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1.
An electrochemically functional nanocomposite through the adsorption of methylene blue onto the multi-walled nanotubes (MB-MWNTs)
was prepared, and a sensitive voltammetric sensor was fabricated. The modified electrode showed excellent electrocatalytic
activity toward dopamine (DA) and uric acid (UA) in 0.1 M phosphate solution medium (pH 3.0). Compared to the bare electrode,
the MB-MWNTs film-modified electrode not only remarkably enhanced the anodic peak currents of DA and UA, i.e., shifted the
anodic peak potential of DA negatively, but also avoided the overlapping of the anodic peaks of DA and UA. The interference
of ascorbic acid (AA) was eliminated. Under the optimized conditions, the peak separation between AA and DA and between DA
and UA was 219 and 174 mV, respectively. In the presence of 1.0 mM AA and 10.0 μM UA, the anodic peak current was linear to
the concentration of DA in the range of 0.4–10.0 μM with a detection limit of 0.2 μM DA. The anodic peak current of UA was
linear to the concentration in the range of 2.0–20.0 and 20.0–200.0 μM with a lowest detection limit of 1.0 μM in the presence
of 1.0 mM AA and 1.0 μM DA. 相似文献
2.
A very stable electroactive film of catechin was electrochemically deposited on the surface of activated glassy carbon electrode.
The electrochemical behavior of catechin modified glassy carbon electrode (CMGCE) was extensively studied using cyclic voltammetry.
The properties of the electrodeposited films, during preparation under different conditions, and the stability of the deposited
film were examined. The charge transfer coefficient (α) and charge transfer rate constant ( k
s) for catechin deposited film were calculated. It was found that the modified electrode exhibited excellent electrocatalytic
activity toward hydrazine oxidation and it also showed a very large decrease in the overpotential for the oxidation of hydrazine.
The CMGCE was employed to study electrocatalytic oxidation of hydrazine using cyclic voltammetry, rotating disk voltammetry,
chronoamperometry, amperometry and square-wave voltammetry as diagnostic techniques. The catalytic rate constant of the modified
electrode for the oxidation of hydrazine was determined by cyclic voltammetry, chronoamperometry and rotating disk voltammetry
and was found to be around 10 −3 cm s −1 . In the used different voltammetric methods, the plot of the electrocatalytic current versus hydrazine concentration is
constituted of two linear segments with different ranges of hydrazine concentration. Furthermore, amperometry in stirred solution
exhibits a detection limit of 0.165 μM and the precision of 4.7% for replicate measurements of 40.0 μM solution of hydrazine. 相似文献
3.
A new simple, selective and rapid cyclic voltammetric method is reported for the accurate and precise determination of captopril
using chlorpromazine as a suitable electrocatalyst. It has been shown by cyclic voltammetry, single step chronoamperometry
and electrochemical impedance spectroscopy that chlorpromazine can catalyze the oxidation of captopril in aqueous buffer solution
and produces a sharp oxidation peak current at about 0.625 V vs. saturated calomel reference electrode. The catalytic oxidation
peak current of captopril is linearly dependent on its concentration and enables the determination of captopril over the concentration
range of 8–1000 μM at pH 5.0, with a detection limit of 4.8 μM. The relative standard deviation for the determination of 400
μM captopril is 0.66% ( n = 9). The influence of potential interfering substances on the determination of captopril was studied. The method was satisfactorily
applied to the determination of captopril in real samples such as drug and urine. 相似文献
4.
Electrochemical synthesis of ruthenium oxide (RuOx) onto Nafion-coated glassy carbon (GC) electrode and naked GC electrode
were carried out by using cyclic voltammetry. Electrochemical deposition of RuOx onto Nafion-coated electrode was monitored
by in situ electrochemical quartz crystal microbalance (EQCM). Surface characterizations were performed by scanning electron
microscope (SEM) and atomic force microscope (AFM). SEM and AFM images revealed that ruthenium oxide particles incorporated
onto the Nafion polymer film. In addition, a GC electrode modified with ruthenium oxide–Nafion film (RuOx–Nf–GC) was shown
excellent electrocatalytic activity towards dopamine (DA) and ascorbic acid (AA). The anodic peak current increases linearly
over the concentration range of 50 μM–1.1 mM for DA with the correlation coefficient of 0.999, and the detection limit was
found to be (S/N = 3) 5 μM. Owing to the catalytic effect of the modified film towards DA, the modified electrode resolved
the overlapped voltammetric responses of AA and DA into two well-defined voltammetric peaks with peak-to-peak separation about
300 mV. Here, RuOx–Nf–GC electrode employed for determination of DA in the presence of AA. This modified electrode showed
good stability and antifouling properties. 相似文献
5.
This work describes the electrochemical behavior of nickel-dipicolinic acid (Ni-DPA) film immobilized on the surface of bimetallic
Au-Pt inorganic-organic hybrid nanocomposite glassy carbon electrode and its electrocatalytic activity toward the oxidation
of fructose. The electrode possesses a three-dimensional (3D) porous network nano architecture, in which the bimetallic Au-Pt
serving as metal nano-particle based microelectrode ensembles are distributed in the matrix of interlaced 3,3′,5,5′-tetramethylbenzidine
(TMB) organic nanofibers (NFs). The surface structure and composition of the sensor was characterized by scanning electron
microscopy (SEM). Electrocatalytic oxidation of fructose on the surface of modified electrode was investigated with cyclic
voltammetry and chronoamperometry methods and the results show that the Ni-DPA film displays excellent electrochemical catalytic
activities towards fructose oxidation. The hydrodynamic amperometry at rotating modified electrode at constant potential versus
reference electrode was used for detection of fructose. Under optimized conditions the calibration plots are linear in the
concentration range 0.5 to 70 μM and detection limit was found to be 0.1 μM. 相似文献
6.
In this paper, a novel method for detection of formaldehyde (HCHO), based on its electrocatalytic oxidation of HCHO at a nickel
electrode, is reported. The mechanism of electrocatalytic oxidation and quantification of HCHO have been investigated by cyclic
and staircase voltammetry, respectively. The electrocatalytic oxidation peak potential of HCHO is at about 475 mV vs. Ag/AgCl
electrode; the peak current responds proportionally to concentrations of HCHO in alkaline solution. The linear range of detection
is from 46.8 to 1640 μg/L (1.56 × 10 −6 to 5.46 × 10 −5 M) with a correlation coefficient of 0.996 and a detection limit of 23.4 μg/L (7.80 × 10 −7 M). The relative standard deviation (RSD) is less than 6% ( n = 5), and the recovery is in the range 98–106% for real samples. The result is consistent with that from the spectrophotometry.
The text was submitted by the authors in English. 相似文献
7.
Cyclic voltammetry, chronoamperometry, and rotating disk electrode voltammetry were used to investigate the electrochemical
behavior of thiobencarb (TB) at carbon paste electrode modified with an azo dye, 2-(4-((4-ethoxyphenyl)diazenyl)phenylamino)ethanol
(EDPE), EDPE/modified carbon paste electrode (MCPE). The modified electrode showed high electrocatalytic activity toward thiobencarb.
The current was enhanced significantly relative to the situation prevailing when a bare glassy carbon electrode was used.
The kinetics parameters of this process were calculated, the apparent electron transfer rate constant k
s and α (charge transfer coefficient between electrode and EDPE) were 14.6 s −1 and 0.48, respectively. The experimental parameters were optimized, and the mechanism of the catalytic process was discussed.
The best defined cathodic peak was obtained with 0.1 M acetate buffer (pH 3.0). The response of the sensor was very quick,
and response time was approximately 5 s. The differential pulse voltammetry response of the MCPE was linear against the concentration
of TB in the range of 0.96 to 106 μg L −1. The limit of detection was found to be 0.025 μg L −1. The precision was examined by carrying out eight replicate measurements at a concentration of 25 μg L −1 TB; the relative standard deviation was 2.9%. 相似文献
8.
In this work, 3-aminopropyltriethoxysilane modified Fe 3O 4 nanoparticles (ATPS-Fe 3O 4) were used to modify glassy carbon electrode for aminopyrine determination. ATPS-Fe 3O 4 showed obviously catalytic activity and adsorptivity towards aminopyrine oxidation proven by the increased oxidation peak
current and the decreased oxidation peak potential. The best analytical response was obtained by immobilizing 8 μL 3 mg/mL
APTS-Fe 3O 4 dispersion with an accumulation time of 200 s at −0.2 V in 0.1 M phosphate buffer solution (pH 9.0). The oxidation peak current
of aminopyrine showed linear relationship with its concentration in the range from 0.5 to 100 and 100 to 1600 μM. The detection
limit was 0.1 μM (S/N = 3). The proposed method showed satisfactory repeatability and anti-interference ability. The fabricated
electrode was successfully applied to determine aminopyrine in pharmaceutical formulations. 相似文献
9.
A sensitive hydrazine sensor has been fabricated using copper oxide nanoparticles modified glassy carbon electrode (GCE) to
form nano-copper oxide/GCE. The nano-copper oxide was electrodeposited on the surface of GCE in CuCl 2 solution at −0.4 V and was characterized by Scanning electron microscopy and X-ray diffraction. The prepared modified electrode
showed a good electrocatalytic activity toward oxidation of hydrazine. The electrochemical behavior of hydrazine on nano-copper
oxide/GCE was explored. The oxidative current increased linearly with improving concentration of hydrazine on nano-copper
oxide/GCE from 0.1 to 600 μM and detection limit for hydrazine was evaluated to be 0.03 μM at a signal-to-noise ratio of 3.
The oxidation mechanism of hydrazine on the nano-copper oxide/GCE was also discussed. The fabricated sensor could be used
to determine hydrazine in real water. 相似文献
10.
A method for forming a composite film on the surface of a graphite electrode is proposed. Conditions for detecting the maximum catalytic current under batch and flow conditions are determined. A procedure for the electrocatalytic determination of ascorbic acid at the graphite electrode modified with a polyaniline film containing palladium particles is proposed. The catalytic effect of this electrode manifests itself by a ~300-mV decrease in the peak potential of ascorbic acid oxidation and by a multiple increase in the peak current of ascorbic acid oxidation as compared to the unmodified electrode. The linear dependence of the electrocatalytic response of the composite electrode on the concentration of ascorbic acid is observed down to 1 × 10 ?8 M and 2.5 nmol of ascorbic acid under batch and flow-injection analysis conditions, respectively. 相似文献
11.
A carbon ionic liquid electrode ( CILE) was fabricated by mixing N-butylpyridinium hexafluoro-phosphate ( BPPF
6
) with graphite powder and further used for the investigation on the electrochemical behavior of L-tryptophan ( Trp). The fabricated CILE showed good conductivity, inherent electrocatalytic ability and strong promotion to the electron transfer
of Trp. On the CILE, an irreversible oxidation peak appeared at 0.948 V (vs. saturated calomel reference electrode). For 5.0
× 10 −5 M Trp the oxidation peak current increased about 5 times and the oxidation peak potential decreased on 0.092 V compared to
carbon paste electrode. The results indicated that an electrocatalytic reaction occurred on CILE. The conditions for the electrochemical
detection were optimized and the electrochemical parameters of Trp on CILE were carefully investigated. Under the selected
conditions, the oxidation peak current showed linear relationship with Trp concentration in the range of 8.0 × 10 −6 ∼1.0 × 10 −3 M for cyclic voltammetry and the detection limit was estimated as 4.8 × 10 −6 M (3σ). The interferences of other amino acids or metal ions on the determination were tested and the proposed method was
successfully applied to the synthetic sample analysis. 相似文献
12.
The electrochemical oxidation of thiocytosine on the surface of carbon-paste electrode modified with Schiff base (salophen
derivatives) complexes of cobalt is studied. The effect of the substituents in the structure of salophen on the catalytic
property of the modified electrode is investigated by using cyclic and differential pulse voltammetry. Cobalt (II)-5-nitrosalophen,
because of its electrophilic functional groups, leads to a considerable enhancement in the catalytic activity, sensitivity
(peak current), and a marked increase in the anodic potential of the modified electrode. The differential pulse voltammetry
is applied as a very sensitive method for the detection of thiocytosine. The linear dynamic range was between 1 × 10 −3 to 4 × 10 −6 M with a slope of 0.0168 μA/μM, and the detection limit was 1 × 10 −6 M. The modified electrode is successfully applied for the voltammetric detection of thiocytosine in human synthetic serum
sample and also pharmaceutical preparations. A linear range from 1 × 10 −3 to 1 × 10 −5 M with a slope of 0.0175 μA/μM is resulted for the standard addition of thiocytosine spiked to the buffered human serum,
which is differing from the curve in buffer solution about 4%. The electrode has a very good reproducibility (relative standard
deviation for the slope of the calibration curve is less than 3.5% based on six determinations in a month), high stability
in its voltammetric response and low detection limit for thiocytosine, and high electrochemical sensitivity with respect to
other biological thiols such as cysteine. 相似文献
13.
Au electrode modified with the self-assembled monolayer of a heterocyclic thiol, mercaptotriazole (MTz), is used for the electroanalysis
of uric acid (UA) and ascorbic acid (AA). MTz forms a less compact self-assembly on Au electrode. The self-assembly of MTz
on Au electrode favors the oxidation of UA and AA at less positive potential. Significant decrease (∼400 mV) in the overpotential
and enhancement in the peak current for the oxidation of interfering AA with respect to the unmodified electrode is observed.
The negative shift in the oxidation peak potential of AA favors electrochemical sensing of UA without any interference. Two
well-separated voltammetric peaks for AA and UA are observed in their coexistence. The large separation between the two voltammetric
peaks allows the simultaneous or selective sensing of the analytes without compromising the sensitivity. Linear response is
obtained for a wide concentration range. This electrode could sense as low as 1 μM of UA in the presence of 10-fold excess
of interfering AA. No change in the sensitivity (0.012 μA/μM) of the electrode toward UA in the presence and absence of AA
is observed. Reproducible and stable amperometric flow injection response was obtained upon repetitive injection. 相似文献
14.
This study reports the preparation and characterization of gold nanoparticles deposited on amine-functioned hexagonal mesoporous
silica (NH 2–HSM) films and the electrocatalytic oxidation of glucose. Gold nanoparticles are fabricated by electrochemically reducing
chloroauric acid on the surface of NH 2–HSM film, using potential step technology. The gold nanoparticles deposited have an average diameter of 80 nm and show high
electroactivity. Prussian blue film can form easily on them while cycling the potential between −0.2 and 0.6 V (vs saturated
calomel electrode) in single ferricyanide solution. The gold nanoparticles loading NH 2–HSM-film-coated glassy carbon electrode (Au–NH 2–HSM/GCE) shows strong catalysis to the oxidation of glucose, and according to the cathodic oxidation peak at about 0.16 V,
the catalytic current is about 2.5 μA mM −1. Under optimized conditions, the peak current of the cathodic oxidation peak is linear to the concentration of glucose in
the range of 0.2 to 70 mM. The detection limit is estimated to be 0.1 mM. In addition, some electrochemical parameters about
glucose oxidation are estimated. 相似文献
15.
By immobilizing rutin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWCNT),
a new modified electrode has been fabricated and its electrochemical behavior was investigated by cyclic voltammetry. Cyclic
voltammograms of the resulting modified electrode show stable and a well defined redox couple with surface confined characteristics.
The results show that the reversibility of rutin is significantly improved at a MWCNT modified GCE in comparison with GCE
alone. The charge transfer coefficient, α, was calculated to be 0.4, and charge transfer rate constant, k s, was 46.7 s −1 in pH 8, indicating great facilitation of the electron transfer between rutin and MWCNT deposited on the electrode surface.
The rutin MWCNT (RMWCNT) modified GCE showed excellent mediation of hydrazine oxidation: a decrease in the overvoltage of
hydrazine electrooxidation was observed as well as a dramatic increase in the peak current compared to that seen at a rutin
modified GCE (RMGCE), activated GCE or bare GCE. Hydrazine was determined amperometrically at the surface of RMWCNT modified
GCE in pH 8. Under the optimized conditions the calibration curve is linear in the concentration range 2.0–190.0 μM hydrazine.
The detection limit and sensitivity are 0.61 μM and 0.0656 μA μM −1, respectively. Finally the kinetic parameters of the electron transfer coefficient, α, the heterogeneous rate constant of
dependent to different potentials, k′(E), and the standard heterogeneous rate constant, k 0, for oxidation of hydrazine at the RMWCNT surface were determined using various electrochemical methods. The advantages of
this modified electrode for hydrazine determination are high sensitivity, excellent catalytic activity, short response time,
wide linear range, and high exchange current density. 相似文献
16.
Glassy carbon electrode modified with electrodeposited nickel oxide nanoparticles (NiOxNPs) was used as electrocatalyst for
oxidation of omeprazole and pentoperazole in alkaline solution. The modified electrode exhibited efficient electrocatalytic
activity for the oxidation of omeprazole and pentoperazole with relatively high sensitivity, excellent stability, and long
lifetime. Hydrodynamic amperometric method is used for determination of selected analytes. Under optimized condition, the
linear concentration range, detection limit, and sensitivity of modified electrode toward omeprazole detection are 4.5–120 μM,
0.4 μM (at signal to noise 3), and 40.1 nA μM −1 cm −2, respectively. For pantoperazole, hydrodynamic amperometric determination yielded calibration curve with linear range of
2.5–180 μM, detection limit of 0.2 μM, and sensitivity of 39.2 nA μM −1 cm −2, respectively. The proposed method was successfully applied to pentoperazole and omeprazole determination in drug samples. 相似文献
17.
The electrochemical response of phenol at acetylene black (AB)-dihexadecyl hydrogen phosphate (DHP) composite modified glassy
carbon electrode in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. In this system, a sensitive oxidation
peak at 0.62 V (SCE) was obtained. The electrode process and the influence of CTAB on the oxidation of phenol were explored
by chronocoulometry and linear sweep voltammetry (LSV). Experimental conditions for the determination of phenol were optimized.
In the range of 5.0 × 10 −7 to 1.2 × 10 −5 M, the phenol concentration was linear with the oxidation peak current and the detection limit was found to be 1.0 × 10 −7 M for 3 min accumulation. The method was applied for the determination of phenol in lake water and the results were satisfactory.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 222–229.
The text was submitted by the authors in English. 相似文献
18.
A glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNT) was prepared and the determination of trace amount of vanadium(V) based on the anodic adsorptive voltammetry of the vanadium-alizarin red S (ARS) complex is described for the first time. The results show that the sensitivity and the selectivity of the method are excellent. The second derivative linear scan voltammograms of the complex were recorded using a polarographic analyzer in the range from 0 to 1,000 mV (vs. SCE). It was found that the complex can be adsorbed on the surface of the electrode, yielding a peak at about 706 mV, corresponding to the oxidation of ARS in the complex. The peak current increases linearly with the V(V) concentration in the range of 6.0 nM to ∼1.0 μM (4.0 μM ARS), 2.0 μM∼10 μM (40 μM ARS) and the detection limit (at S/N = 3) was 2.0 nM (accumulation time 120 s). The method was successfully applied to the determination of trace amounts of vanadium in water samples. 相似文献
19.
Poly(3,4-ethylenedioxythiophene-co-(5-amino-2-naphthalenesulfonic acid)) (PEDOT-PANS) film modified glassy carbon electrode was prepared by electrochemical polymerization technique. The properties of modified electrode was studied. It was found that the electrochemical properties of modified electrode was very much dependent on the experimental conditions, such as monomer oxidation potential and pH. The modified electrode surface was characterized by scanning electron microscopy (SEM). The PEDOT-PANS film modified electrode shows electrocatalytic activity toward oxidation of dopamine (DA) in acetate buffer solution (pH 5.0) and results in a marked enhancement of the current response. The linear sweep voltammetric (LSV) peak heights are linear with DA concentration from 2 × 10 −6 to 1 × 10 −5 M. The detection limit is 5 × 10 −7 M. More over, the interferences of ascorbic acid (AA) and uric acid (UA) were effectively diminished. This work provides a simple and easy approach for selective determination of dopamine in the presence of ascorbic acid and uric acid. 相似文献
20.
The electrocatalytic oxidation of glutathione (GSH) has been studied at the surface of ferrocene-modified carbon paste electrode
(FMCPE). Cyclic voltammetry (CV), double potential step chronoamperometry, and differential pulse voltammetry (DPV) techniques
were used to investigate the suitability of incorporation of ferrocene into FMCPE as a mediator for the electrocatalytic oxidation
of GSH in buffered aqueous solution. Results showed that pH 7.00 is the most suitable for this purpose. In the optimum condition
(pH 7.00), the electrocatalytic ability of about 480 mV can be found and the heterogeneous rate constant of catalytic reaction
was calculated as . Also, the diffusion coefficient of glutathione, D, was found to be 3.61 × 10 –5 cm 2 s −1. The electrocatalytic oxidation peak current of glutathione at the surface of this modified electrode was linearly dependent
on the GSH concentration and the linear analytical curves were obtained in the ranges of 3.2 × 10 –5 M–1.6 × 10 –3 M and 2.2 × 10 –6 M–3.5 × 10 –3 M with cyclic voltammetry and differential pulse voltammetry methods, respectively. The detection limits (3 σ) were determined as 1.8 × 10 –5 M and 2.1 × 10 –6 M using CV and DPV, respectively. Finally, the electrocatalytic oxidation of GSH at the surface of this modified electrode
can be employed as a new method for the voltammetric determination of glutathione in real samples such as human plasma. 相似文献
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