Electrochemical determination of nitrite in water samples using a glassy carbon electrode modified with didodecyldimethylammonium bromide

Multiwalled carbon nanotubes were used as solid phase extraction (SPE) adsorbent for the determination of four chloroacetanilide herbicides (alachlor, acetochlor, metolachlor and butachlor) in water. The primary factors that influence the efficiency of the SPE performance, such as the amount of the adsorbent, the eluent solvent, the pH and the sample volume, were investigated and optimized. Under optimized conditions, the recoveries of the four herbicides at three spike levels were in the range 76.7–104.4%, and the RSDs ranged from 2.5–12.7%. Good linearity was obtained for the pesticides in the concentration range 0.0025–2.5 mg L^?1, and the detection limits were 0.01–0.03 μg L^?1 at signal-to-noise ratios of 3:1. The method was successfully applied to the determination of these analytes in tap water and river water.     

Electrochemical determination of lead using bismuth modified glassy carbon electrode

Electrochemical application of bismuth film modified glassy carbon electrode was studied with the objective of lead detection. Bismuth film on glassy carbon substrate was formed in a plating solution of 2 mmol/L Bi(NO₃)₃, in 1 mol/L HCl at ?1.1 V (vs. Ag/AgCl) for 300 s. Lead was detected by differential pulse anodic voltammetry in acetate buffer of pH 5.0 in the concentration range of 7.5 nmol/L to 12.5 μmol/L. Factors influencing the anodic stripping performance, including deposition time, solution pH, Bi(III) concentration, potential, pulse amplitude, pulse width, have been optimized. Three linear calibration plots in the range 7.5 nmol/L to 0.1 μmol/L, 0.25 to 1 μmol/L, 2.5 to 12.5 μmol/L with regression coefficients of 0.991, 0.986 and 0.978 respectively were obtained. The theoretical detection limit equivalent to three times standard deviation for 7.5 nmol/L lead (n = 5) was calculated to be 5.25 nmol/L utilizing a 5 min deposition time and sensitivity 83.97 A L/mol. The sensitivity and detection limit of the method was compared with reported voltammetric methods for detection of lead and the result obtained was found to be promising for determination of lead.     

Electrochemical studies of determination of C.I. Direct Red 80 based on a gold nanoparticles-modified carbon paste electrode

In this paper, a simple, convenient and sensitive electrochemical method has been developed for the determination of C.I. Direct Red 80. A gold nanoparticle modified carbon paste electrode was fabricated and used for study and sensitive determination of Direct Red 80 by cyclic voltammetry and differential pulse voltammetry. The overall analysis involved a two-step procedure: an accumulation step under open-circuit conditions, followed by voltammetric measurements of Direct Red 80 in a 0.1?M phosphate buffer solution at pH?=?3.0. The experimental conditions, such as the medium, pH and accumulation time, were optimised. The oxidation peak current was proportional to the concentration of Direct Red 80 from 5.0?×?10^?8 to 5.0?×?10^?7?M and 5.0?×?10^?7 to 3.0?×?10^?6?M, and the detection limit was 1.15?×?10^?8?M (S/N?=?3). The proposed method was used to detect Direct Red 80 in natural water and sewage with good accuracy.     

Electrochemical determination of malachite green using a multi-wall carbon nanotube modified glassy carbon electrode

A multi-wall carbon nanotube (MWNT) film-modified electrode is described for the determination of malachite green (MG). The electrochemical profile of MG was examined using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), suggesting that the MWNT film facilitates the electron transfer of MG in terms of a potential shift and then significantly enhances the oxidation peak current of MG. The experimental parameters, such as supporting electrolyte, thickness of MWNT film, scan rate and accumulation time, were optimized. Consequently, a sensitive and convenient electrochemical method is proposed for the determination of MG. The oxidation peak current is proportional to the concentration of MG over the range from 5.0 × 10⁻⁸ to 8.0 × 10⁻⁶ mol L⁻¹ obeying the following equation: i_p = 0.09 + 1.19 × 10⁷ C (r = 0.995, i_p in μA, C in mol L⁻¹). The detection limit is 6.0 × 10⁻⁹ mol L⁻¹ (signal to noise = 3) after 5 min of accumulation. Moreover, this method possesses good reproducibility (RSD is 5.6%, n = 8) as well as long-term stability. Finally, the new method was employed to determine MG in fish samples. Correspondence: W. Huang, Department of Chemistry, Hubei Institute for Nationalities, Enshi 445000, P.R. China     

芦丁在纳米金修饰玻碳电极上的电化学行为及其测定

采用循环伏安法将纳米金电沉积于玻碳电极表面,制备了纳米金修饰玻碳电极(NG/GCE).在pH3.29的Britton-Robinson(B-R)缓冲溶液中,用循环伏安法研究了芦丁在NG/GCE上的电化学行为.结果表明,NG/GCE对芦丁的氧化还原反应有良好的电催化作用.用方波伏安法测得芦丁的还原峰电流与其浓度在2.0×10-8～2.0×10-6mol/L范围内呈线性关系,检出限为1.0×10-8mol/L(S/N=3).     

Electrochemical determination of tartaric acid at nano gold/nano carbon modified glassy carbon electrode

Nano gold/nano carbon coating the surface of glassy carbon electrode is prepared. Electrochemical behavior of tartaric acid at nano gold/graphene modified glassy carbon electrode is investigated. A simple, sensitive, and inexpensive method for determination of tartaric acid in drinks is proposed.     

Electrochemical determination of paraquat using a glassy carbon electrode decorated with pillararene-coated nitrogen-doped carbon dots

An electrochemical sensor(carboxylatopillar[5]arene-coated nitrogen-doped carbon dots, namely CCDs)based on carboxylatopillar[5]arene(CP[5]) functionalized nitrogen-doped carbon dots(N-CDs) has been developed in a facile and economic manner. To improve the performance of this electrochemical sensor in pesticide detection, the optimal solution p H(p H 7) and loading amount of CCDs on the electrode(0.50 mg/m L) have been determined. By virtue of the good conductivity of N-CDs and the molecular rec...     

多贝斯在纳米金修饰玻碳电极上的电化学行为与测定

采用循环伏安法将纳米金电沉积于玻碳电极表面,制备了纳米金修饰玻碳电极(NG/GCE).在0.05 mol/L H2SO4溶液中,用循环伏安法研究了多贝斯在NG/GCE上的电化学行为.结果表明,NG/GCE对多贝斯的氧化还原反应有明显的电催化作用.建立了测定多贝斯的新方法,用方波伏安法测得多贝斯的氧化峰电流与其浓度在4....     

黄芩甙在玻碳电极上的电化学行为及其应用

用线性扫描伏安法(LSV)、循环伏安法(CV)和常规脉冲伏安法(NPV)等多种电化学方法研究了黄芩甙在玻碳电极上的电化学行为,并建立了尿样和血清样品中黄芩甙的微分脉冲伏安(DPV)测定法。实验结果表明:黄芩甙在玻碳电极上的吸附符合Frumkin吸附等温式,吸附自由能为-35.01kJ mol。采用整体电解法求得电极反应电子数为2,并结合Nernst方程式推导了反应机理。黄芩甙在玻碳电极上预富集后,在4.20×10-10～1.05×10-5mol L范围内分段呈线性关系,对5.60×10-7mol L黄芩甙溶液连续6次测定的RSD=2.0%,检出限为2.8×10-10mol L。     

Electrochemical determination of acetaminophen using a glassy carbon electrode coated with a single-wall carbon nanotube-dicetyl phosphate film

Single-wall carbon nanotubes (SWNT) were dispersed into water in the presence of dicetyl phosphate (DCP), and then a SWNT-DCP film-coated glassy carbon electrode (GCE) was constructed. The electrochemical behavior of acetaminophen at bare GCE and SWNT-DCP modified GCE were compared, suggesting that the SWNT-DCP-modified GCE significantly enhances the oxidation peak current of acetaminophen. A sensitive and simple electrochemical method with a good linear relationship in the range of 1.0 × 10⁻⁷–2.0 × 10⁻⁵ mol L⁻¹, was developed for the determination of acetaminophen. The detection limit is 4.0 × 10⁻⁸ mol L⁻¹ for 3-min accumulation. This method was successfully demonstrated with tablets.     

Electrochemical determination of nitrite and iodate based on Pt nanoparticles self-assembled on a chitosan modified glassy carbon electrode

A promising electrochemical sensor was fabricated by the self-assembling of Pt nanoparticles (nano-Pts) on a chitosan (CS) modified glassy carbon electrode (GCE). A field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM) and electrochemical techniques were used for characterization of these composites. It has been found that nano-Pts are inserted into the CS layer uniformly, and have a larger surface area compared to the chitosan modified glassy carbon electrode. Electrocatalytic experiments for the oxidation of nitrite and the reduction of iodate have shown that nano-Pts/CS/GCE can decrease the over-potential and increase the faradic current, which can be used for the sensitive determination of nitrite and iodate. Moreover, the prepared modified electrode exhibits good reproducibility and stability, and it is possible that this novel electrochemical sensor can be applied in the sensing and/or biosensing field.     

Electrochemical behavior and determination of clozapine on a glassy carbon electrode modified by electrochemical oxidation.

The adsorptive and electrochemical behaviors of clozapine (CLZ) were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to 1.0 V vs. Ag/AgCl reference electrode. Based on the obtained electrochemical results, an electrochemical-chemical (EC) mechanism was proposed to explain the electrochemical oxidation of CLZ. The resulting electrochemically pretreated glassy carbon electrode (EPGCE) showed good activity to improve the electrochemical response of the drug. CLZ was accumulated in a phosphate buffer (pH 6) at a certain time, and then determined by differential pulse voltammetry. The anodic and cathodic peak currents showed a linear function in the concentration ranges of 0.1 - 1, 1 - 10 and 10 - 100 microM with various accumulation times. The proposed method was successfully used for the determination of CLZ in pharmaceutical preparations. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The recovery levels of the method reached 96% (RSD, 1.8%) and 90% (RSD, 2.8%) for urine and plasma samples, respectively.     

活化玻碳电极伏安法测定锰的研究

采用活化玻碳电极(GC)以伏安法对测定锰进行了研究。结果表明:沉积于电极表面的二氧化锰对锰(Ⅱ)的电化学氧化具有自催化作用,活化GC电极可极大地提高测定锰的灵敏度。在0.04mol LNH3 NH4Cl(pH9.0)底液中,锰浓度在6.0×10-8～1.0×10-5mol L范围内成线性关系,检出限为4.0×10-8mol L。用3×10-7mol L锰溶液重复测定9次,RSD为1.6%。     

Electrochemical determination of nitrite via covalent immobilization of a single-walled carbon nanotubes and single stranded deoxyribonucleic acid nanocomposite on a glassy carbon electrode

A novel method has been developed for determination of nitrite by modifying the surface of a glassy carbon electrode (GCE) using single-walled carbon nanotubes with covalently immobilized single-strand deoxyribonucleic acid. The modified electrodes were characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The results demonstrate that the nanotube-DNA nanocomposite has been successfully immobilized on the surface of the GCE. The new electrode, under optimum conditions at room temperature, exhibits excellent electrocatalytic activity towards the oxidation of nitrite, with a significantly reduction of the overpotential. The linear range for the detection of nitrite is from 0.6 to 540 μM, with a sensitivity of 0.216 μA?μM^?1, and a detection limit as low as 0.15 μM. The electrode showed good reproducibility and high stability and was successfully used to analyze nitrite in water and sausage samples.     

Electrochemical sensor of nitrite based on an inorganic film modified glassy carbon electrode

The electrocatalysis of nitrite in solutions at an inorganic film modified glassy carbon electrode was studied. The modifier was an electrodeposited thin inorganic film of the copper-heptacyanonitrosylferrate (CuHNF). Cyclic voltammetry of the modified electrode in a nitrite solution revealed that both oxidation and reduction of nitrite were catalyzed and the electrocatalytic currents were controlled by the diffusion of nitrite. Voltammetric and amperometric responses were investigated. When applied as an amperometric sensor in a flow injection system, the modified electrode permitted detection at — 0.55 V, over 500 mV lower than at the naked electrode surface. A linear response range extending from 1 × 10^–6 to 1 × 10^–3 M nitrite was obtained, with a detection limit of 3 × 10^–7 M. The relative standard deviation for 50 repetitive injections with a 5 × 10^–5 M nitrite solution was less than 4%. The procedure was applied to the determination of nitrite in saliva and nitrate.