Amperometric Detection Of Hydrogen Peroxide Research Articles

A FIA procedure for enzymatic determination of high glucose concentrations. Application to parenteral solutions analysis

A flow injection system for the determination of high levels of glucose in parenteral solutions based on amperometric detection of hydrogen peroxide produced in the glucose oxidase reaction was developed. The determinations were made without any sample pre-treatment. The flow injection manifold includes two dialysis units to perform dilution of the samples and to mai n- tain the enzyme in a closed re-circulation loop. Due to the hydrodynamic characteristics of the analytical system, the variables were optimized using a parameter design of Taguchi. Under optimal conditions, a linear response for glucose concentrations, between 0.1 and 1.0 M was achieved. A good reproducibility (r.s.d. < 3%) and a sampling rate of 30 determinations/hour were observed. The results obtained are in a good agreement with those obtained using the spectrophotometric enzymatic method.

Wet and dry chemistry kits for total creatine kinase activity using a microfabricated, planar, small-volume, amperometric cell

A novel microfabricated amperometric microcell is used for total creatine kinase (CK) activity determination. The microcell employs a photolithograpically prepared flat form electrode pair for detection. The enzyme-catalyzed reaction takes place in a thin liquid film, supported by a replaceable porous, hydrophillic membrane, resting on the working electrode surface. Simple, two electrode, amperometry was used, to avoid overvoltage shocks caused by “open” circuits. An electrochemically prepared size-exclusion membrane was utilized on the working electrode to provide selectivity for the amperometric detection of hydrogen peroxide. Two different analytical reaction sequences following the CK catalyzed creatine phosphate hydrolysis were investigated. Both result in hydrogen peroxide production. The rate of hydrogen peroxide production is proportional to the total CK activity, and it is followed after the dispensation of sample into the microcell. The slope of the amperometric current–time curve is evaluated as the analytical signal.

Minimal-fouling enzyme electrode for continuous flow measurement of whole blood lactate

A new membrane system evaluated in an enzyme electrode for monitoring of whole blood lactate under continuous flow conditions has been developed. The membrane confers functional haemocompatibility and has been coupled to an electrode based on amperometric detection of hydrogen peroxide with lactate oxidase interposed between the haemocompatible membrane acting as diffusion barrier and an inner membrane excluding interfering electroactive species. Here, the enzyme electrode is combined with a flow-through measuring chamber and a double lumen catheter permitting continuous sampling and heparinization of blood. The blood contacting membranes have unique haemocompatibility properties and were produced through modification of poly(vinyl chloride), with the non-ionic surfactant Pluronic F-68. On-line monitoring of whole blood samples with different amounts of added lactate was carried out to simulate fluctuations in blood lactate levels during extracorporeal and results were compared with a standard lactate analyser.

Blood compatibility and extended linearity of lactate enzyme electrode using poly(vinyl chloride) outer membranes

A functionally haemocompatible lactate enzyme electrode system with an extended linear range has been developed. The electrode is based on classical amperometric detection of hydrogen peroxide produced by the enzyme lactate oxidase, immobilised in a glutaraldehyde matrix. The sensor system comprises an outer poly(vinyl chloride), PVC, membrane with incorporated non-ionic surfactant which acts both as a haemocompatible interface and a diffusion barrier, extending the sensor linear range up to at least 90 mM lactate. Electroactive interferents, such as ascorbate, urate and acetaminophen, are effectively excluded by the further use of an inner sulphonated polyether-ether sulphone/polyether sulphone membrane. Membrane composition and fabrication were investigated. The blood compatibility of the outer PVC membranes was evaluated by comparing sensitivity of the electrode before and after exposure to undiluted whole blood. Scanning electron microscopy (SEM) was also used to examine the membrane surface. Measurements of whole blood and plasma lactate concentrations when compared with those obtained with a standard lactate analyser gave, respectively, y = 1.2x + 0.50, r 2 = 0.97, n = 6 and y = 0.89x + 0.13, r 2 = 0.96, n = 20.

Fabrication of multilayer films containing 1:12 phosphomolybdic anions on the surface of a gold electrode based on electrostatic interaction and its application as an electrochemical detector in flow-injection amperometric detection of hydrogen peroxide

Abstract Novel multilayer films containing 1:12 phosphomolybdic anions were achieved on the surface of a gold electrode by alternating deposition of 1:12 phosphomolybdic anion with water-soluble polypyrrole. The chemically-modified electrode (CME) was shown to exhibit an electrocatalytic response for the reduction of hydrogen peroxide. Hydrogen peroxide was detected by flow-injection analysis at the modified electrode with high sensitivity. The method gave a linear range from 1 × 10 −2 mol l −1 to 1 × 10 −5 mol 1 −1 and a detection limit of 1 × 10 −6 mol 1 −1 (signal-to-noise ratio 3).

Solvent-resistant carbon electrodes screen printed onto plastic for use in biosensors

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. Heat stabilised polyester sheets were used as base materials in combination with carbon basal tracks and an epoxy-based polymer protective coating. The new electrodes avoid problems with solvent induced baseline shifts displayed by conventional screen-printed electrodes. The material for the underlying basal track has been changed from silver to carbon ink to reduce the number of materials involved in the production and avoid possible interferences. In addition, the design is readily applied in biosensor applications. Different methods for the incorporation of a rhodium catalyst are discussed. The application of the electrode system modified with the rhodium catalyst for the amperometric detection of hydrogen peroxide in different concentrations of methanol, isopropanol and ethanol is demonstrated.

Carbon-polymer biocomposites for amperometric sensing

New electrochemical sensing biocomposite materials are reported. These materials are based on polymer technology and are prepared mixing graphite powder, a non-conducting polymer resin and a lyophilized enzyme. The resulting biosensing material is inexpensive, robust, polishable and easy to machine. A survey of potentially suitable polymeric matrices was carried out. Epoxy, silicone, methacrylate and polyester polymers have been used to prepare rigid conducting composite materials of the graphite-polymer type. For each material, an optimal graphite content was determined. Amperometric transducers built with these materials were characterized electrochemically using cyclic voltammetry and linear-sweep voltammetry. Their linear response to hydrogen peroxide was evaluated. The applicability of these conducting polymer-graphite composites has been extended to the construction of conventional glucose biosensors. In these devices the conducting composite is bulk-modified with the addition of glucose oxidase. The amperometric detection of hydrogen peroxide serves as the analytical signal. Following the same construction method, it is also possible to obtain other biosensing systems. New biocomposites have been prepared, using a different enzyme in each case, i.e. acetylcholinesterase and peroxidase.

Mathematical modeling of an amperometric enzyme electrode based on a porous matrix of Stöber glass beads

The mathematical model of a glucose sensor based on the amperometric detection of hydrogen peroxide using immobilized glucose oxidase (GOD) has been described. In this sensor GOD is immobilized on Stöber glass beads that are attached to a platinum electrode. The influence of the bead radius ( r b, ranging 20, 45, 70, 100 and 200 nm) on the performance of the sensor has been analyzed. The total enzyme concentration defined per unit interfacial area increases directly with the bead radius and the effective diffusivity of the substrate in the enzyme layer decreases with increasing bead radius. The model describes approximate analytical solutions for the behavior of the system, which is assumed to follow the Michaelis-Menten scheme of reaction. Two distributions of the enzyme in the bead layer have been taken into consideration in the discussion. Numerical solutions have also been presented to give a complete picture of the behavior of the system. Comparison of numerical solutions and approximate analytical solutions suggests that the model is consistent in the regions of approximations. The model predicts different behavior of the system on either side of the critical radius (approximately 26 nm). The process is essentially diffusion controlled for the sensors with beads of radius smaller than the critical radius and the current response of the sensors in this case increases with the increase in bead radius. The current response of the sensors with beads of radius greater than the critical radius decreases with the increase in bead radius. The regime of operation (kinetic control or diffusion control) for this case depends on the value of the Thiele modulus.

Transcutaneous lactate monitoring based on a micro-planar amperometric biosensor

A transcutaneous lactate monitoring method has been developed by combining a suction effusion fluid (SEF) collecting technique with a micro-planar amperometric biosensor. SEF is directly collected by a weak suction through the skin from which the stratum corneum has been removed. A micro-planar biosensor, has also been developed for determining lactate concentrations in very small samples. The biosensor utilizes a lactate oxidase immobilized membrane on a micro planar platinum electrode to yield a lactate sensor. The sensor is based on amperometric detection of hydrogen peroxide generated by the lactate oxidase-catalyzed oxidation of l-lactate. The linearity of the lactate sensor response was obtained from 0.5 mM to 25 mM and the response time was about 10 s. The sensor was applied to the SEF lactate measurement of a rabbit during induced high lactate levels. Lactate concentrations measured with SEF showed good correlation with those obtained directly from whole blood. This result suggests the feasibility of transcutaneous lactate monitoring without the use of blood sampling.

Carbon paste electrode incorporated with cobalt(II) octaethoxyphthalocyanine for the amperometric detection of hydrogen peroxide

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 an L‐lactate‐sensing enzyme sensor; the sensor could be used for more than 4 weeks and 400 assays.

A reagentless amperometric biosensor for hydrogen peroxide determination based on asparagus tissue and ferrocene mediation

A new reagentless biosensor for the amperometric detection of hydrogen peroxide was developed by co-immobilisation of ground asparagus tissue ( Asparagus officinalis) and ferrocene in a carbon paste matrix. The asparagus tissue acts as a source of peroxidase. Ferrocene is utilised as a mediator to facilitate efficient electron transfers between the electrode surface and hydrogen peroxide. The detection of hydrogen peroxide was based on the measurement of amperometric response due to the reduction at the electrode of ferricinium ion generated from the enzymatic reaction at 0.00 mV vs. SCE. The response characteristics and optimisation of the bioelectrode design are evaluated. The bioelectrode exhibits linear response up to a hydrogen peroxide concentration of 6 × 10 −5 M with a detection limit of 4.0 × 10 −7 M. Response times ( t 90) as low as 2 s and a relative standard deviation of replicate measurements of 1 × 10 −5 M hydrogen peroxide of 1.95% ( n = 15) were achieved. The bioelectrode sensitivity decreased to 50% of the original value within 30 days of continuous use.

Amperometric enzymatic glucose electrode based on an epoxy-graphite composite

An inexpensive, robust, polishable and easy to mechanize amperometric transducer showing a long lifetime, based on a composite material made of graphite and non-conducting epoxy resin (Epo-Tek H77), was constructed. This composite was characterised electrochemically using cyclic voltammetry and linear-sweep voltammetry. The applicability of this amperometric transducer was demonstrated in the construction of a glucose biosensor based on the amperometric detection of hydrogen peroxide produced by the catalytic action of glucose oxidase covalently immobilized on a nylon mesh. The sensor shows a linear response range for glucose in the range 10−5−10−2 M when a potential of 1150 mV is applied with respect to an Ag/AgCl electrode in a pH 7.00 buffered solution with 0.1 M phosphate and 0.1 M KCl. The resulting biosensor was compared with a commercial glucose analyser.

Electrocatalysis and flow-injection analysis of hydrogen peroxide at a chemically modified electrode

A chemically modified electrode for the amperometric detection of hydrogen peroxide is described. By electrodeposition of a copper heptacyanonitrosylferrate(II) (CuHNF) film on the surface of a glassy carbon electrode, the overvoltages for both oxidation and reduction of hydrogen peroxide can be drastically decreased. Cyclic voltammetry at the resulting modified electrode reveals the peresence of two pairs of redox peaks corresponding to the Cu(I)-Cu(II) and Fe(II)(CN) 5NO-Fe(III)(CN) 5NO redox couples, respectively. The modified electrode is less prone to fouling and shows enhanced sensitivity for hydrogen peroxide. Various electrochemical response characteristics were investigated. When applied as an electrochemical sensor in a flow-injection system, the modified electrode permitted detection of hydrogen peroxide at lower potentials than at the unmodified electrode surface. This greatly improved the selectivity. A linear amperometric response range with hydrogen peroxide was obtained between 0.4 μM and 1 mM. The relative standard deviation for 30 repetitive injections with a 10 μM hydrogen peroxide solution over a 30-min period was less than 4%.

Rapid and sensitive discriminating determination of acetylcholinesterase activity in amniotic fluid with a choline sensor

A simple method for the separate determination of acetylcholinesterase and butyrylcholinesterase activities in amniotic fluid is reported. This determination is performed with an enzyme electrode involving an immobilized choline oxidase membrane associated with the amperometric detection of hydrogen peroxide. Acetylcholine or butyrylcholine, in the presence of samples containing acetylcholinesterase or butyrylcholinesterase are specifically hydrolyzed, the formation of choline being detected vs time by the sensor with no need for a selective inhibitor. The dynamic linear ranges for acetylcholinesterase and butyrylcholinesterase are respectively 100 μU to 10 mU and 30 μU to 3 mU per ml sample.

Gas-diffusion dilution flow-injection method for the determination of ethanol in beverages without sample pretreatment

The combination of immobilized alcohol oxidase (AOD) with a gas-diffusion membrane in a flow-injection system greatly enhanced the specificity of ethanol determination. This gas-diffusion flow-injection system with amperometric detection of hydrogen peroxide had a linear range of analysis from 0.0006 up to 60% (v/v) ethanol. Silicone-modified polypropylene membranes of different thickness were used. Undiluted samples of beer, wine, spirits and medicine could be investigated with excellent correlation with standard methods ( r > 0.997). The frequency of analysis was 120–180 samples h −1 and the operational half-life of the immobilized enzyme was 8000 injections within 44 h.

An interface between the IBM PC/XT and the PAR model 273 potentiostat/galvanostat

An interface between an IBM PC/XT and a Princeton Applied Research (PAR) model 273 Potentiostat/Galvanostat using serial communication is described. Instrument control and data processing are achieved with the ASYST programming language. Data are filtered by the potentiostat with point averaging, and by the microcomputer with software smoothing. An application is presented whereby cholesterol is determined by the amperometric detection of hydrogen peroxide following an enzymatic reaction with cholesterol oxidase.

Amperometric enzyme electrodes in analytical chemistry

An overview is given of works on the construction and application of amperometric enzyme electrodes for the determination of metabolites in biological solutions. The following electrodes are dealt with: monoenzyme and polyenzyme electrodes involving amperometric detection of hydrogen peroxide, bienzyme electrodes with oxidase-peroxidase, electrodes based on organic metals and chemically modified electrodes, dehydrogenase electrodes, amperometric hydrolase electrodes and highly sensitive electrodes involving chemical amplification. Biocatalytic stripping and macrokinetic behaviour of the electrodes are discussed.

FIA system for measurement of optical purities of amino acids utilizing amino acid enzymeelectrodes.

A simple and rapid method is presented for the measurement of the optical purities of amino acids, using the FIA system with L-and D-amino acid enzyme-electrodes which give specific response for L-and D-amino acids respectively. The enzyme electrode is made up of cross-linking L-amino acid oxidase or D-amino acid oxidase with bovine serum albumin using glutaraldehyde on a flow-through platinum electrode silanized with (3-aminopropyl)triethoxysilane. Both enzyme electrodes are based on the amperometric detection of hydrogen peroxide generated by the enzymatic reactions. The proposed method is high-sensitive for some amino acids (methionine, tyrosine, leucine and phenylalanine) and is useful for the specific detection of L-and D-isomers of amino acids. The peak current is linearly related to the concentration of L-or D-amino acids in the range 10-52×10-3 M, for injections of 20-μl samples. The measurements can be performed at a rate of 100120 samples h-1 with satisfactory precision (1.12.8% R.S.D.). The enzyme electrodes retained 8291% of their original activities after repetitive use for two months.

酵素電極を検出器として用いた高速液体クロマトグラフィーによるアセチルコリンとコリンの定量

A simple and rapid method was presented for the determination of acetylcholine and choline, using the high-performance liquid chromatographic system with enzyme electrodes as the electrochemical detector. The enzyme electrode was made up of cross-linking acetylcholinesterase (AChE) and choline oxidase (ChO) with bovine serum albumin (BSA) or AChE, ChO and peroxidase (POD) with BSA using glutaraldehyde on a platinum electrode silanized with (3-aminopropyl)triethoxysilane. The AChE-ChO and AChE-ChO-POD electrodes were based on the amperometric detection of hydrogen peroxide and hexacyanoferrate(III)generated by the enzymic reactions, respectively. The method was high-sensitive and specific for the determination of acetylcholine and choline. The detection limit was 1.5pmol for choline and 2.9 pmol for acetylcholine. The enzyme electrodes could be used continuously for at least 20 d.

A carbon electrode sputtered with palladium and gold for the amperometric detection of hydrogen peroxide

A modified carbon electrode for the amperometric determination of hydrogen peroxide is described. By deposition of a 15-nm thick layer of a 40:60 mixture of palladium and gold on the surface of the electrode the overvoltages for both the oxidation and the reduction can be decreased by at least 800 mV. When applied as an electrochemical sensor in a flow-injection system, linear calibration graphs were obtained between 10 −7 and 5 × 10 −3 M hydrogen peroxide. The modified electrodes were stable for months.