共查询到20条相似文献,搜索用时 109 毫秒
1.
A fluorescence quenching method for the determination of vanadium (V) based on the vanadium- catalyzed oxidation of rhodamine
6G (R6G) with periodate in the presence of ethylenediaminetetraacetic acid disodium salt (EDTA) in sulfuric acid medium is
described. The fluorescence was measured with excitation and emission wavelengths of 525 and 555 nm, respectively. The calibration
graph for vanadium (V) had linear ranges of 3.0 × 10−9–1.5 × 10−8 mol/l and 1.5 × 10−8–4.0 × 10−8 mol/l, respectively. The detection limit was 1.7 × 10−9 mol/l. The proposed method was successfully applied to the determination of vanadium (V) in river water, rain water and cast
iron samples.
Received June 29, 2001 Revision October 9, 2001 相似文献
2.
Lopes IC De Souza D Machado SA Tanaka AA 《Analytical and bioanalytical chemistry》2007,388(8):1907-1914
This work describes the application of an ordinary pyrolitic graphite electrode modified by metallophthalocyanine allied to
square wave voltammetry for the study of the electrochemical behavior of the herbicide paraquat and the development of a method
for its analytical determination in natural water samples. Preliminary experiments indicated that the best responses, considering
the intensities of the current and voltammetric profile for the paraquat reduction process, were obtained when the electrode
modified by cobalt phthalocyanine was employed, which had a better catalytic activity as a result of this modification compared
with that for an unmodified electrode and electrodes modified by iron, manganese and the acid form of the phthalocyanines.
Studies of the concentration of cobalt phthalocyanine and the adsorption time showed that 1.0 × 10−4 mol L−1 cobalt phthalocyanine with an adsorption time of 10 min was sufficient to obtain reliability and stability of modification
for employment in the development of the electroanalytical procedure for paraquat determination in natural water samples.
The variation in pH of a 0.10 mol L−1 Britton–Robinson buffer solution and the square wave parameters indicated that the best conditions to reduce paraquat were
pH 7.0, a frequency of 100 s−1, a scan increment of 2 mV and a square wave amplitude of 50 mV. Under such conditions, the variation of paraquat concentrations
from 5.00 × 10−7 to 2.91 × 10−5 mol L−1 showed a linear relation, with detection and quantification limits of 26.53 and 88.23 μg L−1; those values were lower than the maximum limits for drinking water permitted by the Brazilian Environmental Council (100 μg
L−1), indicating that the method could be employed to analyze paraquat in drinking water samples. 相似文献
3.
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
4.
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
5.
An electrochemical study of the doxazosin oxidative process at carbon paste electrodes using different voltammetric techniques
has been carried out. The process is irreversible and controlled by adsorption, giving rise to an oxidation wave around 1.0 V
in citric acid-citrate buffer (pH 3.0). A mechanism based on the oxidation of the amine group is postulated. Two methods based
on adsorptive stripping (AdS) of doxazosin at the C8-modified carbon paste electrode (C8-MCPE), before its voltammetric determination, are studied, using differential pulse voltammetry (DPV) and square wave voltammetry
(SWV) as redissolution techniques. By means of AdS-DPV and C8-MCPE, doxazosin can be determined over the 1.0 × 10−9 to 3.0 × 10−8 mol L−1 range with a variation coefficient of 2.2% (2.0 × 10−8 mol L−1) and a limit of detection of 7.4 ×10−10 mol L−1. If AdS-SWV is used, a linear range from 1.0 × 10−9 to 4.0 × 10−8 mol L−1 is obtained, the variation coefficient being 2.8% (2.0 × 10−8 mol L−1, and the limit of detection reached 7.7 × 10−10 mol L−1. The AdS-DPV procedure was applied to the determination of doxazosin in urine and formulations.
Received March 13, 1999. Revision December 23, 1999. 相似文献
6.
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
7.
Chunya Li 《Mikrochimica acta》2007,157(1-2):21-26
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. 相似文献
8.
Vega D Agüí L González-Cortés A Yáñez-Sedeño P Pingarrón JM 《Analytical and bioanalytical chemistry》2007,389(3):951-958
The voltammetric behaviour and amperometric detection of tetracycline (TC) antibiotics at multi-wall carbon nanotube modified
glassy carbon electrodes (MWCNT-GCE) are reported. Cyclic voltammograms of TCs showed enhanced oxidation responses at the
MWCNT-GCE with respect to the bare GCE, attributable to the increased active electrode surface area. Hydrodynamic voltammograms
obtained by flow-injection with amperometric detection at the MWCNT-GCE led us to select a potential value E
det = +1.20 V. The repeatability of the amperometric responses was much better than that achieved with bare GCE (RSD ranged from
7 to 12%), with RSD values for i
p of around 3%, thus demonstrating the antifouling capability of MWCNT modified electrodes. An HPLC method with amperometric
electrochemical detection (ED) at the MWCNT-GCE was developed for tetracycline, oxytetracycline (OTC), chlortetracycline and
doxycycline (DC). A mobile phase consisting of 18:82 acetonitrile/0.05 mol L−1 phosphate buffer of pH 2.5 was selected. The limits of detection ranged from 0.09 μmol L−1 for OTC to 0.44 μmol L−1 for DC. The possibility to carry out multiresidue analysis is demonstrated. The HPLC-ED/MWCNT-GCE method was applied to the
analysis of fish farm pool water and underground well water samples spiked with the four TCs at 2.0 × 10−7 mol L−1. Solid-phase extraction was accomplished for the preconcentration of the analytes and clean-up of the samples. Recoveries
ranged from 87 ± 6 to 99 ± 3%. Under preconcentration conditions, limits of detection in the water samples were between 0.50
and 3.10 ng mL−1. 相似文献
9.
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
10.
M. H. Pournaghi-Azar H. Dastangoo M. Ziaei 《Journal of Solid State Electrochemistry》2007,11(9):1221-1227
The electrocatalytic activity of a Prussian blue (PB) film on the aluminum electrode by taking advantage of the metallic palladium
characteristic as an electron-transfer bridge (PB/Pd–Al) for electrooxidation of 2-methyl-3-hydroxy-4,5-bis (hydroxyl–methyl)
pyridine (pyridoxine) is described. The catalytic activity of PB was explored in terms of FeIII [FeIII (CN)6]/FeIII [FeII (CN)6]1− system. The best mediated oxidation of pyridoxine (PN) on the PB/Pd–Al-modified electrode was achieved in 0.5 M KNO3 + 0.2 M potassium acetate of pH 6 at scan rate of 20 mV s−1. The mechanism and kinetics of the catalytic oxidation reaction of PN were monitored by cyclic voltammetry and chronoamperometry.
The results were explained using the theory of electrocatalytic reactions at chemically modified electrodes. The charge transfer-rate
limiting reaction step is found to be a one-electron abstraction, whereas a two-electron charge transfer reaction is the overall
oxidation reaction of PN by forming pyridoxal. The value of α, k, and D are 0.5, 1.2 × 102 M−1 s−1, and 1.4 × 10−5 cm2 s−1, respectively. Further examination of the modified electrodes shows that the modifying layers (PB) on the Pd–Al substrate
have reproducible behavior and a high level of stability after posing it in the electrolyte or Pyridoxine solutions for a
long time. 相似文献
11.
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
12.
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
13.
Self-assembled monolayer gold electrode for surfactant analysis 总被引:2,自引:0,他引:2
Marc Gerlache Zühre Senturk Guy Quarin Jean-Michel Kauffmann 《Journal of Solid State Electrochemistry》1997,1(2):155-160
A gold electrode coated with a self-assembled monolayer of octane-thiol (SAM/Au) has been used as an amperometric detector
for the determination of surfactants. This detector operated in the presence of a high percentage of organic solvent and was
adapted to an HPLC System. At the SAM/Au, the electrochemical response of an electroactive tracer (potassium ferricyanide)
was completely inhibited, but, in the presence of a cationic surfactant, the electrochemical reduction was progressively restored.
In flow injection analysis, using the SAM/Au in an amperometric flow-through detector polarised at 0.0 V vs Ag/AgCl, a linear
response (i=f{[surfactant]}) was observed for cationic surfactants e.g. cetylpyridinium chloride in the concentration range 2 × 10−6–1 × 10−3 M. The electrochemical data along with the determination of the ion pair stoichiometry between the redox tracer and the surfactant
suggest an electrochemical response related to ion pair formation and governed by electron transfer by tunneling effect.
Received: 28 January 1997 / Accepted: 7 March 1997 相似文献
14.
Radoi A Compagnone D Batic M Klincar J Gorton L Palleschi G 《Analytical and bioanalytical chemistry》2007,387(3):1049-1058
Bulk screen-printed electrodes (bSPEs) modified with zirconium phosphate (ZrP) and Meldola blue (MB) and by electrochemical deposition of a Reineckate film
(bMBZrPRs-SPEs) have been constructed and used as NADH sensors. Cyclic voltammetric investigation of these bulk electrochemically
modified screen-printed electrodes revealed stable catalytic activity in oxidation of the reduced form of the coenzyme nicotinamide
adenine dinucleotide (NADH). Flow-injection analysis (FIA) coupled with amperometric detection confirmed the improved stability
of the bMBZrPRs-SPEs (10−4 mol L−1 NADH, %RSD = 4.2, n = 90, pH 7.0). Other conditions, for example applied working potential (+50 mV relative to Ag|AgCl), flow rate (0.30 mL min−1) and pH-dependence (range 4.0–10.0) were evaluated and optimized. A glycerol biosensor, prepared by immobilizing glycerol
dehydrogenase (GDH) on the working electrode area of a bMBZrPRs-SPE, was also assembled. The biosensor was most stable at pH 8.5 (%RSD = 5.6, n = 70, 0.25 mmol L−1 glycerol). The detection and quantification limits were 2.8 × 10−6 and 9.4 × 10−6 mol L−1, respectively, and the linear working range was between 1.0 × 10−5 and 1.0 × 10−4 mol L−1. To assess the effect of interferences, and recovery by the probe we analyzed samples taken during fermentation of chemically
defined grape juice medium and compared the results with those obtained by HPLC. 相似文献
15.
The electrochemical behaviors of metol on an ionic liquid N-butylpyridinium hexafluorophosphate modified carbon paste electrode (IL-CPE) were studied in this paper. The results indicated
that a pair of well-defined quasi-reversible redox peaks of metol appeared with the decrease of overpotential and the increase
of redox peak current, which was the characteristics of electrocatalytic oxidation. The electrocatalytic mechanism was discussed
and the electrochemical parameters were calculated with results of the charge-transfer coefficient (α) as 0.45, the electrode reaction rate constant (k
s) as 4.02 × 10−3 s−1, and the diffusion coefficient (D) as 6.35 × 10−5 cm2/s. Under the optimal conditions, the anodic peak current was linear with the metol concentration in the range of 5.0 × 10−6 ∼ 1.0 × 10−3 mol/L (n = 11, γ = 0.994) and the detection limit was estimated as 2.33 × 10−6 mol/L (3σ). The proposed method was successfully applied to determination of metol content in synthetic samples and photographic solutions. 相似文献
16.
Jelena S. ?or?evi? Ana M. Kalijadis Ksenija R. Kumri? Zoran M. Jovanovi? Zoran V. Lau?evi? Tatjana M. Trti?-Petrovi? 《Central European Journal of Chemistry》2012,10(4):1271-1279
In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000°C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E p ) of linuron oxidation in 0.1 mol dm−3 H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm−3 H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005–0.1 μmol cm−3) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds. 相似文献
17.
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
18.
A novel type of glassy carbon electrode modified with magnetic carbon-coated nickel nanoparticles (C-Ni/GCE) was fabricated
and the electrochemical properties of brucine were studied using it. The carbon-coated nickel nanoparticles showed excellent
electrocatalytic activity for the redox of brucine and an enhanced electron transfer rate. The electrochemical behavior of
brucine on the C-Ni/GCE was explored by cyclic voltammetry (CV), and a redox mechanism for brucine was proposed. A series
of electrochemical parameters were calculated for brucine by CV and controlled-potential electrolysis. The C-Ni/GCE showed
good sensitivity, selectivity and stability, and was applied to determine the concentration of brucine. The differential pulse
voltammetry (DPV) response of the C-Ni/GCE showed that the catalytic current was linear with the concentration of brucine
in the range of 4.7 × 10−8 to 2.4 × 10−4 mol l−1, with a correlation coefficient of 0.998. The detection limit was 1.4 × 10−8 mol l−1. 相似文献
19.
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
20.
Newly developed, simple, low-cost and sensitive ion-selective electrodes have been proposed for determination of some antiepileptic
drugs such as lamotrigine, felbamate, and primidone in their pharmaceutical preparations as well as in biological fluids.
The electrodes are based on poly(vinyl chloride) membranes doped with drug–tetraphenyl borate (TPB) or drug–phosphotungstic
acid (PT) ion-pair complexes as molecular recognition materials. The novel electrodes displayed rapid Nernstian responses
with detection limits of approximately 10−7 M. Calibration graphs were linear over the ranges 5.2 × 10−7–1.0 × 10−3, 1.5 × 10−6–1.0 × 10−3, and 2.6 × 10−7–1.0 × 10−3 M for drug–TPB and 5.8 × 10−7–1.0 × 10−3, 1.8 × 10−7–1.0 × 10−3, and 6.6 × 10−7–1.0 × 10−3 M for drug–PT electrodes, respectively, with slopes ranging from 52.3 to 62.3 mV/decade. The membranes developed have potential
stability for up to 1 month and proved to be highly selective for the drugs investigated over other ions and excipients. The
results show that the selectivity of the ion-selective electrodes is influenced significantly by the plasticizer. The proposed
electrodes were successfully applied in the determination of these drugs in pharmaceutical preparations in four batches of
different expiry dates. Statistical Student’s t test and F test showed insignificant systematic error between the ion-selective electrode methods developed and a standard method. Comparison
of the results obtained using the proposed electrodes with those found using a reference method showed that the ion-selective
electrode technique is sensitive, reliable, and can be used with very good accuracy and high percentage recovery without pretreatment
procedures of the samples to minimize interfering matrix effects.
Figure Structure of lamotrigine, felbanate and primidone 相似文献