Electrochemical Behavior of Caffeic Acid Assayed with Gold Nanoparticles/Graphene Nanosheets Modified Glassy Carbon Electrode

A gold nanoparticle (AuNP) and graphene nanosheet (GN) modified glassy carbon electrode (GCE) is proposed as voltammetric sensor for caffeic acid assay. The sensor exhibits a surface‐confined and reversible process for oxidation of caffeic acid revealed by cyclic voltammetry. The results show more favorable electron transfer kinetics than the bare GCE. The linear response of the sensor is from 5×10^?7 to 5×10^?5 M with a detection limit of 5×10^?8 M (S/N=3). The AuNP/GN nanocomposite shows more favorable electrochemical activity and should be a kind of more robust and advanced functional material, which provides a promising platform for electrochemical sensors and biosensors. The method was successfully applied to detect caffeic acid in pharmaceutical tablets with satisfactory results.     

Application of a Glassy Carbon Electrode Modified with Poly(Glutamic Acid) in Caffeic Acid Determination

Glassy carbon electrodes were coated with films of poly(glutamic acid) (PG), and the modified electrode proved to be very effective in the oxidation of caffeic acid. The performance of the film was also tested with ascorbic acid, coumaric acid, ferulic acid, sinapic acid and chlorogenic acid. At pH 5.6, all the hydroxycinnamic acids yield a higher peak current intensity when oxidized after incorporation in the PG-modified electrode, and only the oxidation of ascorbic acid exhibits overpotential reduction. At pH 3.5 only caffeic and chlorogenic acid are incorporated in the modified electrode and exhibit a well-defined oxidation wave at +0.51 V and +0.48 V, which is the base for their determination. Linear calibration graphs were obtained from 9 × 10⁻⁶ mol L⁻¹ to 4 × 10⁻⁵ mol L⁻¹ caffeic acid by linear voltammetric scan and from 4 × 10⁻⁶ mol L⁻¹ to 3 × 10⁻⁵ mol L⁻¹ by square wave voltammetric scan. The method was successfully applied to the determination of caffeic acid in red wine samples without interference from other hydroxycinnamic acids or ascorbic acid.     

Electrochemical Detection of NADH,Cysteine, or Glutathione Using a Caffeic Acid Modified Glassy Carbon Electrode

A modified electrode was prepared using electrodeposition methods to immobilize caffeic acid (CAF) onto the surface of a glassy carbon electrode (GCE) to create a polymer suitable for biosensor development. The polymer film coverage of the surface bound species was further optimized using electrodeposition methods, thus increasing the surface coverage to ca. 10^?9 mol cm^?2. Using cyclic voltammetry, the modified carbon electrode was used to facilitate and observe the electrocatalytic oxidation of coenzymes such as NADH, cysteine, and glutathione at different concentrations. A calibration curve was determined in each case within the concentration range; 300 nM to 10 mM, with the limits of detection (LOD) of 246 µM, 99 µM, 2.2 µM for NADH, cysteine, and glutathione respectively.     

聚氨基磺酸修饰玻碳电极在抗坏血酸共存时测定肾上腺素

研究了聚氨基磺酸修饰玻碳电极的制备及肾上腺素和抗坏血酸在此修饰电极上的电化学行为。在磷酸盐缓冲液pH为 7. 0的条件下,肾上腺素在修饰电极上呈现 2个氧化峰和 1个还原峰。其峰电位都随着pH值的增加而负移。当肾上腺素与抗坏血酸共存时,EP较正处氧化峰电位与AA氧化峰电位差达 190mV。肾上腺素氧化峰电流与其浓度在 1. 0×10-7 ~1. 0×10-4 mol/L的范围时呈良好的线性关系,其线性回归方程为ip(10μA) = 1. 455 + 0. 3765C(mol/L), 相关系数r=0. 9977,检出限为 1. 0×10-8 mol/L。实验结果表明:该修饰电极能同时测定肾上腺素和抗坏血酸; 100倍的马尿酸、半胱氨酸、柠檬酸不干扰测定。方法用于注射液中肾上腺素的检测,结果令人满意。     

Over‐Oxidized Poly (Phenol Red) Film Modified Glassy Carbon Electrode for Anodic Stripping Voltammetric Determination of Ultra‐Trace Antimony (III)

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over‐oxidized poly(phenol red) modified glassy carbon electrode (PPhRed_ox/GCE) in 0.1 mol L^‐1 HCl medium. The formation of both poly(phenol red) and over‐oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRed_ox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRed_ox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 ‐ 1.218 μg L⁻¹ and 3.40 – 18.26 μg L⁻¹ with a detection limit of 0.0075 μg L⁻¹. The proposed over‐oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE‐EnviroMAT™ EP−L‐2).     

Determination of Dopamine in the Presence of Ascorbic Acid Using a Poly(Amidosulfonic Acid) Modified Glassy Carbon Electrode

A glassy carbon electrode (GCE) was modified with electropolymerized films of amidosulfonic acid in pH 7.0 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine (DA). In pH 7.0 PBS, the anodic peak current increased linearly with the concentration of DA in the range of 5.0×10^–7 1.0×10^–4moldm^–3, with a correlation coefficient of 0.9932, and a detection limit (S/N=3) of 1.0× 10^–7moldm^–3. The relative standard deviation of 10 successive scans was 2.5% for 1.0×10^–6moldm^–3 DA. The interference of ascorbic acid (AA) with the determination of DA could be eliminated because of the very distinct attracting interaction between DA cations and the negatively poly(amidosulfonic acid) film in pH 7.0 PBS. The proposed method exhibited good recovery and reproducibility.     

Electrocatalytic Oxidation and Determination of Norepinephrine at Poly(Cresol Red) Modified Glassy Carbon Electrode

A glassy carbon electrode (GCE) was modified with electropolymerized films of cresol red in pH 5.6 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode shows an excellent electrocatalytic effect on the oxidation of norepinephrine (NE). The peak current increases linearly with the concentration of NE in the range of 3×10^?6–3×10^?5 M by the differential pulse voltammetry. The detection limit was 2×10^?7 M. The modified electrode can also separate the electrochemical responses of norepinephrine and ascorbic acid (AA). The separation between the anodic peak potentials of NE and AA was 190 mV by the cyclic voltammetry. And the responses to NE and AA at the modified electrode were relatively independent.     

Simultaneous Determination of Rosmarinic Acid and Protocatechuic Acid at Poly(o‐Phenylenediamine)/Pt Nanoparticles Modified Glassy Carbon Electrode

A system of Pt nanoparticles and poly(ortho‐phenylenediamine) film electrochemically deposited onto a glassy carbon electrode (GCE/PoPD/Pt) was fabricated. Scanning electron microscopy, Fourier‐transform infrared spectroscopy, and atomic force microscopy techniques were used to identify the surface characteristics of the composite electrode. The conductive polymers and Pt nanoparticles together resulted in a synergistic effect, and the new formed surface was highly active against polyphenolic structures. Rosmarinic acid (RA) and protocatechuic acid (PCA) are phenolic compounds found in plants, and they are used in many applications, particularly as pharmaceuticals. The GCE/PoPD/Pt was used for the simultaneous determination of RA and PCA in a pH 2.0 H₂SO₄ solution for the first time. The RA and PCA concentrations were determined using differential pulse voltammetry (DPV) and chronoamperometry. By the amperometry measurement, for RA and PCA, a linear relation was observed in the concentration ranges of 1–55 μmol L^?1 and 1–60 μmol L^?1, with detection limits of 0.5 μmol L^?1 and 0.6 μmol L^?1, respectively. In the simultaneous determination with DPV, the detection limits for both RA and PCA were calculated as 0.7 μmol L^?1. The GCE/PoPD/Pt was successfully used for the simultaneous determination of RA and PCA in a real sample, and its accuracy was verified by high‐performance liquid chromatography studies.     

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes‐gold Nanoparticles Modified Glassy Carbon Electrode

A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)‐gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT‐GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10^?8 to 2×10^?5 mol L^?1, with a limit of detection of 7.5 nmol L^?1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results.     

阿魏酸聚合修饰玻碳电极的制备及其对NADH的催化氧化

研究了阿魏酸修饰电极的制备、性质及对NADH的电催化作用.该电极在0.1mol/L磷酸缓冲溶液(pH=6.60)中,于-0.1～+0.50V(vs.Ag/AgCl)电位范围内呈现一对氧化还原峰,其式量电位E₀为+0.188V(vs.Ag/AgCl),且E₀随pH增加而负向移动.电子转移系数为0.496,表观电极反应速率常数(ks)为6.6s^-1.电极反应的电子数为1且有1个质子参与.该修饰电极对NADH氧化具有很好的催化作用.在NADH存在下,电极过程由扩散控制,扩散系数为1.76×10^-6cm²/s.NADH浓度在0.01～5.0mmol/L范围内与峰电流呈现良好的线性关系.通过计时安培法测得催化速率常数为6.82×10³mol^-1·L·s^-1.     

Electrocatalytic Oxidation of Acyclovir on Poly(p‐Aminobenzene Sulfonic Acid) Film Modified Glassy Carbon Electrode

Acyclovir is an antiviral effective drug active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p‐aminobenzene sulfonic acid (p‐ABSA) in phosphate buffer solution (PBS). The polymer film‐modified electrode was used to electrochemically detect acyclovir. Polymer film showed excellent electrocatalytic activity for the oxidation of acyclovir. The anodic peak potential value of the acyclovir at the poly(p‐ABSA) modified glassy carbon electrode was 950 mV obtained by DPV. A linear calibration curve for DPV analysis was constructed in the acyclovir concentration range 2×10^?7–9×10^?6 mol L^?1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 5.57×10^?8 and 1.85×10^?7 mol L^?1 respectively. The proposed method exhibits good recovery and reproducibility.     

咖啡酸修饰电极的电化学性质及其对肾上腺素的电化学研究

研究了咖啡酸(CFA)修饰玻碳电极的制备和其电化学性质 ,测定了电极反应的动力学常数。实验结果表明 ,在 pH7.0的磷酸盐缓冲溶液中 ,肾上腺素(Ep)在该修饰电极上产生一灵敏的氧化峰 ,峰电流与Ep浓度在5.0×10 -6～1.0×10 -4mol/L范围内线性关系良好 ,检出限为7.0×10 -7mol/L。并对修饰电极反应的机理进行了初步探讨。修饰电极制备简单 ,稳定性良好     

基于金纳米粒子/聚阿魏酸/多壁碳纳米管修饰电极的DNA计时库仑法生物传感器的制备

构建了基于金纳米粒子/聚阿魏酸/多壁碳纳米管(AuNPs/PFA/MWCNTs)修饰电极的DNA计时库仑法生物传感器.利用循环伏安技术在多壁碳管修饰的玻碳电极表面上聚合一层阿魏酸,在恒电位条件下,在阿魏酸表面沉积金纳米粒子,巯基DNA作为探针通过金硫键固定在金纳米粒子表面.电化学交流阻抗技术(EIS)与扫描电镜(SEM...     

Determination of Trichloroacetic Acid (TCAA) Using CdO Nanoparticles Modified Carbon Paste Electrode

In this paper, the electrochemical behavior of a carbon paste electrode modified with CdO nanoparticles as a potential electrocatalyst for the reduction of trichloroacetic acid (TCAA) was investigated using cyclic voltammetry and double‐potential step chronoamperometry. The modified electrode showed a great enhancement in cathodic peak current with respect to reduction of TCAA in acidic aqueous solution. Using this increment, a quantitative method was developed for the determination of TCAA in aqueous solution. The detection limit and linear dynamic range of TCAA are 2.3×10^?6 M and 2.3×10^?4–3×10^?6 M, respectively.     

Direct Electrochemistry and Electrocatalysis of Hemoglobin at PAMAM Dendrimer-MWNTs-Au Nanoparticles Composite Film Modified Glassy Carbon Electrode

The direct electron transfer of hemoglobin at the PAMAM-MWNTs-AuNPs composite film modified glassy carbon electrode was studied. In a phosphate buffer solution(PBS, pH=7.0), the formal potential(E 0' ) of Hb was –0.105 V versus SCE, the electron transfer rate constant was 4.66 s –1 . E 0′ of Hb at the modified electrode was linearly varied in a pH range of 5.0—8.0 with a slope of –49.2 mV/pH. The Hb/PAMAM-MWNTs-AuNPs/GCE gave an ex-cellent electrocatalytic response to the reduction of hydrogen peroxide. The catalytic current increased linearly with H 2 O 2 concentration in a range of 1.0×10 ?6 to 2.2×10 ?3 mol/L. The detection limit was 2.0×10 ?7 mol/L at a signal to noise ratio of 3. The Michaelis-Menten constant(K ma pp ) was 2.95 mmol/L.     

Determination of Nitric Oxide by Glassy Carbon Electrodes Modified with Poly(Neutral Red)

Nitric oxide can be oxidized to NO⁻₂ (then to NO⁻₃) and reduced to N₂O at a glassy carbon electrode modified with the film of poly(neutral red). When the modified electrode is further coated with a thin Nafion film, the interference of NO⁻₂ can be almost thoroughly eliminated, and the electrode can be employed to detect nitric oxide.     

聚刚果红修饰玻碳电极的制备及其电催化性能

在含刚果红的硼砂缓冲溶液中,用循环伏安法扫描,在玻碳电极上形成聚合物薄膜.在 -0. 8V~+1. 8V(vsAg/AgCl)的扫描电位范围形成的薄膜具有较高的电活性和稳定性.该电极对抗坏血酸、邻苯二酚的电化学氧化有催化作用,增大了氧化峰电流.催化峰电流与抗坏血酸和邻苯二酚浓度分别在 20 ~1 200mmol/L, 50 ~2 000mmol/L范围内呈良好的线性关系.     

纳米银/石墨烯修饰电极测定青蒿素

本文建立一种新型的青蒿素传感器。首先,在玻碳电极上滴涂氧化石墨,通过电化学方法将氧化石墨还原为石墨烯,然后,在石墨烯上沉积纳米银得到石墨烯/纳米银修饰电极,它作为检测青蒿素的电化学传感器。用此电极对青蒿素进行测定,并通过循环伏安法、差分脉冲伏安法、交流阻抗法等研究其电化学行为。该修饰电极在测定青蒿素溶液时,表现出较正的还原电位和较大的峰电流等优势;对其实验条件如电解质溶液的p H、应用电势等进行了探查,该电化学传感器在青蒿素溶液浓度范围为1.0×10-8~3.0×10-5mol/L时与其还原峰电流呈现良好的线性关系,最低检出限为1.2×10-9mol/L(S/N=3)。此外,对该传感器的稳定性和重现性等也进行了研究,获得令人满意的结果。     

聚阿魏酸修饰电极的电化学特性及电催化性能

研究了阿魏酸在玻碳电极表面电聚合成膜的方法和条件,测量了应用电化学方法制备不同厚度的阿魏酸修饰电极的循环伏安行为及其它电化学性质.对厚度为0.5 μm的阿魏酸膜,测得的电子转移系数为0.49,表观电极反应速率常数(ks)为6.56 s－1.扩散系数DR为7.9×108 cm2•s－1,Do为4.48×108 cm2•s－1.该修饰电极对烟酰胺腺嘌呤二核苷酸（NADH）氧化具有很好的催化作用.NADH浓度在0.01～5.0 mmol•dm－3范围内与峰电流呈现良好的线性关系.     

用聚吲哚乙酸修饰电极测定肾上腺素

报道了聚吲哚乙酸修饰电极的制备，并研究了肾上腺素在该修饰电极上的循环伏安特性及测定方法。实验表明，在ＰＨ７．０的磷酸盐缓冲溶液中，用该电极测定肾上腺素的线性范围为１．０＊１０＾－７－６．０＊１０＾－６ｍｏｌ／Ｌ，检出限为４．０＊１０＾Ｔ－８ｍｏｌ／Ｌ。将此法用于药剂中肾上腺素的测定，结果满意。