部分电化学还原氧化石墨烯修饰玻碳电极用于苦参碱的测定

以部分电化学还原的氧化石墨烯(pErGO)修饰的玻碳电极(GCE)作为工作电极(pErGO/GCE),用于苦参碱(MT)含量的电化学测定.在活化好的GCE上滴涂氧化石墨烯(GO),用恒电位法在-0.75 V下还原GCE表面的GO 200 s,得到的电极即为pErGO/GCE.以0.1 mol·L-1 NaH2 PO4-...     

循环伏安法研究利福平的电化学行为

采用循环伏安法研究了利福平在多壁碳纳米管修饰电极(MWCNT′s/GCE)上的电化学行为。结果表明:在pH 1.2的0.2mol.L-1硫酸-硫酸钠溶液中,修饰电极对利福平有良好的电催化作用,能够显著提高氧化还原峰电流,还原峰电流与利福平浓度分别在6.6×10-8～6.8×10-6 mol.L-1,6.8×10-6～4.8×10-5 mol.L-1范围内呈线性关系,检出限(3S/N)为3.0×10-8 mol.L-1。对利福平在修饰电极(MWCNT′s/GCE)上的电化学动力学性质进行了研究。     

苯甲酰肼在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电化学动力学性质

研究了苯甲酰肼(BH)在MWCNT/GCE上的电化学行为。实验结果表明,BH在GCE上的直接电化学氧化十分迟缓,无氧化峰出现,但在MWCNT/GCE上BH在0.20 V处出现了一个不可逆氧化峰,且峰电流大幅度增大,表明MWCNT/GCE对BH电化学氧化具有良好的催化作用。同时用计时库仑法(Chro-nocoulometry,CC)和计时电流法(Chronoamperometry,CA)测定了电极过程动力学参数:扩散系数D=8.73×10-5cm2.s-1,电子转移系数α=0.85,电极反应速率常数kf=1.45×10-3s-1。稳态电流-时间实验结果表明,电流响应信号随其浓度成比例增长,响应时间小于6 s,最低响应浓度为1×10-6mol/L。该方法可用于BH电化学定量测定。     

铂/多壁碳纳米管修饰玻碳电极用于微分脉冲伏安法测定左旋多巴

采用微波辅助加热多元醇技术制备了载铂多壁碳纳米管复合材料,并将该复合材料分散在N,N′-二甲基甲酰胺溶液中得到悬浮液,取14μL悬浮液滴涂在玻碳电极表面,制备铂/多壁碳纳米管修饰电极(Pt/MWCNT′s/GCE)。循环伏安法研究了在0.05mol·L~(-1)硫酸支持电解质中,在0.30～0.70V(vs.SCE)电位范围内,左旋多巴在修饰电极上的电化学行为,结果表明:左旋多巴在Pt/MWCNT′s/GCE上于电位0.548V处可见明显的氧化峰,且氧化峰电流显著高于在MWCNT′s/GCE和裸玻碳电极上的氧化峰电流。提出了用微分脉冲伏安法测定左旋多巴的方法。左旋多巴的浓度在8.0×10~(-6)～2.0×10~(-1)mol·L~(-1)范围内与其氧化峰电流呈线性关系,检出限(3S/N)为1.9×10~(-6)mol·L~(-1),平均回收率为102.8%。     

延胡索酸泰妙菌素在乙炔黑-离子液体复合修饰玻碳电极上的电化学行为及电分析方法

用乙炔黑(Acetylene black,AB)和离子液体(Ionic liquid,IL)制备了乙炔黑-离子液体复合修饰玻碳电极(AB-ILs/GCE),并用电化学阻抗谱(EIS)进行了表征。采用循环伏安法(Cyclic voltammetry,CV)和计时电流法(Chronoamperometry,CA),方波伏安法(Square wave voltammetry,SWV)研究了延胡索酸泰妙菌素(TF)在此电极上电化学行为及电化学动力学性质。结果表明,TF在玻碳电极(GCE)上于0.74 V处出现一个不可逆氧化峰,与GCE相比TF在AB/GCE上的氧化峰电位基本不变,氧化峰电流增大1.8倍;而与AB/GCE相比,TF在AB-ILs/GCE上的氧化峰电位略有负移,氧化峰电流增大3倍。实验结果表明,AB-ILs/GCE对TF电化学氧化有明显的催化作用。同时考察了实验条件对TF电化学行为的影响,测定了电极反应过程动力学参数,并用本方法对TF针剂中TF含量进行了定量测定,RSD在1.1%～2.9%之间,加标回收率在98.6%～101.8%之间。据此建立了TF电化学定量测定方法。     

更昔洛韦在碳纳米管-离子液体修饰电极上的电催化氧化及电分析方法

将疏水性离子液体与多壁碳纳米管修饰在玻碳电极上,制备了多壁碳纳米管-离子液体修饰玻碳电极(MWCNTs-IL/GCE).运用循环伏安法进一步研究了更昔洛韦(GCV)在MWCNTs-IL/GCE上的电化学行为.结果表明,GCV在GCE电极上于1.06 V处有一不可逆氧化峰.与GCE相比,GCV在MWCNTs-IL/GCE上的峰电位约负移100 mV,峰电流明显增强,表明MWCNTs-IL/GCE对GCV具有良好的电催化氧化作用.在40 ～400 mV/s范围内,其氧化峰电流与扫描速率呈良好的线性关系,表明GCV在MWCNTs-IL/GCE上的电极反应受吸附控制.测定了GCV在MWCNTs-IL/GCE上的电荷转移系数α、电极反应速率常数K′s.采用微分脉冲伏安法测得GCV氧化峰电流与其浓度在2.0×10-7 ～2.5×10-5 mol/L范围内呈良好的线性关系,检出限为5.4×10-8 mol/L.该法用于GCV药物的含量测定,RSD为2.4% ～3.6%,加标回收率为96% ～101%.     

甲氧苄啶在多壁碳纳米管-Nafion修饰电极上的电催化氧化及电分析方法

用循环伏安法(CV),计时库仑法(CC),计时电流法(CA),线性扫描伏安法(LSV)及电流-时间曲线研究了甲氧苄啶(trimethoprim, TMP)在碳纳米管-Nafion修饰电极(MWCNTs-Nafion/GCE)上的电化学行为,电化学动力学性质以及电分析方法.结果表明,TMP在GCE上有一个极弱的氧化峰,而在MWCNTs-Nafion/GCE上出现一个敏锐的氧化峰,表明MWCNTs-Nafion/GCE对TMP电化学氧化具有良好的催化作用.在扫描速度为10～800 mV/s时其氧化峰电流与扫描速度平方根(v1/2)呈良好线性关系,表明TMP在MWCNTs-Nafion/GCE上的伏安行为是受扩散控制的电化学过程.TMP在MWCNTs-Nafion/GCE上氧化峰电流与浓度在5.0×10-6～1.0×10-3 mol/L范围内呈良好线性关系;检出限为6.6×10-7 mol/L;RSD在0.75%～1 69%之间;加标回收率在98.1%～101.1%之间.本方法简便快捷,测定结果令人满意,可用于TMP的电化学定量测定.     

盐酸吡哆辛在石墨烯-碳纳米管/聚烟酸复合修饰电极上的电化学行为研究及其测定

通过滴涂和电聚合的方法制备了石墨烯(GN)-多壁碳纳米管(MWCNTs)/聚烟酸(PNA)修饰玻碳电极。利用循环伏安法和差分脉冲伏安法考察了盐酸吡哆辛(VB6)在此修饰电极上的电化学行为和测定方法。结果表明,VB6在此修饰电极上有一明显的不可逆氧化峰(Epa=1.049 V),该电极与GCE、PNA/GCE以及GN/MWCNT/GCE相比,VB6的氧化峰电流显著提高,电极反应为扩散控制的一电子两质子反应。利用差分脉冲伏安法对VB6进行测定,线性范围为0.05~200μmol/L,检出限为0.02μmol/L,相对平均偏差为3.1%(n=8)。本方法可用于测定VB6片和B族维生素片中的VB6含量测定,加标回收率为在96.1%~104.5%之间。     

抗坏血酸在离子液体修饰玻碳电极上的电化学行为

利用离子液体1-丁基-3-甲基咪唑四氟硼酸盐(BMIMBF4)对玻碳电极(GCE)进行修饰,制备了BMI-MBF4/GCE电极.在0.1mol/L的磷酸盐缓冲溶液中,采用循环伏安法研究了抗坏血酸在BMIMBF4/GCE电极和裸玻碳电极(GCE)上的电化学行为.结果表明,pH=5.7的磷酸盐缓冲溶液为最佳测定底液,最佳富集时间为120s;BMIMBF4/GCE对抗坏血酸的氧化反应有很好的电化学催化作用.抗坏血酸的氧化峰电流与其浓度在2.0×10-4～1.0×10-2 mol/L的范围内呈良好的线性关系,相对标准偏差为4.53%(n=5).     

咖啡酸在多壁碳纳米管修饰玻碳电极上的电化学行为及其测定

制备了多壁碳纳米管(MWNT)修饰玻碳电极,并研究了咖啡酸在该电极上的电化学行为及其测定方法,与裸玻碳电极(GCE)相比,MWNT膜修饰电极(MWNT/GCE)能显著提高咖啡酸的氧化峰电流.在pH=3.29的B-R缓冲溶液中,咖啡酸在MWNT/GCE电极上出现1对准可逆的氧化还原峰,Epa=0.47 V,Epc=0.32 V,峰电流与其浓度在5.0×10-7～2.0×10-5 mol/L范围内成线性关系,检出限为5.0×10-7mol/L.实际样品测定的相对标准偏差(RSD)为0.82％(n=5),平均回收率为100.7％.MWNT膜对咖啡酸的电化学氧化有明显的催化作用.该法是一种快捷、可靠、灵敏的检测方法,可以用于咖啡酸含量的测定.     

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。     

Sensitive voltammetric determination of paracetamol by poly (4-vinylpyridine)/multiwalled carbon nanotubes modified glassy carbon electrode

A novel glassy carbon electrode (GCE) modified with a composite film of poly (4-vinylpyridine) (P4VP) and multiwalled carbon nanotubes (P4VP/MWCNT GCE) was used for the voltammetric determination of paracetamol (PCT). This novel electrode displayed a combined effect of P4VP and MWCNT on the electro-oxidation of PCT in a solution of phosphate buffer at pH 7. Hence, conducting properties of P4VP along with the remarkable physical properties of MWCNTs might have combined effects in enhancing the kinetics of PCT oxidation. The P4VP/MWCNT GCE has also demonstrated excellent electrochemical activity toward PCT oxidation compared to that with bare GCE and MWCNT GCE. The anodic peak currents of PCT on the P4VP/MWCNT GCE were about 300 fold higher than that of the non-modified electrodes. By applying differential pulse voltammetry technique under optimized experimental conditions, a good linear ratio of oxidation peak currents and concentrations of PCT over the range of 0.02–450 μM with a limit of detection of 1.69 nM were achieved. This novel electrode was stable for more than 60 days and reproducible responses were obtained at 99% of the initial current of PCT without any influence of physiologically common interferences such as ascorbic acid and uric acid. The application of this electrode to determine PCT in tablets and urine samples was proposed.     

普鲁士蓝/多壁碳纳米管修饰电极测定维生素C

利用电化学方法在多壁碳纳米管修饰的玻碳电极表面聚合一层普鲁士蓝,制备普鲁士蓝/多壁碳纳米管修饰玻碳电极,运用循环伏安法研究了维生素C(vc)在该修饰电极上的电化学行为.该修饰电极对Vc显示出快速的电化学响应和较好的电催化活性,在pH为4.0的磷酸盐溶液中,Ve浓度与其氧化峰电流在8.0×10-4～1.0×10-2 mol/L范围内呈现良好的线性关系,相关系数为0.9993,检测限为6.4×10-5mol/L.该电极具有较好的稳定性和重现性.     

Fabrication of an electrochemical sensor based on the electrodeposition of Pt nanoparticles on multiwalled carbon nanotubes film for voltammetric determination of ceftriaxone in the presence of lidocaine, assisted by factorial-based response-surface methodology

A glassy carbon electrode (GCE) is modified with platinum nanoparticle (PtNPs) decorated multiwalled carbon nanotube (MWCNT). The modified electrode is applied for the determination of ceftriaxone (CFX) in the presence of lidocaine. Different methods were used to characterize the surface morphology of the modified electrode. The electrochemical behavior of CFX was investigated at GCE, MWCNT/GCE and PtNPs/MWCNT/GCE. A factorial-based response-surface methodology was used to find out the optimum conditions with minimum number of experiments. Under the optimized conditions, oxidation peak currents increased linearly with CFX concentration in the range of 0.01–10.00 μM with a detection limit of 9.01 nM. The results prove that the modified electrode is also suitable for the determination of CFX in pharmaceutical and clinical preparations.     

Electrochemical behavior of electrodeposited rutin film on a multi-wall carbon nanotubes modified glassy carbon electrode. Improvement of the electrochemical reversibility and its application as a hydrazine sensor

By immobilizing rutin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWCNT), a new modified electrode has been fabricated and its electrochemical behavior was investigated by cyclic voltammetry. Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple with surface confined characteristics. The results show that the reversibility of rutin is significantly improved at a MWCNT modified GCE in comparison with GCE alone. The charge transfer coefficient, α, was calculated to be 0.4, and charge transfer rate constant, k_s, was 46.7 s⁻¹ in pH 8, indicating great facilitation of the electron transfer between rutin and MWCNT deposited on the electrode surface. The rutin MWCNT (RMWCNT) modified GCE showed excellent mediation of hydrazine oxidation: a decrease in the overvoltage of hydrazine electrooxidation was observed as well as a dramatic increase in the peak current compared to that seen at a rutin modified GCE (RMGCE), activated GCE or bare GCE. Hydrazine was determined amperometrically at the surface of RMWCNT modified GCE in pH 8. Under the optimized conditions the calibration curve is linear in the concentration range 2.0–190.0 μM hydrazine. The detection limit and sensitivity are 0.61 μM and 0.0656 μA μM⁻¹, respectively. Finally the kinetic parameters of the electron transfer coefficient, α, the heterogeneous rate constant of dependent to different potentials, k′(E), and the standard heterogeneous rate constant, k⁰, for oxidation of hydrazine at the RMWCNT surface were determined using various electrochemical methods. The advantages of this modified electrode for hydrazine determination are high sensitivity, excellent catalytic activity, short response time, wide linear range, and high exchange current density.     

Electroanalytical Determination of Estrone in Seawater Samples Using Functionalized Multiwalled Carbon Nanotubes

In this work, a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes functionalized with carboxylic groups (MWCNT−COOH) was used to determine the hormone estrone in seawater samples. Modification of the electrode was optimized using three successive 10-μL aliquots of the MWCNT−COOH dispersion in ethanol (1 : 5 mL). The cyclic voltammetry results showed an oxidation peak at 0.59 V with characteristics of an irreversible process, pH dependent and controlled by adsorption of species. The results of square-wave voltammetry showed that the intensities of peak currents for the MWCNT−COOH/GCE were about 2.5 times higher than for GCE. The calibration curve showed a linearity of 0.9981 and a sensitivity of 0.1521 μA/mol L⁻¹. The limits of detection and quantification were 0.117 and 0.392 μmol L⁻¹, respectively. The recovery obtained using seawater samples was 91%, indicating the applicability of the method in marine environments.     

Electroanalysis of some common pesticides using conducting polymer/multiwalled carbon nanotubes modified glassy carbon electrode

The cyclic voltammetric behaviour of three common pesticides such as isoproturon (ISO), voltage (VOL) and dicofol (DCF) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNTs/GCE), polyaniline (PANI) and polypyrrole (PPY) deposited MWCNT/GCE. The modified electrode film was characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The electroactive behaviour of the pesticides was realized from the cyclic voltammetric studies. The differential pulse voltammetric principle was used to analyze the above-mentioned pesticides using MWCNT/GCE, PANI/MWCNT/GCE and PPY/MWCNT/GCE. Effects of accumulation potential, accumulation time, Initial scan potential, amplitude and pulse width were examined for the optimization of stripping conditions. The PANI/MWCNT/GCE performed well among the three electrode systems and the determination range obtained was 0.01-100 mgL(-1) for ISO, VOL and DCF respectively. The limit of detection (LOD) was 0.1 microgL(-1) for ISO, 0.01 microgL(-1) for VOL and 0.05 microgL(-1) for DCF on PANI/MWCNT/GCE modified system. It is significant to note that the PANI/MWCNT/GCE modified system results in the lowest LOD in comparison with the earlier reports. Suitability of this method for the trace determination of pesticide in spiked samples was also realized.     

Electro-oxidation and determination of antihistamine drug, cetirizine dihydrochloride at glassy carbon electrode modified with multi-walled carbon nanotubes

A multi-walled carbon nanotube (MWCNT) film-modified glassy carbon electrode (GCE) was constructed for the determination of an antihistamine drug, cetirizine dihydrochloride (CTZH) using cyclic voltammetry (CV). Owing to the unique structure and extraordinary properties of MWCNT, the MWCNT film has shown an obvious electrocatalytic activity towards oxidation of CTZH, since it facilitates the electron transfer and significantly enhances the oxidation peak current of CTZH. All experimental parameters have been optimized. Under the optimum conditions, the oxidation peak current was linearly proportional to the concentration of CTZH in the range from 5.0×10(-7) to 1.0×10(-5)M. The detection limit was 7.07×10(-8)M with 180s accumulation. Finally, the proposed sensitive and simple electrochemical method was successfully applied to CTZH determination in pharmaceutical and urine samples.     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT?GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, ??, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4?±?0.5?s^?1 and 0.51, respectively at pH?=?7.0. The obtained results indicate that hydrazine peak potential at OMWCNT?GCE shifted for 14, 109, and 136?mV to negative values as compared with oxadiazole-modified GCE, MWCNT?GCE, and activated GCE surface, respectively. The electron transfer coefficient, ??, and the heterogeneous rate constant, k??, for the oxidation of hydrazine at OMWCNT?GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0???M and 10.0 to 400.0???M and detection limit of 0.17???M for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT?GCE was shown to be successfully applied to determine hydrazine in various water samples.     

Fabrication of an Electrochemical Sensor Based on Multiwalled Carbon Nanotubes for Almotriptan

In the present work, the electrochemical behavior of an antimigraine drug, almotriptan malate (ALM), on a multiwalled carbon nanotube (MWCNT) film modified glassy carbon electrode under cyclic voltammetry was described for the first time. A significant enhancement in the oxidation peak current of ALM was noticed at MWCNT‐GCE. This property was exploited to develop a simple, sensitive and time‐saving differential pulse voltammetric method for the determination of ALM in bulk and pharmaceutical samples. A linear relationship was observed between concentration and peak current with a correlation coefficient of 0.9915 in the range of 0.25–37.5 µM ALM.