共查询到20条相似文献,搜索用时 46 毫秒
1.
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
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.
Liang Wang Jun Yue Bai Peng Fei Huang Hong Jing Wang Xiao Wei Wu Yu Qing Zhao 《Mikrochimica acta》2007,158(1-2):73-78
The electrochemical behaviors of uric acid (UA) at the penicillamine (Pen) self-assembled monolayers modified gold electrode
(Pen/Au) have been studied. The Pen/Au electrode is demonstrated to promote the electrochemical response of UA by cyclic voltammetry
(CV). The diffusion coefficient D of UA is 6.97 × 10−6 cm2 s−1. In differential pulse voltammetric (DPV) measurements, the Pen/Au electrode can separate the UA and ascorbic acid (AA) oxidation
potentials by about 120 mV and can be used for the selective determination of UA in the presence of AA. The detection limit
was 1 × 10−6 mol L−1. The modified electrode shows excellent sensitivity, good selectivity and antifouling properties. 相似文献
4.
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
5.
Covalent modification of a glassy carbon electrode with penicillamine for simultaneous determination of hydroquinone and catechol 总被引:1,自引:0,他引:1
Liang Wang Peng Fei Huang Jun Yue Bai Hong Jing Wang Li Ying Zhang Yu Qing Zhao 《Mikrochimica acta》2007,158(1-2):151-157
A simple and highly selective electrochemical method has been developed for the simultaneous determination of hydroquinone
(HQ) and catechol (CC) at a glassy carbon electrode covalently modified with penicillamine (Pen). The electrode is used for
the simultaneous electrochemical determination of HQ and CC and shows an excellent electrocatalytical effect on the oxidation
of HQ and CC upon cyclic voltammetry in acetate buffer solution of pH 5.0. In differential pulse voltammetric measurements,
the modified electrode was able to separate the oxidation peak potentials of HQ and CC present in binary mixtures by about
103 mV although the bare electrode gave a single broad response. The determination limit of HQ in the presence of 0.1 mmol L−1 CC was 1.0 × 10−6 mol L−1, and the determination limit of CC in the presence of 0.1 mmol L−1 HQ was 6.0 × 10−7 mol L−1. The method was applied to the simultaneous determination of HQ and CC in a water sample. It is simple and highly selective. 相似文献
6.
Jahan Bakhsh Raoof Abolfazl Kiani Reza Ojani Roudabeh Valiollahi Sahar Rashid-Nadimi 《Journal of Solid State Electrochemistry》2010,14(7):1171-1176
Gold nanoparticles (GNs) could be efficiently immobilized on binary mixed self-assembled monolayers (SAMs) on a gold surface
composed of 1,6-hexanedithiol and 1-octanethiol (nano-Au/SAMs gold electrode). This GN chemically modified electrode was used
for electrochemical determination of ascorbic acid (AA) and dopamine (DA) in aqueous media. The result showed that the GN-modified
electrode could clearly resolve the oxidation peaks of AA and DA, with a peak-to-peak separation (∆E
p) of 110 mV enabling determination of AA and DA in the presence of each other. The linear analytical curves were obtained
in the ranges of 0.3–1.4 mM for AA and 0.2–1.2 mM for DA concentrations using differential pulse voltammetry. The detection
limits (3σ) were 9.0 × 10−5 M for AA and 9.0 × 10−5 M for DA. 相似文献
7.
A novel L-cysteine film modified electrode has been fabricated by means of an electrochemical oxidation procedure, and it
was successfully applied to the electrochemical determination of acetaminophen. This method utilizes the electrooxidation
of amines to their analogous cation radicals to form a chemically stable covalent linkage between the nitrogen atom of the
amine and edge plane sites at the glassy carbon electrode surface. The electrochemical behaviour of acetaminophen at the film
electrode was investigated in 0.1 mol L−1 phosphate buffer (pH 6.20). It was found that the redox peak current of acetaminophen was enhanced greatly on the film electrode.
Linearity between the oxidation peak current and the acetaminophen concentration was obtained in the range of 1.0 × 10−4–2.0 × 10−7 mol L−1 with a detection limit of 5.0 × 10−8 mol L−1. For seven parallel detections of 1.0 × 10−5 mol L−1 acetaminophen, the relative standard deviation (RSD) was 1.46%, suggesting that the film electrode has excellent reproducibility.
Application to the determination of acetaminophen in drug tablets and human urine demonstrated that the film electrode has
good stability and high sensitivity. 相似文献
8.
A self-assembled electrode with a meso-2,3-dimercaptosuccinic acid (DMSA) monolayer has been characterized by electrochemical
quartz crystal microbalance and complex impedance analysis, surface enhanced Raman spectroscopy and cyclic voltammetry. The
self-assembled electrode was used for the simultaneous electrochemical detection of epinephrine (EP) and uric acid (UA) in
phosphate buffer of pH 7.7. The simultaneous oxidation of EP and UA was performed by cyclic voltammetry (CV) and differential
pulse voltammetry (DPV), and the signals for each method were well separated with a potential difference of over 330 mV and
without interference by each other. The detection limit of EP is 5.4 × 10−8 mol L−1 by CV and 5.3 × 10−8 mol L−1 by DPV and that of UA is 8.4 × 10−8 mol L−1 by CV and 4.2 × 10−8 mol L−1 by DPV. The DMSA self-assembled electrode can be applied to the simultaneous determination of EP and UA. 相似文献
9.
Jun Yue Bai Liang Wang Hong Jing Wang Peng Fei Huang Yu Qing Zhao Sheng Di Fan 《Mikrochimica acta》2006,156(3-4):321-326
The electrochemical behavior of epinephrine (EP) at a mercaptoacetic acid (MAA) self-assembled monolayer modified gold electrode
was studied. The MAA/Au electrode is demonstrated to promote the electrochemical response of epinephrine by cyclic voltammetry.
The possible reaction mechanism is also discussed. The diffusion coefficient D of EP is 6.85 × 10−6 cm2 s−1. In 0.1 mol L−1 phosphate buffer (pH 7.20), a sensitive oxidation peak was observed at 0.177 V, and the peak current is proportional to the
concentration of EP in the range of 1.0 × 10−5–2.0 × 10−4 mol L−1 and 1.0 × 10−7–1.0 × 10−6 mol L−1. The detection limit is 5 × 10−8 mol L−1. The modified electrode is highly stable and can be applied to the determination of EP in practical injection samples. The
method is simple, quick, sensitive and accurate. 相似文献
10.
Gang Li Suling Yang Lingbo Qu Ran Yang Jianjun Li 《Journal of Solid State Electrochemistry》2011,15(1):161-166
A Nafion/multi-wall carbon nanotubes (MWNT) composite film-modified electrode was fabricated. The modified electrode showed
excellent electrocatalytic activity toward ascorbic acid (AA) and uric acid (UA) in 0.1-mol L−1 NaCl medium (pH 6.5). Compared to the bare electrode that only displayed a broad and overlapped oxidation peak, the Nafion/MWNT
film-modified electrode not only remarkably enhanced the anodic peak currents of AA and UA but also avoided the overlapping
of the anodic peaks of AA and UA with a 320-mV separation of both peaks. Under the optimized conditions, the peak currents
of AA and UA were proportional to their concentration at the ranges of 8.0 × 10−5 to 6.0 × 10−3 mol L−1 and 6.0 × 10−7 to 8.0 × 10−5 mol L−1, respectively. The proposed method was used for the detection of AA and UA in real samples with satisfactory results. 相似文献
11.
We used a carbon paste electrode modified with multi-walled carbon nanotubes as a working electrode and studied the electrochemical
behavior of zirconium-alizarin red S complex on it. It was found that the modified electrode exhibited a significant catalytic
effect toward the reduction of free alizarin red S and the complex. The second derivative linear scan voltammograms of the
complex were recorded by a polarographic analyser from 0 to −1000 mV (vs. SCE), and it was found that the complex can be adsorbed
on the surface of the modified electrode, yielding a peak at about −470 mV, corresponding to the reduction of alizarin red
S in the complex. The linear range was found to be 2.0 × 10−11–8.0 × 10−7 mol L−1, and the detection limit was 1.0 × 10−11 mol L−1 (S/N = 3) for 3 min accumulation. The procedure was successfully applied to the determination of trace amounts of zirconium in
the ore samples.
Correspondence: Pei-Hong Deng, Department of Chemistry and Material Science, Hengyang Normal University, Hengyang Hunan 421008,
P.R. China 相似文献
12.
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
13.
A multi-walled carbon nanotube paste electrode (MWCPE) is prepared as an electrochemical sensor with high sensitivity and
selectivity in responding to isoniazid. The electrochemical oxidation of isoniazid is investigated in buffered solution by
cyclic and differential pulse voltammetry. The electrode is shown to be very effective for the detection of isoniazid in the
presence of other biological reductant compounds. The electrochemical oxidation of cysteine, due to the high overvoltage,
is completely stopped at the surface of MWCPE. The electrode exhibits a very good resolution between the voltammetric peak
of isoniazid and the peaks of ascorbic acid (AA) and dopamine (DA). A resolution of more than 450 mV between the anodic peak
potentials makes the MWCPE suitable for simultaneous detection of isoniazid in the presence of AA or DA in clinical and pharmaceutical
preparations. Differential pulse voltammetry (DPV) is applied as a sensitive method for the determination of isoniazid. The
linear range in these determinations is 1 × 10−6–1 × 10−3 M for isoniazid and the detection limit is 5 × 10−7 M. The electrode was applied to the simultaneous determinations in isoniazid and AA mixtures and also, isoniazid and DA mixture
over a wide concentration range. The slope variation for the calibration curves of isoniazid (RSD) was less than 4.5% (based
on ten measurements over a period of three months). 相似文献
14.
Lin Cui Lifang Li Shiyun Ai Huanshun Yin Peng Ju Tao Liu 《Journal of Solid State Electrochemistry》2011,15(6):1253-1261
Guanosine-5′-monophosphate (GMP) was investigated the electrochemical behaviors based on solid-phase extractionon (SPE) at
Cu-Mg-Al hydrotalcite-like compound (HTLC) modified glass carbon electrode. Cu-Mg-Al hydrotalcite-like compound (HTLC) was
proved as a new sorbent for SPE of GMP, which showed an irreversible adsorption oxidation process on the HTLC/GCE with the
oxidation peak potential located at 1.15 V (vs. SCE) in a pH 5.0 acetate buffer solution. Influencing factors of the electrochemical
behavior of GMP on the HLTC/GCE were optimized and kinetic parameters were calculated. Under the optimal conditions, with
differential pulse voltammetry (DPV), a linear relationship was obtained between the oxidation peak current and the GMP concentration
in the range from 1.0 × 10− 6 to 8.0 × 10−4 mol L−1 with the detection limit as 5.0 × 10−7 mol L−1 (signal-to-noise ratio of 3). The modified electrode surface has very good reproducibility and stability. 相似文献
15.
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
16.
Single-wall carbon nanotubes (SWNT) were dispersed into water in the presence of dicetyl phosphate (DCP), and then a SWNT-DCP
film-coated glassy carbon electrode (GCE) was constructed. The electrochemical behavior of acetaminophen at bare GCE and SWNT-DCP
modified GCE were compared, suggesting that the SWNT-DCP-modified GCE significantly enhances the oxidation peak current of
acetaminophen. A sensitive and simple electrochemical method with a good linear relationship in the range of 1.0 × 10−7–2.0 × 10−5 mol L−1, was developed for the determination of acetaminophen. The detection limit is 4.0 × 10−8 mol L−1 for 3-min accumulation. This method was successfully demonstrated with tablets. 相似文献
17.
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
18.
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
19.
Xiaomei Cao Yanhong Xu Liqiang Luo Yaping Ding Ying Zhang 《Journal of Solid State Electrochemistry》2010,14(5):829-834
A glassy carbon electrode (GCE) modified with the film composed of chitosan incorporating cetylpyridine bromide is constructed
and used to determine uric acid (UA) and ascorbic acid (AA) by differential pulse voltammetry (DPV). This modified electrode
shows efficient electrocatalytic activity and fairly selective separation for oxidation of AA and UA in mixture solution.
UA is catalyzed by this modified electrode in phosphate buffer solution (pH 4.0) with a decrease of 80 mV, while AA is catalyzed
with a decrease of 200 mV in overpotential compared to GCE, and the peak separation of oxidation between AA and UA is 260
mV, which is large enough to allow the determination of one in presence of the other. Under the optimum conditions, the anodic
peak currents (I
pa) of DPV are proportional to the concentration of UA in the range of 2.0 × 10−6 to 6.0 × 10−4 M, with the detection limit of 5.0 × 10−7 M at a signal-to-noise ratio of 3 (S/N = 3) and to that of AA in the range of 4.0 × 10−6 to 1.0 × 10−3 M, with the detection limit of 8.0 × 10−7 M (S/N = 3). 相似文献
20.
Ying Xu Fei Wang Le Wang Fangyuan Zhao Baocheng Yang Baoxian Ye 《Journal of Solid State Electrochemistry》2012,16(4):1473-1480
A novel voltammetric sensor, based on single-walled carbon nanotubes (SWNT) dispersed in Nafion and modified glassy carbon
electrode (GCE), was fabricated and used to determine the trace amounts of dihydromyricetin (DMY). The electrochemical behavior
of DMY at this sensor was investigated in 0.1 mol L−1 sulfuric acid solutions + 0.1 mol L−1 NaCl by cyclic voltammetry and squarewave voltammetry. Compared with bare GCE, the electrode presented an excellent response
of DMY through an adsorption-controlled quasi-reversible process. Under the optimum conditions, the response peak currents
were linear relationship with the DMY concentrations in the range of 1.0 × 10−7–1.0 × 10−5 mol L−1 with a detection limit of 9 × 10−8 mol L−1. Based on this voltammetric sensor, a simple and sensitive electroanalytical method for DMY was proposed and applied to quantitative
determination of DMY in Ampelopsis grossedentata samples. In addition, the oxidation mechanism was proposed and discussed, which could be a reference for the pharmacological
action of DMY in clinical study. 相似文献