Sensitive voltammetric determination of rutin at an ionic liquid modified carbon paste electrode

An ionic liquid modified carbon paste electrode (IL/CPE) had been fabricated by using hydrophilic ionic liquid 1-amyl-3-methylimidazolium bromide ([AMIM]Br) as a modifier. The IL/CPE was characterized by scanning electron microscope and voltammetry. Electrochemical behavior of rutin at the IL/CPE had been investigated in pH 3.29 Britton-Robinson (B-R) buffer solution by cyclic voltammetry (CV) and square wave voltammetry (SWV). The experimental results suggested that the modified electrode exhibited an electrocatalytic activity toward the redox of rutin. The electron transfer coefficient (α) and the standard rate constant (k_s) of rutin at the modified electrode were calculated. Under the selected conditions, the reduction peak current was linearly dependent on the concentration of rutin in the range of 4.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ (r = 0.9998), with a detection limit of 1.0 × 10⁻⁸ mol L⁻¹ (S/N = 3). The relative standard deviation (R.S.D.) for six times successful determination of 8.0 × 10⁻⁷ mol L⁻¹ rutin was 1.2%. The proposed method was applied to determine rutin in tablet and urine sample. In addition, the IL/CPE exhibited a distinct advantage of simple preparation, surface renewal, good reproducibility and good stability.     

离子液体BMIMPF6修饰碳糊电极电化学测定维生素E

用疏水性离子液体1-丁基-3-甲基咪唑六氟磷酸([BMIM]PF6)作粘合剂制备了离子液体修饰碳糊电极(IL/CPE)。采用循环伏安法(CV)研究了维生素E(vitamin E,VE)的氧化产物生育酚红在IL/CPE和未修饰碳糊电极(CPE)上的电化学行为,结果表明生育酚红在IL/CPE上氧化过程更易于进行,峰电流响应ip也明显增加,表明IL/CPE对生育酚红的氧化还原反应具有良好的电催化作用。同时测定了电极过程的动力学参数:电荷转移系数α=0.8746,扩散系数D=1.65×10-3cm2/s,电极反应速率常数kf=6.64×10-2cm/s。采用方波伏安法(SWV)发现生育酚红氧化峰电流与其浓度在1.53×10-4mol/L～8.39×10-7mol/L范围内呈线性关系,检出限为1.58×10-8mol/L。该法可用于VE实际样品的分析测定。     

Sensitive and rapid determination of nifedipine using polyvinylpyrrolidone-modified carbon paste electrode

A sensitive, rapid and convenient electrochemical method was developed for the determination of nifedipine based on the greatly-increased oxidation signal on polyvinylpyrrolidone (PVP) surface. In pH 7.5 phosphate buffer, an irreversible oxidation peak at 0.75 V was observed for nifedipine. Compared with the unmodified carbon paste electrode (CPE), the PVP-modified CPE remarkably enhanced the oxidation peak current of nifedipine, showing strong signal enhancement effect. The influence of pH value, amount of PVP, accumulation potential and time on the oxidation peak current of nifedipine was studied. The linear range was from 75 nM to 50 μM, and the detection limit was 20 nM. The proposed method was used to determine the content of nifedipine in tablet samples, and the results consisted with the declared values. Moreover, the recovery tests were performed and the value of recovery was over the range from 97.3 to 102.7%.     

Voltamperometric determination of kinetin with a carbon paste modified electrode

The electrochemical behaviour of kinetin (6-furfurylaminopurine) on a carbon paste modified with OV-17 silicone electrode, is studied. The determination of kinetin is possible working in square wave voltammetric techniques, reaching limits of determination of 38.7 ng ml⁻¹. The proposed method was successfully applied to determine the cytokinin in extracts of apples (previously spiked with kinetin) and the obtained results were in accordance with the results obtained with HPLC-UV.     

Direct electrochemistry of single-stranded DNA on an ionic liquid modified carbon paste electrode

Electrochemical oxidation of thermally denatured single-stranded DNA (ssDNA) was studied on a room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (IL-CPE). A distinct oxidation peak appeared at +0.772 V (vs. SCE) on the IL-CPE after preconcentration of ssDNA at +0.35 V for 160 s in pH 7.0 phosphate buffer solution (PBS), which was attributed to the oxidation of guanine residue on the ssDNA molecular structure. The results showed an apparent negative shift of the oxidation peak potential and a great enhancement of the oxidation peak current on the IL-CPE compared with that of CPE. The electrochemical parameters of ssDNA on the IL-CPE were further calculated. Under the selected conditions, a linear calibration curve for ssDNA detection was obtained in the concentration range from 10.0 to 110.0 μg mL⁻¹ with the detection limit of 1.5 μg mL⁻¹(3σ).     

Direct electrochemistry of double stranded DNA on ionic liquid modified carbon paste electrode

The direct electrochemistry of herring sperm double-stranded DNA (dsDNA) on an ionic liquid N-butylpyridinium hexafluorophosphate modified carbon paste electrode was investigated. The cyclic voltammogram showed two irreversible oxidation peaks at 0.868 V and 1.188 V (vs. SCE), which corresponded to the oxidation of guanine and adenine residues, respectively. Compared to the common carbon paste electrode the electrochemical response was greatly improved. The electrochemical behavior of dsDNA on the modified electrode was carefully investigated with the electrochemical parameters were calculated. Under optimal conditions the dsDNA can be directly determined in the concentration range from 50 to 600 μg mL^?1 with a detection limit of 17 μg mL^?1 (3σ).     

Electrochemical determination of paraquat using a DNA-modified carbon ionic liquid electrode

Deoxyribonucleic acid (DNA) was electrochemically deposited on a carbon ionic liquid electrode to give a biosensor with excellent redox activity towards paraquat as shown by cyclic voltammetry and differential pulse voltammetry. Experimental conditions were optimized with respect to sensing paraquat by varying the electrochemical parameters, solution pH, and accumulation time of DNA. Under the optimized conditions, a linear relation exists between the reduction peak current and the concentration of paraquat in the range from 5?×?10^?8 mol L^?1 to 7?×?10^?5 mol L^?1, with a detection limit of 3.6?×?10^?9 mol L^?1. The utility of the method is illustrated by successful analysis of paraquat in spiked real water samples.

Sensitive voltammetric determination of xanthinol nicotinate at a carbon nanotubes-ionic liquid gel modified electrode

The electrochemistry of xanthinol nicotinate(Xan) was studied by cyclic voltammetry at a glassy carbon electrode modified by a gel containing multi-walled carbon nanotubes(MWNTs) and room-temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate(BMTMPF_6).The modified electrode exhibited good promotion to the electrochemical oxidation of Xan and an ultrasensitive electrochemical method was proposed for the determination of Xan.This method was successfully applied to the determination of...     

Simultaneous determination of ascorbic acid,dopamine, and uric acid using a carbon paste electrode modified with multiwalled carbon nanotubes,ionic liquid,and palladium nanoparticles

We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNT) and an ionic liquid (IL). Electrochemical studies revealed an optimized composition of 60 % graphite, 20 % paraffin, 10 % MWCNT and 10 % IL. In a next step, the optimized CPE was modified with palladium nanoparticles (Pd-NPs) by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. It gives three sharp and well separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA), with peak separations of 180 and 200 mV for AA-DA and DA-UA, respectively. The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.6 to 112, 0.1 to 151, and 0.5 to 225 μM, respectively, and with 200, 30 and 150 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. Figure

The CPE was modified with multiwalled carbon nanotubes and an ionic liquid. After optimization the electrode was further modified with palladium nanoparticles. The resulting electrode gives three sharp and well separated oxidation peaks for ascorbic acid, dopamine and uric acid     

Highly sensitive determination of promazine in pharmaceutical and biological samples using a ZnO nanoparticle-modified ionic liquid carbon paste electrode

In this work we describe the first report for the determination of promazine using a nanostructuremodified ionic liquid carbon paste electrode in aqueous solutions. To achieve this goal, a novel modified carbon paste electrode using ZnO nanoparticles and 1-methyl-3-butylimidazolium bromide as a binder(ZnO/NPs/ILs/CPE) was fabricated. The oxidation peak potential of promazine at the surface of the ZnO/NPs/ILs/CPE appeared at 685 m V, which was about 65 m V lower than the oxidation potential at the surface of CPE under similar conditions. Also, the peak current was increased to about 4.0 times higher at the surface of ZnO/NPs/ILs/CPE compared to that of CPE. The linear response range and detection limit were found to be 0.08–450 and 0.04 mmol/L, respectively. The modified electrode was successfully used for the determination of promazine in real samples with satisfactory results.     

Simultaneous determination of ascorbic acid,dopamine, and uric acid using a carbon paste electrode modified with multiwalled carbon nanotubes,ionic liquid,and palladium nanoparticles

We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNT) and an ionic liquid (IL). Electrochemical studies revealed an optimized composition of 60 % graphite, 20 % paraffin, 10 % MWCNT and 10 % IL. In a next step, the optimized CPE was modified with palladium nanoparticles (Pd-NPs) by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. It gives three sharp and well separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA), with peak separations of 180 and 200 mV for AA-DA and DA-UA, respectively. The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.6 to 112, 0.1 to 151, and 0.5 to 225 μM, respectively, and with 200, 30 and 150 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine.

The CPE was modified with multiwalled carbon nanotubes and an ionic liquid. After optimization the electrode was further modified with palladium nanoparticles. The resulting electrode gives three sharp and well separated oxidation peaks for ascorbic acid, dopamine and uric acid

     

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×...     

Silver particle-decorated carbon paste electrode based on ionic liquid for improved determination of nitrite

A simple silver particle-modified carbon paste electrode is proposed for the determination of low concentration levels of nitrite ions. The electrode consists of a carbon powder decorated with silver sub-micrometre particles (AgPs) and a hydrophobic ionic liquid trihexyltetradecylphosphonium chloride as a binder. It has been shown that AgPs exhibit a strong electrocatalytic effect on the nitrite oxidation. For optimal electroanalytical performance the electrode was conditioned via silver oxidation/reduction cycle. The electrode revealed a linear square-wave voltammetric response in a wide examined concentration range of 0.05 to 1.0 mmol L^− 1, limit of detection (LOD) of 3 μmol L^− 1 and excellent repeatability with RSD of 0.3%.     

花旗松素在碳纳米管-离子液体修饰碳糊电极上的电催化氧化及其测定

制备了碳纳米管(MWCNTs)和疏水性离子液体N-丁基吡啶六氟磷酸盐([Bu Py]PF6)复合修饰碳糊电极(MWCNTs-[Bu Py]PF6/CPE),利用循环伏安法研究了花旗松素在MWCNTs-[Bu Py]PF6/CPE上的电化学氧化行为。结果表明,花旗松素在修饰电极上出现一对灵敏、准可逆的氧化还原峰,氧化峰电位Epa=0.60 V,还原峰电位Epc=0.24 V,△Ep=0.46 V,氧化峰电流ipa=3.96μA,还原峰电流ipc=5.03μA,ipa/ipc=0.79,表明MWCNTs-[Bu Py]PF6/CPE对花旗松素具有良好的电催化氧化作用。用差分脉冲伏安法(DPV)测得花旗松素的氧化峰电流ipa与浓度c在1.2×10-5~4.0×10-2g·L-1范围内呈良好线性,检出限为2.2×10-6g·L-1。该法用于水红花子中花旗松素含量的测定,RSD为1.1%~1.5%,加标回收率为97.3%~101.3%。     

对乙酰氨基酚在离子液体修饰碳糊电极上的电化学行为及其测定

用亲水性离子液体1-丁基-3-甲基咪唑四氟硼酸作修饰剂制备了离子液体修饰碳糊电极(IL/CPE).在pH4.78的Britton-Robinison缓冲溶液中,用循环伏安法和方波伏安法研究了对乙酰氨基酚在IL/CPE上的电化学行为.研究表明,IL/CPE对对乙酰氨基酚的氧化还原反应有良好的电催化作用.在方波伏安曲线上,对乙酰氨基酚的氧化电流与其浓度在8.0×10<'-7>～2.0×10<'-4>mol/L范围内呈线性关系,检出限为3.0×10<'-7>mol/L(S/N=3).建立了测定片剂中对乙酰氨基酚含量的新方法.     

Sensitive determination of 4-nitrophenol based on multi-walled carbon nano-tube/ionic liquid/chitosan composite film modified electrode

A composite film modified glassy carbon electrode (GCE) fabricated with spinning coating of multiwalled carbon nano-tube (MWNT) /1-butyl-3-methylimidazolium tetrafluoroborate/chitosan sol was developed for the electrochemical determination of 4-nitrophenol (4-NP). An obvious reduction peak located at about −0.688 V was observed with voltammetric measurements in the potential range from 0.200 V to −1.00 V. Compared with the bare GCE, the reduction peak potential shifted positively and the peak current increased significantly. All experimental parameters for the determination of 4-NP were optimized. It was found that the reduction peak current was proportional to 4-NP concentration in the range from 3.00 × 10⁻⁷ to 2.00 × 10⁻⁵ mol l⁻¹ with the detect limitation of 1.00 × 10⁻⁷ mol l⁻¹ (S/N = 3) after accumulation for 90 s. The proposed method was successfully applied for the determination of trace amounts of 4-NP in lake water.     

Simultaneous determination of catechol and hydroquinone by carbon paste electrode modified with hydrophobic ionic liquid-functionalized SBA-15

Hydrophobic ionic liquid-functionalized SBA-15 modified carbon paste electrode (CPSPE) was fabricated, and its electrochemical performance was investigated by cyclic voltammetry, electrochemical impedance spectra, and chronocoulometry in K₃Fe(CN)₆/K₄Fe(CN)₆ solution. Compared with carbon paste electrode (CPE) and SBA-15 modified carbon paste electrode (CSPE), the electron transfer ability was in the sequence as: CPSPE>CSPE>CPE. Meanwhile, the electrocatalytic activity of CPSPE to catechol and hydroquinone was evaluated by cyclic voltammetry, and then, the linear concentration ranges were obtained by the amperometric detection from 2.0?×?10^-5 to 3.2?×?10^-4 M for catechol and 5.0?×?10^-5 to 5.5?×?10^-4 M for hydroquinone, with the detection limits of 5.0?×?10^-7 and 6.0?×?10^-7 M, respectively. The advantages of both ionic liquids and heterogeneous supports made CPSPE exhibit high electrocatalytic activity towards the redox of catechol and hydroquinone by significantly improving their reversibility and enhancing their peak currents. In addition, the present method was applied to the determination of catechol and hydroquinone in artificial wastewater sample, and the results were satisfactory.     

Electrochemical determination of naproxen in the presence of acetaminophen using a carbon paste electrode modified with activated carbon nanoparticles

In this study, cyclic voltammetry and differential pulse voltammetry were used to determine the electrochemical properties and concentration of naproxen in pharmaceutical formulation and human serum samples by using a carbon paste electrode modified with activated carbon nanoparticles. Optimum conditions were obtained at an electrode with 0.005 g activated carbon nanoparticles in a phosphate buffer solution of pH 6 as a supporting electrolyte. Linear calibration curves were obtained in the range of 0.1–120 μM, and the detection limit of naproxen determined was 0.0234 μM. The modified electrode shows good selectivity for naproxen in the presence of some organic and inorganic interferences and very good precision in real samples. Finally, naproxen was measured in the presence of acetaminophen.     

Electrochemical determination of homocysteine using carbon nanotubes modified paste electrode and isoprenaline as a mediator

Homocysteine (HCy) is an important amino acid containing thiol group and is known as a risk factor in relation to ischemic heart disease and stroke. In this study the electrochemical determination of homocysteine (HCy) has been described using isoprenaline hydrochloride (ISP) as a mediator on multiwall carbon nanotubes modified paste electrode (MWCNTPE). Electrochemical behavior of homocysteine was investigated by cyclic voltarrtmetry and chronoamperometry. The cyclic voltammograms showed that the electrocatalytic oxidation of homocysteine occurs in the presence of ISP on the surface of MWCNTPE at a potential about 640 mV. Also, results showed that the oxidatation peak current of HCy at the modified carbon nanotubes electrode was more than unmodified electrode. The diffusion coefficient and the kinetic parameters including electron transfer coefficient and rate constant of electrocatalytic reaction were determined using electrochemical approaches. Linear sweep voltammetry results showed that electrocatalytic oxidation peak current of HCy had linear dynamic range in the range of 5.0 to 800 μmol L^?1 with a detection limit of 3.3 μmol L^?1 in pH 3.5 (universal buffer).