Voltammetric determination of 2-nitrophenol at a bentonite-modified carbon paste electrode

A bentonite-modified carbon paste electrode has been applied to the determination of 2-nitrophenol by differential pulse voltammmetry. The electrochemical reduction of 2-nitrophenol at –0.8 V is carried out in an artificial sea water-formic acid/sodium formate medium at pH 4. The peak height was found to be dependent on the pH over the range 2–11; the presence of a secondary process was observed in the pH range 8–11. The peak potential showed a dependence on pH, with two linear regions with different slopes. A linear relationship between peak intensity and concentration was obtained in the range 0.07–10 mgl^–1, with a detection limit of 0.03 mg 1^–1 and a coefficient of variation of 1.3% at 5 mg 1^–1. The effects of organic and inorganic species on the 2-nitrophenol determination were studied with a view to testing the resolution of the voltammetric technique. The proposed method has been applied to sea water samples with good results.     

Voltammetric behavior and determination of bismuth on sodium humate modified carbon paste electrode

The preconcentration and voltammetric behavior of Bi^III on a sodium humate modified carbon paste electrode was studied by means of cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The proposed measurement involves an initial nonelectrolytic preconcentration step in which Bi^III is complexed by the surface modifier in a solution of 0.05 M KNO₃-0.0106 M HNO₃ (pH 2.0) and a subsequent electrochemical scan step in which the preconcentrated Bi^III was reduced and then oxidized promptly in supporting electrolyte of 0.5 M HNO₃. The resulting DPSV anodic current was proportional to the concentration of Bi^III ion over the range of 4.78 × 10⁻⁸–1.44 × 10⁻⁵ M. The detection limit was 4.78 × 10⁻⁸ M. The proposed method was used to determine bismuth in various samples. Various factors affecting the electrode behavior were also investigated at the same time.     

Voltammetric study of 2-methyl-4,6-dinitrophenol at a modified carbon paste electrode

The voltammetric behavior of 2-methyl-4,6-dinitrophenol at a modified carbon paste electrode has been studied. Among the modifiers tested, hidepowder was found to give the best results. Cyclic voltammetry and differential pulse voltammetry were used to study the nature of the reaction; the possibility of accumulation of the analyte onto the electrode was studied by differential pulse voltammetry. An irreversible behavior and the adsorption of 2-methyl-4,6-dinitrophenol on the electrode were confirmed. The reduction signal shows two peaks. A linear relationship between the first peak height and the concentration of 2-methyl-4,6-dinitrophenol was obtained in the range 0.001–5 mg l⁻¹, with a detection limit of 3.2 μg l⁻¹ and a relative standard deviation of 3.20%. The interferences with the reduction peak of 2-methyl-4,6-dinitrophenol of several nitro- and chloro-phenols and inorganic species were tested.     

Voltammetric determination of azithromycin at the carbon paste electrode

Azithromycin (AZ) is the first member of a class of macrolide azalides antibiotics called azolides. A simple and selective square-wave voltammetric (SWV) method has been developed for the determination of azithromycin in pure form, in pharmaceutical preparation and in biological samples. Determination of azithromycin was accomplished with hand-make carbon paste electrode (CPE) in oxidative screen mode. The counter and reference electrodes were a Pt wire and a Ag/AgCl, respectively. Various parameters that can influence the peak signal (effect of buffer, ionic strength, accumulation time, pH and the composition of the paste) have been scrutinized. The best results were obtained in acetonitrile—aqueous 1 M sodium acetate-acetic acid buffer (pH 4.6) containing 0.1 M KCl (1:9; v/v) using a 15% paraffin oil CPE. The limits of detection and quantification of the pure drug are 0.463 and 1.544 ppb (with the correlation coefficient, r=0.9785and the standard deviation, S.D.=0.1 (n=5), for the accumulation time of 60 s), respectively. The method was successfully applied to the determination of the drug in urine and two forms of pharmaceutical formulations. Recoveries were 99.2—100.5% with S.D.=0.1—and 0.8% (n=5).     

对乙酰氨基酚在碳纳米管-离子液体糊修饰电极上的电化学行为及分析应用

制备了碳纳米管-离子液体糊修饰电极并用电化学方法对其进行了表征,研究对乙酰氨基酚在碳纳米管-离子液体糊修饰电极上的电化学行为,建立了以碳纳米管-离子液体糊修饰电极测定对乙酰氨基酚(APAP)的灵敏的电化学方法.在优化的实验条件下,对乙酰氨基酚的氧化峰电流与其浓度在1.0×10-7～1.0×10-6 mol/L和1.0×...     

Electrochemical determination of vitamin C in the presence of uric acid by a novel TiO2 nanoparticles modified carbon paste electrode

<正>The electrochemical behavior of vitamin C(ascorbic acid or AA) is investigated on the surface of a carbon-paste electrode modified with TiO_2 nanoparticles and 2,2'-(1,2 butanediylbis(nitriloethylidyne))-bis-hydroquinone(BBNBH).The prepared modified electrode showed an efficient catalytic role in the electrochemical oxidation of AA,leading to remarkable decrease in oxidation overpotential and enhancement of the kinetics of the electrode reaction.This modified electrode exhibits well-separated oxidation peaks for AA and uric acid(UA).The modified electrode is successfully applied for the accurate determination of AA in pharmaceutical preparations.     

Voltammetric sensor for glutathione determination based on ferrocene-modified carbon paste electrode

The electrocatalytic oxidation of glutathione (GSH) has been studied at the surface of ferrocene-modified carbon paste electrode (FMCPE). Cyclic voltammetry (CV), double potential step chronoamperometry, and differential pulse voltammetry (DPV) techniques were used to investigate the suitability of incorporation of ferrocene into FMCPE as a mediator for the electrocatalytic oxidation of GSH in buffered aqueous solution. Results showed that pH 7.00 is the most suitable for this purpose. In the optimum condition (pH 7.00), the electrocatalytic ability of about 480 mV can be found and the heterogeneous rate constant of catalytic reaction was calculated as . Also, the diffusion coefficient of glutathione, D, was found to be 3.61 × 10^–5 cm² s⁻¹. The electrocatalytic oxidation peak current of glutathione at the surface of this modified electrode was linearly dependent on the GSH concentration and the linear analytical curves were obtained in the ranges of 3.2 × 10^–5 M–1.6 × 10^–3 M and 2.2 × 10^–6 M–3.5 × 10^–3 M with cyclic voltammetry and differential pulse voltammetry methods, respectively. The detection limits (3σ) were determined as 1.8 × 10^–5 M and 2.1 × 10^–6 M using CV and DPV, respectively. Finally, the electrocatalytic oxidation of GSH at the surface of this modified electrode can be employed as a new method for the voltammetric determination of glutathione in real samples such as human plasma.     

Voltammetric determination of quercetin at a multi-walled carbon nanotubes paste electrode

Quercetin can effectively accumulate at multi-walled carbon nanotubes-paraffin oil paste electrodes (CNTPE) and cause a sensitive anodic peak at around 0.32 V (vs. SCE) in a 0.10 M phosphate buffer solution (pH = 4.0). Under optimized conditions, the anodic peak current is linear to quercetin concentration in the ranges of 2.0 × 10^− 9−1.0 × 10^− 7 M and 1.0 × 10^− 7−2.0 × 10^− 5 M, and the regression equations are i_p (μA) = 0.0017 + 0.928c (μM, r = 0.999) and i_p (μA) = 0.183 + 0.0731c (μM, r = 0.995), respectively. This paste electrode can be regenerated by repetitively cycling in a blank solution for about 2 min. A 1.0 × 10^− 6 M quercetin solution is measured for 10 times using the same electrode regenerated after every determination, and the relative standard deviation of the peak current is 1.7%. The method has been applied to the determination of quercetin in hydrolysate product of rutin and the recovery is 99.2–102.6%. In comparison with graphite paste electrode, carbon nanotubes-nujol paste electrode and carbon nanotubes casting film modified glassy carbon electrode, the CNTPE gives higher ratio of signal to background current and better defined voltammetric peak.     

碳纳米管-TiO2修饰电极伏安法测定维生素K3

利用碳纳米管、二氧化钛两种纳米材料制成碳纳米管-TiO2复合膜修饰电极,进行了维生素K3电化学行为的研究。维生素K3在碳纳米管-TiO2复合膜修饰电极的电化学响应优于碳纳米管修饰电极,表明前者具有更好的催化作用。通过条件实验的优化,结果表明维生素K3在pH=9.42的氨水-NH4Cl底液中,富集时间为10s,富集电位于-0.60V,扫描速度为0.1V/s时有稳定的灵敏的氧化还原峰。峰电流与维生素K3浓度在3.0×10-6～8.0×10-5mol/L范围内呈良好的线性关系,检出限为5.0×10-7 mol/L。考查了修饰电极的重现性,5次平行测量的RSD为1.78%。该方法用于片剂药品中维生素K3含量的测定,回收率在97.5%～102%之间。     

Voltammetric determination of 2-chlorophenol using a glassy carbon electrode coated with multi-wall carbon nanotube-dicetyl phosphate film

Multi-wall carbon nanotubes (MWNT) were dispersed into water in the presence of dicetyl phosphate (DCP), and MWNT-DCP composite film coated glassy carbon electrodes (GCE) were constructed. The electrochemical properties of 2-chlorophenol at a bare GCE and MWNT-DCP modified GCE were compared. It was found that MWNT-DCP modified GCEs significantly enhance the oxidation peak current of 2-chlorophenol and lowers its oxidation overpotential, suggesting great potential in the sensitive determination of 2-chlorophenol. Finally, a sensitive and simple voltammetric method was developed for the determination of 2-chlorophenol. The oxidation peak current increases linearly with the concentration in the range of 1.0 × 10⁻⁷–2.0 × 10⁻⁵ mol L⁻¹, and the detection limit is 4.0 × 10⁻⁸ mol L⁻¹ for 2 min accumulation. The method was successfully used to determine 2-chlorophenol in waste water samples.     

聚L-丝氨酸修饰电极伏安法测定对乙酰氨基酚

对乙酰氨基粉(扑热息痛)为芳环对位取代的酰氨类药物,有解热、镇痛作用。临床上广泛用于感冒发烧、关节痛、神经痛及偏头痛、癌性痛及手术后止痛[1]。但过多服用对乙酰氨基酚对人体会造成伤害,对消化系统的影响主要表现为恶心、呕吐、压食、出汗、腹痛等症状;对泌尿系统、血液系统、呼吸系统都有影响,还能使对阿司匹灵过敏患者的支气管痉挛加重,严重时会抑制呼吸中枢。因此建立对乙酰氨基酚的灵敏检测方法是非常必要的。当前用于检测对乙酰氨基酚的方法主要有滴定法[2]、分光光度法[3]、高效液相色谱法[4]、毛细管电泳[5]、荧光法[6]以及电…     

Multi-walled carbon nanotube paste electrode for selective voltammetric detection of isoniazid

A multi-walled carbon nanotube paste electrode (MWCPE) is prepared as an electrochemical sensor with high sensitivity and selectivity in responding to isoniazid. The electrochemical oxidation of isoniazid is investigated in buffered solution by cyclic and differential pulse voltammetry. The electrode is shown to be very effective for the detection of isoniazid in the presence of other biological reductant compounds. The electrochemical oxidation of cysteine, due to the high overvoltage, is completely stopped at the surface of MWCPE. The electrode exhibits a very good resolution between the voltammetric peak of isoniazid and the peaks of ascorbic acid (AA) and dopamine (DA). A resolution of more than 450 mV between the anodic peak potentials makes the MWCPE suitable for simultaneous detection of isoniazid in the presence of AA or DA in clinical and pharmaceutical preparations. Differential pulse voltammetry (DPV) is applied as a sensitive method for the determination of isoniazid. The linear range in these determinations is 1 × 10⁻⁶–1 × 10⁻³ M for isoniazid and the detection limit is 5 × 10⁻⁷ M. The electrode was applied to the simultaneous determinations in isoniazid and AA mixtures and also, isoniazid and DA mixture over a wide concentration range. The slope variation for the calibration curves of isoniazid (RSD) was less than 4.5% (based on ten measurements over a period of three months).     

Homogeneous and nanomolar detection of hydrazine by indigocarmine as a mediator at the surface of TiO2 nanoparticles modified carbon paste electrode

The homogeneous electrocatalytic oxidation of hydrazine（HZ） has been studied by indigocarmine（IND） as a mediator at the surface of TiO₂ nanoparticles modified carbon paste electrode（TNMCPE）.Cyclic voltammetry was used to study the electrochemical behavior of IND at different scan rates.The voltammetric response of the modified electrode was linear against the concentration of HZ in the ranges of 3.0×l0^-8-7.0×10⁶ mol/L with differential pulse voltammetry method.The detection limit（3σ） was determined as 27.3 nmol/L.To evaluate the applicability of the proposed method to real samples,the modified CPE was applied to the determination of HZ in water samples.     

Voltammetric sensor for nitrite determination based on its electrocatalytic reduction at the surface of p-duroquinone modified carbon paste electrode

A p-duroquinone (tetramethyl-p-benzoquinone) modified carbon paste electrode (DMCPE) was employed to study the electrocatalytic reduction of nitrite in aqueous solutions using cyclic voltammetry (CV), double potential-step chronoamperometry, and differential pulse voltammetry (DPV). It has found that under an optimum condition (pH 1.00), the reduction of nitrite at the surface of DMCPE occurs at a potential of about 660 mV less negative than that of an unmodified carbon paste electrode (CPE). The catalytic rate constant, k′_h, based on Andrieux and Saveant theoretical model was calculated as for scan rate 10 mV s^-1. Also, the apparent diffusion coefficient, D _app, was found as 2.5 × 10^–10 and 3.61 × 10^–5 cm² s^-1 for p-duroquinone in carbon paste matrix and nitrite in aqueous buffered solution, respectively. The values for αn_α were estimated to be −0.65 and −0.19 for the reduction of nitrite at the surface of DMCPE and CPE, respectively. The electrocatalytic reduction peak currents showed a linear dependence on the nitrite concentration, and a linear analytical curve was obtained in the ranges of 5.0 × 10^–5 M to 8.0 × 10^–3 M and 6.0 × 10^–6 M to 8.0 × 10^–4 M of nitrite concentration with CV and DPV methods, respectively. The detection limits (2σ) were determined as 2.5 × 10^–5 M and 4.3 × 10^–6 M by CV and DPV methods. This method was also applied as a simple, selective and precise method for determination of nitrite in real samples (the weak liquor from the wood and paper factory of Mazandaran province in Iran) by using a standard addition method.     

嵌入式碳纳米管石墨电极测定灯盏花素的研究

制备嵌入式多壁碳纳米管修饰石墨电极,利用循环伏安法(CV)研究灯盏花素在嵌入式多壁碳纳米管修饰石墨电极(ESCFE)上的电化学氧化行为,结果表明,灯盏花素在修饰电极上出现一对明显的准可逆氧化还原峰,峰电位分别为Epa=0.17 V和Epc=0.05 V(△E=0.12 V),峰电流分别为ipa=42.79μA,ipc=...     

Voltammetric determination of nicotinic acid by glassy-carbon electrode modified with multiwall carbon nanotubes

A glassy-carbon electrode modified with a thin film of multiwall carbon nanotubes is used for the determination of nicotinic acid (NA). At the electrode, the latter yields a well-defined and very sensitive oxidation peak at 0.21 V (SCE). Investigation of the electrochemical behavior of NA shows that the electrode significantly enhances the NA oxidation peak current, compared with the non-modified electrode. Based on this, a very sensitive and simple electrochemical method is proposed for the NA determination after the optimization of all experimental parameters. The oxidation peak current is proportional to the NA concentration over the range 2×10⁻⁷ to 4×10⁻⁵ M, and the detection limit is 8×10⁻⁸ M after a 4-min accumulation. The relative standard deviation of 5.4% for the successive determination of 1×10⁻⁶ MNA (n=10) indicates excellent reproducibility. The analysis method is successfully demonstrated using tablet samples. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 2, pp. 190–195. The text was submitted by the author in English.     

Voltammetric determination of catechol using a sonogel carbon electrode modified with nanostructured titanium dioxide

In this study, we investigate highly efficient sonogel carbon electrode (SGC/TiO₂) modified with nanostructured titanium dioxide synthesized via sol-gel method employing surfactant template for tailor-designing the structural properties of TiO₂. The stable SGC/TiO₂ electrode detects catechol, a neurotransmitter, in the presence of ascorbic acid, a common interferent, using cyclic voltammetry. A possible rationale for the stable catechol detection of SGC/TiO₂ electrode is attributed to most likely the adsorption of catechol onto highly porous TiO₂ (surface area of 147 m² g⁻¹ and porosity of 46.2%), and the formation of C₆H₄(OTi)₂ bond between catechol and TiO₂. The catechol absorbed onto TiO₂ rapidly reaches the SGC surface, then is oxidized, involving two electrons (e⁻) and two protons (H⁺). As a result, the surface of TiO₂ acts as an electron-transfer accelerator between the SGC electrode and catechol. In addition to the quantitative and qualitative detection of catechol, the SGC/TiO₂ electrode developed here meets the profitable features of electrode including mechanical stability, physical rigidity, and enhanced catalytic properties.     

聚磺胺嘧啶修饰电极伏安法测定对乙酰氨基酚

利用循环伏安法制备了聚磺胺嘧啶修饰电极, 研究了对乙酰氨基酚在该修饰电极上的电化学行为. 该电极对对乙酰氨基酚有较强的电催化作用. 在pH 9.0的PBS缓冲溶液中, 用循环伏安法和差分脉冲伏安法在该电极上测定了对乙酰氨基酚, 其线性范围分别为4.0×10-6～3.0×10-4 mol/L和2.0×10-7～1.0×10-5 mol/L, 检出限分别为9.0×10-7 mol/L和8.0×10-8 mol/L.     

Voltammetric determination of N-acetylcysteine using a carbon paste electrode modified with copper(II) hexacyanoferrate(III)

The preparation and electrochemical characterization of a carbon paste electrode modified with copper(II) hexacyanoferrate(III) (CuHCF) as well as its behavior as electrocatalyst toward the oxidation of N-acetylcysteine were investigated. The electrochemical behavior of the modified electrode and the electrooxidation of N-acetylcysteine were explored using sweep linear voltammetry. The best voltammetric response was observed for a paste composition of 20% (w/w) copper(II) hexacyanoferrate(III) complex, acetate buffer solution at pH of 6.0 as the electrolyte and scan rate of 10 mV s^− 1. A linear voltammetric response for N-acetylcysteine was obtained in the concentration range from 1.2 × 10^− 4 to 8.3 × 10^− 4 mol L^− 1, with a detection limit of 6.3 × 10^− 5 mol L^− 1. The proposed electrode is useful for the quality control and routine analysis of N-acetylcysteine in pharmaceutical formulations.     

对乙酞氨基酚和色氨酸存在下采用改进的碳纳米管糊电极伏安法测定抗坏血酸(英文)

A carbon paste electrode (CPE) modified with carbon nanotubes and 5‐amino‐3’,4’‐dimethyl‐ bi‐ phenyl‐2‐ol (5ADB) is prepared. Under the optimum pH of 7.0, the oxidation of ascorbic acid (AA) on the modified CPE occurs at a potential about 280 mV less positive than that on the unmodified CPE. Some kinetic and thermodynamic parameters for electrocatalytic oxidation of AA, including electron transfer coefficient (α = 0.58) and diffusion coefficient (D = 2.2 × 10-6 cm2/s), are also determined. AA, acetaminophen (AC), and tryptophan (TRP) were detected simultaneously using the modified CPE. The peak potentials recorded using the modified CPE in phosphate‐buffered solution at pH 7.0 were 265, 465, and 780 mV for AA, AC, and TRP, respectively. The modified CPE was successfully used to determine the concentrations of AA, AC, and TRP in real samples.