Showing papers in "Electroanalysis in 2001"
TL;DR: In this article, fundamental aspects of deposition, structure and electrochemistry of Prussian Blue and its analogues are discussed, and the future prospects of chemical and biological sensors based on metal hexacyanoferrates are outlined.
Abstract: This article reviews fundamental aspects of deposition, structure and electrochemistry of Prussian Blue and its analogues. Special attention is given to the metal hexacyanoferrates with potential analytical applications. Prussian Blue and its analogues as advanced sensing materials for nonelectroactive ions are discussed. In contrast to common ‘smart materials’, the sensitivity and selectivity of metal hexacyanoferrates to such ions is provided by thermodynamic background. Prussian Blue itself is recognized as the most advantageous low-potential transducer for hydrogen peroxide over all known systems. Both high sensitivity (ca. 1 A M−1 cm−2) and selectivity in relation to oxygen reduction are more than three orders of magnitude higher, than for platinum electrodes. Biosensors based on different transducing principles containing enzymes oxidases are compared, and the devices operated due to hydrogen peroxide detection with the Prussian Blue based transducer are shown to be the most advantageous ones. The future prospects of chemical and biological sensors based on metal hexacyanoferrates are outlined.
827 citations
TL;DR: A review of the history of electrochemical glucose biosensors can be found in this paper, which discusses their current status and assesses future prospects in connection primarily to the control and management of diabetes.
Abstract: Forty years have passed since Clark and Lyons proposed the concept of glucose enzyme electrodes. Excellent economic prospects and fascinating potential for basic research have led to many sensor designs and detection principles for the biosensing of glucose. Indeed, the entire field of biosensors can trace its origin to this glucose enzyme electrode. This review examines the history of electrochemical glucose biosensors, discusses their current status and assesses future prospects in connection primarily to the control and management of diabetes.
595 citations
TL;DR: In this paper, an overview of the use of pure, chemically modified, and sol-gel-derived silicates for designing electrode materials that are then exploited in various electroanalytical applications is presented.
Abstract: An overview is presented dealing with the use of pure, chemically modified, and sol-gel-derived silicates for designing electrode materials that are then exploited in various electroanalytical applications. The exploration of the potential consequences of such inorganic solids when used in electrochemical environments has intensified since 1995. This review focuses on recent advances achieved with silica-modified electrodes (SiO2-MEs) in the fields of electroanalysis. After a description of the attractive properties of silica-based materials for the electrochemical community, an outline of the preparation methods for SiO2-MEs is given, and their relevance to various areas of electroanalysis is discussed.
195 citations
TL;DR: In this article, the interaction of double stranded DNA (dsDNA) and single strand DNA (ssDNA) with Ru(II) complex with 2,2′-bipyridine ligand (Ru(bpy)3]2+) and methylene blue (MB) was explored by using voltammetric and spectrophotometric methods.
Abstract: The interaction of double stranded DNA (dsDNA) and single stranded DNA (ssDNA) with Ru(II) complex with 2,2′-bipyridine ligand (Ru(bpy)3]2+) and methylene blue (MB) were explored by using voltammetric and spectrophotometric methods. The electrochemistry of [Ru(bpy)3]2+ and MB was also investigated at a dsDNA-modified carbon paste electrode (CPE), a ssDNA-modified CPE and a bare CPE by means of differential pulse voltammetry (DPV), and cyclic voltammetry (CV) and the increased peak currents were observed, in respect to the order of electrodes. The structure of DNA was determined by the magnitudes of the voltammetric peaks of [Ru(bpy)3]2+ and MB. The hypochromicity of the visible absorption bands of [Ru(bpy)3]2+ and MB upon the interaction with dsDNA and ssDNA was observed. Numerous factors affecting the DNA immobilization, indicator binding reactions and ionic strength were optimized to maximize the sensitivity and reduce the assay time.
189 citations
TL;DR: In this article, the influence of various experimental variables upon the stripping lead signal at the bismuth-coated thick-film sensor is explored, and the square-wave voltammetric stripping response is highly linear over the 10-100-ppb lead range examined (2'min deposition).
Abstract: Bismuth-coated screen-printed carbon electrodes offer reliable quantitation of trace lead in connection to anodic stripping voltammetry. Such use of bismuth films (instead of mercury coatings) does not affect the reliability of stripping measurements of trace lead. The influence of various experimental variables upon the stripping lead signal at the bismuth-coated thick-film sensor is explored. The square-wave voltammetric stripping response is highly linear over the 10–100 ppb lead range examined (2 min deposition), with a detection limit of 0.3 ppb (10 min deposition) and good precision (RSD=7.4 % at 20 ppb lead). The rapid square-wave stripping voltammetric mode facilitates the use of nondeaerated samples. Applicability to drinking water samples is demonstrated. The attractive behavior of the new disposable “mercury-free” carbon strip electrodes, coupled with the negligible toxicity of bismuth, hold great promise for “one-shot” decentralized lead testing (including blood lead screening).
183 citations
TL;DR: In this paper, the compositions, configurations and chemistry of carbon ceramic electrodes are reviewed for diverse fields of electrochemistry, including electrochemical sensing, biosensing and energy storage cells.
Abstract: Sol-gel electrochemistry is gaining popularity as a versatile general method for the production of inorganic-organic electrodes and electrochemical sensors. Carbon-ceramic electrodes constitute a fine example that demonstrates the disadvantages, capabilities and promise of sol-gel electrochemistry. The compositions, configurations and chemistry of carbon ceramic electrodes are reviewed. Application for diverse fields of electrochemistry, including electrochemical sensing, biosensing and energy storage cells are reviewed.
174 citations
TL;DR: In this paper, heme proteins involving cytochrome c, myoglobin and hemoglobin were attempted to be assembled onto a nanocrystalline TiO2 film, their electrochemical behaviors on such interface were characterized with cyclic voltammetry.
Abstract: Nanosized TiO2 is now an attractive biocompatiable material widely used in toothpaste and cosmetics. Due to its unique physiochemical properties and its inclination to selectively combine with some groups of biomolecules, nanosized TiO2 has been proposed as a promising interface for the immobilization of biomolecules. In this article, heme proteins involving cytochrome c, myoglobin and hemoglobin were attempted to be assembled onto a nanocrystalline TiO2 film, their electrochemical behaviors on such interface were characterized with cyclic voltammetry. It was proved that TiO2 film could not only offer a friendly platform to assemble protein molecules, but also enhance the electron transfer process between protein molecules and the electrode. The electrode kinetic parameters of each hemoprotein on such electrode as well as the effect of scan rate on the electrochemical behavior of each protein are discussed in details.
161 citations
TL;DR: In this article, the influence of surface-active macromolecules on the stripping voltammetric response of bismuth film electrodes was evaluated, and a permselective/protective Nafion coating was applied for measurements at large sample-instrument distances.
Abstract: The influence of model surface-active macromolecules on the stripping voltammetric response of bismuth film electrodes was evaluated. Gelatin, albumin, humic acid, and Triton X-100 were used as representative surfactants, while lead and cadmium were employed as test metal ions. The adsorption of these surfactants onto the bismuth electrode caused a gradual decrease of the stripping peaks. The faster and larger suppressions observed at the bismuth electrode (compared to the mercury one) in the presence of albumin and Triton X-100 reflect differences in the adsorption kinetics and equilibrium of these surfactants at these electrodes. The surfactant interference at bismuth stripping electrodes can be circumvented using a permselective/protective Nafion coating. The effective resistance to surfactant effects makes the Nafion-coated bismuth electrode very attractive for practical stripping applications. A Nafion-modified stripping electrode is applied for measurements at large sample-instrument distances.
100 citations
TL;DR: In this article, an electrochemical oxidation of thermally denatured DNA at an electrochemically pretreated glassy carbon electrode was studied by means of adsorptive stripping voltammetry.
Abstract: Electrochemical oxidation of thermally denatured DNA at an electrochemically pretreated glassy carbon electrode was studied by means of adsorptive stripping voltammetry. The sensitivity for thermally denatured DNA detection at GCE was improved greatly by modifying the electrode with a simple and effective electrochemical oxidation at +1.75 V (vs. SCE) for 300 s in pH 5.0 phosphate buffer. Thermally denatured DNA was preconcentrated at pretreated GCE by its adsorption in open circuit for 5 min or at the potential of +0.3 V for 90 s, and produced two well-defined oxidation peaks of guanine and adenine residues at +0.80 V and +1.11 V in pH 5.0 phosphate buffer, respectively, while the native DNA almost did not appear at the same condition. This adsorptive stripping method can be used to study the properties of DNA using simple CV technique. A convenient quantitation of the low level of thermally denatured DNA was proposed. The detection limit of thermally denatured DNA was ca. 2.0 μg mL−1 when the accumulation time is 150 s at the potential of +0.3 V. As comparison, the acid-denatured DNA (treated in HClO4 solution) was tested at the same condition and a detection limit of 0.10 μg mL−1 was obtained.
97 citations
TL;DR: In this paper, the authors exploited a novel route to synthesize nanosized TiO2 particles with TiCl4 as a precursor and the resulting particles were in the size range at about 5'nm.
Abstract: Porous nanocrystalline TiO2 may be a promising material for enzyme immobilization owing to its high biocompatiability and large specific surface area of nanosized particles. We exploited a novel route to synthesize nanosized TiO2 particles with TiCl4 as precursor. With this method, high purity of the oxide product can be obtained and the resulted particles were in the size range at about 5 nm. The enzyme loading with such material was 13 % (w/w, GOD/TiO2). The interaction between the enzyme and TiO2 matrix was investigated by IR and Raman, as the main characteristic peaks of native GOD could be found in TiO2-GOD at almost the same positions, it implied that the immobilization process did little harm to the structure of GOD. The nanocrystalline TiO2-GOD based sensor was fabricated. Amperometric detection of glucose with such an unmediated sensor at 0.7 V (vs. SCE) resulted in a rapid, stable and linear response in the concentration range of 0–3 mM with apparent Michaelis-Menten constant KMapp of 6.08 mM, indicating that the immobilized GOD on nanosized TiO2 matrix retained its native activity.
91 citations
TL;DR: In this article, a selective and sensitive electroanalytical method was developed for the determination of uric acid in urine samples, which was preconcentrated and electroanalyzed at electrochemically activated glassy carbon electrodes.
Abstract: A selective and sensitive electroanalytical method was developed for the determination of uric acid in urine samples. Uric acid was preconcentrated and electroanalyzed at electrochemically activated glassy carbon electrodes. No pretreatment of uric acid sample was necessary prior to electroanalysis. Linear response was observed over the range from 0.04 to 2.0 μM with a large slope of 55.6 A M−1 and a correlation of 0.999. The detection limit (3σ) was estimated to be about 9 nM.
TL;DR: In this paper, a disposable carbon paste electrode was used as the basis of an amperometric immunosensor incorporating the electroactive polymer polyaniline, which was manufactured using a semiautomated screen-printing system.
Abstract: Screen-printed electrodes are widely used in modern biosensor applications. The conditions under which screen-printing takes place contribute to the electrical properties of the electrodes produced. This article describes a disposable carbon paste electrode that is used as the basis of an amperometric immunosensor incorporating the electroactive polymer polyaniline. The electrodes are manufactured using a semiautomated screen-printing system. The conditions used for the screen-printing of the carbon ink were investigated using physical methods such as scanning electron microscopy and cyclic voltammetry to establish how differences in the carbon surface translated into changes in the performance characteristics of the electrode. A process of electrochemical surface pretreatment was studied with a view to maximizing amperometric responses for subsequent enzyme and antibody-based biosensor applications. Comparisons between the screen-printed electrodes and glassy carbon electrodes are also made.
TL;DR: The total amounts of polyphenols in several wine and tea samples detected by the present method are well correlated with those determined by the Folin-Ciocalteu method.
Abstract: Horseradish peroxidase (HRP) is covalently immobilized on a self-assembled monolayer of mercaptopropionic acid on vapor-deposited gold electrode. The electrode allows the polyphenol detection down to 2 µM with a linear relationship up to 25 µM. The reduction current of oxidized polyphenols, formed during the enzymatic oxidation of polyphenolic compounds in the presence of H2O2, is proportional to their concentration. The sensitivity of the detection of various polyphenols by the present method depends on both the electron-donating properties of polyphenols and the electron-accepting properties of oxidized polyphenols. The total amounts of polyphenols in several wine and tea samples detected by the present method are well correlated with those determined by the Folin-Ciocalteu method. In addition, this method has several advantages over the Folin-Ciocalteu method: shorter detection time, smaller sample volume, and more torelant to interference substances.
TL;DR: In this article, the initial products of the electrochemical polymerization of methylene blue were studied using a thin-layer flow cell coupled on-line with electrospray mass spectrometry.
Abstract: The initial products of the electrochemical polymerization of methylene blue were studied using a thin-layer flow cell coupled on-line with electrospray mass spectrometry. A potentiostatic technique was applied to initiate the polymerization while the soluble n-mers generated were monitored by mass spectrometry. Methylene blue dimers and trimers were observed at m/z values consistent with either “nitrogen-to-ring” coupling of the monomers or with “ring-to-ring” coupling of demethylated monomers during the electropolymerization. Experiments accomplished in D2O-based solutions prove that “nitrogen-to-ring” coupling is the dominant process.
TL;DR: In this paper, a glucose biosensor was fabricated using chitosan film for the immobilization of glucose oxidase (GOX) and mediator in the following "sandwich" configuration.
Abstract: A glucose biosensor was fabricated using chitosan film for the immobilization of glucose oxidase (GOX) and mediator in the following “sandwich” configuration:chitosan-ferrocene:GOX:chitosan using a carbon paste electrode as the basic electrode. To prevent loss of immobilized GOX under optimized conditions, the biosensor surface was cross-linked with glutaraldehyde (GA). Despite the multilayer configuration, the biosensor exhibited a relatively fast response (less than 10 s) and a linear response with glucose in the range of 8×10−4 to 1.7×10−2 M. The biosensor retained about 65 % of its original activity after 30 days of storage in a phosphate buffer at 4 °C. Applicability of the biosensor was demonstrated in real samples and the results obtained by this biosensor corroborate well with a classical UV spectrophotometric technique.
TL;DR: In this article, a pseudo-first-order catalytic mechanism in which both reactant and product of the redox reaction are strongly immobilized on the electrode surface is theoretically analyzed under conditions of square wave voltammetry (SWV).
Abstract: A pseudo-first-order catalytic mechanism in which both reactant and product of the redox reaction are strongly immobilized on the electrode
surface is theoretically analyzed under conditions of square-wave voltammetry (SWV). A mathematical procedure is developed for diffusionless
conditions. The relationships between the properties of the voltammetric response and both the kinetic parameters of the redox
reaction and the parameters of the excitement signal are studied. The phenomenon of the quasireversible maximum is discussed. The
theoretical results are confirmed with the experiments of azobenzene performed in a presence of hydrogen peroxide. In acetate buffer with
pH 4.2 the standard rate constant of charge transfer of azobenzene is ks ¼ 12 s�1 and the catalytic rate constant in the presence of hydrogen
peroxide is kc ¼ 2.246104 s�1 mol�1 L.
TL;DR: In this paper, the voltammetric properties of electroinactive metal complexes are reviewed in terms of their finite rates of dissociation into electroactive free metal ions, and the limiting conditions for the reaction layer-based flux expressions are made explicit by comparison with rigorous derivations.
Abstract: Starting from the original reaction layer concept, the voltammetric properties of electroinactive metal complexes are critically reviewed in terms of their finite rates of dissociation into electroactive free metal ions. The limiting conditions for the reaction layer-based flux expressions are made explicit by comparison with rigorous derivations. The so-called lability of metal complexes is adequately defined by a set of two basic criteria, one referring to the association/dissociation kinetics of the volume complexation reaction and the other to the interracial flux of free metal due to dissociation of complex species. The physical significance of the resulting cases is outlined and the lability aspects of a number of new nonequilibrium speciation techniques are briefly discussed.
TL;DR: In this paper, the voltammetric properties of electrodes made from carbon film resistors of 2'Ω have been studied and compared with those of commercially available glassy carbon, before and after electrochemical preconditioning in perchloric acid.
Abstract: The voltammetric properties of electrodes made from carbon film resistors of 2 Ω have been studied and compared with those of commercially available glassy carbon, before and after electrochemical preconditioning in perchloric acid. The potential window and background currents have been measured in different aqueous solutions. Cyclic voltammetry of hexacyanoferrate(II) oxidation has been carried out and compared with glassy carbon and diamond film electrodes. Promising results have been obtained for the anodic stripping voltammetry of metal ions, particularly zinc ion, without interference from hydrogen evolution, and augurs well for substituting mercury electrodes in stripping analysis.
TL;DR: In this paper, an alternative construction of a contactless conductivity detector in which semitubular instead of tubular electrodes were used is described, and the detector performance was tested under the electrophoretic conditions using model sample solutions of potassium chloride in the concentration range from 10−3 to 10−8 mol/L. This construction permits a simple exchange of the separation capillary and makes the connection of individual electrodes with the detector electronics easier and more reliable.
Abstract: An alternative construction of a contactless conductivity detector in which semitubular instead of tubular electrodes were used is described. The electrodes are made of a strip of aluminium foil formed into a semitubular shape. They are positioned between two Plexiglass plates in a groove matching the outer diameter of a separation capillary. One Plexiglass plate is immovable, the other is free and can be detached from the immovable plate after the fixing screws are released. The separation capillary is inserted between the plates into the groove and flattened to the electrodes by the tightening of the fixing screws. This construction permits a simple exchange of the separation capillary and makes the connection of individual electrodes with the detector electronics easier and more reliable. The detector performance was tested under the electrophoretic conditions using model sample solutions of potassium chloride in the concentration range from 10−3 to 10−8 mol/L. It was shown (for K+ ion) that the operational characteristics of the detector with semitubular electrodes, namely dynamic range, 0.5–1000 μM, linear dynamic range, 5–1000 μM, limit of detection, 0.5 μM (LOD here represents the concentration from that the detector signal ceases to change with further concentration decrease) and sensitivity (1.2 mV/pg), are comparable with those for the detectors with common tubular electrodes.
TL;DR: In this paper, eugenol (4allyl-2methoxyphenol) was polymerized oxidatively by cyclic voltammetry at platinum and glassy carbon electrodes to obtain a uniform, compact film which could serve as a permselective membrane for analytes of small molecular size.
Abstract: Eugenol (4-allyl-2-methoxyphenol) was polymerized oxidatively by cyclic voltammetry at platinum and glassy carbon electrodes. It was found that at platinum the polymerization gives rise to a uniform, compact film which could serve as a permselective membrane for analytes of small molecular size. Applications of such films in selective detection of hydrogen peroxide and nitric monoxide were proposed. Monomer oxidation at glassy carbon resulted in less compact films. Interestingly, at higher potentials a porous structure containing large amount of unoxidized o-methoxyphenyl groups was created. This structure underwent electrochemical demethoxylation leading to the generation of redox active o-quinone functionalities when the modified electrode was cycled in acidic solution. A small amount of p- quinone functionalities was also generated. As could be anticipated the redox couples were capable of mediating electrochemical oxidation of ascorbic acid and NADH. Additionally polymeric eugenol-coated GC exhibited preconcentration capabilities towards dissolved metal cations. This effect was demonstrated on the electrochemical oxidation of preconcentrated Ce(III) and reduction of Cu(II).
TL;DR: A software feedback control system for the constant-current-mode operation of the light-addressable potentiometric sensor (LAPS) was developed and the detection limit for penicillin G was found to be at least as low as 100 µM.
Abstract: A software feedback control system for the constant-current-mode operation of the light-addressable potentiometric sensor (LAPS) was developed. The constant-current-mode LAPS (CLAPS) is suitable for online monitoring and recording of changes in the pH value or the ion concentration. An enzyme LAPS was fabricated by adsorptive immobilization of penicillinase on the pH-sensitive layer of Ta2O5. This sensor was operated in the constant-current-mode and the detection limit for penicillin G was found to be at least as low as 100 µM.
TL;DR: In this paper, a highly selective and sensitive PVC-membrane electrode for Cu(II) ion was developed by using a new thiophene-derivative Schiff's base.
Abstract: A highly selective and sensitive PVC-membrane electrode for Cu(II) ion was developed by using a new thiophene-derivative Schiff’s base. The electrode exhibits a Nernstian slope of 29.3 � 0.7 mV per decade at 25 � C over a very wide concentration range (1.0610 � 1 – 6.0610 � 8 M) with a detection limit of 2.0610 � 8 M (1.28 ng/mL). The ion selectivity of this electrode for Cu 2þ was greater than 3.0610 3 times over various metal ions. It was successfully applied to the determination of trace amounts of copper in Iranian black tea, and as indicator electrode, in potentiometric titration of copper ion.
TL;DR: In this paper, instead of the conventional mercury-based accumulation and stripping procedure, mercury-free boron-doped diamond electrodes are employed for the deposition and anodic stripping detection by square-wave voltammetry of Pb2+ in a 0.1m HNO3 solution.
Abstract: Microwave activation of electrochemical processes has recently been introduced as a novel technique for the enhancement and control of processes at the electrode-solution interface and is employed here to improve the analytical detection of Pb2+. Instead of the conventional mercury-based accumulation and stripping procedure, mercury-free boron-doped diamond electrodes are employed. The deposition and anodic stripping detection by square-wave voltammetry of Pb2+ in a 0.1 M HNO3 solution is shown to be strongly enhanced by microwave activation at boron-doped diamond electrode. The temperature at the electrode-solution interface is calibrated with reversible redox couple Fe3+/Fe2+ (4 mM Fe3+, 4 mM Fe2+) in 0.1 M HNO3 and a standard addition procedure is developed for the sensitive detection of Pb2+ concentrations from 1 µM to 5 µM. The limit of detection by square-wave voltammetry after 20 s deposition time was found to be 0.1 µM and 1.0 µM with microwave activation and without microwave activation, respectively. Then, the Pb content in a water sediment sample detected by anodic stripping voltammetry at boron-doped diamond electrodes is shown to be in good agreement with two other independent analytical procedures based on ICP mass spectroscopy and on sono-cathodic stripping voltammetry.
TL;DR: In this paper, a new approach to overcome the interferences from NO, NO2 and SO2 is proposed whereby formaldehyde is selectively adsorbed from the sample stream with an aluminum oxide filter.
Abstract: The direct amperometric detection of low levels of formaldehyde in the gas phase with an acidic electrochemical cell based on a gold coated Nafion membrane as working electrode was investigated. The sensor was found to show a linear response from the detection limit of 13 ppb up to at least 10 ppm. Influences of the flow rate and the humidity of the gas stream were studied. Also determined were the cross-sensitivities to a number of organic and inorganic gases. A new approach to overcome the interferences from NO, NO2 and SO2 is proposed whereby formaldehyde is selectively adsorbed from the sample stream with an aluminum oxide filter. By forming the difference for the measurements with and without filter a net signal for formaldehyde could be obtained in presence of the interferants.
TL;DR: Graphite-Teflon-peroxidase composite electrodes, constructed by simple physical inclusion of the enzyme into the bulk of the electrode matrix, have been used for the amperometric detection of 18 phenolic compounds as mentioned in this paper.
Abstract: Graphite-Teflon-peroxidase composite electrodes, constructed by simple physical inclusion of the enzyme into the bulk of the electrode matrix, have been used for the amperometric detection of 18 phenolic compounds. Monitoring of the enzyme reaction was carried out by the electrode reduction of the generated phenoxy radicals, in the presence of a constant concentration of 5.0×10−4 mol L−1 H2O2, at an applied potential of 0.00 V. Different aspects regarding the stability of the composite bioelectrode showed the robustness of the biosensor design. The kinetic constants of the enzyme reactions for the phenolic compounds tested were calculated. The limits of detection obtained were better than those found in the literature for peroxidase biosensors using other composite matrices, and the differences in sensitivity observed for the different phenolic substrates are discussed in terms of their pKa values and substituents. The analytical signals obtained with the graphite-Teflon-HRP electrodes have been compared with those yielded by a graphite-Teflon-tyrosinase composite electrode constructed in a similar way. With the aim of monitoring the largest possible number of phenolic compounds with the highest possible sensitivity, coimmobilization of peroxidase and tyrosinase into the composite electrode matrix was carried out.
TL;DR: In this paper, the ECL of an acridan ester (2′,3′,6′-trifluorophenyl 10-methylacridan-9-carboxylate), luminol, and a ruthenium chelate (ruthensium tris 2,2′-bipyridyl) were compared using ITO electrodes.
Abstract: Transparent indium tin oxide (ITO) electrodes are attractive for use in electrochemiluminescence (ECL). In this work the ECL of an acridan ester (2′,3′,6′-trifluorophenyl 10-methylacridan-9-carboxylate), luminol, and a ruthenium chelate (ruthenium tris 2,2′-bipyridyl) are compared using ITO electrodes. The electrochemistry of all the compounds is described and related to their ECL mechanisms; three possible mechanisms for luminol ECL are described, and it is suggested that the currently accepted mechanism involving luminol and superoxide radicals may not always be correct. Maximum light emission in ruthenium chelate ECL occurs at 1.5 V (vs. Ag/AgCl), but potentials of more than 1 V have a corrosive effect on ITO. The effect of this limitation on ruthenium chelate ECL is discussed as part of a wider assessment of the advantages and disadvantages of ITO as an electrode material for ECL. The effects of pH and H2O2 concentration on ECL detection of the acridan ester and luminol in a planar flow cell are described. The limits of detection of the acridan ester and luminol were 65 pM and 72 pM, respectively.
TL;DR: In this article, a fast and sensitive voltammetric method for the determination of arsenite and total inorganic arsenic in natural water systems is described using square-wave cathodic stripping voltammetry at a hanging mercury drop electrode.
Abstract: A fast and sensitive voltammetric method for the determination of arsenite and total inorganic arsenic in natural water systems is described using square-wave cathodic stripping voltammetry at a hanging mercury drop electrode. All the determinations were done in 1 M HCl, in the presence of 5 ppm copper(II) and dissolved oxygen. Discrimination between both oxidation states is achieved just by varying the composition of the supporting electrolyte: reduction of As(V) to As(III) is carried out at room temperature by a mixture of potassium iodide and ascorbic acid and inorganic arsenic determined as As(III)+As(V), while As(III) is measured in the absence of the reducing agent. For an accumulation time of 60 s the detection limits were 0.7 ppb for As(III) in 1 M HCl, and 5 ppm Cu(II), 0.6 ppb for As(III)+As(V) in 1 M HCl, 5 ppm Cu(II) and 0.04 % (w/v) KI+0.02 % (w/v) ascorbic acid. The precision, expressed as relative standard deviation (RSD) at 95 % confidence level, was calculated as 9 % from ten individual measurements taken at 2 ppb standard. The method was tested by the measurement of As(V) and As(III) in real and synthetic natural water samples.
TL;DR: In this paper, a renewing silver working electrode is investigated and the results indicate that the reproducibility of the response is increased when the electrode is oscillated sinusoidally.
Abstract: Issues concerning the use of mercury electrode in environmental analyses has led to considerable research effort aimed at finding alternative tools with acceptable performance. A renewing silver working electrode is investigated. This system has shown a good response to lead and cadmium. Concentrations as low as 10 µg L−1 have been detected for both ions in 0.1 M HCl solutions. The system shows also little interference from copper. A detection limit of 0.5 µg L−1 is estimated for these systems. The electrode system may be used repeatedly without maintenance over a considerable period of time as a new silver film is formed prior to each scan. The silver electrode has been excited, oscillated with both triangular and sinusoidal audio frequency waves. The results indicate that the reproducibility of the response is increased when the electrode is oscillated sinusoidally. A study of the oscillating frequency has also been carried out. The result shows that the detection sensitivity improved considerably when low frequencies typically in the range 40 to 80 Hz are used. Good detection sensitivity, along with the simplicity of use and maintenance renders this system potentially attractive for use in online and field instruments.
TL;DR: In this paper, a β-cyclodextrin (CD) modified poly(N-acetylaniline) (PNAANI) glassy carbon electrode (GCE) was used to study the electrode reaction of uric acid (UA).
Abstract: A β-cyclodextrin (CD) modified poly(N-acetylaniline) (PNAANI) glassy carbon electrode (GCE) was used to study the electrode reaction of uric acid (UA). The formation of a supramolecular complex between β-CD and UA improves the sensitivity and selectivity of the UA determination. The mechanism of selective detection of UA at the β-CD/PNAANI/GCE is proposed. Also, an analytical procedure involving square-wave voltammetry has been developed for determination of UA in the concentration range 1.0×10−5 to 2.0×10−4 mol dm−3.