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排序方式: 共有110条查询结果,搜索用时 78 毫秒
31.
Leslie A. Sombers Dr. Nathan J. Wittenberg Dr. Marc M. Maxson Dr. Kelly L. Adams Andrew G. Ewing Prof. Dr. 《Chemphyschem》2007,8(17):2471-2477
We have amperometrically measured dopamine release from rat pheochromocytoma cells (PC12 cells) in high osmolarity conditions with and without L ‐3,4‐dihydroxyphenylalanine (L ‐DOPA) treatment. We observe an increase in the number of release events displaying a prespike feature or “foot” when the cells are stimulated in high osmolarity saline. We also see an increase in foot area and duration when cells are stimulated in high osmolarity saline, or high osmolarity saline subsequent to incubation with the dopamine precursor L ‐DOPA in isotonic saline, which serves to increase the vesicle size. The data suggest that membrane biophysics are an important component in defining the rate, duration and amount of neurotransmitter release via the fusion pore. 相似文献
32.
Lucas Vinícius deFaria Thalles Pedrosa Lisboa Gustavo Chevitarese Azevedo Rafael Arromba Sousa Maria Auxiliadora CostaMatos Rodrigo Alejandro Abarza Muoz Renato CamargoMatos 《Electroanalysis》2019,31(4):646-651
Dipyrone (metamizole sodium) is one of the most consumed drugs in the world. In this work a novel analytical method was developed for dipyrone sensing. This method involves the amperometric detection on a chemically‐reduced graphene‐oxide (CRGO)‐modified glassy carbon electrode. Raman spectroscopy and scanning electron microscopy revealed the presence of multilayer graphene layers that contributed to the electrocatalytic oxidation of dipyrone and increase in the electroactive area. Advantages of this sensor include elimination of previous separations, solvent extraction, or sample filtration, low detection limit (0.13 μmol L?1) with a linear range from 48 to 246 μmol L?1 and adequate recovery values (97–103 %). Applied to commercial pharmaceutical samples, this method showed results ranging from 451 to 541 mg of dipyrone per tablet, which agreed with the expected values. The results obtained by amperometry were compared statistically with the official method recommended by the Brazilian Pharmacopoeia (iodometric method), with no significant differences between them at 95 % confidence level. The proposed method is accurate for the monitoring of sodium dipyrone in pharmaceutical formulations, highlighting the lower reagent consumption and interferences in the analytical process. 相似文献
33.
34.
Ljiljana S. Jovanović Nikola J. Ević Luka J. Bjelica Biljana F. Abramović Ferenc F. Gaál Nándor L. Rehák 《Monatshefte für Chemie / Chemical Monthly》1992,123(12):1071-1079
Summary The acid-base properties of the -oxo bridged dimeric iron complexes [FeL]2O with the ligands based on S-alkyl-1,4-bis(substituted salicylidene)isothiosemicarbazide and a tetramer with S-methyl-1,4-bis(salicylidene)isothiosemicarbazide, {[FeL]2O}2I3·I2, were investigated by cyclic voltammetry at glassy carbon electrode inDMF. Studies were carried out in the presence of either a weak (phenol) or a strong (HClO4 aq.) acid. The stoichimoetry of the reaction, changes in the general voltammetric pattern and the electrode reaction mechanism were discussed. These studies served as the basis for three-electrode amperometric titrations to determine the content of several of these complexes.
Voltammetrische und titrimetrische Untersuchung der Säure-Base-Eigenschaften einiger -oxo dimerer Eisen(III)-Komplexe inDMF-Lösungen
Zusammenfassung Die Säure-Base-Eigenschaften einiger dimerer -oxo-Eisen(III)-Komplexe [FeL]2O mit Liganden auf Basis von 1,4-bis(substituierten Salicyliden)S-(alkyl)isothiosemicarbaziden sowie eines tetrameren Komplexes mit 1,4-Bis(salicyliden)S-methylisothiosemicarbazid, {[FeL]2O}2I3·I2, wurden mittels zyklischer Voltammetrie an der Glaskohlenstoffelektrode inDMF-Lösungen untersucht. Die Messungen wurden in Gegenwart entweder einer schwachen (Phenol) oder einer starken (HClO4 aq.) Säure ausgeführt. Die Stöchiometrie der Reaktion, die Änderungen der voltammetrischen Kurven und der Elektroden-Reaktionsmechanismus wurden diskutiert. Diese Untersuchungen stellten eine Basis für Drei-Elektroden amperometrische Titrationen dar, die für die Bestimmung des Gehalts einiger dieser Komplexe angewendet wurden.相似文献
35.
《Electroanalysis》2005,17(14):1269-1278
Oxidation/reduction of polypyrrole films coupled with ion exchange on the polymer/solution interface can be utilized for amperometric sensing of electroinactive ions. Anion or cation exchanging films (polypyrrole doped by chloride or poly(4‐styrenesulfonate) ions, respectively) can be used to determine common anions (as Cl?, NO , SO etc) or cations (K+, Na+, Li+, Ca2+, Mg2+) under conditions of alternating current (AC) amperometry in the range 10?4–1 M. A sensitivity can be tuned by choosing appropriate electrode potential, corresponding to polypyrrole oxidation (anion‐exchanging films) or reduction (cation‐exchangers). Electrochemical impedance spectroscopy and AC‐voltammetry studies have shown that applied frequency and potential could also affect the observed dependence of the signal (admittance or AC‐current) on ion concentration. For high frequency the sensitivity is higher but selectivity lower, due to influence of solution conductivity on the response. For low frequencies the sensitivity is lower; however, a selectivity increase was observed due to diverse mobility of ions in the polymer film. Selectivity of AC‐amperometric responses was studied both in separate and mixed solutions. 相似文献
36.
The article reviews the use of electrochemical biosensors for detecting lactate, a key metabolite of the anaerobic glycolytic
pathway. This compound plays an important role in (sports) medicine, in the nutritional sector, in food quality control and
touches environmental concerns. Amperometric biosensors offer a sensitive and selective means to monitor organic analytes
like lactate. A detailed study on different aspects of amperometric lactate biosensor preparation is described: the main configuration
aspects are compiled regarding electrode materials, biorecognition elements, immobilization methods, mediators and cofactors
as well as fields of application. Comparative studies are conducted correlating different configuration aspects and performance
of the resulting biosensors. This review contains 214 references from the years 1974 to 2007.
Correspondence: Beate Strehlitz, UFZ, Helmholtz Centre for Environmental Research – UFZ, Environmental and Biotechnology Centre
(UBZ), Permoserstrasse 15, D-04318 Leipzig, Germany 相似文献
37.
Ta-Feng Tseng Yang-Li Yang Min-Chieh Chuang Shyh-Liang Lou Michal Galik Gerd-Uwe Flechsig Joseph Wang 《Electrochemistry communications》2009,11(9):1819-1822
We illustrate how the use of heated electrodes enhances the performance of glucose biosensors based on amperometric detection of the glucose-oxidase generated hydrogen peroxide. Nafion is shown to be an excellent matrix to protect glucose-oxidase from thermal inactivation during the heating pulses. The influence of the electrode temperature upon the amperometric response is examined. Temperature pulse amperometry (TPA) has been used to obtain convenient peak-shaped analytical signals. Surprisingly, up to 67.5 °C, the activity of Nafion-entrapped glucose-oxidase is greatly enhanced (24-fold) by accelerated kinetics rather than decreased by thermal inactivation. Amperometric signals even at elevated temperatures are stable upon prolonged operation involving repetitive measurements. The linear calibration range is significantly extended. 相似文献
38.
In the present work the total content of phenolic antioxidants in juice of some fruit and vegetables, in wines, water extracts of tea and herb were measured by amperometry. Efficiency of the method allowed determining the total antioxidant content in their binary and multimixes, including processes of frosting-defrosting and juice diluting as well. The deviation of experimentally received values of the total antioxidant content in some drink mixes from the values calculated proceeding from the additivity principle of the antioxidant content in separate drinks has been revealed. 相似文献
39.
XU He ZHENG QiaoLi YANG Ping LIU JianShe XING SuJie & JIN LiTong School of Environmental Science Engineering Donghua University Shanghai China 《中国科学B辑(英文版)》2011,(6)
A simple and rapid approach for the electrochemical synthesis of Ag nanoparticles-coated gold nanoporous film (AgGNF) on a gold substrate was reported. The solid gold electrode (SGE) was directly anodized under a high potential of 5 V, and then reduced to obtain gold nanoporous film (AuNF) by freshly prepared ascorbic acid. The Ag nanoparticles (AgNPs) were grown on the AuNF electrode by potential-step electrodeposition. The resulting AgGNF composites electrodes were characterized by scanning electron micro... 相似文献
40.
《Arabian Journal of Chemistry》2020,13(1):335-345
A simple, rapid and low-cost electroanalytical method is proposed for the determination of acetaminophen (ACP) and codeine (COD) at nanomolar levels in pharmaceutical and biological samples. The analytical procedure is based on a flow injection analysis system coupled to electrochemical detection, which was multiple pulse amperometry (FIA-MPA). Boron-doped diamond was used as the working electrode for electrochemical detection. The electrode was subjected to a cathodic pretreatment and was selected in this work due its good electrochemical performance. By applying the FIA-MPA method, after a number of optimization assays, the analgesics were simultaneously determined at excellent linear concentration ranges. The analytical curves ranged from 80 nmol L−1 to 100 µmol L−1 for ACP and from 50 nmol L−1 to 10 µmol L−1 for COD, and the obtained limits of detection were 30 nmol L−1 and 35 nmol L−1 for ACP and COD, respectively. The practical applicability of the electroanalytical method was evaluated from the ACP and COD determination in two sample matrices: commercial pharmaceutical samples and biological fluids. In the case of pharmaceutical formulation samples, the obtained results were statistically similar to those obtained using a reference chromatographic method. In addition, these drugs were simultaneously quantified in biological fluid samples of urine and human serum with excellent recovery percentages. 相似文献