Showing papers on "Amperometry published in 1997"
Patent•
08 Dec 1997
TL;DR: In this paper, a face-to-face sandwich configuration is provided for the amperometric assay of glucose in aqueous media, which comprises a sensing electrode strip containing a first redox mediator in an electrically conductive coating and a reference electrode strip in simultaneous contact with a reagent strip containing another mediator which is sandwiched between the active electrode surfaces.
Abstract: A highly sensitive sensor for the amperometric assay of glucose in aqueous media having a face-to-face sandwich configuration is provided which comprises a sensing electrode strip containing a first redox mediator in an electrically conductive coating and a reference electrode strip in simultaneous contact with a reagent strip containing a second redox mediator which is sandwiched between the active electrode surfaces. An opening is provided in the reference electrode for the introduction of samples. In one embodiment, a whole blood separation membrane is interposed between the reference electrode and the reagent strip to filter red blood cells and other particles from whole blood to enable direct assay of glucose without sample preparation. The sensing electrode comprises a non-conductive support member having an electrically conductive layer containing the first redox mediator. The reference electrode is typically a Ag/AgCl electrode formed by coating an ink containing Ag/AgCl dispersed in a resin on a non-conductive base. The reagent strip is a porous or fibrous carrier, typically a paper, impregnated with a mixture containing the second redox mediator, glucose oxidase, horseradish peroxidase, at least one surfactant and at least one stabilizer comprising an aqueous thickening agent. In one version of the sensor, the sensing electrode comprises a support member of polyester film coated with an electrically conductive graphite composition containing dimethylferrocene as the first redox mediator and the second redox mediator comprises potassium ferrocyanide.
148 citations
TL;DR: An amperometric peroxide biosensor was prepared by electrochemical deposition of horseradish peroxidase (HRP) on a Pt disc electrode modified with polyaniline (PANI) film doped with polyvinyl sulphonate (PVS).
111 citations
TL;DR: The amperometric enzyme-channeling immunosensor enabled the performance of separation-free EIAs without washing steps, resulting in a relatively short assay time of 5-30 min for the complete immunoassay, compared with at least 1-3 h for ELISA methods.
110 citations
TL;DR: In this paper, a carbon paste electrode bulk modified with MnO was investigated as an amperometric detector for hydrogen peroxide in flow, with an operating potential of +0.46 V versus Ag/AgCl.
Abstract: A carbon paste electrode bulk modified with MnO
2
was
investigated as an amperometric detector for hydrogen peroxide in flow
injection analysis (FIA). With an operating potential of +0.46 V
versus Ag/AgCl, H
2
O
2
produces catalytic
oxidation currents which can be exploited for quantitative determinations.
Factors influencing the analytical performance of the electrode, such as
paste composition and pH, were studied both for batch voltammetry and for
FIA. For the flow system the influence of the injection volume and flow
rate were examined. The amperometric signals are linearly proportional to
H
2
O
2
concentrations in the range 0.5–350 mg
l
-
1
, showing a detection limit (three times
the signal-to-noise ratio) of 45 µg
l
-
1
.
106 citations
TL;DR: In this article, the authors investigated electrochemical measurements with interdigitated array (IDA) electrodes in both stationary solutions and flow systems, and they achieved a very low detection limit of 10 pM of reversible redox species by using substitutional stripping voltammetry, which is a new type of stripping voltageammetry using an IDA microelectrode.
100 citations
TL;DR: In this article, a method to electrically wire flavoenzymes with electrode surfaces was developed by reconstitution of the apo-flavoenzyme with a ferrocene-tethered FAD diad.
90 citations
TL;DR: The use of the coupling capillary electrophoresis with wall-jet amperometric detection for the separation and detection of compounds present in human plasma samples was reported.
89 citations
TL;DR: In this article, cyclic voltammetry was used to investigate the electrochemical behavior of ascorbic acid (AA) at the poly(glutamic acid) chemically modified electrode (PME) in phosphate buffer solution.
83 citations
TL;DR: Assembly of the photoactive enzymes as monolayers on the Au-electrode results in functionalized surfaces for the cyclic ‘ON-OFF’ amplified amperometric transduction of recorded optical signals.
80 citations
TL;DR: In this article, high-sensitive amperometric creatinine sensors based on the adsorption of three enzymes are described, where the base electrodes are fabricated using electrochemical deposition of Pt black on a flexible electro-conductive polymer film (polyanion doped polypyrrole).
79 citations
TL;DR: Findings indicate that under conditions of physiological stimulation the direct voltammetric measurement of O(2) in brain tissue with a CPE can be used as a reliable index of increases in rCBF, resulting in an improvement in time resolution from 5 min (H2 clearance) to <1 s (amperometry).
TL;DR: The development of the new concept utilising various peroxidases for determination of phenolic compounds in flow injection (FI) mode and the selectivity of these electrodes was studied, finding that the best electrodes gave a detection limit for p-cresol of 0.4 μM.
TL;DR: The resulting enzyme electrode exhibits excellent electrocatalysis for the oxidation of reduced nicotinamide-adenine dinucleotide (NADH), based on the electrochemical detection of NADH which is generated in the enzymatic reaction of ethanol with NAD(+) under catalysis of ADH.
TL;DR: In this article, an osmium (4,4′-dimethyl 2,2′-bipyridine) 2 (1,10-phenanthroline-5,6-dione) mediator was used to improve the performance of tyrosinase electrodes.
TL;DR: In this paper, a rutheniumoxide-type catalytic film (RuOx) was produced on carbon fiber microelectrodes by cycling the electrode potential between 0.65 and −0.85V vs. SSCE at 100 V s−1 in an air-equilibrated acidic solution of RuCl3.
TL;DR: A novel amperometric biosensor for the determination of lactate was constructed by immobilizing lactate oxidase and an osmium redox polymer on the surface of a glassy carbon electrode, followed by coating with a sol-gel film derived from methyltriethoxysilane (MTEOS).
TL;DR: In this paper, the influence of various experimental parameters on the electrochemical response of zeolite-modified electrodes (ZMEs) have been studied using ion-exchange voltammetry, with regard to their application as amperometric sensors.
TL;DR: Capillary zone electrophoresis (CZE) was employed to the analysis of bovine serum albumin (BSA) using an end-column amperometric detector with a carbon fiber microdisk array electrode as discussed by the authors.
Patent•
18 Aug 1997
TL;DR: In this paper, a method of determining the concentration of glycoproteins and glycosylated hemoglobin in whole blood and whole blood components by means of an amperometric biosensor and a biosensor for this determination is provided.
Abstract: A method of determining the concentration of glycoproteins and glycosylated hemoglobin in whole blood and whole blood components by means of an amperometric biosensor and an amperometric biosensor for this determination are provided. In one embodiment, whole blood is introduced into a version of an amperometric sensor having a component that removes erythrocytes. Redox mediators are used to obtain a current flow based on the oxidation of fructosamine derivatives that can be correlated with the concentration of glycosylated proteins in the fraction of the blood from which erythrocytes have been excluded. To obtain the concentration of glycosylated hemoglobin, whole blood is introduced into a version of the sensor which includes a component that produces lysis of the erythrocytes yielding a current flow proportional to the total quality of glycosylated proteins including glycosylated hemoglobin. The glycosyltaed hemoglobin concentration is obtained by subtracting the glycoprotein concentration in the absence of erythrocytes from the glycoprotein concentration of the lysed whole blood. The sensor generally comprises a sensing electrode having a first redox mediator dispersed in an electrically conductive medium such as an electrically conductive graphite formulation; a reference electrode such as a standard silver-silver chloride electrode; a reagent strip containing a pH buffer and a second redox mediator system in a gel medium; and a whole blood treatment component consisting of either a membrane or other means to filter erythrocytes from whole blood or a means to lyse erythrocytes. In a preferred form, that has high sensitivity, the sensing electrode and the reference electrode may be formed as coatings on separate non-conductive strips such as polyester film with these strips arranged so that they form "the bread" of a sandwich in which the electrode coatings are face-to-face and the reagent strip and the filtration or lysing component form the "filling" of the sandwich. The filtration or cell lysing component covers an opening in the reference electrode through which samples are introduced, and is superimposed on the reagent strip.
TL;DR: In this paper, an alternative approach to the fabrication of an amperometric biosensor, which combines electrochemical polymerization of a bilayer film and covalent binding of the enzyme, is presented.
Abstract: An alternative approach to the fabrication of an amperometric
biosensor, which combines electrochemical polymerization of a bilayer film
and covalent binding of the enzyme, is presented. A Pt electrode modified
by an anti-interferent poly(pyrrole) layer is covered by a poly(tyramine)
film, exposing amino groups that are then used for the covalent attachment
of lactate oxidase after activation with glutaraldehyde. In this way, a
fabrication procedure is obtained that combines the advantages of
electrochemical polymerization (high spatial control, no restrictions in
electrode shape and dimension, reproducible film thickness even in the
sub-micrometre range) with those of covalent binding of the enzyme (no
enzyme loss, higher response stability and increased lifetime of the
sensor). The interferent rejection efficiency is dictated by the
diffusional barrier provided by the bilayer membrane and by the degree of
permselectivity that can be built up in the poly(pyrrole) film. A peculiar
property was displayed by the bilayer, i.e., the ability to
separate L-lactate and residual interferent responses in the
time domain in both flow injection and batch addition experiments. The
resulting L-lactate amperometric biosensor was characterized in
terms of sensitivity, response time, linear response range, stability and
rejection of electroactive interferents.
TL;DR: In this paper, three different electrochemical approaches for the detection of α-naphthol were compared with respect to measurable range, detection limit, reproducibility, sample throughput and suitability for in field use.
TL;DR: A new mediated amperometric biosensor for fructose based on a commercially available D-fructose dehydrogenase that achieves electron transfer at 0·1 V (versus Ag/AgCl) with maximum apparent current densities of 1·2 mA/cm2 is described.
TL;DR: In this paper, a new bienzymatic electrode for glucose sensing has been constructed with the aid of the sol−gel process by simultaneous immobilization of graphite microparticles and two enzymes (horseradish peroxidase (HRP) and glucose oxidase (GOD)) in a silica gel matrix.
Abstract: A new bienzymatic electrode for glucose sensing has been constructed with the aid of the sol−gel process. This mediatorless sensor was made by the simultaneous immobilization of graphite microparticles and two enzymes (horseradish peroxidase (HRP) and glucose oxidase (GOD)) in a silica gel matrix. The amperometric detection of glucose was assayed by potentiostating the biosensor at 0 V vs SCE in order to reduce the enzymically generated H2O2. The active graphite particles evenly dispersed within the silica gel matrix establish an efficient electrical communication between the electrode surface and the HRP active center. The effect of graphite and HRP amounts have been investigated in order to improve the analytical characteristics of the amperometric H2O2 biosensor. For determination of glucose, a bilayer structure where HRP and GOD were immobilized in two separated silica films exhibited the higher analytical performances.
TL;DR: A prototype amperometric fructose biosensor based on membrane-bound fructose dehydrogenase and the coenzyme ubiquinone-6 immobilized in a membrane mimetic layer on a gold electrode has been constructed and tested and indicates that this construct could be particularly useful for quantitation of fructose in citrus juice.
Abstract: A prototype amperometric fructose biosensor based on membrane-bound fructose dehydrogenase (Gluconobacter sp.) and the coenzyme ubiquinone-6 immobilized in a membrane mimetic layer on a gold electrode has been constructed and tested. A bare gold electrode first was modified through chemisorption of a mixture of octadecyl mercaptan and two short-chain disulfides, 3,3‘-dithiodipropionic acid and cystamine dihydrochloride. The membrane-bound enzyme, coenzyme, and additional phospholipid were codeposited through a detergent dialysis protocol. The short-chain modifiers may provide electrostatic interactions with enzyme surface charges, while the alkanethiolate and phospholipids enable hydrophobic interaction with the largely lipophilic, membrane-bound enzyme. At oxidizing potentials, the enzyme electrode responded with catalytic current densities up to 45 μA/cm2 when exposed to fructose at 10 mM. The sensor exhibited a response time of less than 20 s, a sensitivity of 15 μA/cm2·mM and a detection limit of less...
TL;DR: In this paper, the measurement of a steady state current at a Pt microdisc electrode (radii 2.5-10 μm) is used as the basis of a rapid and simple procedure for the determination of trace nitrite in waters.
TL;DR: Carbon-based screen-printed electrodes are suitable for uric acid detection and Optimum conditions were found for the determination of Hypoxanthine, Inosine (HxR) and InOSine monophosphate (IMP).
TL;DR: In this article, a three electrode design using solvent resistant materials is reported, enabling the production of screen printed electrodes for use in biosensor applications involving water-miscible organic solvents.
TL;DR: A bimetallic electrode composed of copper microparticles dispersed onto a gold surface (Au/Cu) has been investigated as an amperometric sensor using glucose as a model compound as discussed by the authors.
TL;DR: A reagentless lactate amperometric biosensor, constructed by immobilising the enzymes glutamic pyruvic transaminase (GPT) and l-lactate dehydrogenase (LDH) together with its cofactor nicotinamide adenine dinucleotide (NAD+) in carbon paste using an electropolymerised poly(o-phenylenediamine) (PPD) film, is described in this paper.
TL;DR: In this paper, cyclic voltammetry was used to investigate the electrochemical behavior of a nafion/ruthenium modified glassy carbon towards the electrooxidation of hydrazine compounds in perchloric acid solutions.