A New Sensor for Simultaneous Determination of Tyrosine and Dopamine Using Iron(III) Doped Zeolite Modified Carbon Paste Electrode

A new chemically modified electrode is constructed based on iron(III) doped zeolite modified carbon paste electrode (Fe³⁺Y/ZMCPE). The new sensor could be used for the simultaneous determination of the biologically important compounds dopamine (DA) and tyrosine (Tyr). The measurements are carried out using differential pulse voltammetric (DPV) method. The prepared modified electrode shows voltammetric responses of high sensitivity, selectivity and stability for DA and Tyr under optimal conditions, which makes it a suitable sensor for simultaneous trace detection of DA and Tyr in solution. Application of the DPV method demonstrates that in the Briton Robinson buffer solutions (pH=5) containing 50 µmol/L Tyr, there is a linear relationship between the oxidation peaks and the concentrations of DA over the range of 0.1–200 µmol/L, with a detection limit of 0.05 µmol/L (S/N=3). For Tyr a linear correlation between oxidation peak current and concentration of Tyr over the range of 0.5–200 µmol/L (containing 50 µmol/L DA), with a detection limit of 0.08 µmol/L is obtained. The analytical performances of this sensor are evaluated for the detection of DA and Tyr in human serum and a medicine.     

碳糊电极和化学修饰碳糊电极的制备及性能综述

碳糊电极在电化学研究中起着非常重要的作用．从电极材料选用和修饰剂选择方面综述了碳糊电极和化学修饰碳糊电极制备的几种方法,分析了碳糊电极和化学修饰碳糊电极制备技术存在的主要问题及其原因,评价了碳糊电极和化学修饰碳糊电极的表征技术、性能以及影响电极性能的因素．概括了近年来本课题组在碳糊电极研究中的一些结果．     

Determination of Arsenic(III) at a Nanogold Modified Solid Carbon Paste Electrode

A selective and sensitive electroanalytical method was developed for arsenic determination based on a nanogold (AuNP) modified solid carbon paste working electrode (SCPE) modified in two steps (i) physisorption and (ii) additional electrodeposition of nanogold particles in the presence of iodide. Copper(II) interference was solved by covering the gold layer by a self assembled mono layer (SAM) of glutathione. Using DPASV a linear response of the signal was obtained as a function of As(III) in the concentration range 0.05–20 µM (4–1498 ppb) with a limit of detection of 0.01 µM (0.9 ppb). Sample stirring and degassing were not needed. Application to the determination of arsenic(III) and (V) in underground water samples from Burkina Faso was successfully achieved.     

Cu(II) Hexacyanoferrate(III) Modified Carbon Paste Electrode; Application for Electrocatalytic Detection of Nitrite

Copper hexacyanoferrate (CuHCF) film‐modified carbon paste electrode (CPE) has been prepared from various electrolytic aqueous solutions using consecutive cyclic voltammetry. The cyclic voltammograms showed the direct deposition of CuHCF films from the mixing of Cu²⁺ and Fe(CN)₆^3? ions and each time with one of the six cations: H⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, and Al³⁺. The CuHCF film showed a single redox couple that exhibited a cation effect (Na⁺, K⁺, Mg²⁺, and NH₄⁺) and anion effect (Cl^?, NO₃^?, SO₄^2?, ClO₄^?, and BrO₃^?) in the cyclic voltammograms. Voltammetric studies have indicated that in presence of nitrite, the cathodic peak current of CuHCF increases, followed by a decrease in the corresponding anodic current. This indicated that nitrite was reduced by the redox mediator immobilized on the electrode surface via an electrocatalytic mechanism. The process of reduction and its kinetics were investigated by using cyclic voltammetry, differential pulse voltammetry, chronoamperometry and chronocoulometry techniques. The electrocatalytic ability about 800 mV can be seen. The rate constant of the catalytic reduction of nitrite was found to be 7.9×10⁵ cm³ mol^?1 s^?1. Linearity range obtained was 5×10^?5?8.4×10^?3 by cyclic voltammetry and 8×10^?6?1.3×10^?3 and 4×10^?3?2×10^?2 by differential pulse voltammetry.     

嵌入式超薄微晶纤维素/碳糊电极的构建及应用

以镍铬合金为基体,在其表面通过直接嵌入微晶纤维素修饰的碳糊膜,构建了嵌入式超薄微晶纤维素/碳糊电极(ISM/CPE). 用扫描电子显微镜和循环伏安法表征了电极的特性;以抗坏血酸(AA)为目标物考察其在该电极上的电化学行为. 结果表明,在ISM/CPE上,AA的氧化峰电位为0.38 V,较传统碳糊电极负移了0.05 V;峰电流与AA的浓度在1.0×10-6～1.0×10-3 mol/L范围内呈良好线性关系,相关系数r=0.999 3,检测限(S/N=3)为7.5×10-7 mol/L. 表明合金表面嵌入的超薄微晶纤维素/碳糊膜,改变了基体电极的电化学性质,可用于实际样品中AA的测定.     

利眠宁汞修饰碳糊电极的制作及应用

以利眠宁与硝酸汞配合比为2∶1的配位化合物作为电活性物质,研制了利眠宁 汞修饰碳糊电极,得到了良好的电极响应曲线,响应斜率为28.8mV/pc,线性范围达4个数量级,检出限为1.0×10-5mol/L。十多种常见无机离子与一些有机物对电极基本无干扰。可采用直接电位法测定市售利眠宁片含量。     

Poly(allylamine hydrochloride) Functionalized Multiwalled Carbon Nanotube Modified Carbon Paste Electrode as Acetylcholinesterase Biosensor Transducer

In this work, a sensitive, practical and reliable acetylthiocholine (ATCh) biosensor based on poly(allylamine hydrochloride) functionalized multiwalled carbon nanotube (PAH/MWCNT) was fabricated and used for pesticide detection. As far as we know, this is the first work that constitutes the usage of PAH and MWCNT for ATCh biosensor. The developed system was characterized by using scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The influence of parameters such as enzyme amount and pH were examined and a linearity between 5×10^?5 M?2.0×10^?3 M for ATCh was obtained. The proposed biosensor was applied for a model pesticide, monocrotophos, detection. The analytical curve showed an excellent linearity in the monocrotophos concentration range of 1–25 pg/mL with an incubation time of 5 min. Limit of detection and limit of quantification values were calculated as 0.88 and 2.9 pg/mL, respectively. The system was also applied for detection of monocrotophos in grape, tomatoe, tap and mineralized water samples and promising recovery values were obtained.     

Electrocatalytic Reduction of Dioxygen at Carbon Paste Electrode Modified with a Novel Cobalt(III) Schiff's Base Complex

A carbon paste modified electrode with a new cobalt(III) Schiff's base complex (CPME) and its application to electrocatalytic activity for dioxygen reduction is developed. The electrochemical behavior and stability of the CPME as well as the two‐electron reduction of O₂ at the electrode were investigated using cyclic voltammetry, chronoamperometry and rotating disk electrode methods. At the CPME, the reduction of dioxygen to hydrogen peroxide occurs at potentials where it is not observed at a bare carbon paste electrode. The CPME exhibited potent and persistent electrocatalysis for O₂ reduction in acetate buffer solutions of pH 4.0 with an overpotential of about 800 mV lower than unmodified CPE and drastic increase in the peak current. The heterogeneous rate constant for the reduction of O₂ at the surface of CPME was determined by hydrodynamic voltammetry using the Koutecky–Levich plot. A possible catalytic mechanism is proposed and discussed.     

Carbon Paste Electrode Modified with Functionalized Nanoporous Silica Gel as a New Sensor for Determination of Silver Ion

A new dipyridyl‐functionalized silica gel (DPSG) was synthesized. The potentiometric response of silver ion was investigated at a carbon paste electrode chemically modified with functionalized nanoporous silica gel. The electrodes with a DPSG proportions of 10.1% (w/w), showed very stable potential. Calibration plots with Nernstian slopes for Ag⁺ were observed, 58.7 (±0.9) mV decade^?1, over a wide linear range of concentration (5.0×10^?7 to 1.0×10^?1 M). The electrode has a detection limit of 1.0×10^?7 M. The selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode has fast response time, high performance, high sensitivity in wide cation activity ranges, and good long term stability (more than 6 months). The method was satisfactory and used to determine the concentration of silver ion in waste waters contaminated by this metal.     

5-氟脲嘧啶碳糊修饰电极的研制及应用

以５－氟脲嘧啶离子与汞离子的配合比为１∶２ 的配位化合物作为电活性物质，首次研制了５－氟脲嘧啶碳糊修饰电极。得到了良好的电极响应曲线，响应斜率为３４．８ ｍ Ｖ／ｐｃ，线性范围达４ 个数量级，检出限为１０－ ５ｍ ｏｌ／Ｌ。在适宜的酸度范围Ｈ＋ 对电极无干扰。十多种常见无机离子与一些嘧啶类离子对电极基本无干扰。电极稳定性较好，响应时间＜ ５ ｍ ｉｎ，寿命至少为６ 个月。可采用直接电位法和回收试验测定商业药品。     

新型超支化聚合物修饰碳糊电极的制备及应用

制备了超支化聚(胺-酯)化学修饰碳糊电极,研究了Cu2+在修饰电极上的电化学行为.在0.25 mol/L KCl溶液(pH 4.0)中, Cu2+与超支化聚(胺-酯)形成电化学包络物,分别于0.27和0.06 V处产生一对灵敏的氧化还原峰,具有明显的催化还原增敏作用.研究了超支化聚合物结构和代数对电极性能的影响.实验表明: 5代超支化聚合物修饰电极性能最好.建立了线性扫描伏安法测定痕量铜的方法,线性范围1.0×10-8 ～ 3.0×10-5 mol/L;检出限为4.0×10-9 mol/L. 用于人发样品的测定,获得满意结果.     

ssDNA/十八酸修饰碳糊电极的制备及伏安法表征

将石墨粉与十八酸在80 ℃下混合制成表面富含—COOH的基底碳糊电极(SA/CPE), 然后在活化剂N-羟基琥珀酰亚胺(NHS)和1-乙基-3-(3-二甲基氨丙基)碳二亚胺盐酸盐(EDC)存在下将ssDNA固定到电极表面制备ssDNA修饰电极(ssDNA/SA/CPE). 以亚甲基蓝(MB)为指示剂, 用循环伏安法对SA/CPE和ssDNA/SA/CPE进行电化学表征, 发现其在ssDNA/SA/CPE上较在SA/CPE上的氧化峰电流(i_pa)和还原峰电流(i_pc)分别增大1.9倍和1.7倍, 式电势(E_f)负移8 mV. 把ssDNA/SA/CPE放在互补ssDNA溶液中杂交后, MB的i_pa 和i_pc较在SA/CPE上分别增大1.0倍和0.8倍, E_f负移18 mV. 用0.5 mol/L 的NaOH溶液冲洗使电极表面杂交而成的dsDNA变性洗脱, MB的伏安信号几乎与在ssDNA/SA/CPE上一样. i_pc与SA/CPE上固定的ssDNA质量在1.0×10^－7～5.0×10^－6 g范围内成线性关系, 检测限为2.0×10^－9 g (S/N＝3). 这种既廉价又灵敏的电化学生物传感器有望在转基因植物产品检测研究中得到应用.     

Coal as a New Carbon Paste Electrode Modifier with Sorption Properties

A new type of carbon paste electrode modified with subbituminous and bituminous coal is presented. The operability of the coal carbon paste electrode with respect to the working potential window attainable was tested in various electrolytes. Cyclic voltammetry of the reference redox system [Fe(CN)₆]^3?/4? was performed to evaluate electron transfer kinetics. Open‐circuit sorption of Cd(II), Pb(II), and Cu(II) with subsequent anodic stripping voltammetry was used to pilot coal sorption ability. The coal modified carbon paste electrode was also examined as a support for mercury film deposition and anodic stripping voltammetry of metals.     

A Novel Modified Carbon Paste Electrode for Potentiometric Determination of Mercury(II) Ion

A new modified carbon paste electrode (CPE) based on a recently synthesized ligand of Ethyl‐2‐(benzoylamino)‐3‐(2‐hydroxy‐4‐methoxyphenyl)‐2‐propenoate (EBHMP) as a suitable carrier for Hg²⁺ ion was described. The electrode exhibit a super Nernstian slope of 48.5±1.0 mV per decade for Hg²⁺ ion over a wide concentration range from 3.0×10^?7–3.1×10^?2 M. The lower detection limits are 1.0×10^?7 M Hg²⁺. The electrode has a fast response time (ca. 5 s), a satisfactory reproducibility and relatively long life time. The proposed sensor shows a fairly good selectivity toward Hg²⁺ ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 1.0–4.0. The proposed electrode was used as an indicator electrode in potentiometric titration of mercuric ion with standard solution of EDTA. The direct determination of mercury in spiked wastewater and an amalgam sample gave results that compare favorably with those obtained by the cold vapor atomic absorption spectrometric method.     

Catalytic Determination of Perchlorate Using a Modified Carbon Paste Electrode

Abstract

A method for the catalytic voltammetric determination of perchlorate using a carbon paste electrode modified with a liquid anion exchanger is presented. The fundamental catalytic effect is based on the chemical reoxidation of electrochemically generated Tl(O) by perchlorate which can be monitored by an increase of the corresponding current flow. Perchlorate can be preconcentrated, together with tetrachlorothallate(III) as a catalyst, from hydrochloric acid solutions onto the modified carbon paste electrode under open circuit conditions. For analytical purposes, the increase of the current response for the reoxidation of Tl(O) to Tl(I) is exploited for quantifications. Methodical parameters such as pH, ionic strength of the media, preconcentration time and thallium concentration are investigated; the influence of interferents is studied. The dependence of the current increase on the concentration of perchlorate with different accumulation times is presented. The detection limit (3σ) is 50 μg˙l^?1 ClO₄ ^? (12 min accumulation). To show the applicability of the method to the analysis of real samples spiked drinking water was investigated.     

Anodic Stripping Voltammetric Determination of Iron(II) at a Carbon Paste Electrode Modified with Dithiodianiline (DTDA) and Gold Nanoparticles (GNP)

A differential pulse anodic stripping voltammetric procedure was developed for the determination of trace amounts of iron(II) in the presence of iron(III) at a carbon paste electrode (CPE) modified with dithiodianiline and gold nanoparticle. At the pH working of 3.0, a wide concentration range from 0.1 nM to 100 nM was observed with the detection limit of 0.05 nM. The relative standard deviation for a solution containing 50 nM of iron(II) was found to be 3.11 % (n=9). Possible interferences from the coexisting ions were also investigated. The validity of the method and applicability of the sensor were successfully tested by determining of iron(II) in lentil, wheat seed and barley seed samples.     

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。     

Ruthenium Hexacyanoferrate (III) Modified Glassy Carbon Electrode for Determination of Captopril

A glassy carbon electrode modified with a ruthenium (III) hexacyanoferrate film was investigated for the determination of captopril in pharmaceutical formulations. The RuOHCF film was deposited on the surface of the electrode after applying 50 successive cycles and subsequent stabilization in a mixture of NaNO₃ 0.50 mol L^?1+HCl 0.050 mol L^?1 used as supporting electrolyte. The main processes responsible for the redox electrode response are attributed to the system Ru^II/Ru^III/Ru^IV, and appeared at ?0.080, 0.86 and 1.01 V (vs. SCE). The redox process at ?0.080 V was selected for the determination of captopril in the present study, once it provided higher sensibility and occurs in a lower potential than the other ones which can prevent interferences. The experimental parameters used in the determination of the analyte, using differential pulse voltammetry were optimized: pulse amplitude: 50 mV, scan rate: 5 mV s^?1 and potential window: ?0.5 to 0.2 V (vs. SCE). The analytical application of the sensor in real samples demonstrated a linear range between 0.060 and 0.80 µmol L^?1 (r=0.998) with a detection limit of 0.047 µmol L^?1. A mechanism based on co‐precipitation of captopril and the Ru (III) complex in the film is presented once the signal of the Ru^II/III redox couple decreases with increasing the analyte concentration. Recoveries of 99 to 100 % were achieved in pharmaceutical samples and the proposed procedure agreed with the HPLC official method within 95 % confidence level, according to the t‐Student test.