ISSN:1040-0397    

DOI:10.1002/elan.1140091202

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

ISSN:1040-0397    

DOI:10.1002/elan.1140091204

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe principle and potentialities of an original electrochemical procedure of biosensor construction based on amphiphilic pyrrole derivatives are reviewed. The two‐step procedure consists of the adsorption of an aqueous amphiphilic pyrrole monomers–biomolecule mixture on an electrode surface followed by the electrochemical polymerization of the adsorbed amphiphilic monomers. This method is compared with the more conventionally used electrochemical procedures of biosensor construction. Examples of multienzyme and additive entrapments, organic phase enzyme electrode, microelectrode functionalization and the electrical wiring of immobilized enzymes are presen

ISSN:1040-0397    

DOI:10.1002/elan.1140091206

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe potential response of reference devices consisting of parallel arrays of cation‐ and anion‐selective membrane electrodes is studied on a theoretical basis. A general treatment of the overall electric potential difference is offered that accounts for contributions by diffusion potentials, boundary potentials, ohmic potential drops, and streaming potentials. Explicit solutions are given for special cases. The treatment makes it possible to recognize the capabilities and the limitations of membrane‐based reference devices, and to compare their performance with the behavior of conventional reference electrodes using liquid‐junction contacts. The applicability of membrane‐based reference systems is found to be restricted to relatively specifi

ISSN:1040-0397    

DOI:10.1002/elan.1140091207

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA new sol‐gel‐derived electrocatalytic carbon composite electrode was prepared by dispersing cobalt phthalocyanine (CoPC) in a carbon ceramic network. The performance of the CoPC‐modified sol‐gel carbon composite electrode compares favorably with that of common CoPC‐containing carbon pastes in term of electrocatalytic properties and short‐ and long‐term stability. The greatly improved stability and electrocatalytic action are illustrated in cyclic‐voltammetric and flow injection amperometric measurements of hydrogen peroxide, hydrazine, oxalic acid, cysteine and thiourea. Such improvements are coupled with the versatility, mechanical stability and renewability features of sol‐gel

ISSN:1040-0397    

DOI:10.1002/elan.1140091208

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractWe have developed an on‐line electrochemical sensor for the continuous measurement of acetylcholine (ACh). The sensor comprises a small volume prereactor containing immobilized choline oxidase (ChOx) and catalase (or horseradish peroxidase, HRP), a small volume enzymatic reactor containing immobilized acetylcholine esterase (AChE) and ChOx and a glassy carbon electrode modified with Os‐polyvinylpyrridine ‐HRP. The sensor can measure ACh selectively even when the choline (Ch) concentration is more than 1000 times that of ACh, when th ChOx and catalase are immobilized in the prereactor. The sensor shows a wide linear relationship from 5 nM to 1 μM and a detection limit of 5 nM (S/N = 2), which is comparable to the ACh detection limit achieved by liquid chromatography/electrochemistry. It also shows high selectivity against other neurotransmitters and interferents. The properties of the sensor combined with a microdialysis (MD) probe were also studied by measuring a solution containing a much higher concentration of Ch th

ISSN:1040-0397    

DOI:10.1002/elan.1140091209

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractLanthanum fluoride and cerium fluoride single crystals, used as the sensing membranes of the fluoride ion‐selective electrode (F‐ISE), were investigated for their hydroxide interference and surface reactions with OH−in high pH conditions. While these membranes show fast response and excellent Nernstian behavior over a wide concertration range in buffered F−solutions, they deviate from the theoretical slope at high pH. CeF3, in particular, exhibits a much larger deviation from the Nernstian slope and a substantially slower response to a F−activity change compared to LaF3. This larger deviation is due to more extensive and faster formation of hydroxo‐complexes, with the release of a greater amount of the fluoride ion into the hydrated gel layer. The slower response of the CeF3membrane after contact with OH−is due to the formation of CeIVoxide on the surface, which acts as a blocking layer to the e

ISSN:1040-0397    

DOI:10.1002/elan.1140091210

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA reactive electrode (reactrode) made of silver(i) hexacyanoferrate(III) (Ag‐hcf), graphite and paraffin has been developed for the determination of iron(III) ions in solutions down to a concentration of 0.12 mg L−1. Silver ions are reduced to Ag0and the liberated hecacyanoferrate ions react with iron(III) ions from the solution to form Prussian blue. After this preconcentration step, the iron ions can be determined electrochemically by the characteristic signals of Prussian blue in differential pulse voltammetry. A nonlinear calibration plot is obtained which has a standard deviation of 13%. Pb2+, Cu2+and Ni2+interfere when they are at the same concentration as iron(III), whereas Cd2+does not interfere even at higher concentrations. The incorporation of an active reagent into the electrode material remarkably facilitates the analytical procedure and makes the use of a mercury electrode unnecess

ISSN:1040-0397    

DOI:10.1002/elan.1140091211

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThis work describes the application of object oriented software design to the development of a low cost, functionally versatile, PC‐controlled potentiostat system. The implementation time for the electroanalytical techniques has been drastically reduced within the object oriented environment and it is shown how this approach simplifies the addition of new techniques without recourse to extensive software or hardware redesign. The pertinent aspects to the object oriented technique in the design of the potentiostat software are described in detail and experimental results are presented for chronoamperometry, cyclic voltammetry and square wave voltammetry for the one‐electron transfer compound, potassium hexacyanoferrate(II) in aqueous solution. It is also shown how new electroanalytical techniques based on novel potential‐time waveforms can be rapidly and easily incorporated, and experimental results for the highly sensitive pulsed amperometric detection of glucose in a stirred cell are pres

ISSN:1040-0397    

DOI:10.1002/elan.1140091212

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractDifferent types of PVC‐matrix ion‐selective electrodes (ISEs) that respond to the cationic form of diphenhydramine (Dph) are described. Three ion‐pairing agents, namely tetraphenylborate (TPB), phosphotungstate (PT), reineckate (RN) are investigated. The best PVC polymeric membrane contains Dph‐TPB as active material. The electrode, based on the ion‐pair complex with TPB anion shows near‐Nernstian response in the concentration range 10−2to 3.5 × 10−5M (Dph.HCl). Changing pH within the range 2.0–7.5 did not affect the electrode performance. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coeffcient of the electrode (0.00156 V/°C) The electrode showed a good selectivity for Dph with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were applied to determine Dph amounts in pharmaceutical preparations. The Dph selective membrane electrode was also applied to the determination of the dissolution profile of Dph tablets. The dissolution results were compared with spectrophotometrica

ISSN:1040-0397    

DOI:10.1002/elan.1140091213

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY