Showing papers on "Amperometry published in 1985"
TL;DR: In this article, glassy carbon electrodes subjected to severe electrochemical treatment is saturated chloride solutions exhibit enhanced electrochemical reversibility compared to untreated electrodes, and the most significant improvement is observed in differential pulse measurements, that are highly sensitive to small changes in the rate of electron transfer.
119 citations
TL;DR: A membrane-free glucose sensor was made by covalent immobilization of glucose oxidase on graphite followed by adsorption of N-methyl-phenazinium ion (PMS+) and the mediator was found to be necessary for the electron transfer between the enzyme and the electrode.
118 citations
TL;DR: In this paper, a modified carbon electrode for the amperometric determination of hydrogen peroxide is described, by deposition of a 15nm thick layer of a 40:60 mixture of palladium and gold on the surface of the electrode, the overvoltages for both the oxidation and reduction can be decreased by at least 800 mV.
107 citations
TL;DR: In this paper, an electron mediator between glucose oxidase and a reticulated vitreous carbon (RVC)/graphite support bed was constructed by immobilization of glucose and ferrocene into cross-linked polyacrylamide gels.
95 citations
TL;DR: A new type of biocatalytic membrane electrode utilizing banana pulp tissue slices for sensing catecholamine neurotransmitters is described, which exhibits high bioc atalytic activity, good time stability, and favorable selectivity.
Abstract: A new type of biocatalytic membrane electrode utilizing banana pulp tissue slices for sensing catecholamine neurotransmitters is described. This amperometric-based probe for the measurement of dopamine exhibits high biocatalytic activity, good time stability, and favorable selectivity.
79 citations
TL;DR: In this paper, a procedure for the direct and simultaneous determination of ascorbic acid, isoascorbic acid (IA), and uric acid in human plasma by paired-ion reversed-phase high-performance liquid chromatography was presented.
Abstract: A procedure is presented for the direct and simultaneous determination of ascorbic acid (AA), isoascorbic acid (IA), and uric acid (UA) in human plasma by paired-ion reversed-phase high-performance liquid chromatography. An Ultrasphere ODS (C18) column is used with a pH 5.25 mobile phase containing 0.04M sodium acetate, 0.005M tetrabutylammonium phosphate, and 0.2 mg/mL disodium EDTA. Plasma samples preserved with an equal volume of 10% metaphosphoric acid are diluted 10-fold with mobile phase and filtered through 0.2 micron filters. The injection volume is 10 uL. Detection of AA, IA, and UA is by amperometry using a glassy carbon electrode and Ag/AgCl reference electrode. The applied potential is +0.6 volt and the sensitivity setting is 100 nAmps. As little as 0.25 ng of each component can be detected at this setting and the electrode response is linear over the AA, IA, and UA ranges encountered in human plasma.
74 citations
TL;DR: An assay procedure utilizing amperometric detection at carbon paste electrodes containing cobalt phthalocyanine has been developed for the determination of cysteine and glutathione in blood and plasma samples following preliminary separation by reversed-phase liquid chromatography.
63 citations
56 citations
TL;DR: A flow injection analysis procedure using this detector has been constructed and some interferences assessed as discussed by the authors, and one of the interfering species was found to be ascorbic acid, and the analysis of an extract of a cooked meat was given satisfactory results when ion-interaction chromatography, with amperometric detection, was used.
Abstract: Nitrite ion has been determined amperometrically by oxidation at a glassy carbon electrode. A flow injection analysis procedure using this detector has been constructed and some interferences assessed. One of the interfering species was found to be ascorbic acid, and the analysis of an extract of a cooked meat was found to give satisfactory results when ion-interaction chromatography, with amperometric detection, was used.
56 citations
TL;DR: A flow injection analysis method for determining cyanide amperometrically by oxidation at an electrochemically pre-treated glassy carbon electrode has been developed in this paper, where the determination was made in an eluent consisting of pH 9 Britton-Robinson buffer using a measurement potential of + 1.00 V versus SCE.
Abstract: A flow injection analysis method for determining cyanide amperometrically by oxidation at an electrochemically pre-treated glassy carbon electrode has been developed. The determination was made in an eluent consisting of pH 9 Britton-Robinson buffer using a measurement potential of + 1.00 V versus SCE. The glassy carbon electrode was pre-treated on-line in the same eluent before use by holding it at +1.50 V versus SCE for 15 min and then at –1.00 V for 1 min. Calibration graphs were rectilinear from 1 × 10–5 to 1 × 10–3M cyanide and coefficients of variation (10 determinations) were typically less than 1% except at the lower end of this range.
51 citations
TL;DR: Detection amperometrique indirecte de manogrammes de Cl − et CN − adsorbes sur electrode de platine as discussed by the authors. But this method is not suitable for the detection of manogramme.
Abstract: Detection amperometrique indirecte de manogrammes de Cl − et CN − adsorbes sur electrode de platine
TL;DR: An amperometric technique for quantification of an enzyme immunoassay in which a magnetic working electrode is used, both to separate bound and free analyte and to monitor the electrochemical response.
Abstract: We describe an amperometric technique for quantification of an enzyme immunoassay in which we use a magnetic working electrode, both to separate bound and free analyte and to monitor the electrochemical response. We used a "two-site" immunometric assay with monoclonal antibodies for human choriogonadotropin (hCG) as a model system in which magnetic particles were used as the solid phase. Separation of bound and free label is readily achieved by localizing the particles at the electrode. Activity of the bound enzyme in the environment of the electrode is determined electrochemically, permitting rapid quantification of the analyte without the need for a separate incubation step to measure enzyme activity. The sensitivity of the system is 150 int. units of hCG per litre (1st Int. Ref. Preparation). Correlation between the amperometric measurement of urinary hCG and data for an immunoradiometric assay was r = 0.9. The assay is rapid, requiring a total assay time for each sample of 20 min, which includes 15 min for antibody/antigen binding.
TL;DR: In this paper, high-performance liquid chromatography with electrochemical detection was used for the determination of the four aromatic amines: aniline, methyl anilines, 1-naphthylamine and diphenylamine at trace levels in seawater.
TL;DR: The carbon fibre array electrode is demonstrated as a useful detector for flow injection analysis in the amperometric mode of detection for oxidations of three pharmaceutically important phenothiazine drugs.
Abstract: The carbon fibre array electrode is demonstrated as a useful detector for flow injection analysis in the amperometric mode of detection.A liquid chromatographic internal sampling valve was used to inject the sample into the supporting electrolyte stream and sampling rates as high as 200 samples per hour were feasible using a flow-rate of 1 ml min–1. The oxidations of three pharmaceutically important phenothiazine drugs, namely perphenazine, triflupromazine. HCI and fluphenazine.2HCI, were investigated and an assay procedure was developed for these compounds and their formulations. Detection limits for the analytes were a few tenths of ananogram.
TL;DR: A novel method for amperometric determination of substrates of hydrolytic enzymes has been developed and the pH dependence of electrochemical oxidation of hydrazine in the Tafel region was combined with the urease catalysed splitting of urea to construct an amPerometric membrane electrode for urea.
TL;DR: In this article, a reversed-phase high-performance liquid chromatographic analysis was developed for aqua[1,1-bis(aminomethyl)cyclohexane]sulphatoplatinum(II) (spiroplatin) and its hydrolysis and oligomerization products.
TL;DR: The packed bed wall-jet electrode (PBWJE) as mentioned in this paper consists of a packed bed electrode placed immediately before the jet of a normal wall jet electrode, which allows a fresh copper surface to be plated on the wall jet whenever it is required.
TL;DR: In this article, a glassy carbon electrode held at 1.25 V versus S.C.E. was used to determine EDTA in 0.1 M sulphuric acid by flow injection analysis.
Abstract: Ethylenediaminetetraacetic acid (EDTA) is determined in 0.1 M sulphuric acid by flow injection analysis using amperometric detection at a glassy carbon electrode held at 1.25 V versus S.C.E. The signal at the glassy carbon electrode is increased about eight-fold by pre-treating the electrode by holding it first at 2.0 V for 2 min and then at –0.50 V for 2 min whilst eluent is flowing. Calibration graphs are rectilinear in the range 0.01 to 10 µg ml–1 of the disodium salt.
TL;DR: Hydrodynamic voltammograms of dopamine [2-(3,4-dihydroxyphenyl)ethylamine] show a plateau distinct from that of ascorbic acid and the mercury oxidation cut-off.
Abstract: Ascorbic acid can be determined by flow injection amperometry at a sessile mercury drop electrode without the need to deoxygenate the eluent or sample. The determination is made at +0.19 V vs. S.C.E. in pH 5.5 acetate buffer. The size of the blank signal is equivalent to about 0.01 µg ml–1 of ascorbic acid and the signal is rectilinear up to about 60 µg ml–1. Chloride gives an oxidation signal at the mercury electrode but at a more positive potential and at the 1 µg ml–1 level of ascorbic acid 1000 µg ml–1 of chloride ion did not interfere.Hydrodynamic voltammograms of dopamine [2-(3,4-dihydroxyphenyl)ethylamine] show a plateau distinct from that of ascorbic acid and the mercury oxidation cut-off. Calibration graphs obtained at +0.26 V vs. S.C.E. for dopamine are rectilinear in the range 0.1–60 µg ml–1. At +0.26 V chloride ion gives a signal approximately 1% of that of dopamine on a molar basis and interferes at higher ratios.
TL;DR: In this article, a reaction detector based on bromine consumption for liquid chromatography is presented, which is electrochemically generated on-line in a separate flow, which combines in a post-column mode with the column effluent.
TL;DR: Two methods of high-performance liquid chromatography were used to separate the m- and p-O-methylated products of L-3,4-dihydroxyphenylalanine and meta/para ratios of O-methylation were easily obtained.
TL;DR: In this article, a pH-dependent hydrazine oxidation at a platinum anode was used as the detector reaction to determine urea amperometrically with an enzyme electrode consisting of urease trapped in a polyvinyl alcohol gel and confined by a dialysis membrane.
TL;DR: In this paper, Hansenula anomala was used for the determination of L-lactate using a biosensor using permeabilized yeasts, which can be used either potentiometric or amperometrically.
Abstract: A biosensor using permeabilized yeasts (Hansenula anomala) is described for the determination of L-lactate. The same electrode can be used either potentiometrically or amperometrically. The linear ranges are respectively of 4.10−5M to 2.10−3M for potentiometry and 8.10−7M to 3.10−3M for amperometry with a reproducibility and a precision of ± 2 to 3%. The parameters involved in the optimization of electrode response, such as pH, temperature, cofactor concentration and ionic strength of the buffers, are discussed in details for both types of measurements. The amperometric technique is suitable for lactate determinations in biological media. In this case, differential measurements are used in order to eliminate interferences of biological redox reactions.
TL;DR: Reverse-pulse amperometry (r.p.a) at a static dropping mercury electrode (SDME) is applied for detection in high-performance cation-exchange chromatography for Cu 2, Zn 2+, Ni 2+, Pb 2+,, Cd 2+ and Fe 2+ using a tartrate eluent (pH 3.5 −4.5) as discussed by the authors.
TL;DR: In this article, the voltammetric behavior and measurement of nicardipine at the glassy carbon, carbon paste and hanging mercury drop electrodes are discussed, and the inherent sensitivity of differential pulse voltammetry at the mercury electrode permits convenient measurement at submicromolar level, with detection limit of 2 × 10−8M.
Abstract: The voltammetric behavior and measurement of nicardipine at the glassy carbon, carbon paste and hanging mercury drop electrodes are discussed. Cyclic voltammetry is used to elucidate the redox mechanism. Nicardipine is shown to adsorb on carbon electrodes, with the surface species retaining its electroactive characteristics. The adsorptive accumulation serves as a preconcentration step which improves the voltammetric measurement with respect to selectivity and sensitivity. Coupling this with a medium-exchange step eliminates interferences due to solution-phase electroactive species and permits direct measurement in urine. The inherent sensitivity of differential pulse voltammetry at the mercury electrode permits convenient measurement at the submicromolar level, with detection limit of 2 × 10−8M. Amperometric detection for a flow injection system is illustrated.
TL;DR: In this article, the determination of omeprazole, a reducible benzimidazolyl pyridyl methyl sulphoxide, was investigated in a reversed-phase liquid chromatographic system by electrochemical detection at a static mercury drop electrode.
TL;DR: In this article, the determination of water in organic samples has been investigated using flow injection analysis and pumped sample segmented flow analysis and both amperometric and potentiometric detection systems were studied.
Abstract: The determination of water in organic samples has been investigated using flow injection analysis and pumped sample segmented flow analysis. Karl Fischer solution was the active reagent and both amperometric and potentiometric detection systems were studied. Various electrode combinations and cell configurations were tried for the two detection methods. The best performance was obtained with a potentiometric system using a platinum indicating electrode and a calomel or silver reference electrode. This system was automated with a positive-pressure HPLC autosampler. A linear working range of 0–1500 p.p.m. was obtained with a 50-µl sample volume and methanol or methanol-xylene carrier streams. The method has a maximum sample frequency of 60 h–1 and has been used for the analysis of gasoline-alcohol blends.
TL;DR: Nitroprusside can be determined by flow injection analysis with amperometric detection using two different methods and removal of oxygen is unnecessary in the oxidative method and the rectilinear range is wider.
Abstract: Nitroprusside can be determined by flow injection analysis with amperometric detection using two different methods. In the first method nitroprusside is oxidised at a glassy carbon electrode in 0.5 M sodium hydroxide solution, and in the second method it is reduced at a sessile mercury drop electrode in pH 8 Britton-Robinson buffer. Removal of oxygen is unnecessary in the oxidative method and the rectilinear range is wider (1 × 10–6–5 × 10–3M).