Simultaneous determination of dopamine and ascorbic acid on poly (3,4-ethylenedioxythiophene) modified glassy carbon electrode

Detection of dopamine (DA) in the presence of excess of ascorbic acid (AA) has been demonstrated using a conducting polymer matrix, poly (3,4-ethylenedioxythiophene) (PEDOT) film in neutral buffer (PBS 7.4) solution. The PEDOT film was deposited on a glassy carbon electrode by electropolymerization of EDOT from acetonitrile solution. Atomic force microscopy studies revealed that the electrodeposited film was found to be approximately 100 nm thick with a roughness factor of 2.6 nm. Voltammetric studies have shown catalytic oxidation of DA and AA on PEDOT modified electrode and can afford a peak potential separation of ∼0.2 V. It is speculated that the cationic PEDOT film interacts with the negatively charged ascorbate anion through favorable electrostatic interaction, which results in pre-concentration at a less anodic value. The positively charged DA tends to interact with the hydrophobic regions of PEDOT film through hydrophobic–hydrophobic interaction thus resulting in favorable adsorption on the polymer matrix. Further enhancement in sensitivity to micro molar level oxidation current for DA/AA oxidation was achieved by square wave voltammetry (SWV) which can detect DA at its low concentration of 1 μM in the presence of 1000 times higher concentration of AA (1 mM). Thus the PEDOT modified electrode exhibited a stable and sensitive response to DA in the presence of AA interference.     

Simultaneous determination of ascorbic acid,dopamine, uric acid and tryptophan on gold nanoparticles/overoxidized-polyimidazole composite modified glassy carbon electrode

A novel electrode was developed through electrodepositing gold nanoparticles (GNPs) on overoxidized-polyimidazole (PImox) film modified glassy carbon electrode (GCE). The combination of GNPs and the PImox film endowed the GNPs/PImox/GCE with good biological compatibility, high selectivity and sensitivity and excellent electrochemical catalytic activities towards ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp). In the fourfold co-existence system, the peak separations between AA–DA, DA–UA and UA–Trp were large up to 186, 165 and 285 mV, respectively. The calibration curves for AA, DA and UA were obtained in the range of 210.0–1010.0 μM, 5.0–268.0 μM and 6.0–486.0 μM with detection limits (S/N = 3) of 2.0 μM, 0.08 μM and 0.5 μM, respectively. Two linear calibrations for Trp were obtained over ranges of 3.0–34.0 μM and 84.0–464.0 μM with detection limit (S/N = 3) of 0.7 μM. In addition, the modified electrode was applied to detect AA, DA, UA and Trp in samples using standard addition method with satisfactory results.     

Exploiting micellar environment for simultaneous electrochemical determination of ascorbic acid and dopamine

A simple and reliable method for simultaneous electrochemical determination of ascorbic acid (AA) and dopamine (DA) is presented in this work. It was based on the use of the cationic surfactant cetylpyridinium chloride (CPC) that enables the separation of the oxidation peaks potential of AA and DA. Cyclic voltammetry (CV) as well as pulse differential voltammetry (PDV) were used in order to verify the voltammetric behaviour in micellar media. In the cationic surfactant CPC, a remarkable electrostatic interaction is established with negatively charged AA, as a consequence, the oxidation peak potential shifted toward less positive potential and the peak current increased. On the other hand, the positively charged DA is repelled from the electrode surface and the oxidation peak potential shifts toward more positive potential in comparison to the bare electrode. Therefore, the common overlapped oxidation peaks of AA and DA can be circumventing by using CPC. Parameter that affects the E_pa and I_pa such as CPC concentration and pH were studied. Under optimised conditions, the method presented a linear response to AA and DA in the concentration range from 5 to 75 μmol L⁻¹ and 10 to 100 μmol L⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of AA and DA in dopamine hydrochloride injection (DHI) samples spiked with AA.     

Electrochemical behavior of dopamine at a quercetin-SAM-modified gold electrode and analytical application

A stable quercetin–thioglycolic acid-modified gold electrode (Qu–TCA/Au) was prepared as a self-assembled monolayer (SAM) and its electrochemical behavior was investigated by electrochemical methods. In 0.05-M phosphate buffer solution (pH 7.0) quercetin exhibits quasi-reversible signals at the Qu–TCA/Au electrode. The stability of the quercetin-modified gold electrode is very good. The quercetin self-assembled monolayer is an effective mediator for the oxidation of dopamine, which was investigated by cyclic voltammetry and differential pulse voltammetry. Ascorbic acid does not interfere with determination of dopamine at an electrode modified with a mixture of quercetin–thioglycolic acid and quercetin–11-mercaptoundecanoic acid. This modification allows dopamine to be determined in the presence of ascorbic acid in the range from 3×10^–5 to 3×10^–4 M. The detection limit is 1×10^–6 M. Scanning electrochemical microscopy (SECM) was employed to study the electrochemical performances of the modified gold electrode indicating different feedback modes at differently modified surfaces.     

维生素B6在纳米金/石墨烯修饰电极上的电化学行为

将金纳米粒子电沉积在石墨烯修饰的玻碳电极表面,研究了维生素B6(VB6)在该修饰电极上的电化学行为。扫描电镜用于该修饰电极组装过程的形貌表征。实验结果表明:VB6在此修饰电极上出现一个良好的氧化峰,在最佳实验条件下,其氧化峰电流与VB6浓度在5.0×10-8～2.0×10-5 mol/L范围内呈线性关系,其线性回归方程为I(μA)=0.5697c(μmol/L)+0.06275,R=0.9992,检出限为2.0×10-8 mol/L(S/N=3)。一些常见的干扰物质如抗坏血酸不干扰VB6的检测。方法已用于片剂中VB6的含量的检测。     

Sodium dodecyl sulfate modified carbon nanotubes paste electrode as a novel sensor for the simultaneous determination of dopamine,ascorbic acid,and uric acid

A novel modified multiwall carbon nanotubes paste electrode with sodium dodecyl sulfate as a surfactant (SDS) has been fabricated through an electrochemical oxidation procedure and was used to electrochemically detect dopamine (DA), ascorbic acid (AA), uric acid (UA), and their mixture by cyclic voltammetry (CV) and differential voltammetry (DPV) methods. Several factors affecting the electrocatalytic activity of the hybrid material, such as the effect of pH, of the scan rate and of the concentration were studied. The bare carbon nanotubes paste electrode (BCNTPE) and SDS-modified carbon nanotubes paste electrode (SDSMCNTPE) were characterized using Field Emission Scanning Electron Microscopy (FESEM) and Energy-Dispersive X-ray spectroscopy (EDX). Using the CV procedure, a linear analytical curve was observed in the 1 × 10⁻⁶–2.8 × 10⁻⁵ M range with a detection limit at 3.3 × 10⁻⁷ M in pH 6.5, 0.2 M phosphate buffer solutions (PBS).     

Simultaneous determination of dopamine, ascorbic acid and uric acid at poly (Evans Blue) modified glassy carbon electrode

A sensitive and selective electrochemical method for the determination of dopamine using an Evans Blue polymer film modified on glassy carbon electrode was developed. The Evans blue polymer film modified electrode shows excellent electrocatalytic activity toward the oxidation of dopamine in phosphate buffer solution (pH 4.5). The linear range of 1.0 x 10(-6)-3.0 x 10(-5) M and detection limit of 2.5 x 10(-7) M were observed in pH 4.5 phosphate buffer solutions. The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid and uric acid. The separation of the oxidation peak potentials for dopamine-ascorbic acid and dopamine-uric acid were about 182 mV and 180 mV, respectively. The differences are large enough to determine AA, DA and UA individually and simultaneously. This work provides a simple and easy approach to selectively detect dopamine in the presence of ascorbic acid and uric acid in physiological samples.     

多巴胺在DTNB自组装膜上的电催化研究

在金电极表面制备了DTNB(5,5′ Di thiobis(2 nitrobenzoicacid))自组装单分子层膜(DTNB/AuSAM)。多巴胺在DTNB自组装膜上有一对可逆性良好的氧化还原峰,其氧化峰电流与多巴胺的浓度在5.0×10-6mol/L～1.0×10-4mol/L的范围内呈线性关系,检出限为1.0×10-6mol/L。在pH3.5的缓冲溶液中,在DTNB自组装膜上多巴胺和抗坏血酸的电化学响应可以明显区分,氧化峰电位分离达276mV。可用于抗坏血酸存在下多巴胺的检测。测定了盐酸多巴胺注射液中多巴胺的含量,其平均回收率为104%。     

聚L-酪氨酸修饰电极的制备及对多巴胺的测定

用循环伏安法制备了聚L 酪氨酸修饰玻碳电极,研究了多巴胺在聚L 酪氨酸修饰电极上的电化学行为,建立了循环伏安法测定痕量多巴胺的新方法。多巴胺在pH7.0的磷酸盐缓冲溶液中,在聚L 酪氨酸修饰玻碳电极上产生一对灵敏的氧化还原峰,峰电位分别为Epa=189mV,Epc=131mV。循环伏安法测定多巴胺的线性范围为1.0×10-3～1.0×10-8mol/L,检出限:1.0×10-9mol/L。方法可用于药剂中多巴胺的测定。     

聚邻氨基对酚磺酸修饰电极测定尿酸

尿酸(UA)是核蛋白和核酸的代谢产物,人体内尿酸的水平与肝脏疾患[1]、肾病[2]以及心血管疾病[3]等有着密切的关系.因此,对人体体液中尿酸的定量分析无论在药物控制方面还是在临床诊断方面都具有重要意义.     

肉桂酸修饰电极同时测定多巴胺和抗坏血酸的研究

用电化学聚合方法制备肉桂酸(CA)修饰的玻碳电极(PCA/GC),研究多巴胺(DA)和抗坏血酸(AA)在修饰电极上的电化学行为.结果表明,在DA和AA共存体系中,DA、AA在PCA/GC电极上氧化峰电流增大且氧化峰电位相差200 mV,据此可同时检测DA和AA.在pH 7.0磷酸盐缓冲液中,DA和AA的氧化峰电流与其浓...     

Simultaneous determination of acetaminophen,dopamine and ascorbic acid using a PbS nanoparticles Schiff base-modified carbon paste electrode

A highly sensitive method was investigated for the simultaneous determination of acetaminophen (AC), dopamine (DA), and ascorbic acid (AA) using a PbS nanoparticles Schiff base-modified carbon paste electrode (PSNSB/CPE). Differential pulse voltammetry peak currents of AC, DA and AA increased linearly with their concentrations within the ranges of 3.30 × 10⁻⁸–1.58 × 10⁻⁴ M, 5.0 × 10⁻⁸–1.2 × 10⁻⁴ M and 2.50 × 10⁻⁶–1.05 × 10⁻³ M, respectively, and the detection limits for AC, DA and AA were 5.36 × 10⁻⁹, 2.45 × 10⁻⁹ and 1.86 × 10⁻⁸ M, respectively. The peak potentials recorded in a phosphate buffer solution (PBS) of pH 4.6 were 0.672, 0.390, and 0.168 V (vs Ag/AgCl) for AC, DA and AA, respectively. The modified electrode was used for the determination of AC, DA, and AA simultaneously in real and synthetic samples.     

聚甲基蓝修饰电极的制备及对多巴胺的测定

研究了聚甲基蓝修饰电极的制备及其多巴胺在聚甲基蓝修饰电极上的循环伏安特性,建立了循环伏安法测定多巴胺的新方法。在pH7.0磷酸盐缓冲溶液中,峰电流与多巴胺浓度在8.0×10-7～5.0×10-4mol L范围内呈良好的线性关系,检出限为5.0×10-8mol L。已用于药剂中多巴胺的测定。     

聚茜素红功能化碳纳米管修饰电极对多巴胺和抗坏血酸的电化学研究

采用电聚合方法将茜素红非共价修饰到碳纳米管上,制备了聚茜素红/碳纳米管修饰电极.以多巴胺(DA)和抗坏血酸(AA)为模型化合物,研究该修饰电极的电催化作用.结果表明:电聚合法使茜素红牢固地修饰到碳纳米管上,能显著提高电极的灵敏度和分子识别性能.DA和AA的氧化峰位分离达240 mV.在AA的存在下,DA的差分脉冲伏安法峰电流在1×10-7～1×10-5 mol/L范围内呈良好的线性关系,检测下限达1×10-7 mol/L.     

Fabrication of layer-by-layer modified multilayer films containing choline and gold nanoparticles and its sensing application for electrochemical determination of dopamine and uric acid

A novel electrochemical sensor has been constructed by use of a glassy carbon electrode (GCE) coated with a gold nanoparticle/choline (GNP/Ch). Electrochemical impedance spectroscopy (EIS), field emission scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the properties of this modified electrode. It was demonstrated that choline was covalently bounded on the surface of glassy carbon electrode, and deposited gold nanoparticles with average size of about 100 nm uniformly distributed on the surface of Ch. Moreover, the modified electrode exhibits strong electrochemical catalytic activity toward the oxidation of dopamine (DA), ascorbic acid (AA) and uric acid (UA) with obviously reduction of overpotentials. For the ternary mixture containing DA, AA and UA, these three compounds can be well separated from each other, allowing simultaneously determination of DA and UA under coexistence of AA. The proposed method can be applied to detect DA and UA in real samples with satisfactory results.     

聚对氨基苯磺酸修饰电极测定尿酸

利用循环伏安法制备了聚对氨基苯磺酸修饰电极, 研究了尿酸在该修饰电极上的电化学行为. 结果表明, 该电极对尿酸有较强的电催化作用, 并对抗坏血酸有较强的抗干扰能力. 在pH 5.6的乙酸盐缓冲溶液中, 用循环伏安法和差分脉冲伏安法在该电极上测定了尿酸, 其线性范围分别为1.0×10-5～2.0×10-4 mol/L和4.0×10-7～1.0×10-5 mol/L, 检出限分别为6.0×10-6 mol/L和1.0×10-7 mol/L. 已用于尿液中尿酸的测定.     

Fabrication and characterisation of high performance polypyrrole modified microarray sensor for ascorbic acid determination

In this study, gold microelectrode array (Au/MEA) with electrode of 12 μm diameter was fabricated by photolithography technique. Subsequently, polypyrrole (Ppy) modified gold microarrays sensor (Ppy/Au/MEA) was prepared by cyclic voltammetry technique. The deposition potential range and number of cycles were optimised in order to get optimum thickness of Ppy film. Scanning Electron Microscope and Atomic Force Microscope investigations reveal that Ppy coating formed at 3 cycles is porous with thickness of 1.5 μm which exhibiting high catalytic current for ascorbic acid (AA) in square wave technique (SWV). In contrast to earlier sensors designs, these Ppy/Au/MEA sensors exhibits lower detection limit (LOD) of 10 nm towards AA at physiological conditions. It also exhibits enhanced sensitivity (2.5 mA cm⁻² mM⁻¹) and long range of linear detection limit from 10 nm to 2.8 mM. In the same way, polypyrrole modified macro Au (Ppy/Au/MA) biosensor was also fabricated and its electro catalytic property towards AA was compared with that of Ppy/Au/MEA. The Ppy/Au/MA exhibits sensitivity of only 0.27 mA cm⁻² mM⁻¹, LOD of 5 μM and linear range of 10 μM to 2.2 mM. Hence, our investigations indicate that the Ppy/Au/MEA could serve as highly sensitive sensor for AA than any of the earlier designs. So, the Ppy/Au/MEA electrode was utilised for determination AA in a wide variety of real samples.     

Electrochemical reduced graphene oxide-poly(eriochrome black T)/gold nanoparticles modified glassy carbon electrode for simultaneous determination of ascorbic acid,dopamine and uric acid

This work reports on the preparation of electrochemically reduced graphene oxide (ERGO)-poly(eriochrome black T) (pEBT) assembled gold nanoparticles for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in PBS pH 6.0. Characterisations of the composite were carried out by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. As a result of the synergistic effect, the modified glassy carbon electrode (GCE) possessed an efficient electrochemical catalytic activity with a high selectivity and sensitivity in oxidising AA-DA and DA-UA as compared to the bare GCE. The peak separations of AA and DA, DA and UA were 183 mV and 150 mV, respectively. The linear response ranges for AA, DA and UA were 10–900 μM, 0.5–20 μM and 2–70 μM with detection limits of 0.53 μM, 0.009 μM and 0.046 μM (S/N = 3), respectively. The sensitivity of ERGO-pEBT/AuNPs was measured as 0.003 µA/μM, 0.164 µA/μM and 0.034 µA/μM for AA, DA, and UA, respectively. The modified electrochemical sensor was used in the determination of AA, DA, and UA in vitamin C tablets and urine sample with good recovery.     

Electrochemical oxidation of dopamine and ascorbic acid at a palladium electrode modified with in situ fabricated iodine-adlayer in alkaline solution

The self-assembled iodine-adlayer was fabricated at the palladium (Pd) electrode surface throughout a spontaneous oxidative chemisorption of iodide ions contained in an alkaline supporting electrolyte. It enhances the electron transfer kinetics for the oxidation of dopamine (DA) and ascorbic acid (AA) and was important to separate the peak current of both species with a practical potential difference compared with that occurred at the unmodified electrode. The anodic peak currents of both species were linearly increased with their respective concentrations using linear square stripping voltammetry. The activity of the electrode system was further investigated applying chronoamperometry method. The steady-state amperometric signal for the oxidation of DA in the presence of iodide ions was five times greater than that in its absence. The current-time response was also used to evaluate the diffusion coefficient of DA based on Cottrell plot that results with a value of 4.19 × 10⁻⁸ m² s⁻¹. The proposed method was successfully applied to detect DA and AA in human serum.     

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).