摘要:

AbstractA hydrogen peroxide sensing electrode was prepared by incorporating cobalt(II) octaethoxyphthalocyanine [CoPc(OEt)8] into a carbon paste (CP) matrix. The CoPc(OEt)8‐modified electrode could oxidize hydrogen peroxide at lower potentials than a CP electrode with unsubstituted cobalt phthalocyanine (CoPc). In addition, the CoPc(OEt)8‐based system showed a high stability; the electrode response to 10mM hydrogen peroxide did not decrease for over 6 h, whereas the hydrogen peroxide response from the CoPc‐modified electrode reduced to half the initial value within 2 h. The CoPc(OEt)8, which is a paraffin oil soluble derivative of CoPc, incorporated into the bulk of the CP diffused towards the electrode surface so as to renew the electrode surface, and this resulted in the high stability of the CoPc(OEt)8‐modified electrode. The electrode was used as the transducer for anL‐lactate‐sensing enzyme sensor; the sensor could be used for more than 4 weeks and

ISSN:1040-0397    

DOI:10.1002/elan.1140070802

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractCobalt(II) 4,4′,4″,4″′‐tetraaminophthalocyanine was electropolymerized on glassy carbon by cyclic voltammetry. The formed polymeric films were shown to interact selectively with anions and were used in the design of ion‐selective electrodes. Different polymerization conditions, as well as different conditioning solutions and buffer systems, were investigated in order to optimize the response of the electrodes. The electrodes were found to be most selective for nitrite. The slopes of the calibration plots were sub‐Nernstian and the detection limit for nitrite wa

ISSN:1040-0397    

DOI:10.1002/elan.1140070803

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe detection of the ammonium ion produced by the enzymatic action of urease on urea is investigated electrochemically by means of Facilitated ion transfer reactions at liquid–liquid micro–interfaces. The urease was used either in a dissolved form (free in aqueous solution) or immobilized onto the surface of an ammonia gas permeable membrane. The sensing structure utilizing the ammonia gas permeable membrane allowed the detection of urea from 200μM to 4mM. Thick film technology was utilized in conjunction with UV excimer laser photoablation techniques to fabricate a inicroelectrode strip sensor for the ammonium

ISSN:1040-0397    

DOI:10.1002/elan.1140070804

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractA novel potentiometric peroxidase enzyme sensor based on a tubular graphite‐epoxy design is reported for the determination of hydrogen peroxide in an FIA system. The sensor was formed from horseradish peroxidase (40 mg), graphite (240 mg) and epoxy (780 mg). Hydrogen peroxide, injected into pH 7,0.05 M phosphate buffer at 26°C, was determined with a linear slope of 45.6 mV/decade in the concentration range 7.5 × 10−7to 5.0 × 10−5M. Acceptable reproducibility of 1.2% relative standard deviation was obtained in the flow injection analysis. The advantages of this sensor are low cost, simple electronic circuit design and better selectivity than amperometric sensors and a detection limit comparable with other

ISSN:1040-0397    

DOI:10.1002/elan.1140070805

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractSinigrin, the β‐D‐thioglucoside of the cruciferous plant species was hydrolyzed for 15 min at pH 7 and 30°C by the enzyme myrosinase to liberate glucose and mustard oil allylisothiocyanate as aglucone. A Clark‐type pO2sensor overlaid with a glucose oxidase + catalase membrane served for the glucose measurements, whereas the isothiocyanate component was measured (after conversion to allylthiourea) from the inhibition degree of a tyrosinase membrane/pO2sensor. The total amounts of glucosinolates found with the glucose probe in six assorted samples of rapeseed meal and evaluated in sinigrin equivalents (13.6 −147 μmol/g) agreed with those obtained using gas chromatography as the reference. Poor agreement (results: 111.4–112.3%) was achieved when a different method of fat removal was used prior to electroanalysis. The amounts of progoitrin (not convertible to thiourea) estimated indirectly from the difference of both the glucose and the aglucone biosensor analyses were found to be in the range 6.2–103 μmol/g (44.3–83.8% of the tota

ISSN:1040-0397    

DOI:10.1002/elan.1140070806

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe oxygen consumed during the tyrosinase reaction is significantly amplified byL‐ascorbic acid due to a substrate recycling process; the substrates have to be separated in order to obtain individual amplified current responses of each substrate. In this work, the chemically amplified current responses of catecholamines were obtained individually by liquid chromatography using an immobilized tyrosinase reactor and anL‐ascorbic acid carrier solution. The highly sensitive determinations ofL‐dopa, dopamine, and norepinephrine were carried out individually using a Clark type oxygen electrode detector. The amplification factors of 1 × 10−7ML‐dopa, norepinephrine, and dopamine were found to be 224, 357, and 568, respectively, when 5 × 103ML‐ascorbic acid solution was used as a carrier; the detection limit for dopamine was found to

ISSN:1040-0397    

DOI:10.1002/elan.1140070807

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractA conducting platinum cluster compound K1.64Pt(C2O4)2was electrochemically synthesized on a glassy carbon electrode through the electrooxidation of K2Pt(C,2O4)2in an aqueous medium using single potential step and cyclic voltammetry methods. The precursor K2Pt(C2O4)2was prepared by a ligand exchange reaction between C2O42−and PtCl42−. During single potential step experiments, the electrolytic current corresponding to the oxidation of K2Pt(C2O4)2increased dramatically after a sharp decrease at the beginning (due to the formation of conducting K1.64Pt(C2O4)2on the surface of the working electrode). Two kinds of mechanism account for the current transients at the different applied potentials. Cyclic voltammetry was conducted with K1.64Pt(C2O4)2on the surface of the working electrode and a steady‐state diffusion current was observed. Since the material grew in a fibrous manner, each conducting fiber which was in contact with the electrode could serve as an ultramicroelectrods. The behavior of the working electrode was thus changed from a plain to an ultramicroelectrode

ISSN:1040-0397    

DOI:10.1002/elan.1140070808

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study we report the development of a needle‐type glucose biosensor for the management of hemorrhagic shock. The immobilization technique depends on the electrophoretic deposition of the glucose oxidase enzyme in an electrochemically grown platinum black matrix. The sensor was coated with Nafion to decrease the effect of interferents. Preliminary tests were carried out to evaluate the sensor performance in vitro. These tests included the measurement of glucose levels in buffer solutions containing various potential physiological interferents, as well as in bovine serum. The preliminary results show the sensor to have inearity up to 33 mM and a diminished response to interferents. The advantages of this technique are its simplicity and high controllabilit

ISSN:1040-0397    

DOI:10.1002/elan.1140070809

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractA dicyano‐bis(1,10‐phenanthroline)iron(II)/Nafion modified elecrode was prepared. The voltammetric and the spectroelectrochemical behavior of this electrode were investigated. The influence of pH and the amount of Nafion and dicyano‐bis(1,10‐phenanthroline)iron(II) (DBPI) used in the electrode preparation on the electrochemical behavior is pr

ISSN:1040-0397    

DOI:10.1002/elan.1140070810

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractBiocatalytic accumulation is used to greatly enhance the sensitivity of tyrosinase enzyme electrodes for phenolic compounds. By allowing the enzymatic reaction to proceed for different time periods (under open‐circuit conditions) it is possible to accumulate the quinone product near the transducer surface. The subsequent chronoamperometric response is substantially higher than analogous bioassays without accumulation. For example, with 3 min accumulation, a 28‐fold signal amplification is observed. Assays of microliter (40 μL) samples are reported, yielding a detection limit of 2 × 10−8M (88 pg) catechoi following a 3 min accumulation. The influence of various experimental variables is explored. Applicability to bioassay of relevant environmental samples is illu

ISSN:1040-0397    

DOI:10.1002/elan.1140070811

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY