ISSN:1040-0397    

DOI:10.1002/elan.1140091402

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe present article reports the development of a novel electrochemical carbon dioxide minisenso based on hemoglobin which is incorporated into self‐assembled bilayer lipid membranes (s‐BLMs) on a metal support. The presence of carbon dioxide in solution was found to modulate the ion conductivity of BLMs containing hemoglobin, when using a lipid composition containing egg phosphatidylcholine (egg PC) and dipalmitoylphosphatidic acid (DPPA). The use of stabilized metal‐supported BLMs has allowed the electrochemical investigation of the reversibility of the response to carbon dioxide and of hemoglobin binding to lipid membranes. The effects of hemoglobin concentration, composition of BLMs in DPPA and pH on the sensitivity of the response were examined. The sensor provides the advantages of fast response times (on the order of ca. 10 s) to alterations of carbon dioxide concentration, low detection limits (ca. 0.4 × 10−6M) and capability of analysing small sample volumes. Semisynthetic platelet‐activating factor (PAF; 1‐O‐alkyl‐2‐acetyl‐sn‐glyceryl‐3‐phosphorylcholine, AGEPC) was found to improve the response characteristics of the carbon dioxide sensor (i.e., decrease of the detection limit to nM range and increase of the dynamic range of carbon dioxide determination). The biosensor was routinely mechanically stable and functional for over 48 h. During this time it showed reproducible sensitivity and response to a given concentration of

ISSN:1040-0397    

DOI:10.1002/elan.1140091403

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA nitrate‐selective polypyrrole‐based electrode was used in the development of NOxsensor. The nitrate‐selective film was prepared by electropolymerizing pyrrole in presence of a nitrate salt. This resulted in a film that responded to nitrate in buffered media with near‐Nernstian slopes and excellent reproducibility. This electrode was incorporated into a gas‐sensing arrangement where it was immersed in a buffered compartment and separated from an acidified sample solution by a gas‐permeable membrane. Additions of nitrite to the acidified solution resulted in the production of NOx, which can cross the gas‐pemeable membrane into the buffered internal filling solution where it is trapped as nitrate and sensed by the nitrate‐selective polypyrrole electrode. This sensor arrangement resulted in detection limits in the μM range and had excellent selectivity

ISSN:1040-0397    

DOI:10.1002/elan.1140091404

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA film containing vicinal diol groups has been formed on the quartz surface of a surface acoustic wave sensor through a silanization reaction with 3‐glycidoxypropyltrimethoxysilane. The interactive selectivity of the silane surface for adsorption of several vapor analytes was measured using a gas chromatograph‐acoustic wave device combination. Much larger responses are obtained for compounds containing a nitrofunctional group. Computational chemistry is employed to calculate interaction energies for purported hydrogen‐bond complexes between analyte molecules and ethylene glycol, an analogue of the surface silane species. The results of these calculations are compared to the experimental sensor resp

ISSN:1040-0397    

DOI:10.1002/elan.1140091405

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractPlatinum electrode modified with polyaniline by electropolymerization exhibits amperometric sensitivity to nonprotonated ammonia in aqueous solutions in the anodic range of potentials. Sensitivity of response depends mostly on the kind of doping anions used and the polarization potential applied during measurements. This detection can be utilized for design of amperometric biosensors for urea.

ISSN:1040-0397    

DOI:10.1002/elan.1140091406

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe present work reports the use of self assembled bilayer lipid membranes supported on the surface of a metal (s‐BLMs) as transducers for the direct electrochemical monitoring of DNA hybridization. Characterized oligomers based on single stranded deoxyribonucleic acid (ssDNA) thymidylic acid icosanucleotides that were terminated with C16(dT20‐C16) and deoxyadenylic acid icosanucleotides (dA20) were used for the hybridization procedure at the lipid membrane surface. The decrease of the ion conductivity observed during the hybridization procedure is indicative of the formation of the duplex, which may subsequently be excluded from the membrane. The incorporation of nucleic acids into the lipid matrix was investigated by differential scanning calorimetric (DSC) experiments. The present simple electrochemical biosensor for monitoring of DNA hybridization was regenerable for multiple cycles of application. This approach provides low detection limits for DNA (a few hundreds of fmol), fast response times (on the order of a few minutes), mild conditions of hybridization and capability of analyzing small volumes of sam

ISSN:1040-0397    

DOI:10.1002/elan.1140091407

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractImmobilization of avidin‐modified acetylcholinesterase and choline oxidase (A‐COxACE) on a metal supported biotinylated membrane allowed us to developed a minisensor based on changes in anticholinesterase activity by several environmental pollutants. The concentrations of acetylcholine and choline have been determined amperometrically on the basis of anodic oxidation of hydrogen peroxide, a product of choline oxidase. The immobilization of the complex A COxACE was controlled by the electrostriction method which allowus to determine changes of membrane capacitanceCand elasticity modulusE⟂ in a direction perpendicular to the s‐BLM surface. The binding of the A‐COxACE complex to s‐BLM resulted in a decrease ofCand in an increase ofE⟂ suggesting increase in the membrane ordering. Using the simple amperometric method we were able to use this minisensor for detection of acetylcholine and choline. Detection limits were 0.79 mM and 1.25 mM for acetylcholine and choline, respectively. The biosensor was tested for acetylcholinesterase inhibition in the presence of organophosphorus Trichlorpho

ISSN:1040-0397    

DOI:10.1002/elan.1140091408

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIon selective and amperometric electrodes based on PVC membranes were constructed for the measurement of phenolics and assessed for potential use in monitoring coke works effluent treatment. Potentiometric working ranges are restricted to>100 mM, suffering thiocyanate interference, despite response slopes of13) pH is achieved by stable encapsulation of such an environment beneath ion impermeable PVC within the sensor structure.

ISSN:1040-0397    

DOI:10.1002/elan.1140091409

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractBiosensors for determination of carbamates in vegetables based on five different cholinesterase as biorecognition elements and a screen‐printed electrode system as an amperometric transducer were developed. Measurements were simply performed by dropping solutions (either sample or substrate) directly on the biosensor. The response of biosensors to selected carbamates (aldicarb, carbaryl, carbofuran, methomyl and propoxur) was characterized. The performance was evaluated on extracts of potatoes and carrots, the results from the AChE biosensor and a standard HPLC procedure were compared. Finally, the biosensor was used for the direct analysis of vegetable juices without any pretreatment steps. In this case, 10 μg/L levels of added carbofuran and propoxur were reliably identified. The whole procedure takes less than 20 min including 10 min incubation with samples. The concentrations of carbamates determined with biosensor agreed well for carbofuran. Lower response was observed for propox

ISSN:1040-0397    

DOI:10.1002/elan.1140091410

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractCyclic voltammetric studies of hydrogen peroxide on a polycrystalline gold electrode have permitted to point out that the oxidation of the molecule may occur at two distinct potentials depending on the sample composition and cleanliness and on the redox state of the electrode. At a clean gold surface, the oxidation of hydrogen peroxide gives only one wave at +490 mV (vs. Ag/AgCl) at pH 7.4, besides the gold oxidation wave at +820 mV. Species in solution which adsorb readily on gold (trace impurities originating because of sonication or solution stirring), gold oxide and acidic pH values, inhibit this wave and oxidation of hydrogen peroxide is occurring at a higher potential, i.e., +870 mV in phosphate buffer pH 7.4. Cyclic voltammograms show these two waves, depending on the degree of inhibition of hydrogen peroxide. At oxidized gold electrodes or contaminated by surface active species, oxidation of hydrogen peroxide gives only one wave at +870 mV. From these data it may be inferred that hydroxy species adsorbed on clean gold favor the formation of the first wave. Both waves may be advantageously exploited for quantitative purpose. The latter is not affected by surface active species and permits quantification of hydrogen peroxide down to 20 μM with a detection limit of 4 μ

ISSN:1040-0397    

DOI:10.1002/elan.1140091411

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY