Multiwall Carbon Nanotube‐Ionic Liquid Modified Paste Electrode as an Efficient Sensor for the Determination of Diazepam and Oxazepam in Real Samples

A carbon‐based electrode using multiwall carbon nanotube as a modifier and room temperature ionic liquid as a binder has been applied for the determination of diazepam (DZP) and oxazepam (OZP) in real samples including serum, urine and tablets. Square wave voltammetry as an appropriate electrochemical technique was applied to achieve improved limits of detection and higher sensitivities. The electrochemical studies were investigated under various experimental conditions such as pH, buffer concentration, ionic strength, deposition potential, deposition time and scan rate to achieve higher sensitivities. Linear concentration ranges for DZP and OZP were 0.02–0.76 mg L^?1 and 0.05–1.90 mg L^?1 with the detection limits of 4.1 µg L^?1 and 5.8 µg L^?1, respectively. The proposed method was successfully applied for the analysis of commercially available tablets as well as serum and urine samples and satisfactory results were obtained.     

Electroanalysis of Benazepril Hydrochloride Antihypertensive Drug Using an Ionic Liquid Crystal Modified Carbon Paste Electrode

Electroanalysis of benazepril HCl was successful using a carbon paste electrode modified with an ionic liquid crystal ( 1‐butyl‐1‐methylpiperidinium hexafluorophosphate) in presence of sodium dodecyl sulfate. The electrode performance was compared to ionic liquids (1‐n‐hexyl‐3‐methyl imidazolium tetrafluoroborate and 1‐butyl‐4‐methyl pyridinium tetrafluoroborate). Electrochemical determination of benazepril HCl was in the linear dynamic range of 8.89×10^?7 to 1.77×10^?5 mol L^?1 (correlation coefficient 0.999) and LOD 7.17×10^?9 mol L^?1. benazepril HCl was determined using this sensor in presence of urine metabolites such as uric acid, ascorbic acid. Binary mixtures of dopamine/benazepril and amlodipine/benazepril were also determined successfully.     

室温离子液体六氟磷酸正丁基吡啶修饰碳糊电极的制备与表征

以室温离子液体(RTIL)六氟磷酸正丁基吡啶(BPPF6)代替传统固体石蜡为粘合剂与石墨粉相混合制备了一种新型的离子液体修饰碳糊电极(RTIL/CPE)。优化出制备电极时石墨与BPPF6的比例为3∶1(w/w),采用扫描电子显微镜对其表面形貌进行了表征,以铁氰化钾为电化学探针对RTIL/CPE的电化学行为进行了研究,并与传统石蜡碳糊电极(CPE)进行了比较。结果表明由于BPPF6具有较高的导电性,使RTIL/CPE比CPE具有更高的导电效率,铁氰化钾在电极上的可逆性变好,ΔEp值为64mV,峰电流响应增加3.5倍,电极过程由吸附控制变为扩散控制,根据计时库仑法求解出铁氰化钾的扩散系数为1.39×10-4cm2/s。     

Investigation of the Role of Ionic Liquids in Imparting Electrocatalytic Behavior to Carbon Paste Electrode

In this paper, a survey has been undertaken to clarify the possible reasons for the electrocatalytic activity obtained by the presence of ionic liquid in carbon paste electrode (CPE). For this purpose, the effect of the addition of traces of ionic liquid to conventional CPE was investigated. Fe(CN)₆^3?/4? was used as a probe and two ionic liquids, namely n‐octylpyridinum hexafluorophosphate and 1‐octyl‐3‐methylimidazolium hexaflourophosphate were tested for their electrocatalytic activity. The reasons for this electrocatalytic behavior were evaluated and it was found that different factors such as increase in the ionic conduction of the binder, decrease in the resistance of the modified electrode, increase in ion exchange properties of the electrode and the inherent catalytic activity of ionic liquids are responsible for the considerable improved electrochemical response obtained in the presence of traces of ionic liquid.     

石墨烯/十二烷基硫酸钠复合物修饰碳糊电极测定氯霉素

以液体石蜡和硅油为混合粘合剂,与石墨粉混合制备了碳糊电极基底电极,将石墨烯/十二烷基硫酸钠复合物修饰在基底碳糊电极上,得到了基于石墨烯复合物的新型修饰碳糊电极。应用扫描电镜和循环伏安法分别研究了该电极的表面特性和电化学性质,结果表明,石墨烯和十二烷基硫酸钠修饰的碳糊电极增大了比表面积,有利于电子传递。在pH 3.0的HAc-NaAc缓冲溶液中,该修饰碳糊电极对氯霉素具有良好的电化学响应,氧化峰电位为0.194 V,氧化峰电流是基底碳糊电极的10倍。在最优实验条件下,该氧化峰电流与氯霉素的浓度在1.0×10~(-8)~5.0×10~(-4)mol/L范围内呈良好的线性关系,检出限为5.0×10~(-9)mol/L。该方法简便,重现性及选择性好,用于测定氯霉素滴眼液和虾中氯霉素残留,结果满意。     

土豆汁修饰碳糊电极测定色氨酸的研究

本提出了用于测定色氨酸的土豆汁修饰碳糊电极，该电极选择性好，能有效地消除酪氨酸的干扰，在ｐＨ＝７．４的ＮａＨ２ＰＯ４－ＮａＯＨ生理缓冲液中，电极响应与色氨酸在９．８×１０＾－６～９．８×１０＾－５ｍｏｌ／Ｌ的浓度范围内呈线性关系，最低检出限是１．５×１０＾－６ｍｏｌ／Ｌ．并详细讨论了电极抗干扰能力与测定条件的关系。用该电极测定了实际样品氨基酸注射液中色氨酸的含量，结果与标准值吻合。     

镍纳米粒子-离子液体修饰碳糊电极的制备及其对多巴胺的测定

制备了镍纳米粒子-离子液体修饰电极,在0.1 mol/L磷酸缓冲溶液(pH 6.0)中研究了多巴胺(DA)在修饰电极上的电化学行为.与裸电极相比,DA在该修饰电极上的氧化还原电位明显降低,氧化还原反应的峰电流明显增大,DA的峰电流与其浓度在2.0×10~(-8) ～1.0×10~(-4) mol/L范围内呈良好的线性关系,检出限为6.5×10~(-9) mol/L.该修饰电极对抗坏血酸具有明显的抗干扰能力.     

An Ionic Liquid Bulk-Modified Carbon Paste Electrode and Its Electrocatalytic Activity toward p-Aminophenol

An ionic liquid bulk-modified carbon paste electrode （M-CPE） has been fabricated by using 1-heptyl-3-methylimidazolium bromide as a modifier. Cyclic voltammetry （CV） and differential pulse voltammetry （DPV） were used to evaluate the electrocatalytic activity of the proposed electrode by choosing p-aminophenol （p-AP） as a model compound. Both at a bare carbon paste electrode （CPE） and the M-CPE, p-AP yielded a pair of redox peaks in 0.1 mol·L^-1 phosphate buffer solution （PBS, pH 7.0）. At the CPE, the peak-to-peak potential separation （AEp） was 0.233 V, while at the M-CPE the AEp was decreased to 0.105 V. Furthermore, the current response to p-AP at the M-CPE was 10.2 times of that at the CPE by DPV. The electron transfer rate constant （ks） ofp-AP at the M-CPE was 13.3 times of that at the CPE. Under the optimal condition, a linear dependence of the catalytic current versus p-AP concentration was obtained in the range of 2.0× 10^- 6 to 3.0× 10^- 4 mol·L^-1 with a detection limit of 6.0× 10^-7 mol·L^-1 by DPV. In addition, compared to other modified method the proposed electrode exhibited distinct advantages of simple prapartion, surface renewal, good reproducibility and good stability. It has been used to determine p-AP in simulated wastewater samples.     

Electrochemical Determination of Ascorbic Acid in Room Temperature Ionic Liquid BPPF6 Modified Carbon Paste Electrode

A room temperature ionic liquid N‐butylpyridinium hexafluorophosphate (BPPF₆) was used as a binder to make an ionic liquid modified carbon paste electrode (IL‐CPE), which showed good characteristics such as simple preparation procedure, fast electrochemical response and good conductivity. The electrochemical oxidation of ascorbic acid (AA) on the new IL‐CPE was carefully studied. The oxidation peak potential of AA on the IL‐CPE appeared at 109 mV (vs. SCE), which was about 338 mV decrease of the overpotential compared to that obtained on the traditional carbon paste electrode (CPE) and the oxidation peak current was increased for about four times. The electrochemical parameters of AA on the IL‐CPE were calculated with the charge transfer coefficient (α) and the electrode reaction rate constant (k_s) as 0.87 and 0.800 s^?1, respectively. Based on the relationship of the oxidation peak current and the concentration of AA a sensitive analytical method was established with cyclic voltammetry. The linear range for AA determination was in the range from 1.0×10^?5 to 3.0×10^?3 mol/L with the linear regression equation as I_p (μA)=?2.52–0.064C (μmol/L) (n=13, γ=0.9942) and the detection limit was calculated as 8.0×10^?6 mol/L (3σ). The proposed method was free of the interferences of coexisting substances such as dopamine (DA) and amino acids etc., and successfully applied to the vitamin C tablets determination.     

蒙脱石修饰碳糊电极测定苯酚的研究

本文报道蒙脱石修饰碳糊电极在醋酸盐缓冲溶液(pH=3.6)中,用微分脉冲伏安法测定苯酚。在+0.90 V(vs.Ag/AgCl)有一灵敏的氧化峰,伏安响应要比碳糊电极高得多.对测定苯酚的条件进行了研究,苯酚在0.1～1.0μg/ml范围内呈线性,检出限为40ng/ml,相对标准偏差为6.7％,平均回收率为97.2％。用此方法,不经分离直接测定饮料中的酚。还对苯酚在蒙脱石修饰碳糊电极上的反应机理进行了探讨。     

α-苯偶酰二肟修饰碳糊电极的制备及对合成水样中铜的测定

报道了α苯偶酰二肟修饰碳糊电极的制备及对合成水样中铜的测定，在ｐＨ４．１ 的ＢＲ缓冲溶液中通过在－ １２０Ｖ 电位下富集Ｃｕ２＋后，在－ ０２～＋ ０２Ｖ 电位范围内作阳极溶出伏安法测定。在＋ ００４８Ｖ处有一灵敏的氧化峰，峰电流与Ｃｕ２＋ 浓度在１×１０－ ７～１×１０－ ４ｍ ｏｌ／Ｌ范围内成良好的线性关系，检出限为５×１０－ ８ｍ ｏｌ／Ｌ。     

Voltammetric Determination of Xanthine with a Single‐Walled Carbon Nanotube‐Ionic Liquid Paste Modified Glassy Carbon Electrode

Single‐walled carbon nanotube (SWNT) and room temperature ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium hexaflourophosphate, BMIMPF₆) were used to fabricate paste modified glassy electrode (GCE). It was found that the electrode showed sensitive voltammetric response to xanthine (Xt). The detection limit was 2.0×10^?9 M and the linear range was 5.0×10^?9 to 5.0×10^?6 M. The electrode also displayed good selectivity and repeatability. In the presence of uric acid (UA) and hypoxanthine (Hx) the response of Xt kept almost unchanged. Thus this electrode could find application in the determination of Xt in some real samples. The analytical performance of the BMIMPF₆‐SWNT/GCE was demonstrated for the determination of Xt in human serum and urine samples.     

壳聚糖复合碳纳米管修饰超薄碳糊电极对硝基酚异构体的同时测定

以镍镉合金为基底,将壳聚糖滴涂在碳纳米管修饰的超薄碳糊电极表面制成电化学传感器(CTSCNTs-UTCPE),利用循环伏安法(CV)、半微分伏安法研究硝基酚异构体在该电极上的电化学行为。考察了底液种类、酸碱度、扫描速度、起始电位和富集时间对检测结果的影响。与镍铬合金电极、超薄碳糊电极(UTCPE)和碳纳米管修饰超薄碳糊电极(CNTs-UTCPE)相比,由于壳聚糖和碳纳米管的协同效应,硝基酚异构体在p H 5.72的B-R中氧化电流较高。在最佳条件下,传感器对邻、间、对硝基酚的检测范围分别为4.0×10-7~8.0×10-5mol/L,4.0×10-7~8.0×10-5mol/L,8.0×10-7~8.0×10-5mol/L;检出限(S/N=3)分别为2.3×10-7,2.9×10-7,6.7×10-7mol/L。该传感器显示出良好的稳定性和抗干扰性能,可实现对人工水样中硝基酚异构体的同时检测。     

Fabrication and Application of a Sensitive and Highly Stable Copper Hexacyanoferrate Modified Carbon Ionic Liquid Paste Electrode for Hydrogen Peroxide and Glucose Detection

A three‐factor mixture design and response surface methodology were employed to find the optimal weight ratio of graphite powder, n‐dodecylpyridinium hexafluorophosphate and paraffin for the fabrication of a copper hexacyanoferrate modified carbon ionic liquid paste electrode (CuHCFe‐CILPE). The fabricated sensor showed electrocatalytic activity towards oxidation and reduction of hydrogen peroxide. It also was observed that the electrocatalytic activity for hydrogen peroxide oxidation was much higher than the electrocatalytic activity for hydrogen peroxide reduction. Glucose oxidase was then successfully immobilized on the surface of the proposed sensor to examine the possibility of using CuHCFe‐CILPE for the biosensor fabrication.     

Differential Pulse Adsorptive Stripping Voltammetric Determination of Chlorpyrifos at a Sepiolite Modified Carbon Paste Electrode

Abstract

An adsorptive stripping voltammetric (AdSV) method for the determination of organophosphorus insecticide chlorpyrifos at a bare carbon paste electrode (CPE) and clay modified carbon paste electrode (CMCPE) was developed. A systematic study of various experimental conditions, such as the pH, accumulation variables and composition of a modifier on the adsorptive stripping response, were examined by using differential pulse voltammetry. A significant improvement was observed in the sensitivity by using the present method with CMCPE. When CMCPE was used, a linear response was obtained over the concentration range 0.0001–2.0 ppm with lower detection limit of 0.00008 ppm, at an accumulation time of 80 s. The interference from other herbicides and ions on the stripping signal of the compound was also evaluated. The described method was applied to estimate the chlorpyrifos in environmental samples.     

Carbon Paste Electrode Modified with Biochar for Sensitive Electrochemical Determination of Paraquat

The present work reports for the first time the determination of paraquat (PQ²⁺) by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV) using a carbon paste electrode modified (CPME) with biochar obtained from castor oil cake at different temperatures (200–600 °C). The best voltammetric response was verified using biochar yielded at 400 °C (CPME‐BC400). Linear dynamic range (LDR) for PQ²⁺ concentrations between 3.0×10^?8 and 1.0×10^?6 mol L^?1 and a limit of detection (LOD) of 7.5×10^?9 mol L^?1 were verified. The method was successfully applied for PQ²⁺ quantification in spiked samples of natural water and coconut water.     

Electrochemiluminescent Detection Method for Glyphosate in Soybean on Carbon Fiber-ionic Liquid Paste Electrode

A carbon fiber paste electrode using ionic liquid as the binder (CFILE) was fabricated. The electrochemical characteristics of the electrode was examined in ferro‐/ferricyanide solution and showed better conductivity and reversibility when compared with graphite paste‐ionic liquid electrode (GPILE) and a little better than that on the carbon nanotube paste‐ionic liquid electrode (CNTILE). Glyphosate (GLY), a pesticide, exhibited excellent catalysis to the oxidation of Ru(bpy)²⁺₃ on CFILE and brought an obvious enhancement to the electrochemiluminescence (ECL) intensity of Ru(bpy)²⁺₃. Based on the catalytic ability of GLY, a simple ECL method for GLY detection had been established. Under optimum conditions, the enhanced ECL intensities were found to had linearly respond to the GLY concentration between 3.0×10^?7 and 3.0×10^?5 mol/L, and the detection limit (S/N=3) was 2.0×10^?7 mol/L. The electrode also showed excellent sensitivity in detecting GLY‐spiked soybean samples. The linear range for GLY in soybean samples was 1.0×10^?6–4.0×10^?5 mol/L and the detection limit was 5.0×10^?7 mol/L, equal to 8.45 µg GLY in per gram of soybean. The detection limit in soybean sample was lower than the USA, EU regulation and so on. If the method is coupled with the separation technology, it can be applied to detect the GLY in the contaminated samples.     

Room-Temperature Ionic Liquid and Multi-Walled Carbon Nanotube Composite Modified Carbon-Ceramic Electrode as a Sensitive Voltammetric Sensor for Indomethacin

The electrochemical behavior of indomethacin on the surface of a carbon-ceramic electrode modified with multi-walled carbon nanotubes and an ionic liquid composite film is reported. The results show that the nano-structured film exhibited excellent enhancement effects on the electrochemical oxidation of indomethacin. The developed sensor presented a linear response to indomethacin over the concentration range from 1 to 50 µM with a detection limit of 0.26 µM. The proposed modified electrode was employed for the determination of indomethacin in biological and pharmaceutical samples using differential pulse voltammetry.     

Study on the Attractive Electroanalytical Performance of Carbon‐Ionic Liquid Paste Electrode

Carbon paste electrode made of graphite and ionic liquid n‐octylpyridinum hexafluorophosphate (OPFP) displays many attractive electroanalytical abilities towards lots of species, allowing sensitive, low‐potential, simple, low‐cost, and stable performances. Herein a new hypothesis is proposed to explain the formation of these performances based on the results of electrochemical, scanning electron microscopic and transmission electron microscopic investigations. The mechanical force produces mono‐ or multi‐layered graphene during the grinding process. And the OPFP molecules are prone to combine with the graphene, which cause the avoidance of the agglomeration of the exfoliated flakes. The presence of graphene, which is edge plane characteristic, provides high density of electrochemical reactive sites on the surface of the electrode.     

Carbon Paste Electrode Bulk-Modified with the Conducting Polymer Poly(1,8-Diaminonaphthalene): Application to Lead Determination

Carbon paste electrodes modified with conducting polymers for sensitive and selective determination of lead are presented. A novel method for generating a reproducible polymer-coated electrode surface is developed. We prove that 1,8-diaminonaphthalene (1,8-DAN) mixed with a carbon paste electrode leads to a conducting polymer in acidic medium while, in the same medium, this polymer is known to be non-conducting on platinum electrode. The electrode behaviour of poly(1,8-DAN), electropolymerised into carbon paste, was investigated by cyclic voltammetry in the presence of the ferri-ferrocyanide couple.A carbon paste electrode modified with poly(1,8-DAN) was used to determine Pb²⁺ in aqueous solutions. Pb²⁺ ions were firstly complexed and then electrochemically deposited by a potential step to –0.9V. The accumulated lead after reduction was anodically stripped by differential pulse voltammetry. Different parameters, such as pH of the solution, preconcentration time, and electropolymerisation procedures were studied.For a preconcentration time of ten minutes, the calibration graph was linear from 40 to 2070ngmL^–1 with r²=0.998. The detection limit was found to be 30ngmL^–1, and the relative standard deviation was 6%.