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Made available in DSpace on 2022-04-28T19:41:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Most of commercial WLEDs have a lack of red-emission component resulting in cool white illumination. Aiming this issue, in this paper, we present the synthesis of [Eu(salen)2] with a Schiff base type ligand, the salen (N,N′-ethylene-bis(salicylidenimine)), another lanthanide complex was also investigated, the [Gd(salen)2]. Both complexes were characterized by conventional spectroscopy techniques to confirm their preparation, and the free software LUMPAC was used as a friendly interface to determine the experimental intensity parameters (Ω2 and Ω4) for the Eu-complex, it was also used to optimize the complex structure, perform theoretical calculations of excited states, and intensity parameters. The Eu-complex was immobilized in PMMA films in different amounts, and their photophysics properties were analyzed. The 7.5 wt% doped film showed the best photophisical results (τ = 0.226 ms; ΦEuEu = 9.61%), and it was chosen to coat a UV LED-chip (λem = 400 nm ± 10 nm) to fabricate a red emissive LED-prototype; also, a prototype with a blend between powdered Eu-complex and cyanoacrylate glue was fabricated, and their emission behavior and radiant photostability were compared. The prototype with the doped PMMA film exhibited poorer radiant photostability than the powder prototype after 24 h of operation. Thus, the [Eu(salen)2] powder prototype gather some important characteristics to be used as a red component of warm WLEDs. São Paulo State University (Unesp) School of Technology and Sciences São Paulo State University (Unesp) Institute of Chemistry São Paulo State University (Unesp) Institute of Biosciences Humanities and Exact Sciences São Paulo State University (Unesp) School of Technology and Sciences São Paulo State University (Unesp) Institute of Chemistry São Paulo State University (Unesp) Institute of Biosciences Humanities and Exact Sciences CAPES: 1531833 FAPESP: 2015/03400–5 FAPESP: 2016/09017–1 FAPESP: 2019/26103–7 CNPq: 303282/2020–7 CNPq: 304003/2018–1 CAPES: 88887.341772/2019–00

Made available in DSpace on 2021-06-25T10:31:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The present study evaluated the spatiotemporal variation in concentration of cadmium, lead and copper ions in groundwater wells in the stratigraphic subdivision “Santo Anastácio” that belongs to the Bauru aquifer system in the western region of São Paulo State. Exploratory statistics methods were employed to investigate the response of the concentration of these metals in the aquifer through the pluviometric index of the region. The results show a direct dependence of the mean monthly flow of the metals in the groundwaters to the monthly rainfall flow. The observed behavior was cyclic with a gradual increase and decrease in the flow throughout time. Two groups of cyclic variation were identified. The seasonality of the mean monthly flow of Cd2+ and Pb2+ was inversely proportional to the magnitude of the pluviometric index of the region studied. Meanwhile, the seasonality of Cu2+ was directly correlated to the seasonable rainfall variability. These behaviors lead us to point out that cadmium and lead come from minerals present in the aquifer itself and the presence of copper in groundwater is associated with an anthropogenic action due to the region’s agricultural activity. The study helps us better comprehend the behavior of the whole groundwater system through a comparison with temporal hydrogeochemistry. Department of Chemistry and Biochemistry School of Science and Technology—Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 Department of Chemistry and Biochemistry School of Science and Technology—Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 FAPESP: 2013/07296‐2 CNPq: 301298/2017‐3

Made available in DSpace on 2021-06-25T10:18:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) We have developed electrocatalytic platforms based on palladium metallopolymer-graphene for the water splitting reaction. The platforms presented a low potential for the water oxidation reaction. By cyclic voltammetry and electrochemical impedance spectroscopy (EIS), the interfacial phenomena were investigated, allowing us to obtain important results that helped to determine kinetic and mechanistic information. The studies revealed that the introduction of graphene in the metallopolymer matrix increased the turnover frequency (TOF) value. Analysis of the Tafel plots obtained from the EIS data also revealed a change in the reaction mechanism after the introduction of graphene. The new platform demonstrated its applicability in the water splitting reaction for use in fuel cells. Department of Chemistry and Biochemistry School of Science and Technology - Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 Department of Chemistry and Biochemistry School of Science and Technology - Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 FAPESP: 2016/09017-1 CNPq: 301298/2017-3 CAPES: 88882.434480/2019-01

Made available in DSpace on 2020-12-12T01:21:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-22 The present paper describes the development of a novel photochemiresistor sensor for the determination of chemical oxygen demand (COD). A chemiresistive device was produced by a thin film of the monoclinic phase of bismuth vanadate deposited on an FTO glass surface. The resistive properties of the photosensor were carried out by electrochemical impedance spectroscopy (EIS). The electrical resistance of the platform was dependent on the presence of organic material in aqueous solution and the incidence of light. The decrease in resistance can be explained by considering that by increasing the amount of organic material, the amount of charge transferred to BiVO4 increases, as does the amount of the photogenerated conduction band on the film. This behavior is not observed when carrying out the same measurements in the absence of light. Under the optimal experimental conditions, the linear response of the chemiresistor sensor is between 0.20 and 19.9 mg L-1 COD at a fixed AC frequency of 0.1 Hz. There is a good correlation between the charge transfer resistance and COD concentration in the electrolyte solution. Quantification of COD in waste and lake waters was successfully performed using the novel photochemiresistor sensor. The results achieved in the analysis with the sensor are in accordance with the conventional method. Department of Chemistry and Biochemistry School of Science and Technology Sao Paulo State University (UNESP), Rua Roberto Simonsen, 305 CEP Department of Physics School of Science and Technology São Paulo State University (UNESP) Department of Chemistry and Biochemistry School of Science and Technology Sao Paulo State University (UNESP), Rua Roberto Simonsen, 305 CEP Department of Physics School of Science and Technology São Paulo State University (UNESP)

Made available in DSpace on 2018-12-11T17:21:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A resistance detection device for dissolved molecular oxygen in aqueous solutions is prepared using a chemiresistor material as sensor platform. The chemiresistive circuit element is fashioned from a thin film of a cobalt-salen metallopolymer electrodeposited on a platinum electrode. Electrochemical impedance spectroscopy shows that the resistive and capacitive properties of the sensor platform depend on the presence of dissolved oxygen. The electrical circuit models are R(Q/R)(Q/R) and R(Q/R)(Q/RW) in the absence and presence of oxygen, respectively. The chemiresistor sensor exhibits good sensitivity (0.483 kΩ L mg−1), excellent reversibility and excellent linearity over a range of dissolved oxygen concentrations typically found under environmental conditions (2.72–40.9 mg L−1). The sensor fabricated in this work can potentially serve as an alternative sensor for the detection of dissolved oxygen in environmental samples. Department of Chemistry and Biochemistry School of Science and Technology - Sao Paulo State University (UNESP), Rua Roberto Simonsen 305, CEP 19060-900 Department of Chemistry and Biochemistry School of Science and Technology - Sao Paulo State University (UNESP), Rua Roberto Simonsen 305, CEP 19060-900 CNPq: 113827/2012-1 FAPESP: 2016/09017-1

Department of Chemistry and Biochemistry School of Science and Technology Sao Paulo State University (UNESP), Rua Roberto Simonsen, 305

Made available in DSpace on 2021-06-25T11:17:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) In the present study, we report the use of an electrochemical sensor for uric acid using a molecularly imprinted polymer (MIP) as a molecular recognition platform. The MIP was based on an azopolymer electropolymerized in the presence of uric acid used as a template molecule. The azo group of the polymer contributes to the quantifiable redox capacitance of the electrode surface, which can be probed by impedance/capacitance spectroscopy. Thus, the advantage of the developed sensor is its ability to perform direct measurements without a soluble redox probe. The molecularly imprinted polymer can sensitively transduce the recognition and binding of specific analytes by redox capacitance. Through electrochemical impedance spectroscopy (EIS) and electrochemical capacitive spectroscopy (ECS), unusual approaches were able to obtain different analytical curves with distinct characteristics, reaching a limit of detection of 0.160 μmol L−1. Department of Chemistry and Biochemistry School of Science and Technology – Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 Department of Chemistry and Biochemistry School of Science and Technology – Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 FAPESP: 2016/09017-1 CNPq: 301298/2017-3 CAPES: 88882.434480/2019-01

Made available in DSpace on 2018-12-11T16:46:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The emission of radon gas in regions of geological faults, during the radioactive decay of uranium and thorium, results in the formation of lead isotopes 210Pb, 208Pb, 207Pb and 206Pb. As a consequence, the lead contamination in the soil poses a hazard to humans through ingestion of food, contaminated water, and even by direct contact with the soil contaminant. So far the relationship between the occurrence of geological faults and soil Pb contamination has not been established. Here, we studied lead in soils of regions with geological faults and their possible relationship with radon emissions. Soils were sampled from Presidente Prudente located in the far west of São Paulo State, Brazil. The region has strong evidence of the existence and direction of geological faults at depths of approximately 200 m. Soil sampling was done according to the USEPA 3050 method. Total lead was quantified by anodic stripping voltammetry. Results show that the total Pb concentration increases systematically with soil depth. This finding is explained by the fact that the lead originates from radon emissions. Pearson correlation analysis further proves a relationship of the nuclear track density obtained with CR-39 detectors, and mean Pb levels within each soil profile. Overall, our findings should improve risk evaluation of Pb contamination derived from radon emission and geological faults. Department of Chemistry and Biochemistry Faculty of Science and Technology São Paulo State University (UNESP) Department of Physics Faculty of Science and Technology São Paulo State University (UNESP) Department of Geography Faculty of Science and Technology São Paulo State University (UNESP) Department of Chemistry and Biochemistry Faculty of Science and Technology São Paulo State University (UNESP) Department of Physics Faculty of Science and Technology São Paulo State University (UNESP) Department of Geography Faculty of Science and Technology São Paulo State University (UNESP) CNPq: 234256/2014-1 CNPq: 302728/2012-0

Entidades de todo o mundo estão cada vez mais fortalecendo movimentos em prol de um planeta mais saudável e sustentável. Neste sentido, o intuito deste trabalho é a construção de nanofibras de C/BiVO4 via eletrofiação e posterior carbonização do polímero PVA. Obtendo assim, nanofibras com elevada área superficial quando comparados aos usais métodos de deposição. Possibilitando maior absorção dos fótons e consequentemente elevando a eficiência fotoeletrocatalítica na conversão energética e degradação de poluentes orgânicos. O BiVO4 sintetizado foi caracterizado e assim confirmado a formação da fase monoclínica. A técnica de eletrofiação apresentou fibras com diâmetros na escala nanométrica com a presença do carbono, aumentando consideravelmente a área superficial do material, confirmado pelas microscopias óptica e eletrônica de varredura.

No presente trabalho foi estudado o desenvolvimento de um polímero molecularmente impresso (PMI) baseado no poli(azo-Bismarck Y) para detecção de ácido úrico. O filme PMI foi preparado pela eletropolimerização do monômero Bismarck Brown Y na presença de ácido úrico como molécula molde sobre a superfície do eletrodo de óxido de estanho dopado com flúor (FTO). O sensor PMI-poli(azo-Bismark Y) exibiu boa resposta eletroquímica, alta sensibilidade e seletividade na ligação específica ao ácido úrico. Sob as condições experimentais otimizadas, a resposta voltamétrica do sensor proposto foi linear no intervalo de concentração de 0,20 mmol L-1 a 0,60 mmol L-1, com limite de detecção de 0,17 mmol L−1.

Made available in DSpace on 2018-12-11T16:43:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01 Electropolymerization of a π-conjugated polymer from [N,N′-bis(salicylidene)-o-phenylenediamine]nickel(II) complex ([Ni(salophen)]) on the surface of indium-tin-oxide (ITO) was studied. Two structures of the polymer have been proposed based on the theorem of molecular columns. The highlighted structures are the molecular column of the central aromatic rings (MCCAR) and molecular column of the side aromatic rings (MCSAR). The molecular structures were obtained by control of the potential scan rate in the electropolymerization step. The MCCAR structures are stable and structurally compact, whereas the MCSAR structures are less compact. Electrochemical measurements, atomic force microscopy (AFM), UV–Vis spectroscopy, FTIR Raman spectroscopy and optical microscopy support the formation of the multiblock π-conjugated polymer. Department of Chemistry and Biochemistry Faculty of Science and Technology São Paulo State University (UNESP), Rua Roberto Simonsen 305 São Carlos Institute of Chemistry University of São Paulo (USP) Department of Chemistry Faculty of Science and Technology University of Coimbra Department of Chemistry and Biochemistry Faculty of Science and Technology São Paulo State University (UNESP), Rua Roberto Simonsen 305

Made available in DSpace on 2018-12-11T16:52:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this study, we explore the fabrication and properties of a sensing electrochemical platform that is based on a novel 11-mercaptoundecyl-N′,N″,N‴-trimethylammonium hexacyanoferrate (MAH) and 6-(ferrocenyl)hexanethiol (FT)/glucose oxidase (GOx) on gold substrate. The hexacyanoferrate and ferrocene moieties that were immobilized on the gold surface were examined as electron transfer mediators with the oxidase glucose. The sensing platform, based on 11-mercaptoundecyl-N′,N″,N‴-trimethylammonium hexacyanoferrate (MAH) and 6-(ferrocenyl)hexanethiol (FT)/GOx modified gold electrode, shows the potential to work with two distinct mechanisms for electrochemical response. The hexacyanoferrate anion that was anchored at positive edge charge of the 11-mercaptoundecyl-N′,N″,N‴-trimethylammonium on the gold surface provided an efficient electron transfer. It was demonstrated that in the design of the GOx/MAH, the FT/Au electrode is facilitating the electron transfer from GOx toward the gold substrate. We believe that this study adds a new facet to nanobioelectronics with applications for biofuels and sensorial platforms. Department of Chemistry and Biochemistry School of Science and Technology Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 São Carlos Institute of Chemistry University of São Paulo (USP) São Carlos Department of Physiotherapy School of Science and Technology Sao Paulo State University (UNESP) Department of Chemistry and Biochemistry School of Science and Technology Sao Paulo State University (UNESP), Rua Roberto Simonsen 305 Department of Physiotherapy School of Science and Technology Sao Paulo State University (UNESP) FAPESP: 2012/21703-7 CNPq: 234256/2014-1 CNPq: 302728/2012-0

Made available in DSpace on 2018-12-11T16:44:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This work reports on the sol-gel synthesis of barium- and europium-doped silica xerogel and its use as an electrocatalytic sensor. Barium was chosen to assist the network framing and europium to provide electronic properties, including the Eu2+/Eu3+ redox process. The results from different molecular and structural techniques indicated that this xerogel is a composite material that combines a non-crystalline polymeric silica network with a high level of agglomeration and a low degree of reticulation formed by the hydrolysis and condensation of TEOS and M-O bonds (M = Ba2+ and/or Eu3+), whereas the oxygen atoms belong to the xerogel phase. The electrochemical behavior of the silica xerogel:Ba2+,Eu3+ with different amounts of Eu3+ under several different conditions was investigated. The electrochemical sensing platform showed a well-defined redox coupling with a formal potential of 0.06 V, assigned to europium redox sites in silicate. Electrocatalytic activity was observed with an increasing anodic peak current to the isoniazid oxidation, indicating that the electrochemical sensing platform designed here was successfully achieved. Faculdade de Ciências e Tecnologia UNESP Univ Estadual Paulista, Rua Roberto Simonsen, 305 Instituto de Biociências Letras e Ciências Exatas UNESP Univ Estadual Paulista, Rua Cristóvão Colombo, 2265 Instituto de Química de São Carlos Universidade de São Paulo-USP Faculdade de Ciências e Tecnologia UNESP Univ Estadual Paulista, Rua Roberto Simonsen, 305 Instituto de Biociências Letras e Ciências Exatas UNESP Univ Estadual Paulista, Rua Cristóvão Colombo, 2265

The preparation and electrochemical characterization of a nickel hydroxide modified nickel electrode as well as its behavior as electrocatalyst toward the oxidation of hydrochlorothiazide (HCTZ) were investigated. The electrochemical behavior of the modified electrode and the electrooxidation of HCTZ were explored using cyclic voltammetry. The voltammetric response of the modified electrode in the detection of HCTZ is based on the electrochemical oxidation of the Ni(II)/Ni(III) and a chemical redox process. The analytical parameters for the electrooxidation of HCTZ by the nickel hydroxide modified nickel electrode were obtained in NaOH solution, in which the linear voltammetric response was in the concentration range from 1.39 × 10−5 to 1.67 × 10−4 mol L−1 with a limit of detection of 7.92 × 10−6 mol L−1 and a sensitivity of 0.138 μA L mmol−1. Tafel analysis was used to elucidate the kinetics and mechanism of HCTZ oxidation by the modified electrode.

The mediation of electron-transfer by oxo-bridged dinuclear ruthenium ammine [(bpy)2(NH3)RuIII(µ-O)RuIII(NH3)(bpy)2]4+ for the oxidation of glucose was investigated by cyclic voltammetry. These ruthenium (III) complexes exhibit appropriate redox potentials of 0.131–0.09 V vs. SCE to act as electron-transfer mediators. The plot of anodic current vs. the glucose concentration was linear in the concentration range between 2.52×10−5 and 1.00×10−4 mol L−1. Moreover, the apparent Michaelis-Menten kinetic (KMapp) and the catalytic (Kcat) constants were 8.757×10−6 mol L−1 and 1,956 s−1, respectively, demonstrating the efficiency of the ruthenium dinuclear oxo-complex [(bpy)2(NH3)RuIII(µ-O)RuIII(NH3)(bpy)2]4+ as mediator of redox electron-transfer.

A simple and fast method based on electro- chemical measurements was proposed for estimation of total polyphenols using a carbon paste modified elec- trode. The method was based on catalytic response exhib- ited by a ruthenium complex ((bpy)2(NH3)Ru III (m- O)Ru III (NH3)(bpy)2) 4 + in presence of gallic acid (GA). Calibration plots using chronoamperometry (CA) showed a linear response for GA concentrations ranging from 6.6 � 10 � 6 to 1.9 � 10 � 4 mol L � 1 with a detection limit of 4.9 � 10 � 7 mol L � 1 . Comparative studies using the official method revealed a good agreement between methods suggesting that the proposed method can be applied for polyphenol estimation without any sample treatment.

The supramolecular building blocks from a nickel(II) bisalphen-type complex have been reported. The conjugations through the bridge provide flexibility of the monomer in the electropolymerization stage. Thus, different structures can be obtained with the variation of electrochemical parameters used in the electropolymerization. The structural characterization and the electrochemical behavior in aqueous solution was also evaluated, which demonstrated that the electropolymerization mechanism was similar to that observed for the classical salen polymers, but the molecular organization onto the conductor substrate was different. The supramolecular structure of the polymeric film allows observation of the NiI/NiII and NiII/NiIII redox couples by differential pulse voltammetry. Thus, the comproportionation constant and Gibbs energy were calculated for the NiI/NiII redox couple. These characteristics make these polymers versatile materials in the field of supramolecular chemistry and materials science, in particular in applications as sensors, in electrocatalysts and for energy storage.

An analytical method was developed for quantification of the fungicide thiram (tetramethylthiuram disulfide), based on its capacity to complex Cu2+ ions. A solid-phase reactor (SPR) was coupled in a flow system containing a spectrophotometer as detector. The SPR consisted of a tube filled with finely ground resin, in which copper(II) phosphate was immobilised prior to polymerisation. Contact of thiram with the Cu2+ ions immobilised in the resin resulted in the formation of a strongly coloured Cu2+/thiram complex. Maximum absorbance of the Cu2+/thiram complex was obtained at a wavelength of 439 nm. The usefulness of the methodology has been evidenced by the determination of thiram residues in corn and bean grains. Previously, a variety of transition metal cations which would form coloured complexes with tetramethylthiuram disulfide were tested.

Made available in DSpace on 2020-12-12T01:40:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The present paper describes a nonenzymatic chemiresistor sensor based on an azo-polymer and reduced graphene oxide (rGO) as a resistive platform for superoxide radical detection. The sensorial platform was prepared on layer-by-layer-assembled films of poly(azo-Bismarck Brown Y) and reduced graphene oxide by cyclic voltammetry. The nanocomposite film exhibited interesting synergetic properties based on the redox properties of the azo-polymer combined with the good electronic conductivity and stability of graphene. The electrical conductivity mechanism of the graphene-polymer was analyzed by electrochemical impedance and compared to that of an electrode coated with only polymer. The conductance properties of the interlayer formed by π-π stacking between the conjugated structure of the polymer chains and the structure of the graphene sheet are dependent on the applied potential of the system. The performance of the poly(azo-BBY)/rGO film as a chemiresistor material for the sensing of superoxide anions was evaluated by impedance measurements at the applied potential of +0.30 in PBS (7.4). The charge transfer resistance values change substantially in the presence of superoxide in solution. The effect of superoxide on the resistivity of the device is attributed to changes in the oxidation state of the polymer. The impedance measurements in real time (chrono-impedance) with the poly(azo-BBY)/rGO sensor with different superoxide concentrations revealed good linearity behavior between the real impedance and the superoxide anion concentration (0.12–2.6 ​mmol ​L−1) with a detection limit of 81.0 μmol L−1. Department of Chemistry and Biochemistry School of Science and Technology - Sao Paulo State University (UNESP) Rua Roberto Simonsen 305 Department of Physiotherapy School of Science and Technology - Sao Paulo State University (UNESP) Presidente Prudente Department of Chemistry and Biochemistry School of Science and Technology - Sao Paulo State University (UNESP) Rua Roberto Simonsen 305 Department of Physiotherapy School of Science and Technology - Sao Paulo State University (UNESP) Presidente Prudente

An amperometric glucose biosensor based on on hexacyanoferrate 11-mercaptoundecyl- N’,N”,N”’ -trimethylammonium (HMA)/6-(ferrocenyl)hexanethiol (FT)/GOx modified gold electrode was fabricated and evaluated. The GOx/HMA/FT/Au electrode was characterized using cyclic voltammetry (CV) and used for glucose concentration estimation in standard solutions using CV and amperometric techniques.

The preparation and electrochemical characterization of hausmannite-type manganese oxide to use as a sensing material for sodium ion is described. This paper reports a new via synthetic to obtain of the hausmannite-type manganese oxide and its application in the construction of modified electrode as a voltammetric sensor. The electrochemical activity of hausmannite-type manganese oxide is controlled by intercalation/deintercalation of the sodium ions within the oxide lattice. The detection is based on the measurement of anodic current generated by oxidation of Mn III –Mn IV at electrode surface. The best electrochemical response was obtained for a sensor composition of 20% (w/w) hausmannite oxide in the paste, a TRIS buffer solution of pH 6.0–7.0 and a scan rate of 50 mV s −1 . A sensitive linear voltammetric response for sodium ions was obtained in the concentration range of 2.01 × 10 −5 –2.09 × 10 −4 mol L −1 with a slope of 355 μA L mmol −1 and a detection limit of 7.50 × 10 −6 mol L −1 using cyclic voltammetry. The use of hausmannite has significantly improved the selectivity of the sensor compared to the birnessite-type manganese oxide modified electrode. Under the working conditions, the proposed method was successfully applied to determination of sodium ions in urine samples.

Made available in DSpace on 2018-12-11T16:42:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-07-02 This article explores the assessment of atmospheric deposition, from the analysis of the sampling methods, the analytical procedures for chemical characterisation of pollutants, and the main results from the scientific literature. Atmospheric particulate matter (PM) was collected in four regions of the city of Presidente Prudente (Sao Paulo State, Brazil) characterised by heavy traffic flows and high population density. The Cd, Pb, and Cu metals were determined in samples using differential pulse anodic stripping voltammetry. The PM was collected every fortnight using passive sampling, over a total period of two years. A comparative study between the element deposition fluxes in four sampling sites was performed. The relative contribution of the quantitative descriptors to divergence among the analysis by Tocher grouping method was also studied. Department of Chemistry and Biochemistry Faculty of Sciences and Technology Sao Paulo University State (UNESP) Department of Chemistry and Biochemistry Faculty of Sciences and Technology Sao Paulo University State (UNESP)

Made available in DSpace on 2018-12-11T16:40:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-06-02 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this paper, we report the construction of an electrochemical sensing platform based on platinum nanoparticles supported on carbon (PtNPs/C) for the determination of the antibiotic tetracycline (TTC). Initially, the PtNPs/C was synthesized and characterized by powder X-ray diffraction spectroscopy and transmission electron microscopy. The effect of experimental parameters on the electrochemical behavior of the PtNPs/C coated glassy carbon electrode (PtNPs/C/GCE), including the amount of PtNPs and electroactive area, scan rate and pH, were evaluated. The electrooxidation of TTC on the PtNPs/C/GCE was investigated by cyclic voltammetry and differential pulse voltammetry, with the determination of TTC electrooxidation mechanism. Under optimum experimental conditions, the linear calibration range, detection limit, quantification and sensitivity of the PtNPs/C/GCE were 9.99-44.01 μmol L-1, 4.28 μmol L-1, 14.3 μmol L-1 and 3.32 μA L μmol-1 cm-2, respectively. Finally, the proposed electrochemical sensing platform was successfully applied to determine low TTC concentrations in urine samples, suggesting its great applicability in clinical analysis and quality control. São Carlos Institute of Chemistry University of São Paulo (USP) Faculty of Science São Paulo State University (UNESP) Faculty of Science and Technology São Paulo State University (UNESP) Faculty of Science São Paulo State University (UNESP) Faculty of Science and Technology São Paulo State University (UNESP) CNPq: 302728/2012-0

An amperometric oxygen sensor based on a polymeric nickel– salen ( salen = N , N ′-ethylene bis (salicylideneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel– salen complex at platinum electrode in acetonitrile/tetrabutylammonium perchlorate by cyclic voltammetry. The voltammetric behavior of the sensor was investigated in 0.5 mol L −1 KCl solution in the absence and presence of molecular oxygen. Thus, with the addition of oxygen to the solution, the increase of cathodic peak current (at −0.25 V vs. saturated calomel electrode (SCE)) of the modified electrode was observed. This result shows that the nickel– salen film on electrode surface promotes the reduction of oxygen. The reaction can be brought about electrochemically, where the nickel(II) complex is first reduced to a nickel(I) complex at the electrode surface. The nickel(I) complex then undergoes a catalytic oxidation by the molecular oxygen in solution back to the nickel(II) complex, which can then be electrochemically re-reduced to produce an enhancement of the cathodic current. The Tafel plot analyses have been used to elucidate the kinetics and mechanism of the oxygen reduction. A plot of the cathodic current vs. the dissolved oxygen concentration for chronoamperometry (fixed potential = −0.25 V vs. SCE) at the sensor was linear in the 3.95–9.20 mg L −1 concentration range and the concentration limit was 0.17 mg L −1 O 2 . The proposed electrode is useful for the quality control and routine analysis of dissolved oxygen in commercial samples and environmental water. The results obtained for the levels of dissolved oxygen are in agreement with the results obtained with a commercial O 2 sensor.

In the present work, we investigated the immobilization and electrochemical behavior of Reactive Blue 4 dye on 3-aminopropyl-functionalized silica. The electrochemical behavior of the modified electrode and the electro-oxidation of dipyrone were studied by cyclic voltammetry. The modified electrode showed a well-defined redox coupling with a formal potential of 0.45 V (vs. saturated calomel reference electrode) assigned to anthraquinone/anthrahydroquinone redox process (pH = 2). The modified electrode also demonstrated electrocatalytic activity and an increased peak current towards the oxidation of dipyrone at a reduced overall potential. The electrocatalytic process was found to be highly dependent on the pH of the supporting electrolyte. The voltammetric responses for dipyrone were linear in the concentration range of 49.9 to 440 μmol L−1 at a pH of 2.0 with a detection limit and sensitivity of 22.0 μmol L−1 and 0.0278 μA mmol L−1, respectively.

The electrochemical behavior of a carbon paste electrode modified (CPEM) with nickel-doped potassium strontium niobate (KSr 2 Ni 0.75 Nb 4.25 O 15− δ ) of tetragonal tungsten bronze (TTB)-type structure was investigated as a new sensor for dipyrone. The optimum conditions were found in an electrode composition (in mass) of 20% KSr 2 Ni 0.75 Nb 4.25 O 15− δ , 65% graphite and 15% mineral oil in 0.5 mol L −1 KCl solution at pH 6.0. The electrode exhibits reversible electrochemical behavior in a wide potential range (0.1–0.7 V vs. SCE), high conductivity, and stability/durability electrode in 0.50 mol L −1 KCl solution. The estimated surface concentration was found to equal 1.08 × 10 −9 mol cm −2 . The oxidation of dipyrone was performed at carbon paste electrode unmodified at +0.54 V vs. SCE and carbon paste electrode modified with KSr 2 Ni 0.75 Nb 4.25 O 15− δ at +0.45 V vs. SCE. This result shows that the nickel-doped potassium strontium niobate on electrode surface promotes the oxidation of dipyrone. The reaction can be brought about electrochemically, where the niobium(IV) is first oxidation to a niobium(IV) oxide at the electrode surface. The niobium(IV) then undergoes a catalytic reduction by the dipyrone in solution back to the niobium(III), which can then be electrochemically re-oxidized to produce an enhancement of the anodic current. The identification of the oxidation product of dipyrone was made by mass spectrometry for elucidation of response mechanism of the sensor. Anodic peak current ( I pa ) vs. dipyrone concentration for amperometric method at the modified electrode was linear in the 3.5 × 10 −5 and 3.1 × 10 −4 mol L −1 concentration range and the detection limit was 5.1 × 10 −6 mol L −1 dipyrone. At higher concentrations (>3.1 × 10 −4 mol L −1 ), deviation from linearity occurs. Under this condition, an electrocatalytic reaction takes place and proceeds through a mechanism similar to the Michaelis–Menten model.

The [Mn4IVO5(terpy)4(H2O)2]6+ complex, show great potential for electrode modification by electropolymerization using cyclic voltammetry. The electropolymerization mechanism was based in the electronic transfer between dx2-y2 orbitals of the center metallic and pπ orbital of the ligand, which show great complexity of the system due to orbitals overlap present in octahedral complex of the metal-μ-oxo. The voltammetric behavior both in and after electropolymerization process were also discussed, where the best condition of electropolymerization was observed for low scan rate and 50 potential cycles. A study in ITO/glass electrode for better characterization of polymer was also performed.

Electrochemical behavior of oxo-bridged dinuclear ruthenium(III) complex ([(bpy)2(H2O)RuIII-O-RuIII(H2O)(bpy)2]4+) has been studied in aqueous solution (KCl 0.5 mol L−1) by both cyclic and rotating disk electrode (RDE) voltammetry in order to identify and elucidate the reaction mechanism. Modified electrode containing the oxo-bridged ruthenium complex incorporated into a cation-exchange polymeric film deposited onto platinum electrode surface was studied. Cyclic voltammetry at the modified electrode in KCl solution showed a single-electron reduction/oxidation of the couple RuIII-O-RuIII/RuIII-O-RuIV. The modified electrode exhibited electrocatalytic property toward hydrogen peroxide oxidation in KCl solution with a decrease of the overpotential of 340 mV compared with the platinum electrode. The Tafel plot analyses have been used to elucidate the kinetics and mechanism of the hydrogen peroxide oxidation. The first at low overpotential region there is no significant change in the Tafel slope (∼0.130 V dec−1) with varying peroxide concentration. The second region at higher overpotential the slope values (0.91–0.47 V dec−1) were depended on the peroxide concentration. The apparent reaction order for H2O2 varies from 0.16 to 0.50 in function of the applied potential. The apparent reaction order (at constant potential) with respect to H+ concentration of 10−5 to 10−1 mol L−1 was 0.25. A plot of the anodic current vs. the H2O2 concentration for chronoamperometry (potential fixed = +0.61 V) at the modified electrode was linear in the 1.0 × 10−5 to 2.5 × 10−4 mol L−1 concentration range.

Made available in DSpace on 2013-09-27T14:53:52Z (GMT). No. of bitstreams: 1 WOS000288227800090.pdf: 442251 bytes, checksum: b5dc8c3fb00f96f187e4b8aba1393341 (MD5) Previous issue date: 2011-02-01 Made available in DSpace on 2013-09-30T18:09:39Z (GMT). No. of bitstreams: 1 WOS000288227800090.pdf: 442251 bytes, checksum: b5dc8c3fb00f96f187e4b8aba1393341 (MD5) Previous issue date: 2011-02-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:23:13Z No. of bitstreams: 1 WOS000288227800090.pdf: 442251 bytes, checksum: b5dc8c3fb00f96f187e4b8aba1393341 (MD5) Made available in DSpace on 2014-05-20T13:23:13Z (GMT). No. of bitstreams: 1 WOS000288227800090.pdf: 442251 bytes, checksum: b5dc8c3fb00f96f187e4b8aba1393341 (MD5) Previous issue date: 2011-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. This paper describes the amperometric determination of lithium ions using carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions. Systematic investigations were made to optimize the experimental parameters for lithium sensor by flow injection analysis. The detection was based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and consequently the lithium ions extraction into the spinel structure. An operating potential of 0.50 V (vs. Ag/AgCl/3 KCl mol/L) was exploited for amperometric monitoring. The amperometric signal was linearly dependent on the lithium ions concentration over the range 4.0 x 10(-5) to 1.0 x 10(-3) mol L-1. The equilibrium constant of insertion/extraction of the lithium ion in the spine! structure, apparent Gibbs energy of insertion, and surface coverage of the electrode with manganese oxide, were calculated by peak charge (Q) in different concentration under flow conditions. Considering selectivity, the peak charge of the sensor was found to be linearly dependent on the ionic radius of the alkaline and earth-alkaline cations. (C) 2010 Elsevier Ltd. All rights reserved. Univ State São Paulo UNESP, Fac Sci & Technol, Dept Phys Chem & Biol, BR-19060900 Presidente Prudente, SP, Brazil Universidade Federal do Paraná (UFPR), Dept Quim, BR-80060000 Curitiba, Parana, Brazil Universidade Federal de São Carlos (UFSCar), Dept Quim, BR-13560 São Carlos, SP, Brazil Univ State São Paulo UNESP, Fac Sci & Technol, Dept Phys Chem & Biol, BR-19060900 Presidente Prudente, SP, Brazil FAPESP: 08/07298-7 FAPESP: 09/11079-1 CNPq: 474367/2004-5

In this paper, we studied the development of a selective lithium ion sensor constituted of a carbon paste electrode modified (CPEM) with an aluminum-doped spinel-type manganese oxide (Li 1.05 Al 0.02 Mn 1.98 O 4 ) for investigating the influence of a doping ion in the sensor response. Experimental parameters, such as influence of the lithium concentration in the activation of the sensor by cyclic voltammetry, pH of the carrier solution and selectivity for Li + against other alkali and alkaline-earth ions were investigated. The sensor response to lithium ions was linear in the concentration range 5.62 × 10 −5 to 1.62 × 10 −3 mol L −1 with a slope 100.1 mV/decade over a wide pH 10 (Tris buffer) and detection limit of 2.75 × 10 −5 mol L −1 , without interference of other alkali and alkaline-earth metals, demonstrating that the Al 3+ doping increases the structure stability and improves the potentiometric response and sensitivity of the sensor. The super-Nernstian response of the sensor in pH 10 can be explained by mixed potential arising from two equilibria (redox and ion-exchange) in the spinel-type manganese oxide.

The preparation and electrochemical characterization of a carbon paste electrode modified with layered birnessite-type manganese oxide for use as a sodium sensor is described. The effects of powder synthesis process (sol–gel and redox precipitation) for birnessite on the electrochemical activity of the sensor was investigated by cyclic voltammetry. The carbon paste electrode modified with birnessite-type manganese oxide that was synthesized by the sol–gel method showed a best electrochemical for sodium ions. The detection is based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and consequently the sodium ions extraction into the birnessite structure. The best voltammetric response was obtained for an electrode composition of 15% (w/w) birnessite oxide in the paste, a TRIS buffer solution of pH 8.0 and a scan rate of 50 mV s −1 . A sensitive linear voltammetric response for sodium ions was obtained in the concentration range of 7.89 × 10 −5 to 3.49 × 10 −4 mol L −1 with a slope of 37.5 μA L mmol −1 and a detection limit (3 σ /slope) of 3.43 × 10 −5 mol L −1 using cyclic voltammetry. Under the working conditions, the proposed method was successfully applied to determination of sodium ions in urine samples.

Copper(II) hexacyanoferrate(III) (CuHCF) modified carbon paste electrode was used for the electroanalytical determination of dipyrone and acetaminophen in pharmaceutical preparations by cyclic voltammetry. Several parameters were investigated for the optimization of the sensor such as composition of the electrode, electrolytic solution, effect of pH, scan rate of potential and interference. The best conditions were found for an electrode composition in mass of 20% CuHCF, 55% graphite and 25% mineral oil in acetate buffer containing 0.05 mol L -1 of NaCl. The analytical curve was linear in the dipyrone and acetaminophen concentration ranged from 1.25 x 10 -5 mol L -1 to 1.23 x 10 -3 and 2.84 x 10 -4 to 2.59 x 10 -3 mol L -1 respectively, being successfully applied to the determination of dipyrone and acetaminophen in phar- maceutical preparations. The CuHCF modified carbon paste electrode presented comparable results to those obtained us- ing iodimetry and ultraviolet spectrophotometry methods, respectively.

Made available in DSpace on 2013-09-27T14:53:53Z (GMT). No. of bitstreams: 1 WOS000275995600210.pdf: 171567 bytes, checksum: 8603747737628bbd5ef1b702ec0f6a96 (MD5) Previous issue date: 2009-01-01 Made available in DSpace on 2013-09-30T18:09:38Z (GMT). No. of bitstreams: 1 WOS000275995600210.pdf: 171567 bytes, checksum: 8603747737628bbd5ef1b702ec0f6a96 (MD5) Previous issue date: 2009-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:23:13Z No. of bitstreams: 1 WOS000275995600210.pdf: 171567 bytes, checksum: 8603747737628bbd5ef1b702ec0f6a96 (MD5) Made available in DSpace on 2014-05-20T13:23:13Z (GMT). No. of bitstreams: 1 WOS000275995600210.pdf: 171567 bytes, checksum: 8603747737628bbd5ef1b702ec0f6a96 (MD5) Previous issue date: 2009-01-01 An amperometric dipyrone sensor based on a polymeric nickel-salen (salen = N,N'-ethylenebis(salicydeneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel-salen complex at a platinum electrode in acetonitrile/tetrabuthylamonium perchlorate by cyclic voltammetry. After cycling the modified electrode in a 0.50 mol L-1 KCl solution, the estimated surface concentration was found to be equal to 1.29 x 10(-9) mol cm(-2). This is a typical behavior of an electrode surface immobilized with a redox couple that can usually be considered as a reversible single-electron reduction/oxidation of the nickel(II)/nickel(III) couple. A plot of the anodic current versus the dipyrone concentration for chronoamperometry (potential fixed = +0.50 V) at the sensor was linear in the 4.7 x 10(-6) to 1.1 x 10(-4) mol L-1 concentration range and the concentration limit was 1.2 x 10(-6) mol L-1. The proposed electrode is useful for the quality control and routine analysis of dipyrone in pharmaceutical formulations. Univ State São Paulo UNESP, Dept Phys Chem & Biol, Fac Sci & Technol, Presidente Prudente, SP, Brazil Univ State São Paulo UNESP, Dept Phys Chem & Biol, Fac Sci & Technol, Presidente Prudente, SP, Brazil

Made available in DSpace on 2013-08-28T14:10:25Z (GMT). No. of bitstreams: 1 WOS000270213300002.pdf: 658881 bytes, checksum: 1f5c5299c22dcb801bcf602d01e6372e (MD5) Made available in DSpace on 2013-09-30T18:09:28Z (GMT). No. of bitstreams: 2 WOS000270213300002.pdf: 658881 bytes, checksum: 1f5c5299c22dcb801bcf602d01e6372e (MD5) WOS000270213300002.pdf.txt: 32167 bytes, checksum: b40a80e74296d8f79f86715cebe81471 (MD5) Previous issue date: 2009-09-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:23:09Z No. of bitstreams: 2 WOS000270213300002.pdf: 658881 bytes, checksum: 1f5c5299c22dcb801bcf602d01e6372e (MD5) WOS000270213300002.pdf.txt: 32167 bytes, checksum: b40a80e74296d8f79f86715cebe81471 (MD5) Made available in DSpace on 2014-05-20T13:23:09Z (GMT). No. of bitstreams: 2 WOS000270213300002.pdf: 658881 bytes, checksum: 1f5c5299c22dcb801bcf602d01e6372e (MD5) WOS000270213300002.pdf.txt: 32167 bytes, checksum: b40a80e74296d8f79f86715cebe81471 (MD5) Previous issue date: 2009-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. A sensor based on a nanostructured hollandite-type manganese oxide was investigated for voltammetric detection of potassium ions. The detection is based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and the subsequent extraction of the potassium ions into the hollandite structure. In this work, an amperometric procedure at an operating potential of 0.80 V (versus SCE) is exploited for amperometric monitoring. The current signals are linearly proportional to potassium ion concentration in the range 4.97 x 10(-5) to 9.05 x 10(-4) mol L(-1), with a correlation coefficient of 0.9997. Univ State São Paulo, UNESP, Fac Sci & Technol, Dept Phys Chem & Biol, BR-19060900 Presidente Prudente, SP, Brazil Univ Fed Sao Carlos, Dept Quim, BR-13560 Sao Carlos, SP, Brazil Univ State São Paulo, UNESP, Fac Sci & Technol, Dept Phys Chem & Biol, BR-19060900 Presidente Prudente, SP, Brazil CNPq: 372010/2006-7

The electrochemical preparation described herein involved the electrocatalytic oxidation of sulfite on a platinum electrode modified with nanostructured copper salen (salen = N , N ′-ethylene bis (salicylideneiminato)) polymer films. The complex was prepared and electropolymerized at a platinum electrode in a 0.1 mol L −1 solution of tetrabutylammonium perchlorate in acetonitrile by cyclic voltammetry between 0 and 1.4 V vs . SCE. After cycling the modified electrode in a 0.50 mol L −1 KCl solution, the estimated surface concentration was found to be equal to 2.2 × 10 −9 mol cm −2 . This is a typical behavior of an electrode surface immobilized with a redox couple that can usually be considered as a reversible single-electron reduction/oxidation of the copper(II)/copper(III) couple. The potential peaks of the modified electrode in the electrolyte solution (aqueous) containing the different anions increase with the decrease of the ionic radius, demonstrating that the counter-ions influence the voltammetric behavior of the sensor. The potential peak was found to be linearly dependent upon the ratio [ionic charge]/[ionic radius]. The oxidation of the sulfite anion was performed at the platinum electrode at +0.9 V vs . SCE. However, a significant decrease in the overpotential (+0.45 V) was obtained while using the sensor, which minimized the effect of oxidizable interferences. A plot of the anodic current vs . the sulfite concentration for chronoamperometry (potential fixed = +0.45 V) at the sensor was linear in the 4.0 × 10 −6 to 6.9 × 10 −5 mol L −1 concentration range and the concentration limit was 1.2 × 10 −6 mol L −1 . The reaction order with respect to sulfite was determined by the slope of the logarithm of the current vs . the logarithm of the sulfite concentration.

A clean alternative method for the determination of chemical oxygen demand (COD) was developed using a copper electrode as an electrocatalytic sensor. The measuring principle is based on oxidation current of organic compounds in the wastewater. The effects of important experimental conditions, such as electrolytic solution concentration and potential scan rate, on analytical performance have been investigated. Analytical linear range of 53.0–2,801.4 mg l−1 COD with detection limit of 20.3 mg l−1 COD was achieved. The procedure was successfully applied to the COD determination in wastewater from soft industries. The results obtained using the proposed method were in good agreement with those obtained using the conventional (i.e., dichromate) COD method. In this fashion, the COD value of a sample can be determined in a simple, rapid, accurate manner, and the end products do not contain toxic metals.

A general view of the electroanalytical applications of metal‐salen complexes is discussed in this review. The family of Schiff bases derived from ethylenediamine and ortho‐phenolic aldehydes (N,N′‐ethylenebis(salicylideneiminato)—salen) and their complexes of various transition metals, such as Al, Ce, Co, Cu, Cr, Fe, Ga, Hg, Mn, Mo, Ni, and V have been used in many fields of chemical research for a wide range of applications such as catalysts for the oxygenation of organic molecules, epoxidation of alkenes, oxidation of hydrocarbons and many other catalyzed reactions; as electrocatalyst for novel sensors development; and mimicking the catalytic functions of enzymes. A brief history of the synthesis and reactivity of metal‐salen complexes will be presented. The potentialities and possibilities of metal‐Salen complexes modified electrodes in the development of electrochemical sensors as well as other types of sensors, their construction and methods of fabrication, and the potential application of ...

An oxovanadium-salen complex (N,N � -ethylene-bis(salicylideneiminato) oxovanadium) thin film deposited on a graphite–polyurethane electrode was investigated with regard to its potential use for detection of l-dopa in flow injection system. The oxovanadium(IV)/oxovanadium(V) redox couple of the modified electrode was found to mediate the l-dopa oxidation before its use in the FIA system. Experimental parameters, such as pH of the carrier solution, flow rate, sample volume injection and probable interferents were investigated. Under the optimized FIA conditions, the amperometric signal was linearly dependent on the l-dopa concentration over the range 1.0 × 10 −6 to 1.0 × 10 −4 mol L −1 (Ianodic A) = 0.01 + 0.25 [l-dopamol L −1 ]) with a detection limit (S/N = 3) of 8.0 × 10 −7 mol L −1 and a sampling frequency of 90 h −1 was achieved. For a concentration of 1.0 × 10 −5 mol L −1 l-dopa, the R.S.D. of nine consecutive measurements was 3.7%.

Made available in DSpace on 2018-12-11T16:38:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-06-25 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Abstract This paper describes the development of a selective lithium ion sensor based on spinel-type manganese oxide doped with gallium and anions (Ga0.02Mn1.98O3.98X0.02, where X = S2- and F-). Investigation was made of the influence of cationic and/or anionic doping agents on the potentiometric response of the sensor. Experimental parameters evaluated included the effect of the lithium concentration on activation of the sensor by cyclic voltammetry, the pH of the electrolyte solution, and the selectivity towards Li+ compared to other alkali and alkaline-earth metal ions. There was an important influence of the unit cell size of the material on the linear range, detection limit, and selectivity of the sensor. Reduction in the size of the tunnel for insertion of the lithium in the porous structure of the oxide directly affected the potentiometric performance of the electrode. Sensor performance increased in the order: Ga0.02Mn1.98O4 > Ga0.02Mn1.98O3.98S0.02 > Ga0.02Mn1.98O3.98F0.02. The observed super-Nernstian response could be explained by a mixed potential arising from two equilibria (redox and ion exchange) in the spinel-type manganese oxide. Sensitivity and the influence of pH on the electrode response were directly related to the doping agents present in the oxide structure. Faculty of Science and Technology, São Paulo State University (UNESP) Department of Chemistry, Federal University of Sao Carlos Faculty of Science and Technology, São Paulo State University (UNESP) FAPESP: 2005/01296-4 FAPESP: 474367/2004-5

A simple and rapid flow‐injection spectrophotometric method is reported for the determination of dipyrone in pharmaceutical formulations. The method is based on the reaction of dipyrone with ammonium molybdate in acidic medium to produce blue molybdenum, which was detected spectrophotometrically at 620 nm. The analyte was determined in a single‐line flow system. The calibration curve obtained was linear in the range of 5×10−4 to 8×10−3 mol L–1 for dipyrone concentration and the precision (s r=1.7%) was satisfactory. The method proved to be selective and adequately sensitive. Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 95.3%–101% and relative errors less than 5.0% for five pharmaceutical formulations were found.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:34Z No. of bitstreams: 1 S0100-40422005000500017.pdf: 181681 bytes, checksum: 22c1b5ef47ac6301b4e78aace8b41c89 (MD5) Made available in DSpace on 2013-08-22T18:48:34Z (GMT). No. of bitstreams: 1 S0100-40422005000500017.pdf: 181681 bytes, checksum: 22c1b5ef47ac6301b4e78aace8b41c89 (MD5) Previous issue date: 2005-10-01 Made available in DSpace on 2013-09-30T19:38:33Z (GMT). No. of bitstreams: 2 S0100-40422005000500017.pdf: 181681 bytes, checksum: 22c1b5ef47ac6301b4e78aace8b41c89 (MD5) S0100-40422005000500017.pdf.txt: 22045 bytes, checksum: 49cbc2205ffc8d4b35b4068063304409 (MD5) Previous issue date: 2005-10-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:10:20Z No. of bitstreams: 2 S0100-40422005000500017.pdf: 181681 bytes, checksum: 22c1b5ef47ac6301b4e78aace8b41c89 (MD5) S0100-40422005000500017.pdf.txt: 22045 bytes, checksum: 49cbc2205ffc8d4b35b4068063304409 (MD5) Made available in DSpace on 2014-05-20T15:10:20Z (GMT). No. of bitstreams: 2 S0100-40422005000500017.pdf: 181681 bytes, checksum: 22c1b5ef47ac6301b4e78aace8b41c89 (MD5) S0100-40422005000500017.pdf.txt: 22045 bytes, checksum: 49cbc2205ffc8d4b35b4068063304409 (MD5) Previous issue date: 2005-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The construction and analytical evaluation of a coated graphite-epoxy electrode sensitive to the zinc-1,10-phenantroline complex based on the [Zn(fen)3][tetrakis(4-chlorophenyl)borate]2 incorporated into a poly(vinylchloride) (PVC) matrix are described. A thin membrane film of this ion-pair, dibutylphthalate (DBPh) and PVC were deposited directly onto an electrically conductive graphite-epoxy support located inside a Perspex® tube. The best PVC polymeric membrane contains 65% (m/m) DBPh, 30% (m/m) PVC and 5% (m/m) of the ion-pair. This electrode shows a response of 19.5 mV dec-1 over the zinc(II) concentration range of 1.0 x 10-5 to 1.0 x 10-3 mol L-1 in 1,10-phenantroline medium, at pH 6.0. The response time was less than 20 seconds and the lifetime of this electrode was more than four months (over 1200 determinations by each polymeric membrane). It was successfully used as an indicator electrode in the potentiometric precipitation titration of zinc(II) ions. Universidade Estadual Paulista Universidade Federal de São Carlos (UFSCar) Departamento de Química Universidade de São Paulo Instituto de Química de São Carlos Departamento de Química e Física Molecular Universidade Estadual Paulista

The electrochemical behavior of a carbon paste electrode modified (CPEM) with N,N′-ethylenebis(salicylideneiminato)oxovanadium(IV) complex ([VIVO(Salen)]) was investigated as a new sensor for cysteine. Cyclic voltammetry at the modified electrode in 0.1 mol L−1 KCl solution (pH 5.0) showed a single-electron reduction/oxidation of the couple VO3+/VO2+. The CPEM with [VO(Salen)] presented good electrochemical stability in a wide pH range (4.0–10.0) and an ability to electrooxidate cysteine at 0.65 V versus SCE. These results demonstrate the viability of the use of this modified electrode as an amperometric sensor for cysteine determination.

The preparation and electrochemical characterization of a carbon paste electrode modified with N,N'-ethylenebis(salicylideneiminato)oxovanadium(IV) complex ([VO(Salen)]) as well as its behavior as electrocatalyst toward the oxidation of dipyrone were investigated. The electrochemical behavior of the modified electrode and the electrooxidation of dipyrone were explored using cyclic voltammetry. The voltammetric response of the modified electrode is based on two reactions. One electrochemical related to the oxidation of the metallic center of the [VO(Salen)] and the other involving the chemical redox process involving the oxidized form of the complex and the reduced form of dipyrone. The best voltammetric response was observed for a paste composition of 25% (m/m) [VO(Salen)], KCl solution pH from 5.5 to 8.0 as the electrolyte and potential scan rate of 10 mV s-1 in the presence of dipyrone. A linear voltammetric response for dipyrone was obtained in the concentration range from 9.9 x 10-6 to 2.8 x 10-3 mol L-1, with a detection limit of 7.2 x 10-6 mol L-1. Among of several compounds tested as potential interference, only ascorbic acid presented some interference. The proposed electrode is useful for the quality control and routine analysis of dipyrone in pharmaceutical formulations. A preparação e a caracterização eletroquímica de um eletrodo de pasta de carbono modificado com o complexo N,N´-etilenobis(salicilidenoaminato) de oxovanádio(IV) ([VO(Salen)]), como também o seu comportamento eletrocatalítico na oxidação da dipirona foi investigado. O comportamento eletroquímico do eletrodo modificado e a eletrooxidação da dipirona foram estudados usando a voltametria cíclica. A resposta voltamétrica do eletrodo modificado é baseada em duas reações. Uma relacionada com a oxidação eletroquímica do centro metálico do complexo [VO(Salen)] e a outra que envolve o processo redox entre centro metálico do complexo oxidado e a dipirona. A melhor resposta voltamétrica foi observada para uma composição do eletrodo de 25% (m/m) [VO(Salen)] em solução eletrolítica de KCl para pH entre 5,5 a 8,0 e uma velocidade de varredura de 10 mV s-1 na presença de dipirona. Uma resposta voltamétrica linear para dipirona foi obtida no intervalo de concentração de 9,9 x 10-6 a 2,8 x 10-4 mol L-1, com um limite de detecção de 7,2 x 10-6 mol L-1. Entre os diversos compostos testados como interferente, somente o ácido ascórbico apresentou alguma interferência. O eletrodo proposto é útil para o controle de qualidade e a análise rotineira de dipirona em formulações farmacêuticas.

The electroanalytical determination of isoprenaline in pharmaceutical preparations of a homemade carbon paste electrode modified with copper(II) hexacyanoferrate(III) (CuHCF) was studied by cyclic voltammetry. Several parameters were studied for the optimization of the sensor such as electrode composition, electrolytic solution, pH effect, potential scan rate and interferences in potential. The optimum conditions were found in an electrode composition (in mass) of 15% CuHCF, 60% graphite and 25% mineral oil in 0.5 mol l −1 acetate buffer solution at pH 6.0. The analytical curve for isoprenaline was linear in the concentration range from 1.96×10 −4 to 1.07×10 −3 mol l −1 with a detection limit of 8.0×10 −5 mol l −1 . The relative standard deviation was 1.2% for 1.96×10 −4 mol l −1 isoprenaline solution ( n =5). The procedure was successfully applied to the determination of isoprenaline in pharmaceutical preparations; the CuHCF modified carbon paste electrode gave comparable results to those results obtained using a UV spectrophotometric method.

The L-dopa is the immediate precursor of the neurotransmitter dopamine. Unlike dopamine, L-dopa easily enters the central nervous system and is used in the treatment of Parkinson's disease. A sensitive and selective method is presented for the voltammetric determination of L-dopa in pharmaceutical formulations using a carbon paste electrode modified with trinuclear ruthenium ammine complex [(NH(3))(5)Ru(III)ORu(IV)(NH(3))(4)ORu(III)(NH(3))(5)](6+) (Ru-red) incorporated in NaY zeolite. The parameters which influence on the electrode response (paste composition, potential scan rate, pH and interference) were also investigated. The optimum conditions were found to an electrode composition (m/m) of 25% zeolite containing 6.7% Ru, 50% graphite and 25% mineral oil in acetate buffer at pH 4.8. Voltammetric peak currents showed a linear response for L-dopa concentration in the range between 1.2x10(-4) and 1.0x10(-2)moll(-1) (r=0.9988) with a detection limit of 8.5x10(-5)moll(-1). The variation coefficient for a 1.0x10(-3)moll(-1) L-dopa (n=10) was 5.5%. The results obtained for L-dopa in pharmaceutical formulations (tablet) was in agreement with compared official method. In conclusion, this study has illustrated that the proposed electrode modified with Ru-red incorporated zeolite is suitable valuable for selective measurements of L-dopa.

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel-type manganese oxide (lambda-MnO2), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li against other alkali and alkaline-earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6 10 5 ± 1.0 10 2 mol L 1 1

The use of selective pre-concentration and differential pulse anodic stripping voltammetry (DPASV) using a carbon paste electrode modified (CPEM) with spinel-type manganese oxide has been proposed for the determination of lithium ions content in natural waters. The new procedure is based on the effective pre-concentration of lithium ions on the electrode surface containing spinel-type Mn(IV) oxide with the reduction of Mn(IV) to Mn(III) and consequently the lithium ions intercalation (insertion) into the spinel structure. The best DPASV response was reached for an electrode composition of 25% (m/m) spinel-type MnO(2) in the paste, 0.1moll(-1) tris(hydroxymethyl)aminomethane (TRIS) buffer solution of pH 8.3, scan rate of 5mVs(-1), accumulation potential of 0.3V versus saturated calomel reference electrode (SCE), pre-concentration time of 30s and potential pulse amplitude of 50mV. In these experimental conditions, the proposed methodology responds to lithium ions in the concentration range of 2.8x10(-6) to 2.0x10(-3)moll(-1) with a detection limit of 5.6x10(-7)moll(-1). The determination of the lithium ions content in different samples of natural waters samples using the proposed methodology and atomic absorption spectrophotometry are in agreement at the 95% confidence level and within an acceptable range of error.

The construction and analytical evaluation of a pH sensor based in a matrix containing 20% of [(Mg6Si8O20)](OH)4, a magnesium silicate, talc and 30% graphite dispersed in an epoxy resin (50%) is described. The data obtained from various acid–base titrations were compared with those using a glass electrode in the same conditions. The proposed electrode presented a linear response in the 1–12 pH range with a slope of � 39.9F0.3 mV/pH (at 25 jC) and ca. 15 s of response time. The lifetime of this electrode was higher than 8 months (ca. 1500 determinations) and it showed a good performance for pH determination and end-point indication in the potentiometric titrations of acids and bases.

The use of the differential pulse voltammetry for the determination of lithium ions in pharmaceutical samples using a carbon paste electrode modified with spinel-type manganese oxide has been examined. The best voltammetric response was reached for a modified electrode in borate buffer solution of pH 9.0 and submitted to a scan rate of 5 mV s(-1) and a pulse amplitude of 50 mV. This electroanalytical procedure was able to determine lithium ions in the concentration range of 8.0 x 10(-5)-1.0 x 10(-2) mol l(-1) even in the presence of several alkali metals (1.0 x 10(-3) mol l(-1)) with a detection limit of 7.1 x 10(-7) mol l(-1). Rapidity, precise and good selectivity were also found for the determination of lithium ions in pharmaceutical formulations.