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Maria Valnice Boldrin Zanoni - One of the best experts on this subject based on the ideXlab platform.

  • enhancement of voltammetric determination of quinizarine based on the adsorption at surfactant adsorbed layer in disposable electrodes
    Fuel, 2014
    Co-Authors: Magno Aparecido Gonçalves Trindade, Uendinara Bilibio, Maria Valnice Boldrin Zanoni
    Abstract:

    Abstract Screen-printed carbon electrode (SPCE) surface was easily altered through spontaneous hydrophobic interactions with cationic surfactant cetyltrimethylammonium bromide (CTAB) to form a surfactant-adsorbed-layer. This finding combined the practicality of the SPCE with the CTAB’s anti-fouling ability and preconcentration properties as a suitable alternative to determine the quinizarine in fuel samples using the square-wave voltammetric technique. Under optimized experimental conditions the Electroanalytical Method presented a linear response from 5.00 × 10 −7 to 6.00 × 10 −6  mol L −1 ( r  = 0.998) with a detection limit of 2.70 × 10 −7  mol L −1 . The Methodology was successfully applied in the dye marker quantification in diesel oil and kerosene samples, without matrix interference, with recoveries values highly satisfactory and ranged between 84.0% and 98.7%.

  • simple Electroanalytical Method for determination of guanosine in biological sample
    Analytical and Bioanalytical Electrochemistry, 2010
    Co-Authors: Daniela P Santos, Tamara Fernanda Totta Brunelli, Alex Rodrigo Bianchi, Maria Valnice Boldrin Zanoni
    Abstract:

    Institute of Chemistry University of Sao Paulo State UNESP, C.P. 355, 14801-970 Araraquara, SP

  • a simple Electroanalytical Method for the analysis of the dye solvent orange 7 in fuel ethanol
    Fuel, 2009
    Co-Authors: Daiane Cristina Romanini, Magno Aparecido Gonçalves Trindade, Maria Valnice Boldrin Zanoni
    Abstract:

    Abstract The purpose of this paper is to develop a simple, rapid and accurate Electroanalytical Method for the determination of solvent orange 7 (SO-7), commercially used as a dye marker in fuel ethanol samples. SO-7 is oxidized in a mixture of Britton–Robinson buffer with N,N- dimethylformamide (1:1, v/v) at a glassy carbon electrode and presents a well-defined peak around +0.70 V vs. Ag/AgCl, which can be monitored by linear-scan voltammetry (LSV) and square-wave voltammetry (SWV). Using optimized parameters based on the SWV technique, it is possible to get a linear relationship between the peak current and the SO-7 dye concentration from 4.0 × 10 −6 to 18.0 × 10 −6  mol L −1 ( r  = 0.995). The proposed Method was successfully applied to the direct quantification of the SO-7 dye in fuel ethanol samples, which gave good average recovery for commercial samples containing 5.0 mg L −1 and 10.0 mg L −1 of SO-7 dye, respectively.

  • a square wave voltammetric Method for analysing the colour marker quinizarine in petrol and diesel fuels
    Dyes and Pigments, 2007
    Co-Authors: Magno Aparecido Gonçalves Trindade, Valdir Souza Ferreira, Maria Valnice Boldrin Zanoni
    Abstract:

    Abstract This work presents an Electroanalytical Method based on square-wave voltammetry (SWV) for the determination of quinizarine (QNZ) in a mixture of Britton–Robinson buffer 0.08 mol L−1 with 30% of acetonitrile. The QNZ was oxidized at glassy carbon electrode in and the well-defined peak at +0.45 V vs. Ag/AgCl can be used for its determination as colour marker in fuel samples. All parameters were optimized and analytical curves can be constructed for QNZ concentrations ranging from 2.0 × 10−6 mol L−1 to 1.4 × 10−5 mol L−1, using f = 60 Hz and Esw = 25 mV. The Method offers a limit detection of 4.12 × 10−7 mol L−1 and a standard deviation of 4.5% when six measurements of 1.25 × 10−5 mol L−1 are compared. The Method was successfully applied for determining QNZ in gasoline and diesel oil and the obtained results showed good agreement with those reported previously.

  • anodic stripping voltammetric determination of aurothiomalate in urine using a screen printed carbon electrode
    Electroanalysis, 2006
    Co-Authors: Marcio F Bergamini, Maria Valnice Boldrin Zanoni
    Abstract:

    This work describes an Electroanalytical Method for determining gold(I) thiomalate, aurothiomalate, widely used for treatment of reumatoid arthiritis, using a screen-printed carbon electrode (SPCE). Aurothiomalate (AuTM) was determined indirectly at the same electrode by accumulating it first at −1.5 V vs. printed carbon. At this potential in the adsorbed state, the AuTM is reduced to Au(0), which is then oxidized at two steps at −0.22 V and +0.54 V on SPCE. Using optimized conditions of 60 s deposition time, −1.5 V (vs. printed carbon) accumulation potential, 100 mV s−1 scan rate, linear calibration graphs can be obtained by monitoring the peak at +0.54 V for AuTM in HCl 0.1 mol L−1 from 1.43×10−6 to 1.55×10−4 mol L−1. A limit of detection obtained was 6.50×10−7 mol L−1, and the relative standard deviation from five measurements of 3.0×10−5 mol L−1 AuTM is 4.5%. The Method was successfully applied for AuTM determination in human urine sample.

Miquel Esteba - One of the best experts on this subject based on the ideXlab platform.

  • study of the hg2 binding with chelation therapy agents by differential pulse voltammetry on rotating au disk electrode and electrospray ionization mass spectrometry
    Analytica Chimica Acta, 2009
    Co-Authors: Elena Chekmeneva, Jose Manuel Diazcruz, Cristina Arino, Miquel Esteba
    Abstract:

    Abstract A recently proposed Electroanalytical Method, using differential pulse voltammetry (DPV) on the rotating Au-disk electrode, and electrospray ionization mass-spectrometry (ESI-MS) has been applied to study the binding of the pharmaceutical chelating agents meso-2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercaptopropanesulfate (DMPS) and d -penicillamine ( d -Pen) with Hg2+. From the use of voltammetric titrations it was possible to obtain a detailed picture of the complexation processes at concentrations much lower than in previous studies. Predominant species were Hg(Pen)2, Hg2(DMSA)2 and Hg(DMPS)2. For Pen, Hg(Pen) was also deduced from DPV data, while Hg2(Pen)4 from ESI-MS. For DMSA and DMPS, Hg2L species were detected by DPV, and Hg2L3, Hg3L3 as well as Hg2(DMPS)2 and Hg(DMSA)2 by ESI-MS. When possible, DPV data were analyzed by multivariate curve resolution with alternating least squares (MCR–ALS).

  • binding of hg2 with phytochelatins study by differential pulse voltammetry on rotating au disk electrode electrospray ionization mass spectrometry and isothermal titration calorimetry
    Environmental Science & Technology, 2009
    Co-Authors: Elena Chekmeneva, Jose Manuel Diazcruz, Cristina Arino, Miquel Esteba
    Abstract:

    The binding of Hg2+ with synthetic phytochelatins ((γ-Glu-Cys)n-Gly, PCn, n = 2, 3, 4) was investigated by a recently proposed Electroanalytical Method, using differential pulse voltammetry on the rotating Au-disk electrode, Electrospray ionization mass-spectrometry (ESI-MS) and isothermal titration calorimetry (ITC). ESI-MS experiments provided the exact stoichiometries of the complexes formed at different PCn/Hg2+ ratios. Voltammetry provided more detailed information on the complexation processes through the use of multivariate curve resolution by alternating least squares of the data matrix obtained from titrations with fine increments of metal or ligand. The system Hg2+-GSH-PC2 was investigated by voltammetry in order to obtain an estimation of the Hg2+ behavior in the presence of two related ligands. The additional assessment of the stability of Hg2+-PCn complexes was achieved through ITC by using the therapeutic chelator sodium 2,3-dimercaptopropanesulfate (DMPS) over Hg2+-PCn systems. The stabilit...

Orlando Fatibellofilho - One of the best experts on this subject based on the ideXlab platform.

  • selective and simultaneous determination of indigo carmine and allura red in candy samples at the nano concentration range by flow injection analysis with multiple pulse amperometric detection
    Food Chemistry, 2018
    Co-Authors: Patricia B Deroco, Roberta Antigo Medeiros, Romeu C Rochafilho, Orlando Fatibellofilho
    Abstract:

    Abstract A novel, unique Electroanalytical Method was developed for the simultaneous quantification of the dyes indigo carmine (IC) and allura red (AR) in candies by coupling flow injection analysis and multiple pulse amperometry with a cathodically pretreated boron-doped diamond electrode, using 0.30 mol L−1 H2SO4 as supporting electrolyte. A dual-potential waveform was employed, causing the electrooxidation of either IC solely or IC and AR simultaneously. Thence, subtraction of current signals was used to quantify IC and AR in the concentration ranges of 70.0–1000 nmol L−1 and 40.0–770 nmol L−1, with limits of detection of 40.0 nmol L−1 and 7.0 nmol L−1, respectively. The proposed Method, which permits up to 153 determinations per hour with good precision, was successfully applied in the quantification of these dyes in samples of commercial candies; their obtained contents were similar (at a 95% confidence level) to those from a comparative HPLC Method.

  • a new and simple Method for the simultaneous determination of amoxicillin and nimesulide using carbon black within a dihexadecylphosphate film as electrochemical sensor
    Talanta, 2018
    Co-Authors: Patricia B Deroco, Romeu C Rochafilho, Orlando Fatibellofilho
    Abstract:

    Abstract The first Electroanalytical Method for the simultaneous determination of an important antibiotic (amoxicillin – AMX) and an anti-inflammatory drug (nimesulide –NIM), widely used in combination, is here proposed. In this Method, a glassy carbon (GC) substrate modified with carbon black (CB) immobilized within a dihexadecylphosphate (DHP) film is used as electrochemical sensor (CB–DHP/GC). The electrochemical activity of this sensor was assessed (comparatively to that of GC) by electrochemical impedance spectroscopy, using the [Fe(CN)6]3–/4– redox couple, when two different active electron transfer regions were clearly characterized. Using square-wave voltammetry and a 0.2 mol L−1 phosphate buffer (pH 7.0) as supporting electrolyte, a separation of ca. 180 mV between the oxidation peak potentials of AMX and NIM was obtained with the novel CB–DHP/GC sensor, and the obtained detection limits for AMX and NIM were 0.12 μmol L−1 and 0.016 μmol L−1, respectively. This new Electroanalytical Method was successfully applied in the simultaneous determination of AMX and NIM in biological urine and environmental samples. The here-proposed Method is of great analytical interest, as it is faster and cheaper than the only other Method (based on HPLC) reported in the literature for the simultaneous determination of these drugs.

  • simultaneous voltammetric determination of aspartame and acesulfame k in food products using an anodically pretreated boron doped diamond electrode
    Analytical Methods, 2015
    Co-Authors: Patricia B Deroco, Roberta Antigo Medeiros, Romeu C Rochafilho, Orlando Fatibellofilho
    Abstract:

    A simple, rapid, and low-cost Electroanalytical Method is reported for the simultaneous determination of aspartame (AS) and acesulfame-K (AK) in food products. This Method involves coupling differential pulse voltammetry (DPV) with an anodically pretreated boron-doped diamond (AP-BDD) electrode and 0.30 mol L−1 H2SO4 as the supporting electrolyte. A separation of the oxidation peak potentials of AS and AK greater than 500 mV was attained and the detection limits obtained for their simultaneous determination were 1.60 μmol L−1 (for AS) and 280 μmol L−1 (for AK). The proposed DPV Method was successfully applied in the simultaneous determination of the sweeteners in three types of commercial food products; in the case of AS, the obtained results are similar at 95% confidence level to those obtained using a reference HPLC Method. The proposed Method is of great analytical interest, as it yields detection limits that are lower than those attained by the only other Electroanalytical Method proposed in the literature.

Elena Chekmeneva - One of the best experts on this subject based on the ideXlab platform.

Lei Zhang - One of the best experts on this subject based on the ideXlab platform.

  • one step fabrication of a multifunctional magnetic nickel ferrite multi walled carbon nanotubes nanohybrid modified electrode for the determination of benomyl in food
    Journal of Agricultural and Food Chemistry, 2015
    Co-Authors: Qiong Wang, Jichun Yang, Yuanyuan Dong, Lei Zhang
    Abstract:

    Benomyl, as one kind of agricultural pesticide, has adverse impact on human health and the environment. It is urgent to develop effective and rapid Methods for quantitative determination of benomyl. A simple and sensitive Electroanalytical Method for determination of benomyl using a magnetic nickel ferrite (NiFe2O4)/multi-walled carbon nanotubes (MWCNTs) nanohybrid-modified glassy carbon electrode (GCE) was presented. The electrocatalytic properties and electroanalysis of benomyl on the modified electrode were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In the phosphate-buffered saline (PBS) of pH 6.0, this constructed biosensor exhibited two linear relationships with the benomyl concentration range from 1.00 × 10–7 to 5.00 × 10–7 mol/L and from 5.00 × 10–7 to 1.00 × 10–5 mol/L, respectively. The detection limit was 2.51 × 10–8 mol/L (S/N = 3). Moreover, the proposed Method was successfully applied to determine benomyl in real samples with satisfactory results. The Ni...

  • electrochemical determination of estrogenic compound bisphenol f in food packaging using carboxyl functionalized multi walled carbon nanotubes modified glassy carbon electrode
    Food Chemistry, 2014
    Co-Authors: Xin Wang, Lijun Yang, Lei Zhang
    Abstract:

    Abstract A simple and highly sensitive Electroanalytical Method for the determination of bisphenol F (BPF) was developed, which was carried out on multi-walled carbon nanotubes-COOH (MWCNT-COOH) modified glassy carbon electrode (GCE) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed that MWCNT-COOH remarkably enhanced the oxidation of BPF, which improved the anodic peak current of BPF significantly. The mechanism was oxidation of BPF lose electrons on the electrode surface via adsorption-controlled process, electrode reaction is the two electrons/two protons process. Under the optimised conditions, the oxidation peak current was proportional to BPF concentration the range from 0.12 to 6.01 μg mL −1 . The detection limit was 0.11 μg mL −1 ( S / N  = 3), and the relative standard deviation (R.S.D.) was 3.5% ( n  = 9). Moreover, the MWCNT-COOH/GCE electrode showed good reproducibility, stability and anti-interference. Therefore, the proposed Method was successfully applied to determine BPF in food packing and the results were satisfactory.