共查询到20条相似文献,搜索用时 31 毫秒
1.
A poly(L-methionine) modified electrode, fabricated by electrochemical immobilization of the L-methionine on a glassy carbon
electrode, was used for simultaneous determination of dopamine and epinephrine through cyclic voltammetry. The electrochemical
properties of dopamine and epinephrine have been investigated. This sensor gave two separated cathodic peaks at −0.282 and
0.112 V for EP and DA, respectively. A linear response was obtained in the range of 5.0 × 10−7 to 1.0 × 10−4 mol l−1 for epinephrine, and 1.0 × 10−6 to 5.0 × 10−4 mol l−1 for dopamine. The detection limits were 3.6 × 10−7 mol l−1 and 4.2 × 10−7 mol l−1 for epinephrine and dopamine, respectively. This method was successfully applied for simultaneous determination of dopamine
and epinephrine in human urines.
The text was submitted by the authors in English. 相似文献
2.
A poly(caffeic acid) thin film was deposited on the surface of a glassy carbon electrode by potentiostatic technique in an
aqueous solution containing caffeic acid. The poly(caffeic acid)-modified electrode was used for the determination of ascorbic
acid (AA), dopamine (DA), and their mixture by cyclic voltammetry. This modified electrode exhibited a potent and persistent
electron-mediating behavior followed by well-separated oxidation peaks toward AA and DA at a scan rate of 10 mV s−1 with a potential difference of 135 mV, which was large enough to determine AA and DA individually and simultaneously. The
catalytic peak current obtained was linearly dependent on the AA and DA concentrations in the range of 2.0 × 10−5−1.2 × 10−3 and 1.0 × 10−6−4.0 × 10−5 mol L−1 in 0.15 mol L−1 phosphate buffer (pH 6.64). The detection limits for AA and DA were 9.0 × 10−6 and 4.0 × 10−7 mol L−1, respectively. The modified electrode shows good sensitivity, selectivity, and stability and has been applied to the determination
of DA and AA in real samples with satisfactory results. 相似文献
3.
Covalent modification of glassy carbon electrodes with glycine for voltammetric separation of dopamine and ascorbic acid 总被引:1,自引:0,他引:1
Glycine was covalently grafted on to a glassy carbon electrode (GCE) by amine cation radical formation in electrooxidation
of the amino-containing compound. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry proved the immobilization
of glycine on the GCE. The modified electrode reduced the overpotentials of dopamine (DA) and ascorbic acid (AA) by approximately
0.15 V and 0.23 V, respectively, and resolved the overlapping voltammetric response of DA and AA into two well-defined voltammetric
peaks in cyclic voltammetry (CV) or differential pulse voltammetry (DPV), unlike the unmodified GCE; this can be used for
the simultaneous determination of these species in a mixture. The differential pulse peak current was linearly dependent on
DA and AA concentration in the range 5 × 10–6– 8 × 10–4 mol L–1 and 6 × 10–5– 4 × 10–3 mol L–1, with correlation coefficients of 0.996 and 0.994, respectively. The detection limits (3δ) for DA and AA were 1.8 × 10–6 mol L–1 and 2.1 × 10–5 mol L–1, respectively. The modified electrode is very sensitive, selective and stable, and has been applied to the determination
of DA and AA simultaneously in samples with satisfactory results.
Received: 30 October 2000 / Revised: 9 March 2001 / Accepted: 13 March 2001 相似文献
4.
CeO2 nanoparticles approximately 12 nm in size were synthesized and subsequently characterized by XRD, TEM and UV-vis spectroscopy.
Then, a gold electrode modified with CeO2 nanoparticles was constructed and characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).
The modified electrode demonstrated strong catalytic effects with high stability towards electrochemical oxidation of rutin.
The anodic peak currents (measured by differential pulse voltammetry) increased linearly with the concentration of rutin in
the range of 5.0 × 10−7–5.0 × 10−4 mol · L−1. The detection limit (S/N = 3) was 2.0 × 10−7 mol · L−1. The relative standard deviation (RSD) of 8 successive scans was 3.7% for 5.0 × 10−6 mol · L−1 rutin. The method showed excellent sensitivity and stability, and the determination of rutin in tablets was satisfactory. 相似文献
5.
Sayed Medhi Ghoreishi Mohsen Behpour Mohammad Hassan Motaghedi Fard 《Journal of Solid State Electrochemistry》2012,16(1):179-189
In this work, we investigate the electrochemical activity of dopamine (DA) and uric acid (UA) using both a bare and a modified
carbon paste electrode as the working electrode, with a platinum wire as the counter electrode and a silver/silver chloride
(Ag/AgCl) as the reference electrode. The modified carbon paste electrode consists of multi-walled carbon nanotubes (>95%)
treated with α-cyclodextrine, resulting in an electrode that exhibits a significant catalytic effect toward the electro-chemical
oxidation of DA in a 0.2-M Britton–Robinson buffer solution (pH 5.0). The peak current increases linearly with the DA concentration
within the molar concentration ranges of 2.0 × 10−6 to 5.0 × 10−5 M and 5.0 × 10−5 to 1.9 × 10−4 M. The detection limit (signal to noise >3) for DA was found to be 1.34 × 10−7 M, respectively. In this work, voltammetric methods such as cyclic voltammetry, chronoamperometry, chronocuolometry, differential
pulse and square wave voltammetry, and linear sweep and hydrodynamic voltammetry were used. Cyclic voltammetry was used to
investigate the redox properties of the modified electrode at various scan rates. The diffusion coefficient (D, cm2 s−1 = 3.05 × 10−5) and the kinetic parameters such as the electron transfer coefficient (α = 0.51) and the rate constant (k, cm3 mol−1 s−1 = 1.8 × 103) for DA were determined using electrochemical approaches. By using differential pulse voltammetry for simultaneous measurements,
we obtained two peaks for DA and UA in the same solution, with the peak separation approximately 136 mV. The average recovery
was measured at 102.45% for DA injection. 相似文献
6.
A simple, sensitive, and reliable method based on a combination of multi-walled carbon nanotubes with incorporated β-cyclodextrin
(β-CD-MWNTs) and a polyaniline (PANI) film-modified glassy-carbon (GC) electrode has been successfully developed for determination
of dopamine (DA) in the presence of ascorbic acid (AA). The PANI film had good anti-interference properties and long-term
stability, because of the permselective and protective properties of the conducting redox polymer film. The acid-treated MWNTs
with carboxylic acid functional groups promoted the electron-transfer reaction of DA and inhibited the voltammetric response
of AA. Sensitive detection of DA was further improved by the preconcentration effect of formation of a supramolecular complex
between β-CD and DA. The analytical response of the β-CD-MWNTs/PANI film to the electrochemical behavior of DA was, therefore,
better than that of a MWNTs/PANI film, a PANI film, or a bare glassy-carbon (GC) electrode. Under the conditions chosen a
linear calibration plot was obtained in the range 1.0 × 10−7–1.0 × 10−3 mol L−1 and the detection limit was 1.2 × 10−8 mol L−1. Interference from AA was effectively eliminated and the sensitivity, selectivity, stability, and reproducibility of the
electrodes was excellent for determination of DA. 相似文献
7.
A glassy carbon electrode was modified with electropolymerized film of diphenylamine sulfonic acid (DPASA). Electropolymerization was performed by cyclic voltammetry in 0.1 M KCl solution. The modified electrode showed an excellent
electrocatalytic effect towards oxidation of dopamine (DA) and ascorbic acid (AA). Electrostatic interaction between the negatively charged poly(DPASA) film and either cationic DA species or anionic AA
species favorably contributed to the redox response of DA and AA. Anodic peaks of DA and AA in their mixture were well separated
by ca 168 and −11.8 mV. The proposed modified electrode was utilized for selective determination of dopamine in the concentration
range of 5.0 × 10t7–2.0 × 10−5 M in the presence of high concentration of ascorbic acid. Detection limit was 6.5 × 10−9 M. 相似文献
8.
Lei Zhang 《Mikrochimica acta》2008,161(1-2):191-200
A covalently modified glassy carbon electrode with cysteine has been fabricated via an electrochemical oxidation procedure
and was applied to induce the electrochemical differentiation between dopamine (DA) and ascorbic acid (AA). Based on the electrostatic
interactions between the negatively charged groups on the electrode surface and DA and AA, the modified electrode enhanced
the oxidation of DA, reducing the overpotential by 180 mV, and hindered the oxidation of AA, shifting the oxidation potential
positively by 170 mV. The peak current for DA at the modified electrode was greatly enhanced and that for AA was significantly
decreased, which allows the determination of DA in the presence of AA. The differential pulse peak current was linearly dependent
on DA concentration over the range of 5 × 10−6–2 × 10−4 mol L−1. The detection limit was 1.8 × 10−6 mol L−1. The selectivity and sensitivity for dopamine is due to charge discrimination and analyte accumulation. The modified electrode
has been applied to the determination of DA in the presence of AA.
Correspondence: L. Zhang, Department of Chemistry, College of Life and Environmental Science, Shanghai Normal University,
Guilin Rd 100, Shanghai 200234, P.R. China 相似文献
9.
A method for the determination of trace clenbuterol is described. Multi-walled carbon nanotubes (MWCNTs)-Nafion composite
was used to modify the glassy carbon electrode (GCE). The modified electrode showed high sensitivity and good selectivity
for clenbuterol detection. It offered a linear range of 1.0 × 10−9–1.0 × 10−6 mol · L−1 with a detection limit of 5.0 × 10−10 mol · L−1 in pH = 1.2 solution. The oxidation mechanism of clenbuterol on the electrode was also investigated.
Correspondence: Xiao-Ya Hu, Department of Chemistry, Yang Zhou University, Yang Zhou, Jiang Su, P.R. China 相似文献
10.
A sensitive complex absorptive wave of Ca-ARS was obtained by using differential pulse voltammetry when a mercury film glass
carbon electrode was immersed in 0.1 mol L−1 KOH and 4.5×10−4 mol L−1 ARS solution. The peak potential obtained was −1.17 V (vs Ag-AgCl). The peak current was proportional to the concentration
of calcium in the range of 5.0×10−8−4.2×10−5 mol L−1. The detection limit was 2.0×10−8 mol L−1. This method was applied successfully to determining traces of calcium in blood serum. The electrochemical behavior of the
system was also studied by cyclic voltammetry, and the experiment results showed that the electrode process was an irreversible
absorptive with two electrons participating.
Translated from Journal of Beijing Normal University (Natural Science Edition), 2005, 41(2) (in Chinese) 相似文献
11.
A sensitive adsorptive anodic stripping procedure for the determination of trace zirconium at a carbon paste electrode (CPE)
has been developed. The method is based on adsorptive accumulation of the Zr(IV)-alizarin red S(ARS) complex onto the surface
of the CPE, followed by oxidation of adsorbed species. The optimal experimental conditions include the use of 0.10 mol · L−1 ammonium acetate buffer (pH 4.3), ARS, an accumulation potential of 0.20 V (versus SCE), an accumulation time of 2 min, a
scan rate of 200 mV · s−1 and a second-order derivative linear scan mode. The oxidation peak for the complex appears at 0.69 V. The peak current is
proportional to the concentration of Zr(IV) over the range of 1.0 × 10−9–2.0 × 10−7 mol · L−1, and the detection limit is 3 × 10−10 mol · L−1 for a 2 min adsorption time. The relative standard deviations (n = 8) for 5.0 × 10−8 and 5.0 × 10−9 mol · L−1 Zr(IV) are 3.3 and 4.8%, respectively. The proposed method was applied to the determination of zirconium in ore samples with
satisfactory results. 相似文献
12.
A simple and sensitive method is presented for the determination of dopamine with a nanoscale ceria ion-selective CMC (carboxymethyl
cellulose) membrane electrode by means of the Belousov–Zhabotinsky oscillating chemical reaction. The electrode exhibits excellent
potential response. If the concentration of dopamine is in the range of 4.9 × 10−5 to 2.4 × 10−7 mol · L−1, the change in oscillating amplitude is proportional to the concentration of dopamine, with a correlation coefficient of
0.9987 and a standard deviation of 0.17%. A recovery of 97.5–105.0% was obtained. Interference was also studied. The use of
a nanoscale ceria ion-selective membrane-working electrode improved the sensitivity of the determination method. 相似文献
13.
A 3-amino-5-mercapto-1,2,4-triazole (TA) self-assembled monolayer-modified gold electrode (TA SAM/Au) is characterized by
X-ray photoelectron spectroscopy, A.C. impedance, cyclic voltammetry, chronoamperometry and chronocoulometry. The TA SAM/Au
exhibited good promotion of the electrochemical oxidation of dopamine. Some electrochemical parameters of dopamine such as
electron transfer number, exchange current density, standard heterogeneous rate constant, diffusion coefficient, etc., were
measured by different electrochemical methods. The peak currents of dopamine were linearly dependent on its concentration
in the range of 1.5 × 10−6–1.0 × 10−4 mol L−1, with a detection limit of 5.0 × 10−7 mol L−1. The oxidative peak potentials of dopamine and ascorbic acid were well separated at about 190 ± 10 mV in pH 2.0 BR buffers
at TA SAM/Au, the oxidation peak current increases approximately linearly with increasing concentration of both dopamine and
ascorbic acid in the concentration range of 9.98 × 10−6–4.54 × 10−4 mol L−1. It can be used for simultaneous determination of dopamine and ascorbic acid. 相似文献
14.
A Pt wire coated with a bentonite–carbon composite in a poly(vinyl chloride) membrane was used for detection of lead. The
sensor has a Nernstian slope of 29.42±0.50 mV per decade over a wide range of concentration, 1.0×10−7 to 1.0×10−3 mol L−1 Pb(NO3)2. The detection limit is 5.0×10−8 mol L−1 Pb(NO3)2 and the electrode is applicable in the pH range 3.0–6.7. It has a response time of approximately 10 s and can be used at
least for three months. The electrode has good selectivity relative to nineteen other metal ions. The practical analytical
utility of the electrode is demonstrated by measurement of Pb(II) in industrial waste and river water samples. 相似文献
15.
Determination of chromium(VI) and total chromium in water by in-electrode coulometric titration in a porous glassy carbon electrode 总被引:1,自引:0,他引:1
Chromium(VI) is determined through its direct electrochemical reduction in the bulk of a porous glassy carbon electrode. An
electrode filled with the acidified sample and Cr(VI) is reduced by means of a constant current whereas the potential of the
electrode is monitored. The limits of detection and quantification were found to be 1.9 and 6.0 μg · L−1, resp. The linear range, repeatability and reproducibility were found to be 5–500 μg · L−1, 1.2, and 1.8%, resp. The influence of Fe(III), Ca(II), Mg(II), sulphates, nitrates, humic acids and surfactants was investigated.
Total chromium was measured after chemical oxidation of Cr(III) to chromate by permanganate. The method was applied to analyses
of water samples. 相似文献
16.
Jiming Xu Yanping Wang Yuezhong Xian Hui Li Litong Jin K. Tanaka H. Haraguchi 《Chromatographia》2002,56(7-8):449-453
Summary A sensitive ion-exclusion chromatographic method has been developed for determination of oxalate, thiosulfate, and thiocyanate.
The method is based on separation of these anions on a polymethacrylate-based, weakly acidic cation-exchange resin (TSKgel
OApak-A) and detection by means of a glassy carbon (GC) electrode electrochemically modified with polyvinylpyridine (PVP),
palladium, and iridium oxide (PVP/Pd/IrO2). The electrochemical behavior of oxalate, thiosulfate, and thiocyanate at this chemically modified electrode (CME) have
been investigated by cyclic voltammetry. The results indicated that electrocatalytic oxidation of these anions by the electrode
was efficient and that the sensitivity, stability, and lifetime of the electrode were relatively high. Combined with ion-exclusion
chromatography the PVP/Pd/IrO2 electrode was used as the working electrode for amperometric detection of these anions. All linear ranges were over two orders
of magnitude and detection limits, defined asS/N=3, were 9.0×10−7 mol L−1 for oxalate, 6.7×10−7 mol L−1 for thiosulfate, and 5.6×10−7 mol L−1 for thiocyanate. Correlation coefficients were all>0.998. Coupled with microdialysis sampling the method has been successfully
applied to the determination of oxalate, thiosulfate, and thiocyanate in urine. 相似文献
17.
The simultaneous determination of three isomers of phenylenediamines (o, m, and p-phenylenediamine) and two isomers of dihydroxybenzenes (catechol and resorcinol) in hair dyes was performed by capillary
zone electrophoresis coupled with amperometric detection (CZE–AD). The effects of working electrode potential, pH and concentration
of running buffer, separation voltage, and injection time on CZE–AD were investigated. Under the optimum conditions the five
analytes could be perfectly separated in 0.30 mol L−1 borate–0.40 mol L−1 phosphate buffer (pH 5.8) within 15 min. A 300 μm diameter platinum electrode had good responses at +0.85 V (versus SCE)
for the five analytes. Their linear ranges were from 1.0 × 10−6 to 1.0 × 10−4 mol L−1 and the detection limits were as low as 10−7 mol L−1 (S/N = 3). This working electrode was successfully used to analyze eight kinds of hair dye sample with recoveries in the range
91.0–108.0% and RSDs less than 5.0%. These results demonstrated that capillary zone electrophoresis coupled with electrochemical
detection using a platinum working electrode as detector was convenient, highly sensitive, highly repeatable and could be
used in the rapid determination of practical samples.
Figure Electropherograms obtained from 10 mg mL−1 hair dye sample solutions at a platinum working electrode under optimum CZE–AD conditions: (a) natural black (I), (b) golden: (1) p-phenylenediamine, (2) m-phenylenediamine, (3) o-phenylenediamine, (4) resorcinol, and (5) catechol 相似文献
18.
The fabrication and electrochemical characteristics of a penicillamine (PCA) self-assembled monolayer modified gold electrode
were investigated. The electrode can enhance the electrochemical response of uric acid (UA), and the electrochemical reaction
of UA on the PCA electrode has been studied by cyclic voltammetry and differential pulse voltammetry. Some electrochemical
parameters, such as diffusion coefficient, standard rate constant, electron transfer coefficient and proton transfer number
have been determined for the electrochemical behavior on the PCA self-assembled monolayer electrode. The electrode reaction
of UA is an irreversible process, which is controlled by the diffusion of UA with two electrons and two protons transfer at
the PCA/Au electrode. In phosphate buffer (pH 5.0), the peak current is proportional to the concentration of UA in the range
of 6.0 × 10−5–7.0 × 10−4 mol L−1 and 2.0 × 10−5–7.0 × 10−4 mol L−1 for the cyclic voltammetry and differential pulse voltammetry methods with the detection limits of 5.0 × 10−6 and 3.0 × 10−6 mol L−1, respectively. The method can be applied to determine UA concentration in real samples. 相似文献
19.
de la Escosura-Muñiz A González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,384(3):742-750
A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon
electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was
bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological
reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I)
bound to the anti-HSA was electrodeposited in 0.1 mol L−1 HCl at −1.00 V for 5 min then oxidised in 0.1 mol L−1 H2SO4 solution at +1.40 V for 1 min. Silver electrodeposition at −0.14 V for 1 min followed by anodic stripping voltammetry were
then performed in aqueous 1.0 mol L−1 NH3–2.0×10−4 mol L−1 AgNO3. For both non-competitive and competitive formats, calibration plots in the ranges 5.0×10−10 to 1.0×10−8 mol L−1 and 1.0×10−10 to 1.0×10−9 mol L−1 HSA, respectively, with estimated detection limits of 1.5×10−10 mol L−1 (10 ng mL−1) and 1.0×10−10 mol L−1 (7 ng mL−1), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay
formats. 相似文献
20.
Xiaojiang Zheng Dazhai Zhou Dongshan Xiang Wensheng Huang Shaofang Lu 《Russian Journal of Electrochemistry》2009,45(10):1183-1187
A poly(L-cysteine) thin film was prepared onto electrode surface via electropolymerization. In pH 7.0 phosphate buffer, L-cysteine was oxidized during the cyclic potential sweep between −0.60 and 2.00 V, forming a thin film at the glassy carbon
electrode (GCE) surface. The electrochemical behaviors of ascorbic acid at the bare GCE and the poly(L-cysteine) film-coated GCE were investigated. The oxidation peak potential of ascorbic acid shifts to more negative potential
at the poly(L-cysteine) film-modified GCE. Moreover, the oxidation peak current significantly increases at the poly(L-cysteine) film-modified GCE. These phenomena indicate that poly(L-cysteine) film shows highly-efficient catalytic activity to the oxidation of ascorbic acid. Based on this, a sensitive and
simple electrochemical method was proposed for the determination of ascorbic acid. The oxidation peak current of ascorbic
acid is proportional to its concentration over the range from 1.0 × 10−6 to 5.0 × 10−4 mol l−1. The limit of detection is evaluated to be 4.0 × 10−7 mol l−1. 相似文献