0.9959. The detection limit was 5.0 × 10⁻⁹ M (S/N = 3). The fabricated electrode showed good reproducibility, stability and anti-interference. The proposed method was successfully applied to determine BPA in plastic products and the results were satisfactory.     

银掺杂改性蒙脱土修饰电极测定L-色氨酸的电化学行为

以十八烷基三甲基溴化铵(OTAB)、银氨溶液对蒙脱土掺杂改性制得样品,用作电极修饰的材料。采用XRD、SEM、能谱法和交流阻抗法技术对样品表征,以循环伏安法、方波溶出伏安法探究改性蒙脱土修饰电极上L-色氨酸的电化学行为。结果表明,吸附和扩散对该电化学行为均有影响,反应转移的电子数n与质子数m为1,电极有效面积0.11 cm~2,扩散系数1.76×10-5cm~2/s。当CL-色氨酸在9.0×10-7~8.0×10-4mol/L时,其浓度与其氧化峰电流呈线性关系,检出限为6.53×10-7mol/L,加标回收率为94.3%~101.9%。     

银掺杂改性蒙脱土修饰电极测定L-色氨酸的电化学行为

以十八烷基三甲基溴化铵(OTAB)、银氨溶液对蒙脱土掺杂改性制得样品,用作电极修饰的材料。采用XRD、SEM、能谱法和交流阻抗法技术对样品表征,以循环伏安法、方波溶出伏安法探究改性蒙脱土修饰电极上L-色氨酸的电化学行为。结果表明,吸附和扩散对该电化学行为均有影响,反应转移的电子数n与质子数m为1,电极有效面积0.11 cm²,扩散系数1.76×10-5cm2,扩散系数1.76×10-5cm²/s。当CL-色氨酸在9.0×10-72/s。当CL-色氨酸在9.0×10-7⁸.0×10-4mol/L时,其浓度与其氧化峰电流呈线性关系,检出限为6.53×10-7mol/L,加标回收率为94.3%8.0×10-4mol/L时,其浓度与其氧化峰电流呈线性关系,检出限为6.53×10-7mol/L,加标回收率为94.3%¹01.9%。     

Electrochemical behavior of cysteine at a CuGeO3 nanowires modified glassy carbon electrode

A CuGeO₃ nanowire modified glassy carbon electrode was fabricated and characterized by scanning electron microscopy. The results of electrochemical impedance spectroscopy reveal that electron transfer through nanowire film is facile compared with that of bare glassy carbon electrode. The modified electrode exhibited a novel electrocatalytic behavior to the electrochemical reactions of l-cysteine in neutral solution, which was not reported previously. Two pairs of semi-reversible electrochemical peaks were observed and assigned to the processes of oxidation/reduction and adsorption/desorption of cysteine at the modified electrode, respectively. The electrochemical response of cysteine is poor in alkaline condition and is enhanced greatly in acidic solution, suggesting that hydrogen ions participate in the electrochemical oxidation process of cysteine. The intensities of two anodic peaks varied linearly with the concentration of cysteine in the range of 1 × 10⁻⁶ to 1 × 10⁻³ mol L⁻¹, which make it possible to sensitive detection of cysteine with the CuGeO₃ nanowire modified electrode. Furthermore, the modified electrode exhibited good reproducibility and stability.     

基于多壁碳纳米管修饰电极的磺胺的电化学检测

运用线性扫描伏安法(LSV)研究了磺胺(SA)在多壁碳纳米管修饰电极(MWNTs/GCE)上的电化学行为,探讨并确定了修饰体积和浓度、支持基质种类、最佳pH值、富集电位和时间等磺胺的最佳检测条件。结果表明,在pH=8.0的Na2HPO4-NaH2PO4缓冲体系中,磺胺在多壁碳纳米管修饰电极上检测到一个不可逆的氧化峰,且在1.0×10-5~2.0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%~100.93%。     

基于多壁碳纳米管修饰电极的磺胺的电化学检测

运用线性扫描伏安法(LSV)研究了磺胺(SA)在多壁碳纳米管修饰电极(MWNTs/GCE)上的电化学行为,探讨并确定了修饰体积和浓度、支持基质种类、最佳pH值、富集电位和时间等磺胺的最佳检测条件。结果表明,在pH=8.0的Na2HPO4-NaH2PO4缓冲体系中,磺胺在多壁碳纳米管修饰电极上检测到一个不可逆的氧化峰,且在1.0×10-5².0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%2.0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%¹00.93%。     

Electrochemical behavior of multi-wall carbon nanotubes and electrocatalysis of toluene-filled nanotube film on gold electrode

The cyclic voltammetric behaviors of empty nanotubes and toluene-filled nanotubes were described. When the nanotube films exposed to air for one night, a pair of redox waves was observed that is probably ascribed to the presence of oxygen-containing groups bound to the surface of the nanotubes. Toluene-filled nanotube film is demonstrated to catalyze the electrochemical response of biomolecules such as dopamine and epinephrine, while empty multi-wall carbon nanotube film shows no or less electrocatalytic behavior to these biomolecules. This suggests that filled nanotubes have some particular properties compared to empty multi-wall carbon nanotubes and the development of filled nanotubes is necessary.     

Electrochemical behavior and voltammetric determination of 4-aminophenol based on graphene-chitosan composite film modified glassy carbon electrode

The graphene-chitosan composite film modified glassy carbon electrode (GCE) was fabricated and used to determine 4-aminophenol (4-AP). In 0.1 M pH 6.3 phosphate buffer solution, the redox peak currents of 4-AP increased significantly and the peak-to-peak separation decreased greatly at graphene-chitosan composite film modified GCE compared with bare GCE and chitosan modified GCE, indicating that graphene possessed electrocatalytic activity towards 4-AP. The experimental conditions were optimized and the kinetic parameters were investigated. The oxidation mechanism was discussed. Under the optimal experimental conditions, the oxidation peak current was proportional to 4-AP concentration in the range from 0.2 to 550 μM with the correlation coefficient of 0.9930. The detection limit was 0.057 μM (S/N = 3). Using the proposed method, 4-AP was successfully determined in water samples and paracetamol tablets with standard addition method, suggesting that this method can be applied to determine 4-AP in environments and pharmaceuticals.     

Electrochemical study on cobalt film modified glassy carbon electrode and its application

A novel electroactive material for ascorbic acid (AA) determination was successfully prepared by plating/potential cycling method. The cobalt film was first deposited on the surface of glassy carbon electrode (GCE) in CoSO₄ solution by potential cycling, and then a cobalt film on the surface of GCE was activated by potential cycling in 0.1 mol L⁻¹ NaOH. The electrochemical performance of the resulted film (Co/GCE) and factors affecting its electrochemical activity were investigated by cyclic voltammetry and amperometry. This film electrode exhibited good electrocatalytic activity to the oxidation of AA. This biosensor had a fast response of AA less than 3 s and excellent linear relationships were obtained in the concentration range of 3 × 10⁻⁷ to 1 × 10⁻⁴ mol L⁻¹ with a detection limit of 2 × 10⁻⁷ mol L⁻¹ (S/N = 3) under the optimum conditions. Moreover, the selectivity, stability and reproducibility of this biosensor were evaluated with satisfactory results.     

Electrochemical behavior and adsorptive stripping voltammetric determination of quercetin at multi-wall carbon nanotubes-modified paraffin-impregnated graphite disk electrode

Multi-wall carbon nanotubes-modified paraffin-impregnated graphite disk was fabricated by using choline bond and catalyzer (MWCNT/Ch/WGE), and the properties were, respectively, investigated by field emission scanning electron microscope (FE-SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical behavior of quercetin was studied in detail by FE-SEM, UV-spectroelectrochemical and various electrochemical methods, which related with the two catechol hydroxyl groups and the other three hydroxyl groups, the former is electron-donating group with a two electron two proton reversible reaction, and is pH dependent. A highly sensitive adsorptive stripping voltammetric measurement (AdSV) for quercetin was also shown at this electrode. On the optimum conditions, the adsorptive stripping response of the peak (E = 0.15 V, 3 min accumulation) was proportional to the concentration in a range of 9.0 × 10⁻⁹ to 4.0 × 10⁻⁵ M. A detection limit of 4.8 × 10⁻⁹ M was obtained with a signal-to-noise ratio (s/n) of 3 and a good precision (R.S.D.: 2.1%, n: 9). Such attractive ability of MWCNT/Ch/WGE suggests a great promise for a quercetin amperometric sensor.     

Electrochemical oxidation of glutathione at well-aligned carbon nanotube array electrode

Electrochemical oxidation and determination of glutathione (GSH) were investigated with well-aligned carbon nanotube (CNT) arrays. Square wave voltammetric and amperometric results suggest that aligned-CNT electrode exhibits excellent electrochemical activity and good anti-fouling property for direct electrochemical oxidation of glutathione. Also, the preliminary application of the aligned-CNT electrode for amperometric determination of glutathione was evaluated.     

Electrochemical reduction of dioxygen on a thioglycolic acid-capped CdTe quantum dots modified glassy carbon electrode

A novel modified electrode was constructed by immobilizing thioglycolic acid-capped CdTe quantum dots (QDs) on a glassy carbon electrode (GCE) using Nafion ionomers. The results obtained by electrochemical impedance spectroscopy, cyclic voltammetry, and rotating disk electrode using the modified QDs?CNafion/GCE in a 0.20?M phosphate buffer of pH 7.0 revealed that the QDs act as effective mediators for the electrocatalytic reduction of dioxygen.