共查询到20条相似文献,搜索用时 62 毫秒
1.
Poly(vinylferrocenium) perchlorate–polyaniline (PVF+–PANI) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture
of poly(vinylferrocene) (PVF) polymer and aniline monomer. PVF+ polymer in the composite film was used as an electron transfer mediator. The composite coating showed significant electrochemical
activity towards hydroquinone (HQ) at pH 4, with high sensitivity and a wide linearity range. The interaction of HQ with PVF+ and PANI homopolymer films was investigated electrochemically and spectroscopically. HQ molecules are accumulated on the
electrode surface due to trapping by both polymers in the composite film and then oxidized catalytically by PANI. The most
significant contribution of PVF+ polymer is that it facilitates electron transfer in the composite film. The linear response range was found to be between
1.60 × 10−4 mM and 115 mM (R
2 = 0.999) at 0.45 V vs saturated calomel electrode. The limit of detection (LOD) was 4.94 × 10−5 mM. 相似文献
2.
Both nitrazepam and flunitrazepam have been determined by high-performance liquid chromatography dual electrode detection
(LC-DED) in the reductive–reductive mode, using a carbon fibre veil electrode (CFVE) in conjugation with a glassy carbon electrode.
Initial studies were made to optimise the chromatographic conditions. These were found to be 45% acetonitrile-55% acetate
buffer (50 mM, pH 4.1) at a flow rate of 1.0 ml/min, employing a Hypersil C18, 5 μm, 250 mm × 4.6 mm column. Cyclic voltammetric
studies performed to ascertain the redox behaviour of nitrazepam and flunitrazepam at a CFVE in the optimised mobile phase.
Studies showed that similar voltammetric behaviour was obtained to that report at Hg or glassy carbon based electrodes. Further
studies were then carried out to identify the optimum conditions required for the LC-DED determination of nitrazepam and flunitrazepam
in beverage samples. Hydrodynamic voltammetry was used to optimise the applied potential at the generator and detector cells;
these were identified to be −2.40 and −0.25 V, respectively. A linear range of 2.0 to 100 μg ml−1, with a detection limit of 20 ng ml−1 was obtained. A convenient and rapid method for the determination of both nitrazepam and flunitrazepam in beverage sample
was developed. Following a simple sample extraction procedure, extracts were examined using the optimised LC-DED procedure.
An average percentage recovery of 95.5% (%CV = 4.5%) for nitrazepam and 78.0% (%CV = 8.8%) was achieved for a sample of “Pepsi
Max” spiked at 1.0 μg ml−1 nitrazepam, 1.47 μg ml−1 flunitrazepam.
Presented at the 4th Annual Meeting of the Great Western Electrochemistry Group, 8th June 2005, University of the West of
England, Bristol, UK. 相似文献
3.
A. V. Churikov I. M. Gamayunova A. V. Shirokov 《Journal of Solid State Electrochemistry》2000,4(4):216-224
The electrochemical behaviour of a Li electrode in solutions of LiAlCl4 in thionyl chloride, LiBF4 in γ-butyrolactone and LiClO4 in the mixed solvent propylene carbonate (PC) + dimethoxyethane (DME) in the process of cell storage has been investigated
by the methods of electrode impedance spectroscopy and pulse voltammetry. Analogous studies have been carried out in PC + DME
solution with the Li electrode coated with a specially formed protecting film of Li2CO3. The results have been compared with those obtained earlier for other lithium electrochemical systems. The general regularities
of the Li electrode electrochemical kinetics attributed to the process of Li+ ion transport through a passivating film coating a lithium surface have been discussed.
Received: 22 February 1999 / Accepted: 20 June 1999 相似文献
4.
Fosamprenavir is a pro-drug of the antiretroviral protease inhibitor amprenavir and is oxidizable at solid electrodes. The
anodic oxidation behavior of fosamprenavir was investigated using cyclic and linear sweep voltammetry at boron-doped diamond
and glassy carbon electrodes. In cyclic voltammetry, depending on pH values, fosamprenavir showed one sharp irreversible oxidation
peak or wave depending on the working electrode. The mechanism of the oxidation process was discussed. The voltammetric study
of some model compounds allowed elucidation of the possible oxidation mechanism of fosamprenavir. The aim of this study was
to determine fosamprenavir levels in pharmaceutical formulations and biological samples by means of electrochemical methods.
Using the sharp oxidation response, two voltammetric methods were described for the determination of fosamprenavir by differential
pulse and square-wave voltammetry at the boron-doped diamond and glassy carbon electrodes. These two voltammetric techniques
are 0.1 M H2SO4 and phosphate buffer at pH 2.0 which allow quantitation over a 4 × 10−6 to 8 × 10−5 M range using boron-doped diamond and a 1 × 10−5 to 1 × 10−4 M range using glassy carbon electrodes, respectively, in supporting electrolyte. All necessary validation parameters were
investigated and calculated. These methods were successfully applied for the analysis of fosamprenavir pharmaceutical dosage
forms, human serum and urine samples. The standard addition method was used in biological media using boron-doped diamond
electrode. No electroactive interferences from the tablet excipients or endogenous substances from biological material were
found. The results were statistically compared with those obtained through an established HPLC-UV technique; no significant
differences were found between the voltammetric and HPLC methods. 相似文献
5.
6.
Phenylalanine dehydrogenase (l-PheDH) from Sporosarcina ureae was immobilized on DEAE-cellulose, modified initially with 2-amino-4,6-dichloro-s-triazine followed by hexamethylenediamine
and glutaraldehyde. The highest activity of immobilized PheDH was determined as 95.75 U/g support with 56% retained activity.
The optimum pH value of immobilized l-PheDH was shifted from pH 10.4 to 11.0. The immobilized l-PheDH showed activity variations close to the maximum value in a wider temperature range of 45–55 °C, whereas it was 40 °C
for the native enzyme. The pH and the thermal stability of the immobilized l-PheDH were also better than the native enzyme. At pH 10.4 and 25 °C, K
m values of the native and the immobilized l-PheDH were determined as K
m Phe = 0.118, 0.063 mM and K
m NAD+ = 0.234, 0.128 mM, respectively. Formed NADH at the exit of packed bed reactor column was detected by the flow-injection
analysis system. The conversion efficiency of the reactor was found to be 100% in the range of 5–600 μM Phe at 9 mM NAD+ with a total flow rate of 0.1 mL/min. The reactor was used for the analyses of 30 samples each for 3 h per day. The half-life
period of the reactor was 15 days. 相似文献
7.
Andre Ricardo de Lima Damásio Tony Márcio da Silva Alexandre Maller Jo?o Atílio Jorge Hector Francisco Terenzi Maria de Lourdes Teixeira de Moraes Polizeli 《Applied biochemistry and biotechnology》2010,160(5):1496-1507
An extracellular polygalacturonase (PG) produced from Paecilomyces variotii was purified to homogeneity through two chromatography steps using DEAE-Fractogel and Sephadex G-100. The molecular weight
of P. variotii PG was 77,300 Da by gel filtration and SDS-PAGE. PG had isoelectric point of 4.37 and optimum pH 4.0. PG was very stable
from pH 3.0 to 6.0. The extent of hydrolysis of different pectins by the purified enzyme was decreased with an increase in
the degree of esterification. PG had no activity toward non-pectic polysaccharides. The apparent K
m and V
max values for hydrolyzing sodium polypectate were 1.84 mg/mL and 432 μmol/min/mg, respectively. PG was found to have temperature
optimum at 65 °C and was totally stable at 45 °C for 90 min. Half-life at 55 °C was 50.6 min. Almost all the examined metal
cations showed partial inhibitory effects under enzymatic activity, except for Na+1, K+1, and Co+2 (1 mM) and Cu+2 (1 and 10 mM). 相似文献
8.
López-Flores J Fernández-de Córdova ML Molina-Díaz A 《Analytical and bioanalytical chemistry》2007,388(8):1771-1777
A flow injection–solid-phase spectroscopy (FI-SPS) system implemented with photochemically induced fluorescence (PIF) is described
for the rapid and very sensitive determination of reserpine in biological fluids and pharmaceutical formulations. An intensively
fluorescent photoproduct is in-line generated, retained on C18 silica gel in the detection area and monitored at 394/489 nm (λ
ex/λ
em). After the establishment of the appropriate working variables, the system is calibrated at two different injection volumes,
100 and 800 μL, achieving detection limits of 0.33 and 0.05 ng mL−1, respectively. The RSD for reserpine at 2 ng mL−1 (800 μL) was 1.5% (n = 10). The sampling rates were 46 and 43 h−1 for each injection volume, respectively. The potential interference of some common species coexisting with reserpine in the
analysed samples was also studied. The procedure was successfully applied to commercial formulations, urine and serum without
any previous treatment of samples. Recoveries ranged from 94.9 to 100.2%. 相似文献
9.
The electrochemical solid phase micro-extraction of salicylic acid (SA) at graphite-epoxy-composed solid electrode surface
was studied by cyclic voltammetry. SA was oxidized electrochemically in pH 12.0 aqueous solution at 0.70 V (vs. saturated
calomel electrode) for 7 s. The oxidized product shows two surface-controlled reversible redox couples with two proton transferred
in the pH range of 1.0∼6.0 and one proton transferred in the pH range of 10.0∼13.0 and is extracted on the electrode surface
with a kinetic Boltzman function of i
p = 3.473–4.499/[1 + e(t − 7.332)/6.123] (χ
2 = 0.00285 μA). The anodic peak current of the extracted specie in differential pulse voltammograms is proportional to the
concentration of SA with regression equation of i
p = −5.913 + 0.4843 c (R = 0.995, SD = 1.6 μA) in the range of 5.00∼200 μM. The detection limit is 5.00 μM with RSD of 1.59% at 60 μM. The method
is sensitive and convenient and was applied to the detection of SA in mouse blood samples with satisfactory results. 相似文献
10.
Shuhu Xiao Jiuhui Qu Huijuan Liu Xu Zhao Dongjin Wan 《Journal of Solid State Electrochemistry》2009,13(12):1959-1964
Titanium oxide nanotube electrodes were successfully prepared by anodic oxidation on pure Ti sheets in 0.5 wt.% NH4F + 1 wt.% (NH4)2SO4 + 90 wt.% glycerol mixed solutions. Nanotubes with diameter 40–60 nm and length 7.4 μm were observed by field emission scanning
electron microscope. The electrochemical and photoelectrochemical characteristics of TiO2 nanotube electrode were investigated using linear polarization and electrochemical impedance spectroscopy techniques. The
open-circuit potential dropped markedly under irradiation and with the increase of Cl− concentrations. A saturated photocurrent of approximately 1.3 mA cm−2 was observed under 10-W low-mercury lamp irradiation in 0.1 M NaCl solution, which was much higher than film electrode. Meanwhile,
the highest photocurrent in NaCl solution implied that the photogenerated holes preferred to combine with Cl−. Thus, a significant synergetic effect on active chlorine production was observed in photoelectrocatalytic processes. Furthermore,
the generation efficiency for active chlorine was about two times that using TiO2/Ti film electrode by sol–gel method. Finally, the effects of initial pH and Cl− concentration were also discussed. 相似文献
11.
Jianping Li Xiongzhi Wu Yong Yu Shangwang Le 《Journal of Solid State Electrochemistry》2009,13(12):1811-1818
Gold electrode with self-assembled D,L-cysteine grafted β-cyclodextrin sulfonic acid (Cys-β-CD∼SO3) layer was fabricated and used to investigate the electrochemical behavior of dopamine. The experimental results indicated
that the self-assembled Cys-β-CD∼SO3 layer modified gold electrode has selective electrochemical response to dopamine with high sensitivity and excellent tolerance
of ascorbic acid, which is the most common accompanying component in biological samples. Dopamine could be accurately determined
in the concentration range of 1–200 μM in the presence of ascorbic acid of 5 mM. The relative standard deviation of 1.9% (n = 5) was achieved at a dopamine concentration of 5 × 10−5 M. The proposed sensor was successfully applied to the determination of dopamine in human blood serum samples. 相似文献
12.
M. Soledad García Joaquín Ortuño M. Isabel Albero María Cuartero 《Analytical and bioanalytical chemistry》2009,394(6):1563-1567
A trazodone-selective electrode for application in pharmaceutical quality control and urine analysis was developed. The electrode
is based on incorporation of a trazodone-tetraphenylborate ion exchanger in a poly(vinyl chloride) membrane. The electrode
showed a fast, stable and Nernstian response over a wide trazodone concentration range (5 × 10−5−1 × 10−2 M) with a mean slope of 59.3 ± 0.9 mV/dec of concentration, a mean detection limit of 1.8 × 10−5 ± 2.2 × 10−6 M, a wide working pH range (5–7.5) and a fast response time (less than 20 s). The electrode also showed good accuracy, repeatability,
reproducibility and selectivity with respect to some inorganic and organic compounds, including the main trazodone metabolite.
The electrode provided good analytical results in the determination of trazodone in pharmaceuticals and spiked urine samples;
no extraction steps were necessary. Dissolution testing of trazodone tablets, in different conditions of pH and particle size,
based on a direct potentiometric determination with the new selective electrode is presented as well. 相似文献
13.
Shengqi Liu Suqin Liu Kelong Huang Jiansheng Liu Yongkun Li Dong Fang Hongmei Wang Yufei Xia 《Journal of Solid State Electrochemistry》2012,16(4):1631-1634
Electrolytes of 1 M blend salts (LiPF6 and tetraethylammonium tetrafluoroborate, Et4NBF4) have been investigated in supercapacitor battery system with composite LiMn2O4 and activated carbon (AC) cathode, and Li4Ti5O12 anode. The results obtained with the blend salts electrolytes are compared with those obtained with cells build using standard
1 M LiPF6 dissolved in ethylene carbonate + dimethyl carbonate + ethyl (methyl) carbonate (EC + DMC + EMC, 1:1:1 wt.%) as electrolyte.
It is found that the blend salts electrolyte performs better on both electrochemical and galvanostatic cycling stability,
especially cycled at 4 C rate. When the concentration of LiPF6 is 0.2 M and Et4NBF4 is 0.8 M, the capacity retention of the battery is 96.23% at 4 C rate after 5,000 cycles, much higher than that of the battery
with standard 1 M LiPF6 electrolyte, which is only 62.35%. These results demonstrate that the blend salts electrolyte can improve the galvanostatic
cycling stability of the supercapacity battery. Electrolyte of 0.2 M LiPF6 + 0.8 M Et4NBF4 in EC + DMC + EMC (1:1:1 wt.%) is a promising electrolyte for (LiMn2O4 + AC)/Li4Ti5O12. 相似文献
14.
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
15.
Huanshun Yin Yunlei Zhou Tao Liu Tiantian Tang Shiyun Ai Lusheng Zhu 《Journal of Solid State Electrochemistry》2012,16(2):731-738
In this work, 3-aminopropyltriethoxysilane modified Fe3O4 nanoparticles (ATPS-Fe3O4) were used to modify glassy carbon electrode for aminopyrine determination. ATPS-Fe3O4 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-Fe3O4 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
16.
Spinel Li4Ti5 − x
Zr
x
O12/C (x = 0, 0.05) were prepared by a solution method. The structure and morphology of the as-prepared samples were characterized
by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical performances
including charge–discharge (0–2.5 V and 1–2.5 V), cyclic voltammetry, and ac impedance were also investigated. The results
revealed that the Li4Ti4.95Zr0.05O12/C had a relatively smaller particle size and more regular morphology than that of Li4Ti5O12/C. Zr4+ doping enhanced the ability of lithium-ion diffusion in the electrode. It delivered a discharge capacity 289.03 mAh g−1 after 50 cycles for the Zr4+-doped Li4Ti5O12/C while it decreased to 264.03 mAh g−1 for the Li4Ti5O12/C at the 0.2C discharge to 0 V. Zr4+ doping did not change the electrochemical process, instead enhanced the electronic conductivity and ionic conductivity. The
reversible capacity and cycling performance were effectively improved especially when it was discharged to 0 V. 相似文献
17.
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
18.
Raúl A. Sánchez-Moreno M. Jesús Gismera M. Teresa Sevilla Jesús R. Procopio 《Analytical and bioanalytical chemistry》2010,397(1):331-338
A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis.
The carbon screen-printed electrode was modified with a graphite–epoxy composite. The optimal graphite–epoxy matrix contains
37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal
analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed
sensor exhibits a response time of 20 ± 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour
using 0.1 M NaNO3 solution at pH 3 as the carrier, a flow rate of 2.5 mL·min−1, and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI)
ions and optimal detection limits in both static mode (2.1 × 10−7 M) and online analysis (9.4 × 10−7 M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river
waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful
results in leachates from municipal solid waste landfills. 相似文献
19.
Ai-Lin Liu Jia-Dong Wang Wei Chen Xing-Hua Xia Yuan-Zhong Chen Xin-Hua Lin 《Journal of Solid State Electrochemistry》2012,16(4):1343-1351
A simple, rapid, sensitive, and accurate method for simultaneous electrochemical determination of procaine and its metabolite
(p-aminobenzoic acid, PABA) for pharmaceutical quality control and pharmacokinetic research was developed using a graphite paste
electrode. The differential pulse voltammetric results revealed that procaine and p-aminobenzoic acid, respectively, showed well-defined anodic oxidation peaks on a carbon paste electrode with a current peak
separation of 155 mV at a scan rate of 100 mV s−1. This well separation of the current peaks for these two compounds in voltammetry enables us to simultaneously determine
them. Good linearity (r > 0.998) between oxidation peak current and concentration was obtained in the range of 5.0 × 10−7–5.0 × 10−5 M for procaine and 5.0 × 10−7–2.0 × 10−5 M for PABA in pH 4.50 acetate buffer solution. The detection limit for both analytes is 5 × 10−8 M (S/N = 3:1). The present voltammetric method has been successfully used to determine trace p-aminobenzoic acid in procaine hydrochloride injection and procaine in plasma with a linear relationship of current to its
concentration ranging from 1.0 × 10−6 to 5.0 × 10−5 M (correlation coefficient of 0.9981) with a low detection limit of 5.0 × 10−7 M (S/N = 3:1). This validated method is promising to the study of pharmacokinetics in Sprague–Dawley rat and rabbit plasma after
an intravenous administration of procaine hydrochloride injection. 相似文献
20.
A capillary electrophoretic (CE) method has been optimized for the separation of some common alkali and alkaline-earth metal
cations in anti-asthmatic homeopathic liquid pharmaceutical preparations. Separation was carried out on a 74 cm (62.5 cm to
the detector) × 75 μm ID fused silica capillary at a potential of 25 kV and 25 °C. Baseline separation of NH4
+, K+, Ca2+, Na+, Mg2+ and Li+ was achieved in less than 4.5 min. The proposed method was applied for the determination of the above-mentioned ions in homeopathic
liquid formulations. Limits of quantitation (LOQ) observed were 1.5 ppm for NH4
+, Ca2+ and Mg2+ 0.8 ppm for Na+, 1.6 ppm for K+, and 0.4 ppm for Li+. During electrophoresis, the ingredients used in the preparation of homeopathic formulation did not interfere with the cations
examined. 相似文献