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This work describes the use of polished silver solid amalgam electrode (p-AgSAE) and square wave voltammetry in the voltammetric determination of folic acid (FA). Experimental and voltammetric parameters were previously optimized. A well-defined voltammetric peak indicated a reversible redox reaction involving reactant and product adsorption on the p-AgSAE surface. A linear relationship between peak current and FA concentration was obtained from 4 x 10.sup.-7 to 1.1 x 10.sup.-5 M with a correlation coefficient of 0.9981, inter-day and intra-day precision of 2.1 and 5.3%, respectively, detection limit of 1.1 x 10.sup.-7 M, and quantification limit of 4 x 10.sup.-7 M. This procedure was applied to FA determination in spinach and corn chip samples using a simple extraction, resulting in good percent recovery that confirmed suitable robustness of the proposed methodology and the use of p-AgSAE as an excellent alternative for FA determination without the use of modified electrodes or toxic waste generation from the mercury electrodes utilization., Author(s): Uarlei Douglas dos Santos [sup.1] , Djenaine De Souza [sup.1] , Sérgio Antônio Spínola Machado [sup.2] Author Affiliations: (1) Laboratory of Electroanalytical Applied to Biotechnology and Food Engineering (LEABE), [...]

The successful use of a microband electrode printed on a silicon internal reflection element to perform time resolved infrared spectroscopy is described. Decreasing the critical dimension of the microband electrode to several hundred micrometers provides a sub-microsecond time constant in a Kretschmann configured spectroelectrochemical cell. The high brilliance of synchrotron sourced infrared radiation has been combined with a specially designed horizontal attenuated total reflectance (ATR) microscope to focus the infrared beam on the microband electrode. The first use of a sub-microsecond time constant working electrode for ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is reported. Measurements show that the advantage afforded by the high brilliance of the synchrotron source is at least partially offset by increased noise from the experimental floor. The test system was the potential induced desorption of an adsorbed monolayer of 4-methoxypyridine (MOP) as measured using step-scan interferometry. Based on diffusion considerations alone, the expected time scale of the process was less than 10 microseconds but was experimentally measured to be three orders of magnitude slower. A defect-mediated dissolution of the condensed film is speculated to be the underlying cause of the unexpected slow kinetics. Key words: ATR-SEIRAS, microband electrode, electrochemical time constant, step-scan interferometry, synchrotron infrared radiation. Nous decrivons l'emploi d'une electrode a microbande imprimee sur un element de reflexion interne en silicium que nous avons appliquee a la spectroscopie infrarouge a resolution temporelle. La reduction de la dimension critique de l'electrode a microbande a quelques centaines de micrometres donne lieu a une constante de temps de l'ordre de l'inframi-croseconde dans une cellule spectroelectrochimique de configuration Kretschmann. La forte brillance du rayonnement synchrotron infrarouge a ete conjuguee a un microscope en reflexion totale attenuee (RTA) horizontal specialement concu pour concentrer le faisceau infrarouge sur l'electrode a microbande. Nous faisons etat de la premiere utilisation d'une electrode de travail a constante de temps dans l'inframicroseconde destinee a la spectroscopie d'absorption infrarouge exaltee de surface en RTA (ATR-SEIRAS ou Attenuated Total Reflectance-Surface Enhanced InfraRed Absorption Spectroscopy). Selon les resultats que nous avons obtenus, l'avantage qu'offre la forte brillance de la source synchrotron est annule, du moins partiellement, par l'augmentation du bruit provenant du plancher de l'environnement experimental. L'eventuelle desorption d'une monocouche de 4methoxypyridine (MOP) adsorbee, mesuree par interferometrie a balayage progressif, constituait le systeme de mise a l'epreuve. Sur la base de considerations centrees uniquement sur la diffusion, le processus aurait du se produire sur une echelle de temps inferieure a 10 microsecondes, mais les mesures experimentales ont revele qu'il etait plus lent de trois ordres de grandeur. Nous posons l'hypothese selon laquelle une dissolution du film condense regie par la presence de defauts pourrait etre la cause sous-jacente de la cinetique etonnamment lente. [Traduit par la Redaction] Mots-cles : ATR-SEIRAS, electrode a microbande, constante de temps electrochimique, interferometrie a balayage progressif, rayonnement synchrotron infrarouge., Introduction The electrochemical RC cell constant, the product of the electrolyte resistance and the capacitance of the working electrode, determines the minimum time required for an electrified interface to respond [...]

Purpose: During insertion of the cochlear implant electrode array, the tip of the array may fold back on itself and can cause serious complications to patients. This article presents a sensing system for cochlear implantation in a cochlear model. The electrode array fold-over behaviors can be detected by analyzing capacitive information from the array tip. Method: Depending on the angle of the array tip against the cochlear inner wall when it enters the cochlear model, different insertion patterns of the electrode array could occur, including smooth insertion, buckling, and fold-over. The insertion force simulating the haptic feedback for surgeons and bipolar capacitance signals during the insertion progress were collected and compared. The Pearson correlation coefficient (PCC) was applied to the collected capacitive signals to discriminate the fold-over pattern. Results: Forty-six electrode array insertions were conducted and the deviation of the measured insertion force varies between a range of 20% and 30%. The capacitance values from electrode pair (1,2) were recorded for analyzing. A threshold for the PCC is set to be 0.94 that can successfully discriminate the fold over insertions from the other two types of insertions, with a success rate of 97.83%. Conclusions: Capacitive measurement is an effective method for the detection of faulty insertions and the maximization of the outcome of cochlear implantation. The proposed capacitive sensing system can be used in other tissue implants in vessels, spinal cord, or heart., To date, the insertion of a cochlear implant (CI) electrode array is performed by hand, and the tools used by surgeons do not provide any force feedback or other means [...]

Byline: Sunil. Pradhan, Sucharita. Anand Objective: To report a new patient friendly and convenient technique for phrenic nerve conduction with alternative sites of stimulation and recording. Methods: Phrenic nerve conduction [...]

A new sensor was developed using a screen-printed carbon electrode modified with single-walled carbon nanotubes (SWCNTs) and Prussian blue (PB) coated with chitosan. The modified electrode allowed the oxidation and reduction of rutin at 0.25 and 0.096 V, respectively, with a [DELTA]E of 0.154 V. Furthermore, the peak currents increase nearly 100% compared with the electrode without modification. The process was more reversible compared with the electrode modified with only SWCNTs or PB. Cyclic voltammetry was used to characterize the modified electrode surface. The quantification of rutin was more sensitive with adsorptive stripping voltammetry than with anodic stripping voltammetry. Adsorption potential, adsorption time and pH were optimized based on the oxidation of rutin: [E.sub.ads] = -0.10 V, [t.sub.ads] = 60 s, pH 3.0. The detection limit (3[sigma]/b) was 0.01 [micro]M and the relative standard derivation was 3%. The new sensor was used in the quantification of rutin in black tea, coffee and synthetic drink of tea with satisfactory results. Keywords: rutin, black tea, coffee, synthetic tea drink, adsorptive stripping voltammetry, Prussian blue DOI: 10.1134/S1061934818050064, The importance of study the presence of rutin in foods of mass consumption is based on its multiple benefits for the human health [1]. Also known as vitamin P, rutin [...]

An inorganic film of ruthenium hexachlororuthenate (RuRu[Cl.sub.6]), deposited on the surface of a glassy carbon electrode, exhibits electrocatalytic activity in the oxidation of purine nucleosides, such as guanosine and adenosine. Appropriate operating conditions are found for fabricating a polymer film on the surface of glassy carbon and for recording the maximum electrocatalytic current for the modified electrode. A method for the selective voltammetric determination of guanosine and adenosine in their simultaneous presence at an electrode modified by a RuRu[Cl.sub.6] film is developed. A procedure is proposed for the amperometric detection of purine nucleosides with this modified electrode under the conditions of flow-injection analysis. The linear dependence of the analytical signal on the concentration of guanosine and adenosine is observed up to 5 x [10.sup.-6] M in the stationary mode and up to 5 x [10.sup.-7] M in the flow system. The proposed method for the selective determination of guanosine and adenosine was tested in the analysis of human urine. Keywords: chemically modified electrodes, inorganic polymer films, ruthenium hexachlororuthenate, guanosine, adenosine, electrocatalysis, electroanalysis, flow-injection analysis, Purine bases associated with deoxyribose through an [alpha]-glycosidic bond belong to the class of purine nucleosides known for their metabolic and biological properties. Purine nucleosides, guanosine and adenosine, which are [...]

The gold-cobalt binary system, electrodeposited on the surface of a screen-printed electrode, exhibits catalytic activity in the electrooxidation of DOPA and tyrosine. The catalytic effect is shown in a multiple increase in current compared with the oxidation current of the modifier and a decrease in the oxidation overvoltage of organic compounds. Methods for the flow-injection amperometric determination of DOPA and tyrosine at the proposed modified electrode are developed. The simultaneous amperometric determination of DOPA and tyrosine at a dual screen-printed electrode modified with an Au-Co binary system the under conditions of flow-injection analysis is demonstrated. The linear dependence of the analytical signal on the concentration of DOPA and tyrosine is observed in the ranges from 1 x [10.sup.-9] to 1 x [10.sup.-4] M and from 5 x [10.sup.-8] to 5 x [10.sup.-4] M, respectively. Keywords: chemically modified electrodes, gold-cobalt binary system, dual screen-printed electrode, electrooxidation of DOPA and tyrosine, flow-injection analysis DOI: 10.1134/S1061934818020119, Automation of analytical works enables the rapid analysis of a large number of medicine, pharmaceutical, and environmental samples [1-3]. The use of flow methods, in which manual routine sample preparation [...]

In this study, we describe the application of carbon paste electrode modified with multiwall carbon nanotubes as a voltammetric sensor for determination of penicillamine (PA) in the presence of chlorpromazine as a mediator. This modified electrode showed very efficient electrocatalytic activity for the anodic oxidation of PA. The peak current of linear sweep voltammograms of PA increased linearly with it's concentration in the range of 0.5-500 [micro]M PA. The detection limit for PA was 0.2 [micro]M. The RSDs for 1.0 and 10.0 [micro]M PA were 1.1 and 1.7%, respectively. The proposed sensor was successfully applied for the determination of PA in human urine and tablet. Keywords: penicillamine, carbon nanotubes paste electrode, sensor, voltammetry DOI: 10.1134/S1061934817100136, Penicillamine is a pharmaceutical of the chelator class. The pharmaceutical form is D-penicillamine, whereas its L-penicillamine form is toxic(because it inhibits the action of pyridoxine). Despite having no antibiotic effects, [...]

Nickel oxide (NiO) nanoparticles were synthesized by a rapid method and well characterized. The nanoparticles were then used with graphite powder to prepare modified carbon paste electrode (CPE/NiO) for electrocatalytic oxidation of paracetamol (AC). The CPE/NiO showed higher electro catalytic activity than nickel rod electrode in electrocatalytic oxidation of AC in alkaline media. The assay of AC, mechanism and kinetics of the electrooxidation process were investigated by cyclic voltammetry and chronoamperometry. The catalytic rate constant and the charge transfer coefficient of AC electrooxidation by the active nickel species and the diffusion coefficient of AC were also reported. The linear dependence of the peak current on the concentration of the AC was observed in the range 2-14 mM. This procedure was successfully applied to the determination of AC in tablets. The results showed sufficient precision, accuracy and achieved a mean recovery of 97.2% (RSD = 6.7%). Keywords: paracetamol, electrocatalytic oxidation, carbon paste electrode, NiO nanoparticles, voltammetry DOI: 10.1134/S1061934817070024, NiO has been extensively investigated as an important transition metal oxide. It finds a wide range of applications in various fields, such as catalysis [1, 2], electric batteries [3, 4], [...]

The possibility of using diantipyrylmethane as an ionophore component of a lead-selective electrode membrane was assessed. Membrane composition (wt %) was optimized: polyvinyl chloride (31.89), dioctyl sebacate (63.81), diantipyrylmethane (2.50), and oleic acid (1.80). The proposed model of the electrode works in the concentration range of 1 x [10.sup.-5]--0.1 M with a detection limit of 2 mg/L. A slope of the electrode function of the diantipyrylmethane-based electrode is 29.4 [+ or -] 0.5 mV/pPb. Concentration of Pb(II) ions in various samples was determined. Keywords: potentiometry with ISE, potential, membrane ionophore component, lead, response, selectivity, electrode, determination, samples, Heavy metals belong to the most important biosphere pollutants. This is largely because of the biological activity of many of them. In the choice of a method of analysis, analysts [...]

The surface of a gold disk electrode, for the first time, was modified with a self-assembled monolayer of a synthesized compound, ethyl [(methythio)carbonothioyl] glycinate (ECTG), for construction of an electrode sensitive to riboflavin (vitamin [B.sub.2]). The electrochemical properties of the monolayer assembled on the gold disk were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimized conditions, the voltammetric peak currents resulting from vitamin [B.sub.2] (V[B.sub.2]) species were linear for V[B.sub.2] concentrations in the range from [10.sup.-6] to [10.sup.-2] M. The effect of pH, type of buffer solution and scan rate on the response of the modified electrode was studied. The constructed electrochemical sensor responses very well to V[B.sub.2] in the presence of most common vitamins. Finally, the performance of the Au--ECTG modified electrode was successfully tested for electrochemical detection of V[B.sub.2] in a pharmaceutical sample. Keywords: riboflavin, modified electrode, self-assembled monolayer, voltammetry, Although typically techniques employed in clinical laboratories encompass titrimetry, chromatography, spectrophotometry and immunoassay, the use of electroanalytical interfacial techniques have attracted attention as accurate, sensitive and cost-effective methods of analysis [...]

A new, simple, and fast method is described for determining selenium based on a silver wire electrode flow-through voltammetric detector. A comparison was done between the sensitivity of disk silver, mercury-modified glassy carbon, and mercury-modified gold electrodes. The response of the flow-through voltammetric detector was evaluated with respect to each electrode's operating potential and pH in direct current mode. The limit of detection (3a) for Se(IV) was below 0.01 mg/L. The flow-through system does not need deposition times and the organic matter does not need to be removed before determining selenium in river water. Keywords: flow-through voltammetric sensor, silver electrode, selenium, river water, Selenium is a component of glutathione peroxidase and iodothyronine-5'-deiodinase. Selenium deficiencies may occur in patients on long-term total parenteral nutrition with inadequate supplements, and where soil selenium levels are low. [...]

We developed a procedure for determining manganese(II) in wines by stripping voltammetry on a graphite electrode as a poorly soluble compound. The detection limit of manganese(II) is 50 µg/L. The dependence of the analytical signal of manganese(II) on its concentration in solution is linear in the range 0.1-3 mg/L. It is demonstrated that the results of the stripping voltammetric determination of manganese(II) in wines agree with the data obtained by inductively coupled plasma mass spectrometry and EPR spectrometry. Keywords: stripping voltammetry, inductively coupled plasma mass spectrometry, EPR spectrometry, graphite electrode, manganese, wine DOI: 10.1134/S1061934816010032, Wine contains more than 600 organic and inorganic compounds, including manganese complexes [1-4]. The concentration of manganese in wine depends on grape variety, the degree of its maturity, climatic conditions, [...]

The silver doped poly(L-arginine)-modified glassy carbon electrode was prepared by electropolymerization. Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the electrochemical properties of the modified electrode. The modified electrode exhibits good electrocatalytic activity for the oxidation of vitamin [B.sub.2] (V[B.sub.2]), vitamin C (VC) and vitamin [B.sub.6] (V[B.sub.6]). Under optimal conditions, V[B.sub.2], VC and V[B.sub.6] are oxidized at -0.298, 0.317 and 1.058 V, respectively, at the modified electrode using linear sweep voltammetry method. The linear ranges for V[B.sub.2], VC and V[B.sub.6] are 1.0 x [10.sup.-7] - 2.3 x [10.sup.-5], 5.0 x [10.sup.-6] - 4.0 x [10.sup.-3] and 1.0 x [10.sup.-5] - 3.0 x [10.sup.-3] M, respectively, and the detection limits are 8 x [10.sup.-8], 3 x [10.sup.-6] and 5 x [10.sup.-6] M. The modified electrode has been successfully applied to simultaneous determination V[B.sub.2], VC and V[B.sub.6] in multivitamin tablets with satisfactory results. Keywords: silver doped poly(L-arginine), vitamin [B.sub.2], vitamin C, vitamin [B.sub.6], modified electrode DOI: 10.1134/S1061934815120114, Vitamin [B.sub.2] (riboflavin), vitamin C (ascorbic acid) and vitamin [B.sub.6] (pyridoxine, V[B.sub.6]) are three water-soluble vitamins that play important roles in metabolism and energy production. V[B.sub.2] has an effect on [...]

This work designed a simple, sensitive, low-cost, and disposable electrochemical platform for the detection of antibiotic rifampicin (RIF) by using a hollow manganese oxide@mesoporous silica oxide ([Mn.sub.3][O.sub.4]@Si[O.sub.2]) core-shell nanohybrid as sensitive material. The [Mn.sub.3][O.sub.4]@Si[O.sub.2] core-shell nanohybrid, prepared by a facile polyacrylic acid soft templating method, was applied to modify a homemade carbon paste microelectrode, which provided a feasible pathway for electron transfer of RIF due to the low density, large surface area, excellent loading capacity, high permeability, and abundant amount of active sites. The electrocatalytic behavior was further used for sensitive detection of RIF by square wave voltammetry. Under optimal conditions, the calibration curve was linear in the range from 30 nmol/L to 3.0 µmol/L. The electrochemical method showed good stability, reproducibility, and selectivity. It could effectively be applied to the determination of RIF in human serum and urine samples. Key words: rifampicin, hollow manganese oxide, mesoporous silica oxide, core-shell, electrochemical determination. Dans le cadre de ces travaux, nous avons concu une plateforme electrochimique simple, sensible, peu couteuse et jetable pour la detection de la rifampicine (RIF), un antibiotique, en utilisant comme materiau sensible des particules creuses nanohybrides de type creur-coquille composees d'oxyde de manganese et de silice ([Mn.sub.3][O.sub.4]@Si[O.sub.2]). Par une methode aisee de synthese en moule souple d'acide polyacrylique, nous avons fabrique les particules nanohybrides creur-coquille de [Mn.sub.3][O.sub.4]@Si[O.sub.2] que nous avons appliquees a une microelectrode a pate de carbone, de fabrication artisanale, afin de la modifier. De fait, cette microelectrode constituait une voie possible pour le transfert d'electrons de la RIF en raison de sa faible densite, de sa grande surface de contact, de son excellente capacite d'adsorption, de sa grande permeabilite et de son abondance de sites actifs. Nous avons ensuite utilise ce comportement electrocatalytique pour la detection sensible de la RIF par voltamperometrie a ondes carrees. En conditions optimales, la courbe de calibration etait lineaire dans l'intervalle allant de 30 nmol/L a 3,0 µmol/L. Cette methode electrochimique presentait des bonnes stabilite, reproductibilite et selectivite. Elle pourrait etre efficacement appliquee au dosage de la RIF dans des echantillons humains de serum et d'urine. [Traduit par la Redaction] Mots-cles: rifampicine, nanoparticules creuses d'oxyde de manganese, silice mesoporeuse, creur-coquille, dosage electrochimique., Introduction During the past two decades, microscopic materials have experienced a great structural evolution from simple to complex because they always show a strong correlation between their geometry and their [...]

A biosensor has been developed for detection of L-arginine. The biosensor has been constructed using enzyme arginine deiminase as bio-component extracted from Pseudomonas putida MTCC 1313. The immobilization of enzyme was carried out in acrylamide gel, which was fixed onto the ion selective electrode. The optimization and kinetic characterization of free and immobilized enzyme was also studied. The response time of developed biosensor was found Keywords: microbial arginine deiminase, L-arginine, biosensor, ion selective electrode, fruit juices DOI: 10.1134/S1061934815090129, L-Arginine (L-Arg), a semi-essential amino acid, found in large amounts in protamines, histones and in many plants including red algae, curcurbitaceae and conifers where it functions as nitrogen storage and [...]

A new modified glassy carbon electrode (GCE) based on a synthesized polypyrrole (PPy) was developed for the determination of methylparaben by differential pulse voltammetry (DPV). PPy was covalently immobilized on GCE surface using tetraethyl ammonium perchlorate (TEAP) and acetonitrile (ACN). Methylparaben was oxidized by differential pulse voltammetry and a peak was observed at 1.20 V. The calibration curve obtained with differential pulse voltammetry was linear in the concentration range from 0.01 to 5 mM methylparaben with a limit of detection of 8 x [10.sup.-3] mM and RSD of 0.11%. The improved method was applied to the determination of methylparaben in cream samples using the differential pulse voltammetry method. Keywords: differential pulse voltammetry, modified glassy carbon electrode, methylparaben, polypyrrole DOI: 10.1134/S1061934815060155, Parabens, esters of p-hydroxybenzoic acid, are a group of chemicals used worldwide by cosmetic, pharmaceutical, personal care products, foods and beverages industries as preservative and antimicrobial agents due to their [...]