双层纳米金修饰电极对多巴胺的测定及应用研究

利用含有连续腺嘌呤碱基模块的DNA(CA DNA)构建了双层纳米金,在此基础上制备了由聚番红花红和双层三维分布的纳米金修饰的玻碳电极,并研究了多巴胺(DA)在此修饰电极上的电化学行为,发现对于DA的氧化,CA DNA构建的电极比巯基DNA构建的电极能够起到更明显的电催化作用。利用差分脉冲法(DPV)考察了DA测定的优化条件,并发现其浓度在8.0×10-9~1.2×10-6mol·L-1范围内与氧化峰电流呈良好的线性关系。该电极用于实际样品的测定,结果满意。     

Sensing Lorazepam with a glassy carbon electrode coated with an electropolymerized-imprinted polymer modified with multiwalled carbon nanotubes and gold nanoparticles

We report on an electrode for the amperometric determination of lorazepam. A glassy carbon electrode was coated with a molecular imprint made by electropolymerization of ortho-phenylenediamine and filled with multiwalled carbon nanotubes and gold nanoparticles, which enhances the transmission of electrons. The sensor was studied with respect to its response to hexacyanoferrate (III) as a probe and by electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry. The linear response range to Lorazepam is from 0.5 nM to 1.0 nM and from 1.0 nM to 10.0 nM, with a detection limit of 0.2 nM (at an S/N of 3). The electrode was successfully applied to determine Lorazepam in spiked human serum.

Enhanced conductivity of a glassy carbon electrode modified with a graphene-doped film of layered double hydroxides for selectively sensing of dopamine

A strategy is presented for doping graphene into layered double hydroxide films (LDHs) as a means of improving charge transport of the LDH film in a modified glassy carbon electrode. This result in an enhanced electrocatalytic current for dopamine (DA) and a good separation of the potentials of DA, uric acid and ascorbic acid. Under selected conditions, the square wave voltammetric response of the electrode to DA is linear in the concentration range from 1.0 to 199???M even in the presence of 0.1?mM ascorbic acid, and the detection limit is 0.3???M at a signal-to-noise ratio of 3. The method was applied to the determination of DA in pharmaceutical injections with satisfactory results.

4-Aminobenzoic acid covalently modified glassy carbon electrode for sensing paracetamol at different temperatures

4-Aminobenzoic acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) during an electrochemical oxidation process in 0.1 M KCl aqueous solution. The modified electrode was applied to sense paracetamol (PCT) at serials of simulated physiologic conditions, compared to the bare electrode. The results showed that the modified electrode possessed better stability, reusability, and longevity than the bare GCE at room to physiologic temperatures. This indicated that 4-ABA/GCE can be used as the electrochemical sensing platform of PCT at the physiologic condition.     

Voltammetric determination of 4-chloro-3-methylphenol at a glassy carbon electrode

Summary Thin films of NiCrSi with thicknesses ranging from 3 to 80 nm were irradiated by 15 keV electrons. The angle of incidence was varied between normal and nearly grazing incidence by tilting the sample up to =85°. At oblique incidence the detection limits of energy dispersive electron probe microanalysis for surface layers are higher by at least one order of magnitude than at normal incidence. Less than 1/10 of a monolayer is detectable. Furthermore, one gets informations concerning the depth distribution of the constituents. For example, less than 3 monolayers of Cu were detected and localized under a 9 nm thick NiCrSi film on vitreous carbon.Parts of this paper were presented as lecture No B8L-5 at the European Conference EUROANALYSIS VII, Vienna, August 26–31, 1990     

Voltammetric determination of niclosamide at a glassy carbon electrode

A very sensitive and selective procedure was developed for the determination of niclosamide based on square-wave voltammetry at a glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical reduction of niclosamide at a glassy carbon electrode. Niclosamide was first irreversibly reduced from NO2 to NHOH at -0.659 V in aqueous buffer solution of pH 8.5. Reversible and well defined peaks at -0.164 V and -0.195 V (vs. Ag/AgCl) were obtained that are responsible for two electron peaks between NHOH and NO. Following optimisation of the voltammetric parameters, pH and reproducibility, a linear calibration curve over the range 5 x 10(-8)-1 x 10(-6) mol dm(-3) was achieved. The detection limit was found to be 2.05 x 10(-8) mol dm(-3) niclosamide. For eight successive determinations of 5 x 10(-7) mol dm(-3) niclosamide, a relative standard deviation of 2.4% was obtained. This voltammetric method was applied to the direct determination of niclosamide in tablets. The results of the analysis suggest that the proposed method has promise for the routine determination of niclosamide in the products examined.     

Amperometric sensing of hydrogen peroxide via an ITO electrode modified with gold nanoparticles electrodeposited on a CoMn-layered double hydroxide

Microchimica Acta - An electrochemical sensor for hydrogen peroxide (H2O2) has been fabricated by electrodepositing gold nanoparticles (AuNPs) on an indium tin oxide (ITO) electrode modified with...     

Voltammetric determination of salbutamol on a glassy carbon electrode coated with a nanomaterial thin film

A rapid and convenient electrochemical method is described for the determination of salbutamol based on multi-carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE). The electrochemical behavior of salbutamol at this modified electrode was studied by square wave voltammetry, which indicated that the oxidation peak potential of salbutamol shifted on 40 mV to less positive potential and the peak current increased 4.5 fold, in contrast to that at a bare electrode. Various experimental parameters such as pH value of supporting electrolyte, the amount of modifier, and accumulation time were optimized. Under optimal measurement conditions, there is a good linear relationship between the peak current (I _pa) and salbutamol concentration in the range from 8.0 × 10⁻⁷ to 1.0 × 10⁻⁵ M, and the detection limit is 2.0 × 10⁻⁷ M (S/N = 3) at 2 min accumulation. The method has been successfully employed to detect salbutamol in pharmaceutical formulations.     

Electrochemical oxidation behavior of bisphenol A at surfactant/layered double hydroxide modified glassy carbon electrode and its determination

Electrochemical behavior of bisphenol A (BPA) at glassy carbon electrode-modified with layered double hydroxide (LDH) and anionic surfactant (sodium dodecyl sulfate) is investigated by electrochemical techniques. Compared with the bare electrode and LDH-modified electrode, the oxidation peak potential of BPA shifted negatively and the peak current increased significantly due to the enhanced accumulation of BPA via electrostatic interaction with LDH at the hydrophobic electrode surface. Some determination conditions such as LDH loading, pH, scan rate, accumulation potential, and accumulation time on the oxidation of BPA were optimized. And some kinetic parameters were investigated. Under the optimized conditions, the oxidation current was proportional to BPA concentration in the range of 8 × 10⁻⁹ to 2.808 × 10⁻⁶ M with the detection limit of 2.0 × 10⁻⁹ M by amperometry. The fabricated electrode showed good reproducibility, stability, and anti-interference. The proposed method was successfully applied to determine BPA in water samples, and the results were satisfactory.     

Chronocoulometric DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles, poly(dopamine) and carbon nanotubes

We describe a sensitive chronocoulometric biosensor for the sequence-specific detection of DNA. It is based on a glassy carbon electrode modified with multi-walled carbon nanotubes, polydopamine, and gold nanoparticles. The ruthenium(III)hexammine complex acts as the electrochemical indicator. Electrochemical impedance spectra and scanning electron microscopy are employed to investigate the assembly of the electrode surface. The signals of the ruthenium complex electrostatically bound to the anionic phospho groups of the DNA strands are measured by chronocoulometry before and after hybridization. The difference in signal intensity is linearly related to the logarithm of the concentration of the target DNA in the range of 1.0 nM to 10 fM with a detection limit of 3.5fM (S/N?=?3) under optimal conditions. This biosensor exhibits excellent sensitivity and selectivity and has been used for an assay of complementary target DNA in human serum sample with satisfactory results.

Voltammetric determination of phenylbutazone and oxyphenbutazone at a glassy carbon electrode

Linear-sweep and differential-pulse voltammetric methods are reported for the determination of phenylbutazone and oxyphenbutazone and of their pharmaceutical dosage forms. The methods are based on the electrochemical oxidation of phenylbutazone and oxyphenbutazone at a glassy carbon electrode in 0.1 M sodium acetate—0.1 M acetic acid in 98% ethanol. The mechanisms are discussed. The proposed methods show good reproducibility and are not subject to interference from common tablet excipients and from possible therapeutically active drug substances used in combination with phenylbutazone and oxyphenbutazone. A simple interrupted-sweep procedure can be used to determine phenylbutazone in the presence of oxyphenbutazone.     

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.     

Adsorptive stripping voltammetric determination of 4-aminophenol at a single-wall carbon nanotubes film coated electrode

A single-wall carbon nanotubes (SWNT)-Nafion film coated glassy carbon electrode (GCE) was described for the determination of 4-aminophenol. In pH 3.0 sodium citrate-HCl buffer, the oxidation peak current of 4-aminophenol increases greatly at the SWNT-Nafion film coated GCE in contrast to that at both bare GCE and Nafion-film coated GCE. Moreover, the oxidation peak potential shifts to more negative potential. All the experimental parameters were optimized for the determination of 4-aminophenol. The oxidation peak current is proportional to the concentration of 4-aminophenol over the range from 5×10⁻⁹ to 2×10⁻⁶ mol l⁻¹. The detection limit is 8×10⁻¹⁰ mol l⁻¹ at 4 min of accumulation. Using the proposed method, 4-aminophenol in water samples was determined.     

Voltammetric determination of 4-nitrophenol at a sodium montmorillonite-anthraquinone chemically modified glassy carbon electrode

A new method for the determination of 4-nitrophenol(4-NP) by differential pulse voltammetry (DPV) based on adsorptive stripping technique was described. Cyclic voltammetry (CV) and linear scan voltammetry (LSV) were used in a comparative investigation into the electrochemical reduction of 4-NP at a Na-montmorillonite(SWy-2) and anthraquione (AQ) modified glassy carbon electrode. With this chemically modified electrode, 4-NP was first irreversibly reduced from phiNO(2) to phiNHOH at -0.78 V. A couple of well-defined redox peaks at +0.22 V (vs. SCE) were responsible for a two-electron redox peak between phiNHOH and phiNO. Studies on the effect of pH on the peak height and peak potential were carried out over the pH range 2.0-9.0 with the phosphate buffer solution. A pH of 3.4 was chosen as the optimum pH. The other experimental parameters, such as film thickness, accumulation time and potential etc. were optimized. Anodic peak currents were found to be linearly related to concentration of 4-NP over the range 0.3-45 mg l(-1), with a detection limit of 0.02 mg l(-1). The interference of organic and inorganic species on the voltammetric response have been studied. This modified electrode can be used to the determination of 4-NP in water samples.     

石墨烯修饰玻碳电极伏安法测定美洛昔康

通过在玻碳电极表面电化学还原氧化石墨烯的方法制备了石墨烯修饰电极,研究了美洛昔康在该修饰电极上的电化学行为。优化了包括支持电解质及pH、修饰剂用量、富集电位及时间等测定条件,据此建立了一种直接测定美洛昔康的电化学分析方法。在0.1 mol/L Britton-Robinson缓冲液(pH 3.0)中,氧化峰电流与美洛昔康浓度在1.0×10-6～8.0×10-5mol/L范围内呈现良好的线性关系,检出限为3.0×10-7mol/L(S/N=3)。方法可用于片剂和尿样中美洛昔康的测定。     

Adhesion of gold nanoparticles on an electrochemically pretreated glassy carbon electrode.

This study describes a simple new method for the adsorption of gold nanoparticles on a glassy carbon (GC) electrode. By electrochemically oxidizing the GC electrode and immersing it into a gold colloidal solution, one could induce the adhesion of the gold nanoparticles. The image of the field emission scanning electron microscopy confirmed that the nanoparticles were evenly distributed over the surface. A 2-aminoethanethiol self-assembled monolayer was formed on the surfaces of the adsorbed gold nanoparticles and a reductive desorption wave was observed during the reduction of the adsorbed 2-aminoethanethiol.     

Voltammetric determination of cysteine at a graphite electrode modified with gold nanoparticles

The electrochemical behaviour of cysteine (Cys) at a graphite electrode modified with gold nanoparticles (G-Au_nano electrode) was studied by cyclic voltammetry. It was found that the graphite electrode-Au nanoparticles show an electrocatalytic activity towards the oxidation of Cys in 0.1?M NaOH. At 0.05?V, there is an “inverse” maximum in the cathodic voltammogram of Cys. Using a G-Au_nano electrode, the dependence of the peak current of the “inverse” maximum on Cys concentration was linear in the range from 1 to 14?pM, and the detection limit was 0.6?pM. The proposed analytical method is simple, rapid and sensitive.     

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).     

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。