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81.
M. R. Gregg 《Chromatographia》1985,20(2):129-133
Summary Electrode surface modification by electrochemical pretreatment of glassy carbon electrodes was shown to enhance significantly the sensitivity of the electrodes for the detection of timolol and oxprenolol, but reduce slightly the sensitivity to prenalterol. This method may permit the detection of exprenolol and timolol with increased sensitivity, or may allow their detection at lower applied potentials than is presently possible. Electrode surface modification may prove to be a valuable aid to the detection of compounds that are considered to be outside the practical limits of electrochemical detection. 相似文献
82.
Catalytic wet air oxidation of oleic acid on ceria-supported platinum catalyst.effect of pH 总被引:1,自引:0,他引:1
Beno?t Levasseur Benoist Renard Jacques Barbier Jr. Daniel Duprez 《Reaction Kinetics and Catalysis Letters》2006,87(2):269-279
Summary Catalytic wet air oxidation (CWAO) of oleic acid was carried out in a batch reactor on platinum supported ceria catalyst (Pt/CeO2). Oleic acid is a water insoluble linear unsaturated fatty acid of 18 carbon atoms. To increase the homogeneity of the solution
by saponification, the influence of NaOH additions in oleic acid CWAO mechanism and catalyst performances have been investigated.
The oxidation of such molecule occurs by two types of mechanisms: successive carboxy-decarboxylation which leads essentially
to CO2and/or C-C bonds splitting in the alkyl chain inducing a high formation of acetic acid. With or without NaOH, the 5%Pt/CeO2catalyst is active in the conversion of oleic acid and selective to carbon dioxide. In alkaline medium, oleic acid is initially
saponified which increases the solubility of the reactant before it to be oxidized. Finally the oxidation is slightly delayed
by the presence of NaOH. The catalyst characterizations show no significant difference before and after reaction.</o:p> 相似文献
83.
Kharitonov SV 《Analytical and bioanalytical chemistry》2005,382(7):1642-1651
The construction and electroanalytical response characteristics of poly(vinyl chloride) matrix ion-selective sensors (ISSs) for drotaverine hydrochloride are described. The membranes incorporate ion-association complexes of drotaverine with tetraphenylborate, picrate, tetraiodomercurate, tetraiodobismuthate, Reinecke salt, and heteropolycompounds of Keggin structure—molybdophosphoric acid, tungstophosphoric acid, molybdosiliconic acid and tungstosiliconic acid as electroactive materials for ionometric sensor controls. These ISSs have a linear response to drotaverine hydrochloride over the range 8×10–6 to 5×10–2 mol L–1 with cationic slopes from 51 to 58 mV per concentration decade. These ISSs have a fast response time (up to 1 min), a low determination limit (down to 4.3×10–6 mol L–1), good stability (3–5 weeks), and reasonable selectivity. Permeabilities and ion fluxes through a membrane were calculated for major and interfering ions. Dependences of the transport properties of the membranes on the concentrations of the ion exchanger and near-membrane solution and their electrochemical characteristics are presented. The ISSs were used for direct potentiometry and potentiometric titration (sodium tetraphenylborate) of drotaverine hydrochloride. Results with mean accuracy of 99.1±1.0% of nominal were obtained which corresponded well to data obtained by use of high-performance liquid chromatography. 相似文献
84.
A simple and automated methodology for a sensitive electrochemical detection of enzyme immunoassays that employ alkaline phosphatase (AP) as label has been developed. A flow injection system with programmable pump, valve and cell functions, amperometric detection of indigo and screen-printed electrodes (SPEs) are responsible for the advantages of this methodology. Amperometric detection at a low potential of indigo, the product of the enzymatic hydrolysis of the substrate 3-indoxyl phosphate (IP), is combined with a flow injection system. This incorporates in the flow cell a disposable screen-printed board provided with a graphite working electrode. No electrode pretreatment is necessary to obtain reproducible signals. The system was applied to the determination by an enzyme-linked immunosorbent assays (ELISA) of pneumolysin (PLY), a toxin related to respiratory infections. Linear calibration curves for low and high concentration ranges were obtained. These were also performed in a proteic matrix and linearity was also obtained. 相似文献
85.
Effect of pressure on oxygen enrichment of liquid crystalline cellulose ether membranes at elevated temperature 总被引:1,自引:0,他引:1
Cholesteric liquid crystalline triheptyl cellulose (THC)/ethyl cellulose binary blend membranes were prepared and the effect of pressure on their oxygen enrichment at elevated temperature was investigated using a constant pressure-variable volume method. The oxygen enrichment increased with the increase of transmembrane pressure difference or with slight increase of the THC content in the blend membranes. The oxygen concentration through the membranes increased linearly with decreasing pressure ratio. Air was directly separated through a 17 m-thick THC/EC(1.5/98.5) membrane to prepare an oxygen-enriched air containing 39.5% oxygen at the flux of 6.99×10–4 cm3 (STP)/s.cm2 at the pressure difference of 0.43 MPa and 85 °C. 相似文献
86.
A new type of inorganic biosensor is introduced. The sensor comprises glucose oxidase enzymes encapsulated in a sol-gel-derived
Prussian blue-silicate hybrid network. Glucose is detected by the biocatalytic reduction of oxygen followed by catalytic reduction
of hydrogen peroxide by the Prusian blue catalyst. The sol-gel silicate entails a rigid encapsulating matrix, the Prussian
blue provides chemical catalysis and charge mediation from the reduction site to the supporting electrode, and the enzyme
is responsible for the biocatalysis. The feasibility of a dual optical/electrochemical mode of analysis is also demonstrated. 相似文献
87.
James O'Donnell Bruno Rusterholz Barbara Aebersold Denise Rüegg Wilhelm Simon Ernö Pretsch 《Mikrochimica acta》1994,113(1-2):45-52
In an investigation of octamethylene bis(malonic acid diamides) and their selectivities for magnesium, it was found that presence of secondary amides within the particular ionophore played a considerable role in the enhancement of magnesium selectivity. Similar effects in other ionophores, i.e. tris(malonic acid diamides), were thus systematically looked at with the help of selectivity measurements with the hope of optimizing the number of secondary and tertiary amides so as to improve the magnesium selectivity. The syntheses of several investigated tris(malonic acid diamide) isologues are equally reported.Deceased in November 1992 相似文献
88.
《Electroanalysis》2004,16(17):1451-1458
A new carbon electrode material, obtained by mixing single wall carbon nanotubes (SWNTs) with a mineral oil binder is studied. Carbon nanotube pastes show the special properties of carbon nanotubes combined with the various advantages of composite electrodes such as a very low capacitance (background current) and the possibility of an easy preparation, modification and renewal. A better knowledge of the characteristics of electrode reactions at carbon nanotube paste (CNTP) electrodes was obtained studying the electron transfer rates of various redox couples under different pretreatment conditions. A critical comparison with carbon paste (CP), platinum (Pt) and glassy carbon (GC) electrodes was also carried out. Capacitance and resistance values were also calculated for all electrodes investigated. Both untreated and treated CNTP electrodes showed a low resistance while the capacitance was markedly reduced with CNTP electrodes previously treated with concentrated nitric acid. An electrochemical pretreatment on CNTP electrodes was developed which showed an excellent result towards two‐electron quinonic structure species. After this treatment the heterogeneous standard rate constants for p‐methylaminophenol sulfate (MAP) and dopamine resulted to be significantly higher (2.1×10?2 cm/s and 2.0×10?2 cm/s, respectively) than those obtained with the other electrodes studied. Reproducibility, stability and storage characteristics of CNTP electrodes were also reported. 相似文献
89.
Ibrahim Isildak Murat Yolcu Omer Isildak Nadir Demirel Giray Topal Halil Hosgoren 《Mikrochimica acta》2004,144(1-3):177-181
Two diaza-crown ether compounds were synthesized and evaluated as Ag+-selective carriers in polyvinylchloride (PVC) membrane electrodes of solid-state type. The all-solid-state PVC membrane electrode based on N,N-Dibenzyl-dibenzo-diaza-18-crown-6 exhibited a super-Nernstian response (75±10mV per decade) over the concentration range of 1×10–1 to 7×10–6M of Ag+ ion and a detection limit of 3×10–6M, at a wide range of pH (pH 4–7). The response time of the electrode was fast (less than 10s), and it can be used for three months without any significant deviation in potential. The proposed all-solid-state PVC membrane electrodes revealed high selectivity toward Ag+ ion with respect to alkali, alkaline earth, heavy and transition metal ions. A flow-through cell of all-solid-state PVC membrane Ag+-selective electrode based on N,N-Dibenzyl-dibenzo-diaza-18-crown-6 has also been prepared and applied for flow-injection analysis of Ag+ ion in solution. 相似文献
90.
A nickel-catalysed chemically modified electrode is described which seems to represent a convenient compromise between ease of preparation, reproducibility, precision and detection limits for the determination of carbohydrates in biological matrices. 相似文献