Magnetic chitosan microspheres (MCMS) and thionine were incorporated in a modified electrode for the simultaneous sensitive determination of dopamine (DA) and uric acid (UA). Due to the unique properties of the MCMS and the electron mediation of thionine, this modified electrode showed excellent electrocatalytic oxidation toward dopamine and uric acid with a large separation of peak potentials and a significant enhancement of peak currents. However, the electrochemical behavior of ascorbic acid may be depressed at the modified electrode. Differential pulse voltammetry was used for the simultaneous sensitive determination of dopamine and uric acid in the presence of excess ascorbic acid at this modified electrode. The current responses showed excellent linear relationships in the range of 2–30 µM and 9–100 µM for dopamine and uric acid, respectively. The detection limits were estimated to be 0.5 µM and 2.3 µM for dopamine and uric acid, respectively. In addition, this modified electrode showed excellent repeatability, good stability, and satisfactory reliability, thus indicating potential for the practical applications. 相似文献
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相似文献
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.
Three-dimensional interconnected network graphene foam (GF) was synthesized by chemical vapor deposition. The GF was transferred onto indium tin oxide glass, acting as an electrode for the selective determination of L-dopa in the presence of ascorbic and uric acid. Using differential pulse voltammetry (DPV) method, the oxidation peak current is well linear with L-dopa concentration in the range of 0.05–1 μM with a sensitivity of 2.64 μA μM?1 and in the range of 1–40 μM with a sensitivity of 1.82 μA μM?1. The detection limit of this electrode for L-dopa is about 20 nM. The proposed electrode can also effectively avoid the interference of ascorbic acid and uric acid, making the proposed sensor suitable for the accurate determination of L-dopa in human urine fluids. This electrode will have a wide range of potential application prospect in electrochemical detection. 相似文献
An electrochemical sensor for simultaneous determination of dopamine (DA), uric acid (UA), guanine (G), and adenine (A) has been constructed by copolymerizing melamine monomer and Ag ions on a glassy carbon electrode (GCE) with cyclic voltammetry. The poly-melamine and nano Ag formed a hybridized film on the surface of the GCE. The morphology of the film was characterized by scanning electron microscope. The electrochemical and electrocatalytic properties of this film were characterized by cyclic voltammetry, linear sweep voltammetry, and square wave voltammetry (SWV). In 0.1 M phosphate buffer solution (pH 4.5), the modified electrode resolved the electrochemical response of DA, UA, G, and A into four well-defined voltammetric oxidation peaks by SWV; the oxidation peak current of DA, UA, G, and A increased 13-, 6-, 7-, and 9-fold, respectively, compared with those at the bare GCE and the SWV peak currents of DA, UA, G, and A with linear concentrations in the ranges of 0.1–50, 0.1–50, 0.1–50, and 0.1–60 μM, respectively. Based on this, a method for simultaneous determination of these species in mixture was setup. The detection limits were 10 nM for DA, 100 nM for UA, 8 nM for G, and 8 nM for A. 相似文献
Acrylic acid was first electropolymerized on the surface of a gold electrode. Then, polyaniline (PANI) was electrodeposited on the poly(acrylic acid) (PAA) network to give a PANI–PAA composite film. Scanning electron microscopy and electrochemical studies confirmed the formation of PANI–PAA composite which exhibited excellent electroactivity over a wide pH range. The electro-oxidation of ascorbic acid (AA) was studied in detail. The modified electrode exhibits significantly reduced oxidation overpotential. The response towards AA is linear in the range 1.0 μM to 9.3 mM (R?=?0.9997, n?=?33) at a potential of 0.1 V (vs. SCE). The sensitivity is 207 μA mM-1 cm-2, and the detection limit is 1.0 μM (S/N?=?3). Interferences by uric acid and dopamine are negligible. The electrode thus enables sensitive and selective determination of AA, with a performance superior to many other PANI–based ascorbate sensors. 相似文献
A nafion covered carbon nanotubes-paste electrode modified with poly(m-ferrocenylaniline), (Nf/p(FcAni)-CNTsPE), provides a novel voltammetric sensor for the selective determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). We studied the electrochemical activity of Nf/p(FcAni)-CNTsPE toward DA, UA, and AA by differential pulse voltammetry (DPV). DA and UA anodic peaks appear at 0.30 and 0.45 V, respectively while an anodic peak for AA was not observed. DPV oxidation peak values are linearly dependent on DA concentration over the range 1–150 μM (r2 = 0.992), and on UA concentration over the range 5–250 μM (r2 = 0.997). DA and UA detection limits are estimated to be 0.21 and 0.58 μM, respectively. The modified electrode shows both good selectivity and reproducibility for the selective determination of DA and UA in real samples. Finally, the modified electrode was successfully applied for the determination of DA and UA in pharmaceutical or biological sample fluids. 相似文献
A glassy carbon electrode modified with poly(alizarin red)/electrodeposited graphene (PAR/EGR) composite film was prepared and applied to detect ciprofloxacin (CPFX) in the presence of ascorbic, uric acid and dopamine. The morphology and interface property of PAR/EGR films were examined by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrocatalytic oxidation of CPFX on AR/EGR was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The linearity ranged from 4 × 10−8 to 1.2 × 10−4 M with a detection limit (S/N = 3) of 0.01 μM. The modified electrode could be applied to the individual determination of CPFX as well as the simultaneous determination of CPFX, ascorbic acid, uric acid and dopamine. This method proved to be a simple, selective and rapid way to determine CPFX in pharmaceutical preparation and biological media. 相似文献
A poly(diallyldimethylammonium chloride)-graphene-multiwalled carbon nanotube modified glassy carbon electrode was fabricated and evaluated by cyclic voltammetry and differential pulse voltammetry. The modified electrode offered high sensitivity, selectivity, excellent long-term stability, and electrocatalytic activity for uric acid and dopamine. This sensor showed wide linear dynamic ranges of 5.0 to 350.0 µmol L?1 for uric acid and 10.0 to 400.0 µmol L?1 for dopamine in the presence of 500 µmol L?1 ascorbic acid. The limits of detection were 0.13 for uric acid and 0.55 µmol L?1 for dopamine. This functionalized electrode has potential application in bioanalysis and biomedicine. 相似文献
We are presenting an electrochemical sensor for the simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of even high concentrations of ascorbic acid (AA). It based on a glassy carbon electrode modified with an electroactive film of polymerized dibromofluorescein. The electrochemical behaviors of DA and UA were studied by cyclic voltammetry using the modified electrode. It exhibits excellent electrocatalytic activity towards the oxidation of the two analytes. Most notably, the oxidation potentials differ by 180 and 200?mV between AA-DA and DA-UA, respectively. Thus, excellent selectivity towards the oxidation of DA and UA in the presence of even high concentrations of AA is accomplished. Under the optimum conditions, the anodic peak currents are linearly related to the concentrations of DA and UA in the range from 0.2 to 200?μmol?L-1 and from 1.0 to 250?μmol?L-1, respectively. The detection limits for DA and UA are 0.03?μmol?L-1 and 0.2?μmol?L-1, respectively (at an S/N of 3). The method has good selectivity and sensitivity and was successfully applied to the simultaneous determination of DA and UA in spiked human serum.
Figure
A novel electrochemical sensor based on poly (dibromofluorescein) film modified glassy carbon electrode has been fabricated and used for the simultaneous determination of dopamine and uric acid in the presence of high concentration of ascorbic acid with good selectivity and sensitivity. 相似文献
A novel carbon paste electrode modified with ZrO2 nanoparticles and an ionic liquid (n-hexyl-3- methylimidazolium hexafluorophosphate) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for simultaneous voltammetric oxidation of dopamine and uric acid is described. The electrode was also employed to study the electrochemical oxidation of dopamine and uric acid, using cyclic voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. Square wave voltammetry exhibits linear dynamic range from 1.0 × 10?6 to 9.0 × 10?4 M for dopamine. Also, square wave voltammetry exhibits linear dynamic range from 9.0 × 10?6–1.0 × 10?3 M for uric acid. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of dopamine and uric acid into two well-defined voltammetric peaks. In the mixture containing dopamine and uric acid, the two compounds can be well separated from each other with potential difference of 155 mV, which is large enough to determine dopamine and uric acid individually and simultaneously. Finally, the modified electrode was used for determination of dopamine and uric acid in real samples. 相似文献
In this paper, graphene-multiwall carbon nanotube-gold nanocluster (GP-MWCNT-AuNC) composites were synthesized and used as modifier to fabricate a sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrochemical behavior of the sensor was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The combination of GP, MWCNTs, and AuNCs endowed the electrode with a large surface area, good catalytic activity, and high selectivity and sensitivity. The linear response range for simultaneous detection of AA, DA, and UA at the sensor were 120–1,701, 2–213, and 0.7–88.3 μM, correspondingly, and the detection limits were 40, 0.67, and 0.23 μM (S/N?=?3), respectively. The proposed method offers a promise for simple, rapid, selective, and cost-effective analysis of small biomolecules. 相似文献
A voltammetric sensor is presented for the simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). It is based on a gold electrode (GE) modified with carboxyl-functionalized graphene (CFG) and silver nanocube functionalized DA nanospheres (AgNC@PDA-NS). The AgNC@PDA-NS nanocomposite was characterized by scanning electron microscopy and UV-Vis spectroscopy. The electrochemical behavior of the modified electrode was evaluated by electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The modified electrode displays good electrocatalytic activity towards DA (typically at 0.14 V vs. Ag/AgCl) and UA (typically at 0.29 V vs. Ag/AgCl) even in the presence of ascorbic acid. Response to DA is linear in the concentration range of 2.5 to 130 μM with a detection limit of 0.25 μM. Response to UA is linear in the concentration range of 10 to 130 μM with a detection limit of 1.9 μM. In addition, the sensitivity for DA and UA is 0.538 and 0.156 μA μM?1 cm?2, respectively. The modified electrode also displays good stability, selectivity and reproducibility.
A novel CdTe quantum dots‐modified carbon paste electrode (QDMCPE) was fabricated and used to study the electrooxidation of dopamine and uric acid and their mixtures by electrochemical methods. Using square wave voltammetry (SWV), a highly sensitive and simultaneous determination of dopamine and uric acid was explored at the modified electrode. SWV peak currents of dopamine and uric acid increased linearly with their concentrations in the ranges of 7.5×10?8–6.0×10?4 M, and 7.5×10?6–1.4×10?3 M, respectively. Finally this new sensor was used for determination of dopamine and uric acid in some real samples. 相似文献
A novel permselective film of electrodeposited polydopamine (PDA) on electrochemical reduced graphene oxide (erGO) surface was prepared. The obtained composite films were characterized by atomic force microscope (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The influences of permselectivity with different electropolymerized cycles and concentration of dopamine on electrochemical responses of biomolecules on electrode were investigated. It was found that the composite film held high cationic permeable to dopamine (DA) and good suppression of ascorbic acid (AA) and uric acid (UA) using CV. The anodic peak currents were proportional to dopamine concentration. The significant permselectivity suggested that the PDA/graphene‐modified electrode has opened a new route to high selective dopamine biosensor. 相似文献
A sensitive and selective electrochemical method for the determination of ascorbic acid was developed. It was shown that a hydrated osmium complex‐containing redox polymer film can be electrodeposited at the gold electrode and it exhibits excellent electrocatalytic activity towards the oxidation of ascorbic acid. In contrast to a bare gold electrode, the oxidation current of ascorbic acid increased greatly and the oxidation peak potential shifted negatively to about 0.01 V (vs. SCE) at the modified electrode. Amperometric measurements were performed at an applied potential of 0.01 V and a linear response was obtained in the range of 2–400 μM with a limit of detection (LOD) of 0.6 μM (S/N=3). The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of uric acid and dopamine. The proposed procedure was successfully applied to the determination of ascorbic acid in human urine samples. 相似文献
A chemically modified carbon paste electrode (CPE), consisting of 2,2''-[(1E)-(1,2-phenylenebis(azanylylidene)] bis(methanylylidene)]bis(benzene-1,4-diol) (PBD) and multiwalled carbon nanotubes (CNTs), was used to study the electrocatalytic oxidation of dopamine using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry (DPV). First, the electrochemical behavior of the modified electrode was investigated in buffer solution. Then the diffusion coefficient, electrocatalytic rate constant, and electron-transfer coefficient for dopamine oxidation at the surface of the PBD-modified CNT paste electrode were determined using electrochemical approaches. It was found that under optimum conditions (pH = 7.0), the oxidation of dopamine at the surface of such an electrode occurred at about 200 mV, lower than that of an unmodified CPE. DPV of dopamine at the modified electrode exhibited two linear dynamic ranges, with a detection limit of 1.0 μmol/L. Finally, DPV was used successfully for the simultaneous determination of dopamine, uric acid, and folic acid at the modified electrode, and detection limits of 1.0, 1.2, and 2.7 μmol/L were obtained for dopamine, uric acid, and folic acid, respectively. This method was also used for the determination of dopamine in a pharmaceutical preparation using the standard addition method. 相似文献
A carbon paste electrode (CPE), modified with novel hydroquinone/TiO2 nanoparticles, was designed and used for simultaneous determination of ascorbic acid (AA), uric acid (UA) and folic acid (FA). The magnitude of the peak current for modified TiO2-nanoparticle CPE (MTNCPE) increased sharply in the presence of ascorbic acid and was proportional to its concentration. A dynamic range of 1.0–1400.0 μM, with the detection limit of 6.4 × 10?7 M for AA, was obtained using the DPV technique (pH = 7.0). The prepared electrode was successfully applied for the determination of AA, UA, and FA in real samples. 相似文献