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Amperometric enzyme electrode probes have been constructed for the specific determination of L-lysine and used in batch and flow analysis. The enzyme lysine oxidase was immobilized on a preactivated polymer support which was placed on a platinum electrode. Additional blocking membranes conferred high stability, reprodu... |
This paper reports a multicomponent least-squares regression method based on the use of multiple standards for the simultaneous resolution of substrates involved in kinetic enzymatic processes. The proposed method was applied to the determination of catechol-resorcinol mixtures by oxidation with hydrogen peroxide in th... |
The concept of a generic FIA system is described that allows multi-points assays of enzyme activities, that require a coupled chemical derivation reaction for detection. The enzymatic degradation procedure and the ensuing chemical indicator reaction are completely separated, which inherently allows each of these proces... |
Either an iridium electrode that was anodically pretreated or a glassy carbon electrode that was coated with a film that contained iridium oxide promoted the oxidation of hydrogen peroxide. With flow injection methodology, linear calibration curves were obtained over the 2 x 10(-5) -3.6 x 10-8M range with 0.1M KOH as t... |
Microamounts of Pt(II/IV) (0.25-800 mug/ml) and Pd(II) (5-600 mug/ml) in > 0.5 M hydrochloric acid can readily be determined by means of a simple FIA method based on the selective reaction of tin(II)chloride with these metals. The FIA method has a high linear dynamic range, and is relatively free from interferences of ... |
Heterocyclic ring compounds containing nitrogennitrogen bonds such as 1H-1,2,4 triazole, 2,4,6 trimethylbenzenesulfonyltriazolide and pyridazine can be completely decomposed in the molten state with mixtures of various ratios of concentrated sulphuric acid and lithium sulphate (molten ALS) flux containing a catalyst su... |
The possibilities of amperometric enzyme electrodes in reversed micellar systems for the determination of phenol, 4-chloro-3-methylphenol and 2,4-dimethylphenol are illustrated. The used enzymatic reaction consisted of the oxidation of the phenolic compounds by oxygen, catalysed by tyrosinase. The reduction of the libe... |
Feasibility is demonstrated for a novel gas-sensing, internal enzyme biosensing scheme for the selective measurement of hydrogen peroxide. Two horseradish peroxidase catalysed reactions are evaluated for the detection of hydrogen peroxide as it crosses a microporous Teflon membrane at 37 degrees C. The rate at which hy... |
Selectivity coefficients (k(amp)(ij)) are introduced as well-defined measures of the selectivity of amperometric sensors. For any amperometric device the total current response in the presence of interfering species (j) can be described by the general equation; i(t) = K(C(i) + Sigmak(amp)(ij)C(j)), where i is the targe... |
In this paper, the influence of the water content in the acetonitrile/LiClO(4) system on the electrosynthesis and the properties of poly(N-vinylcarbazole), PNVC, films is examined. By using conventional resonant frequency and impedance measurements of an electrochemical quartz crystal microbalance (EQCM), information a... |
Electroanalytical methods based on biosensor technology and differential pH measurement for the determination of l-lactic and l-malic acids in wine were developed. Lactic acid was determined according to two procedures consisting of the use of two lactate electrochemical biosensors, one based on a Clark O(2) probe and ... |
Enzyme loaded phosphatidylcholine vesicles have been introduced as a new component in the design of sensing layers for the direct coating of an amperometric transducer. For this purpose, choline oxidase was chosen as a model enzyme, and the resulting vesicles were mixed with an amphiphilic pyrrole derivative [12-(pyrro... |
In practical applications biosensors are often forced to operate under less than optimal conditions. Because of their construction, and the physical processes and chemical reactions involved in their operation, compromise conditions are frequently required to synchronize all events taking place. In this communication i... |
A novel approach for the construction of a micro biosensor on the base of amperometric enzyme microelectrode arrays is described in this paper. The technique contains the electrochemical deposition of different enzymes in a conducting organic polymer, e.g. polypyrrole, on a transducer built up with the help of microfab... |
A sensitive flow system for the determination of l- and d-lactate in milk samples is described. l- and d-Lactate dehydrogenase, LDH, were immobilized on aminopropyl-controlled pore glass beads. l- and d-Lactate are oxidized to pyruvate in the presence of NAD(+) and NADH is produced. The electrochemical determination of... |
The use of an enzyme tyrosinase sensor capable of being employed in non aqueous media represents a good opportunity to investigate the effects of the organic solvent on enzyme activity. Six different solvents are considered (n-heptane, n-hexane, n-pentane, toluene, chloroform, acetonitrile) and two properties of these ... |
Enzyme electrodes for the amperometric measurement of urea were prepared by co-immobilizing l-glutamate dehydrogenase and urease onto an Immobilon-AV affinity membrane with attachment to a glassy carbon electrode. Reduced nicotinamide adenine dinucleotide (NADH) was used as the electroactive species. The electrochemica... |
An enzymatic method for the determination of glutamic acid in food samples and pharmaceuticals is described. l-Glutamate dehydrogenase (GLDH) from beef liver was immobilized on isothiocyanate modified Controlled Pore Glass for the construction of a packed bed reactor. The NADH produced from the enzymic reaction was mon... |
A flow-injection system with an immobilized enzyme reactor is proposed for the determination of 3-hydroxybutyrate. 3-Hydroxybutyrate dehydrogenase is immobilized on aminated poly(vinyl alcohol) beads and packed into a stainless-steel column (4 cm x 4 mm I.D.). Serum is diluted and filtered. Sample solution (20 mul) is ... |
A flow-injection system is proposed for the simultaneous determination of sulfite and phosphate in wine. A sulfite oxidase immobilized reactor and purine nucleoside phosphorylase-xanthine oxidase co-immobilized reactor are incorporated at fixed positions (parallel configuration) in the flow line, which is based on the ... |
H(2)O(2) in marine waters may be determined by measuring the absorbance of crystal violet (CV(+)), formed by the oxidation of leuco crystal violet (LCV) by H(2)O(2) in the presence of the enzyme horseradish peroxidase, at 592 nm at pH 4. The detection limit and the precision of the method are about 0.02 muM and +/- 1% ... |
A conductivity cell employing a 61 MHz surface acoustic wave resonator-based measurement circuit was applied to the detection of the urea/urease reaction. The kinetic enzymatic parameters of the urease were estimated from the frequency shifts. The effects of pH, temperature and inhibitor on the response of the enzyme c... |
The feasibility of utilizing a zwitterionic surfactant, 3-(nonyldimethylammonio)propylsulfate, or nonionic surfactant, Triton X-114, mediated phase separation in conjunction with affinity ligands was studied for hydrophilic protein extractions. Below (or above) its critical temperature (so-called cloud point), aqueous ... |
The kinetic behaviors of Cr(VI) and W(VI), which catalyze a common indicator reaction between H(2)O(2) and I(-), were studied. A new concept, 'Rate Spectrum', is proposed. The two catalysts can be determined simultaneously by analyzing the rate spectra of their mixtures as the rate spectra of each catalyst are linearly... |
An ion-exchange method has been developed for the separation of palladium, platinum and rhodium from a solution that is highly acidic and contains a considerable amount of lead, aluminum, iron and cerium, obtained by leaching a used honeycomb type automotive catalytic converter. A column of Amberlite IRA-93 anion-excha... |
Two enzyme reactors prepared by the co-immobilization of two different glucose-6-phosphate dehydrogenases (G6PDH; from Leuconstoc mescenteroides (LM) and yeast (Y) and diaphorase are employed to enhance the sensitivity of NAD(P) coenzymes as on-line amplifiers based on substrate recycling in a chemiluminometric flow-in... |
Two novel biosensors for urea based on immobilized corynebacterium glutamicum 617 and corynebacterium glutamicum ATCC13032 in calcium alginate gel coupled with an ammonia gas-sensing electrode, were designed and constructed. Calibration plots of measured potential difference (mV) vs. log of urea concentration were line... |
The ability of enzymes to work in non-aqueous media offers new and almost unexploited possibilities for the development of new optical biosensors. The advantages of performing biocatalytic reactions in non-aqueous media are discussed in relation to their possible application in optical biosensor design. Attention is fo... |
A new electrochemical biosensor was developed by incorporating an enzyme into a solid-paraffin-graphite-particle matrix. Tyrosinase served as model enzyme and the biosensor response was characterized with respect to its response to dopamine. The influence of different experimental parameters (tyrosinase loading, flow r... |
A tyrosinase-based chemically amplified biosensor, based on the substrate recycling of polyphenols driven by tyrosinase-catalyzed oxidation and chemical reduction by l-ascorbic acid (AsA), has been utilized for the highly sensitive detection of inhibitors of tyrosinase such as kojic acid, benzoic and SCN(-) ion. The am... |
The interactions of Bromophenol Blue (BPB) with bovine serum albumin and gamma-globulin in acidic solutions were investigated by a spectrophotometric method. It was considered that the electrostatic force is the main binding force, and that the color change during the combination is due to the transformation of dye spe... |
A flow injection analysis system incorporating amperometric detection and enzyme reactor for glycerol determination in alcoholic beverages is described. The reactor is based on the glycerol dehydrogenase system, and the enzyme was immobilized through chemical modification on several supporting materials such as aminopr... |
Fourier transform infrared spectroscopy (FTIR) is potentially a powerful tool for determining the global secondary structure of proteins in solution, providing the spectra are analyzed using a statistically and theoretically justified methodology. We have performed FTIR experiments on 14 globular proteins and two synth... |
An extended set of equations which describe coupled arginase-urease reactions is presented. The mathematical treatment leads to the development of new equations which relate the lag-time required for the concentration of urea to reach a defined fraction of its steady-state concentration to the kinetic parameters of the... |
Response properties and selectivity are reported for glutamate biosensors constructed with a film of Nafion between the platinum anode and a layer of immobilized glutamate oxidase. The effects of enzyme loading, sample pH and temperature are established. Operation at pH 7.8 and 37 degrees C results in linearity up to 8... |
A detailed account of the specification of colour using the 1931 Commission International de L'Eclairage tristimulus coordinates and subsequent colour spaces for the measurement of small differences in colour is provided along with a review of the application of quantitative parameters for the evaluation of colour chan... |
A solvent extraction technique involving no critical clean-up steps was developed for the determination of methylmercury (MeHg) in environmental and biological samples by aqueous phase ethylation, room temperature precollection, gas chromatographic separation and cold vapor atomic fluorescence spectrometric detection. ... |
Disposable amperometric inhibition biosensors have been microfabricated by screen printing a tyrosinase-containing carbon ink. The decrease in the substrate (catechol) steady-state current, caused by the addition of various pesticides and herbicides, offers convenient quantitation of micromolar levels of these pollutan... |
A low cost flow-injection analysis (FIA) with a dissolved oxygen (DO) detector and a xanthine oxidase immobilized column for the analysis of hypoxanthine as an index to determine degree of aging in meat was developed for quality control in the food industry. In this system, hypoxanthine is oxidized by an enzyme reactio... |
An Ag/AgCl solid-state electrode was prepared by using urea-formaldehyde resin as the frame material and KCl powder as the active material. Using the prepared Ag/AgCl solid-state electrode as substrate and chlorpheniramine tetraphenylborate ion-pair complex as the active component, a new type of solid-state chlorphenir... |
A flow-injection system with an immobilized enzyme reactor is proposed for the determination of l-phenylalanine. Phenylalanine dehydrogenase from Rhodoccus sp. M4 was immobilized on tresylated poly (vinyl alcohol) beads (13 mum) and packed into a stainless-steel column (5 cm x 4 mm i.d.). Serum sample was deproteinized... |
Surface-enhanced Raman scattering (SERS) spectrometry of the diuretic drug triamterene is discussed. The SERS-active substrate used is a silver foil etched with nitric acid. The influence of solvent and sample doping method on sensivity, intercept and shape of the calibration graphs is discussed. |
Alcohol dehydrogenase (ADH) has been immobilized on a nickel hexacyanoferrate modified microband gold electrode surface by a glutaraldehyde/bovine serum albumin (BSA) cross-linking procedure to provide a new amperometric sensor for the assay of ethanol. The resulting enzyme electrode exhibits excellent electrocatalysis... |
Electroactive biotin ligands were prepared by the reaction of daunomycin with biotinylating reagents with a different spacer. These biotin ligands exhibited similar electrochemical properties to those of daunomycin, but the adsorptivity of the ligands on the electrode increased with increasing length of the spacer. The... |
A miniaturized protein and peptide microsequencer consisting of a fused silica capillary reaction chamber is described. Extremely small volumes of reagents, 2 mul or less, were delivered directly to the reaction chamber through individual fused silica capillary lines using low pressure syringe pumps. Other than an argo... |
The inhibitory effect of different pollutants on the enzyme phosphoenolpyruvate-carboxylase was investigated. For this enzyme, different procedures are described for determining the activity of the enzyme. Determination of the presence of the enzymatically-formed oxaloacetate was found to be more suitable for this purp... |
A new method using a surface acoustic wave (SAW)/conductance sensor has been described in this paper for rapid determination of ribonuclease (RNase) and microanalysis of heparin. The assay of RNase is based on the change in conductance of the solution caused by enzymatic reaction between ribonucleic acid (RNA) and RNas... |
The short-circuit-current response properties of ambient temperature oxygen sensors of the type, Ag|Ag(6)I(4)WO(4)|PbSnF(4)(PSF)| sensing electrode (SE), O(2); SE: mixtures of Pt-black/Pc's/PSF, carbon/Pc's/PSF, Pc's/PSF, Pt-black/PSF, carbon/PSF (phthalocyanines, Pc's: FePc, CoPc, CuPc, H(2)Pc) have been examined to e... |
Based on self-assembled biotinylated disulfide derivative monolayer on gold electrode, the sensors immobilized monolayer or multilayer membranes composed of avidin and biotinlabeled glucose oxidase (B.GOD) or of avidin-B.GOD complex (ABC) and B.COD were prepared. The present technique may be useful for controlling the ... |
The interactions of Coomassie brilliant blue G-250 (CBB) with bovine serum albumin (BSA) and gamma-globulin at low pH are investigated by a spectrophotometric method. It is considered that the binding of CBB to protein is because of the weak interactions (ionic, van der Waals, hydrogen bonding, and hydrophobic). The so... |
A fibre-optic based on immobilized acetylcholinesterase is described and its application in the detection of carbamate and organophosphate pesticides through enzyme inhibition measurements is discussed. The bioactive component of the sensor consists of acetylcholinesterase covalently immobilized on preactivated isothio... |
A multi-sensor cell containing a new photo-cured calcium ion selective electrode sensor is reported. Four membranes containing different components are prepared to determine the one with optimum selectivity and sensitivity. This is shown to consist of the N,N,N',N'-tetracyclohexyl-3-oxapentanediamide ligand (ETH 129) a... |
A new hydrogen donor for peroxidase, Eriochrome black T, was reported for the first time. Steady-state catalytic velocity depends upon enzyme and substrate concentrations, and a Michaelis-Menten K(m) value of 1.72x10(-5) mol l(-1) and a V(max) value of 4.43x10(-3) s(-1) were measured at pH 8.6. Trace amount of hydrogen... |
Electropolymerizations of aniline and pyrrole solutions containing uricase at a neutral pH was performed to immobilize the enzyme on the surface of the gas diffusion carbon felt, and a selective uric acid sensor was fabricated by combining immobilized enzyme carbon felt and an oxygen electrode with oxygen gas permeable... |
Controversy exists concerning the influence of experimental artifacts on the number of component FTIR vibrational bands which may be resolved from the amide I and II envelopes of proteins in water. Whether these bands represent unique populations of vibrating protein groups in a particular global 2 degrees structure or... |
An amperometric diamine sensor is developed for clinical applications in diagnosis of bacterial vaginosis (BV). The sensor is based on crosslinked putrescine oxidase (PUO) which catalyzes the conversion of diamines (mainly putrescine and cadaverine) to products including hydrogen peroxide. The hydrogen peroxide is dete... |
5-methylphenazonium methylsulphate, (commonly named phenazine methosulphate, PMS) mediated electroxidation of beta-nicotinamide adenine dinucleotide (phosphate), reduced form, (NAD(P)h), on platinum, gold and carbon electrodes has been studied by electropolymerization of 1,2-, 1,3-, 1,4-diaminobenzene (DAB), pyrrole-2-... |
Peroxidase entrapment in different Sol-Gel matrices was successful. The enzyme did not show a decrease in activity for at least 2 months as well as storage at room temperature and dry condition for periods exceeding 3 weeks. It was evident that the enzymatic activity was a function in the type of the alkoxysilane precu... |
The electropolymerization of an enzyme-amphiphilic pyrrole ammonium-laponite nanoparticles mixture preadsorbed on the electrode surface provides the simultaneous immobilization of the enzyme and the hydrophilic laponite-clay-nanoparticles in a functionalized polypyrrole film. The presence of incorporated laponite parti... |
A coated graphite-epoxy ion-selective electrode for bismuth(III), based on the ion-pair between the [Bi(EDTA)](-) anion and tricaprylylmethylammonium cation (Aliquat 336S) incorporated onto a poly(vinylchloride) (PVC) matrix is constructed. A thin membrane film of this ion-pair, dibutylphthalate (DBPh) or ortho-nitroph... |
A new semi-automated flow analysis system called bypass trapped flow analysis system (ByT-FAS), is described. ByT-FAS gives an analyst the ability to inject sample and reagent volumes of 50-100 mul or more, into flowing streams and attain physical steady state concentrations in the detection cell within a few seconds (... |
The newly developed flow instrument, bypass trapped-flow analysis system (ByT-FAS), was used to perform enzyme assays and generate data for evaluation of an enzyme's kinetic parameters. The enzyme assay was yeast hexokinase coupled to glucose-6-phosphate dehydrogenase and the production of reduced NADPH was monitored f... |
Bypass trapped flow analysis system (ByT-FAS) is a new trapped flow apparatus designed to perform chemical measurements with flow injection systems at physical steady state using small volumes (10-150 mul) of injected sample and reagent. We have used a micro-volume version of ByT-FAS instrumentation with a chemilumines... |
A new catalytic method for the determination of silver(I) was developed based on a metal exchange reaction between ethylenediaminetetraacetatomercury(II) (Hg(II)-EDTA) in the aqueous phase and bis(diethyldithiocarbamato)copper(II) (Cu(II)-DDTC) in the organic phase. This exchange reaction (Cu(II)-DDTC(org)+Hg(II)-EDTA-... |
A new type of amperometric biosensor based on immobilised acetylcholine esterase was designed and constructed. The enzyme was immobilised on a flow-through working electrode, which was prepared from reticulated vitreous carbon (RVC) or from a composite material consisting of RVC and superporous agarose. The sensor was ... |
Poly(ethylene glycol)-modified glucose oxidase was immobilized in a poly(vinyl alcohol) cryogel membrane, obtained by a freezing-thawing cyclic process, to obtain a suitable amperometric glucose sensor. The covalent linkage between PEG and GOD molecule improved the physical immobilization of enzyme in the polymeric mat... |
A highly selective and sensitive on-line monitoring system is proposed for amperometric assay of trace amounts of l-glutamate. The system includes a microdialysis probe, immobilized enzyme reactor, and poly(1,2-diaminobenzene)-coated platinum electrode. The enzyme reactor prepared by the co-immobilization of l-glutamat... |
A procedure for the enzymatic determination of alpha-glycerophosphate (alpha-GP) has been developed, using an automated in-house FIA system, with immobilized glycerol-3-phosphate oxidase (GPO) on non-porous glass beads, following optimization of the immobilization and analytical parameters. Fabricated single bead strin... |
Reversed phase high-performance liquid chromatography (RP-HPLC) is demonstrated for hydrophobic analytes such as aromatic hydrocarbons on a chemically bonded stationary phase and a mobile phase consisting of only water. Reversed phase liquid chromatography separations using a water-only mobile phase has been termed WRP... |
A procedure to accurately quantitate chromium(V) in environmental and medicinal chemistry samples was developed using electron paramagnetic resonance spectroscopy (EPRS) as the method of detection. It was found to have an error in the order of +/-10% and a detection limit of 0.010 mM (0.5 mg l(-1)) chromium(V). The met... |
An anion-exchange fast protein liquid chromatographic-inductively coupled plasma atomic emission spectrometric procedure (FPLC-ICP-AES) was developed for speciation of Al-citrate and other negatively charged Al complexes. FPLC separations were carried out on a Mono Q HR 5/5 strong anion-exchange FPLC column over a pH r... |
Metallothioneins (MT) are a heterogeneous family of proteins coded from multiple linked genes whose individual expression can be readily determined at the transcriptional level by assay of mRNA using specific DNA probes targeted against the untranslated regions. Analysis of translated protein products is more challengi... |
The aim of this study was to present a new analytical method for the quantitative determination of metallothionein (MT) proteins in human body fluids and tissues, in order to determine the level of environmental and industrial exposure to heavy metals. For MT isolation, covalent affinity chromatography with thiol-disul... |
The performance of electrochemical biosensors developed for the determination of inhibiting species is considered. The role of various factors affecting the analytical characteristics of biosensors, their selectivity toward inhibitors to be tested as well as operational characteristics is discussed. The choice of enzym... |
A rapid, precise and low cost spectrophotometric method is proposed for the determination of methyldopa and dopamine in pharmaceutical formulations. The crude extract of sweet potato root (Ipomoea batatas (L.) Lam.) was used as an enzymatic source of polyphenol oxidase (PPO; EC.1.14.18.1). This enzyme catalyses the oxi... |
Using three enzyme sensors (tyrosinase, catalase and glucose oxidase), capable of functioning also in non-aqueous solvents, we found new correlations between classical indicators, e.g. the log P value of several organic solvents and new empirical indicators such as ;maximum current variation' (MCV) and above all the ;c... |
Infant formula and powdered milk samples were suspended in a medium containing 20% ethanol, 0.65% nitric acid, 6% hydrogen peroxide and 0.1% ammonium dihydrogenphosphate and directly introduced in the electrothermal atomizer. Liquid milk samples were diluted with this suspension solution. The build-up of carbonaceous r... |
A new copolymer made of 8-quinolyl methacrylate, methyl methacrylate and n-butyl acrylate(PQMB) has been used as a solid substrate for the preparation of an optical fiber berberine sensor. The sensing is based on the fluorescence of 1,4-bis(naphth[2,1-d]oxazole-2-yl)benzene(BNOB) immobilized in the copolymer quenched b... |
Imazethapyr is the herbicide developed for use in leguminous crops. In this study, flow-injection liposome immunoanalysis (FILIA) has been shown to be capable of measuring imazethapyr in a buffered solution with a detection limit of 0.1 ppb through the optimization process. Protein A coated glass beads covalently conju... |
Poly(vinyl chloride) based membranes of di-(2-ethylhexyl)phosphoric acid (DEHPA) and dibutyl(butyl)phosphonate (DBBP) have been prepared and investigated as VO(2+)-selective sensors. The membranes containing DEHPA/DBBP and sodium tetraphenylborate, an anion excluder, show near-Nernstian/Nernstian response in the concen... |
The goal of this study was to determine the kinetic parameters involved in the decomposition of 2-(5-methyl-4-isoxazolylamino)-N-(5-methyl-4-isoxazolyl)-1,4-naphthoquinone-4-imine (1) in aqueous solution and to identify the main degradation products. An isocratic HPLC assay was used to study the degradation rate of 1. ... |
Silica gel and glass beads were modified by using acid chloride of metal-tetrakis(4-carboxyphenyl)porphine (M-TCPP) through a peptide bond, and an anion-exchange resin with M-TCPP by ion-exchange reaction and physical adsorption. The carriers modified with Co(3+)-TCPP proved to accelerate the redox reaction which is ca... |
The capability of laser induced breakdown spectrometry (LIBS) for vanadium determination in a xV-2TiO(2)-SiO(2) catalyst is presented. The microplasma was generated onto the sample surface using a pulsed Nd:YAG laser operating in the second harmonic (532 nm). Laser produced plasmas were collected and detected using a c... |
The controlled release of coreactants at the sensing tip of a biosensor is a possible approach to develop self-contained devices. For luciferin which is a firefly luciferase cosubstrate, a new method of retention is evaluated. The two-step procedure consists of incorporating the substrate in acrylic microspheres during... |
Potentiometric biosensors based on urease (E.C. 3.5.1.5.) immobilized on chitosan membranes coupled to all-solid-state nonactin ammonium ion selective electrodes are described. The enzyme was immobilized on the chitosan membranes by four procedures: (A) adsorption; (B) adsorption followed by reticulation with dilute aq... |
Two well known derivatization procedures, pentafluorobenzylation and BF(3)/methanol esterification, were compared for their applications to GC analysis of acidic water micropollutants (chloroacetic and phenoxyalkanoic acids). A two-level factorial design was used to determine the influence of different parameters and t... |
A continuous system for the determination of fish freshness with double enzyme reactors was developed and applied to the determination of the freshness indicator K [Formula: see text] where IMP, HxR and Hx are Inosine monophosphate, Inosine and Hypoxanthine, respectively. The system was assembled with a three electrode... |
A highly sensitive and simple visual autocatalytic method has been developed for the determination of trace cobalt. The cobalt ion released by the oxidative decomposition of inert bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropyl-amino-phenolato] cobaltate (Co(III)-5-Br-PAPS) with peroxomonosulfate acts as a catal... |
Ferric 2-hydroxy-1-naphthaldehyde thiosemicarbazone (Fe(III)-HNT) has been synthesized and used to mimic the active group of horseradish peroxidase (HRP). The catalytic characteristics of this mimic-enzyme catalyst in the oxidation reaction of ascorbic acid with hydrogen peroxide has been studied. The experimental resu... |
A microfabricated, flat form, amperometric microcell (microchip) is used in a simple, two-electrode arrangement for putrescine oxidase enzyme activity determinations. The cell contains a platinum microdisk working electrode and an Ag/AgCl reference electrode covered by a porous, hydrophilic membrane. An electrochemical... |
A novel and robust amperometric enzyme electrode for the determination of glucose was constructed by immobilizing glucose oxidase (GOD) and Os(bpy)(2)Cl-poly(4-vinyl)pyridine (Os-PVP) complex multilayers on thiol self-assembled monolayers surface. The apparent Michaelis-Menton constant K(m)' increased with increasing t... |
A novel tubular device has been developed for hydrogen sulfide determination in air. Several substrates such as commercial silica gel and alumina TLC plates, silica gel powder, alumina, CaSO(4), CaCO(3), BaSO(4), MgO, chalk, alpha-cellulose and ethyl cellulose were tested as solid substrates. 30-70-mesh silica gel was ... |
An anion-exchange fast protein liquid chromatographic-electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was developed for determination of trace amounts of negatively charged Al-citrate in the pH range 3.5-8.0. Aqueous-4 mol dm(-3) NH(4)NO(3) linear gradient elution at a flow rate of 1 cm(3) min(-1)... |
A new method for the determination of acetylcholine is introduced and studied. The method uses enzymatic hydrolysis of acetylcholine carried out in a flow-through analytical reactor column, while for the detection triangle programmed coulometric flow titration is employed. The flow-through coulometric titration system ... |
A new flow-through fluoroimmunosensor for atrazine determination based on the use of protein A immobilized on controlled pore glass as immunoreactor is reported. The support, placed in the optical path of the flow cell, allows the 'in situ' quantification of atrazine by on-line antigen-antibody binding upon successive ... |
Platinum and ruthenium in carbon supported Pt and Pt-Ru catalysts were determined by direct and derivative spectrophotometric methods. Complexes of platinum and ruthenium with SnCl(3)(-) ligands (tin(II) chloride in HCl) were used to determine both metals in solutions obtained after digestion of the samples of the cata... |
Since the induction of putrescine synthesis by ornithine decarboxylase (ODC) is observed in many pathological and physiological processes, a useful and simple method to assay this enzyme activity should be an interesting tool to quantify the biological importance of its induction. An enzymatic method to assay ODC is re... |
A biosensor for the specific determination of hydrogen peroxide was developed using catalase (EC 1.11.1.6) in combination with a dissolved oxygen probe. Catalase was immobilized with gelatin by means of glutaraldehyde and fixed on a pretreated teflon membrane served as enzyme electrode. The electrode response was maxim... |
The covalent immobilization of DNA onto self-assembled monolayer (SAM) modified gold electrodes (SAM/Au) was studied by X-ray photoelectron spectrometry and electrochemical method so as to optimize its covalent immobilization on SAMs. Three types of SAMs with hydroxyl, amino, and carboxyl terminal groups, respectively,... |
A catalytic photometric method was developed for the determination of sub-nanogram levels of cobalt. The method is based on the catalytic effect of cobalt(II) on the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline (DAOS) to form a colored dye (l... |
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