Romeu C. Rocha-Filho

Universidade Federal de São Carlos, São Carlos do Pinhal, São Paulo, Brazil

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Publications (116)287.98 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: For the first time, the electrical and morphological properties of self-organized TiO2 nanotubular samples annealed (for only 2 min) in a microwave oven through hybrid thermal heating (MO–TiO2) are assessed comparatively to those of samples conventionally annealed (for 30 min) in a muffle furnace (MF–TiO2). This comparative assessment was carried out through scanning electron micrographs, cyclic voltammetry and photocurrent density curves, as well as determinations of band-gap energy, donor density, and flat-band potential values. No differences in bang-gap energy and morphology were observed; MO–TiO2 presented a small improvement in the donor density value, which, however, did not lead to higher photocurrent densities in comparison to MF–TiO2. Hence, considering that the morphological and electrical properties of the differently annealed TiO2 nanotubular samples are similar, clearly microwave annealing is an advantageous option to convert amorphous TiO2 nanotubes into the crystalline anatase phase, especially because this procedure is very rapid and facile.
    No preview · Article · Mar 2016
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    ABSTRACT: Sensitive, simple, low-cost, and rapid amperometric flow-injection methods were developed for determination of ivermectin (IVM) and levamisole (LVM) in anthelmintic pharmaceutical drugs and urine samples. These determinations were carried out with a cathodically (for IVM) or anodically (for LVM) pretreated boron-doped diamond electrode using aqueous 0.5 mol L-1 H2SO4 (with and without addition of 30% V/V of ethanol) as supporting electrolyte. The amperometric detection was performed at an applied electrode potential of E = 1.40 V, for IVM, and E = 1.90 V, for LVM, vs. Ag/AgCl (3.0 mol L-1 KCl). The respective analytical curves presented good linearity in the investigated concentration ranges (0.60-50 μmol L-1, for IVM, and 0.010-5.0 μmol L-1, for LVM) and the detection limits were 0.30 μmol L-1 for IVM, and 1 nmol L-1, for LVM. Investigation of possible interferents showed no significant interference with the here-proposed methods; thus, they were used to determine IVM and LVM in pharmaceutical formulations as well as in urine samples, with results that showed good agreement with comparative methods. Furthermore, a mechanism for LVM electrooxidation was proposed using exhaustive potentiostatic electrolysis and NMR measurements.
    Full-text · Article · Jan 2016 · Sensors and Actuators B Chemical
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    ABSTRACT: Simple, fast, and inexpensive electroanalytical procedures were developed for the determination of codeine (COD) solely and paracetamol (PCT) and COD simultaneously in pharmaceutical formulations and human body fluids. The methods involve the combination of square-wave voltammetry (SWV) with a cathodically pretreated boron-doped diamond electrode and a 0.2 mol L-1 acetate buffer (pH 4.0) solution as the supporting electrolyte. Significantly low limits of detection were obtained for COD solely or PCT and COD simultaneously: 1.19 or 18 and 14 nmol L-1 , respectively. The proposed SWV method was successfully applied in the simultaneous determination of PCT and COD in four samples of pharmaceutical tablets, with results similar (at 98% confidence level) to those obtained using a reference high-performance liquid chromatography (HPLC) method. Additionally, adequate results were obtained when concentrations of PCT and COD were determined in human urine or serum samples by addition-recovery. Clearly, the proposed method is an excellent option for the determination of COD solely or PCT and COD simultaneously.
    Full-text · Article · Oct 2015 · Journal of the Brazilian Chemical Society
  • Ricardo F. Brocenschi · Romeu C. Rocha-Filho · Nerilso Bocchi · Sonia R. Biaggio
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    ABSTRACT: Estrone (E1), an endocrine-disrupting chemical (EDC) with health and environmental consequences, is commonly found in wastewater worldwide; thus, effective ways to degrade this EDC are welcome. For the first time, a one-compartment filter-press reactor with a boron-doped diamond (BDD) anode is used in the electrochemical degradation of E1. The effect of the following variables on E1 degradation (monitored through LC/UV–vis) is investigated: flow rate (qV), current density (j), concentration [E1], pH, and absence or presence of Cl– ions in solution. The best degradation performance was attained under the following conditions, with total degradation of E1 (initial concentration, [E1]0 = 500 μg L−1, in 0.1 mol L−1 Na2SO4; 0.5 L) in about 25 min: qV = 2.0 L min−1 (kapp = 2.1 × 10−3 s−1), j = 10 mA cm−2, and pH ≤ 7. The addition of Cl– ions (0.36 mmol L−1) to the E1 solution significantly enhances the rate of E1 degradation (independently of pH), to such an extent that only 10 min were needed to attain total degradation of E1. On the other hand, in the absence of Cl– ions in solution and at j = 10 mA cm−2, the decay of the relative concentration of E1 ([E1]rel) does not depend on [E1]0, as would be expected for processes limited by mass transport; this means that OH radicals are present in excess. Under optimized conditions, the performance attained with the BDD anode was compared with that with a β-PbO2 anode; then, the higher oxidation power of the BDD anode became evident through its significantly better performance: a decay of [E1]rel of about 98 % was attained in just 30 min, compared to only 35 % for the β-PbO2 anode after 60 min of electrolysis.
    No preview · Article · Oct 2015
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    ABSTRACT: Sensitive and simple electroanalytical methods were developed for the determination of the loop diuretic furosemide (FUR) in pharmaceutical formulations and synthetic urine samples by coupling square-wave voltammetry (SWV) with polished basal-plane pyrolytic graphite (BPPG) or cathodically pretreated boron-doped diamond (BDD) and amorphous carbon nitride (a-CNx) as working electrodes. The analytical parameters obtained with the three methods were compared. With BPPG, best results were attained using 0.10molL-1 H2SO4 as supporting electrolyte, whereas with BDD and a-CNx, this was attained using a 0.040molL-1 BR buffer (pH 4.5). Cyclic voltammograms obtained for FUR evidenced an irreversible behavior (with two oxidation peaks), in agreement with the literature. On the BDD and a-CNx electrodes, the electrooxidation of FUR is a purely diffusion-controlled process, whereas on the BPPG electrode some degree of adsorption is also involved. The obtained linear response ranges (detection limits) for the BPPG, BDD, and a-CNx electrodes were 0.60-4.8 (0.47), 0.30-13 (0.30), and 0.50-99 (0.39) μmolL-1, respectively. The proposed methods were successfully applied in the determination of FUR in pharmaceutical formulations (tablets), with results similar to those obtained using a reference spectrophotometric method (at a confidence level of 95 %), and in the recovery of FUR in synthetic urine samples. The analytical conditions obtained with the novel SWV methods here reported are comparatively better than those for other electrochemical methods in the literature. As the pretreatment procedures are much simpler for BDD and a-CNx than for BPPG, one can conclude that the former two materials can be advantageously used to determine FUR with good sensitivity and selectivity.
    Full-text · Article · Oct 2015
  • Gabriel F. Pereira · Romeu C. Rocha-Filho · Nerilso Bocchi · Sonia R. Biaggio
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    ABSTRACT: Galvanostatic electrolyses are performed in a filter-press reactor to investigate the electrochemical degradation of picloram (100 mg L−1, from a commercial herbicide formulation) using a boron-doped diamond (BDD) or β-PbO2 anode. The effect of pH (3, 6, or 10), applied current density (japl = 10, 30, or 50 mA cm−2), and absence or presence of Cl- ions (25 mM) in the supporting electrolyte (aqueous 0.10 M Na2SO4) is investigated, while the picloram concentration, solution chemical oxygen demand (COD) and total organic carbon content (TOC), and energy consumption are monitored as a function of electrolysis time. From the obtained results, it is clear that the electrochemical degradation of picloram is possible using either of the anodes, but with different overall performances. In general, the presence of Cl- ions in the supporting electrolyte (leading to electrogenerated active chlorine) has a positive effect on the performance of both anodes, except for TOC abatement using the BDD anode; the best electrodegradation performances are attained at pH values around 6, when HClO is the predominant active-chlorine species. Faster rates of initial electrodegradation of picloram and of solution TOC abatement are obtained as japl is increased, but, as expected, lower energy consumptions are always attained at the lowest value of japl. The performances of the two anodes are virtually the same in the initial degradation of picloram; however, the BDD anode greatly surpasses the β-PbO2 anode in the abatement of solution COD or TOC. This confirms the importance of the oxidation power of the anode, even when indirect oxidation by active chlorine plays a concomitant role.
    No preview · Article · May 2015 · Electrochimica Acta
  • Gustavo Stoppa Garbellini · Romeu Cardozo Rocha-Filho · Orlando Fatibello-Filho
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    ABSTRACT: Voltammetric methods for the determination of the fluoroquinolone ciprofloxacin (CIP) were developed using a cathodically pretreated boron-doped diamond (BDD) electrode coupled with square-wave voltammetry (SWV) and differential pulse voltammetry (DPV). In cyclic voltammetric measurements, the CIP electrooxidation was an irreversible process controlled by diffusion of the analyte to the electrode surface. Analytical curves were obtained for CIP concentrations from 2.50 to 50.0 µmol L–1, for SWV, and from 0.500 to 60.0 µmol L–1, for DPV, with detection limits of 2.46 and 0.440 µmol L–1, respectively. On the other hand, adequate recovery values were obtained for the determination of CIP in synthetic urine samples by DPV. On the other hand, SWV was employed to evaluate the interaction between CIP and double-stranded dsDNA (calf thymus in aqueous solution). From the obtained results, we inferred that CIP binds to dsDNA by intercalation, with a binding constant calculated as 5.91 × 105 L mol–1. Thus, the cathodically pre-treated BDD electrode was successfully used for the determination of CIP in biological samples and for studies on the interaction of that fluoroquinolone with dsDNA.
    No preview · Article · Mar 2015 · Analytical methods
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    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 supporting electrolyte. Thus, a separation of about 500 mV of the oxidation peak potentials of AS and AK 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 these 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.
    Full-text · Article · Jan 2015 · Analytical methods
  • Gustavo Stoppa Garbellini · Romeu C. Rocha-Filho

    No preview · Article · Jan 2015
  • João Pedro Silva · Sonia R. Biaggio · Nerilso Bocchi · Romeu C. Rocha-Filho
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    ABSTRACT: The spinel LiMn2O4 was obtained by a microwave-assisted solid-state reaction between LiOH·H2O and ε-MnO2 in a practical setup using a domestic microwave oven. XRD analyses showed that the spinel LiMn2O4 was obtained as a single phase after only 3 min of microwave heating. SEM micrographs revealed particles having a prismatic morphology and sizes in the 0.5–1.5 μm range. The characteristic voltammetric profile of the spinel LiMn2O4 was obtained for the synthesized material, while its charge − discharge tests presented good electrochemical stability and a significant initial specific capacity (95 mA h g− 1) at a high discharge rate (C/1). These results indicate that a rapid and facile microwave-assisted synthesis can yield the spinel LiMn2O4 with adequate properties to be used as a cathode material in lithium-ion batteries.
    No preview · Article · Dec 2014 · Solid State Ionics
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    ABSTRACT: The electrodegradation of the Acid Yellow 49 dye (100 mg L-1 in 0.1 mol L-1 Na2SO4) was investigated using boron-doped diamond (BDD), Ti-Pt/beta-PbO2, and Ti/RuO2-TiO2 (DSA (R)) anodes. Galvanostatic electrolyses (5, 15 or 30 mA cm(-2)) were carried out in an electrochemical flow system, with a filter-press reactor. Best performances were attained with the BDD anode and worst with the DSA (R) anode. The dye solution was adequately decolorized using an electrical charge per unit volume of dye solution (Q(apl)) slightly higher than 0.60 A h L-1, applied with the BDD anode at a current density of only 5 mA cm-2. At this current density, COD and TOC abatements of 37% and 20% were attained with Q(apl) values of only 0.60 and 1.20 A h L-1, respectively; this indicates the feasibility of abating the organic load of the dye solution by simply increasing the value of Q(apl).
    Full-text · Article · Nov 2014 · International journal of electrochemical science
  • Carla Dalmolin · Sonia R. Biaggio · Nerilso Bocchi · Romeu C. Rocha-Filho
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    ABSTRACT: The room-temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate, BMIM BF4, was employed as electrolyte in the electrosynthesis of thin polypyrrole (PPy) films on a Pt substrate, and the resulting PPy electrodes were electrochemically characterized. Electrochemical impedance spectroscopy (EIS) was used to comparatively investigate the electric behavior of PPy produced in the RTIL and the one produced in a traditional acetonitrile/lithium salt system, and charge–discharge curves in the range 2.0–4.0 V (vs. Li/Li+) were obtained in a 1.0 M LiBF4 propylene carbonate solution. Although a reduction of the specific capacity for the PPy obtained in the RTIL was observed, compared to that of the PPy film synthesized in the acetonitrilic electrolyte, its chronopotentiometric profile presented a plateau in the 2.7 V region. This is a remarkable result, considering that a linear decrease in this profile is usually observed for the majority of conducting polymer cathodes. PPy films obtained in BMIM BF4 presented globular morphology, with a special arrangement of nanoparticles constituting the globules; the EIS results indicated that this nanoscale structure may be contributing to a better definition of the redox characteristics during the PPy charge–discharge processes, as it happens for the well-organized structure of some metal oxides.
    No preview · Article · Sep 2014 · Materials Chemistry and Physics
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    ABSTRACT: The electrochemical degradation of a real textile effluent was carried out using Ti–Pt/β-PbO2 and Ti/Ti0.7Ru0.3O2 (DSA®) anodes in a filter-press flow cell, in the presence and absence of chloride ions, varying the pH (3, 7, 11) and temperature (25 °C and 45 °C) of the effluent, and monitoring the removal of its turbidity and chemical oxygen demand (COD). The best experimental conditions for turbidity and COD removal were attained in neutral and basic conditions, independently of temperature. Higher COD removal values were attained with the Ti–Pt/β-PbO2 anode, as a consequence of its higher oxidation power; the electric charge applied per unit volume of effluent significantly decreased in the presence of chloride ions, when instantaneous current efficiencies as high as 0.5 were attained in the initial electrooxidation stages. Under these conditions, the electric energy consumption necessary to oxidize the real textile effluent was as low as 50 kW h m−3. The use of chloride ions enabled higher COD removal efficiencies using the Ti–Pt/β-PbO2 and DSA® anodes than a purely mass-transport controlled process due to indirect oxidation processes mediated by the active chloro species.
    No preview · Article · Sep 2014 · The Chemical Engineering Journal
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    ABSTRACT: The growth of oxides on the surfaces of pure Ti and two of its ternary alloys, Ti-6Al-4V and Ti-6Al-7Nb, by micro-arc oxidation (MAO) in a pH 5 phosphate buffer was investigated. The primary aim was to form thick, porous, and aluminum-free oxide layers, because these characteristics favor bonding between bone and metal when the latter is implanted in the human body. On Ti, Ti-6Al-4 V, and Ti-6Al-7Nb, the oxides exhibited breakdown potentials of about 200 V, 130 V, and 140 V, respectively, indicating that the oxide formed on the pure metal is the most stable. The use of the MAO procedure led to the formation of highly porous oxides, with a uniform distribution of pores; the pores varied in size, depending on the anodizing applied voltage and time. Irrespective of the material being anodized, Raman analyses allowed us to determine that the oxide films consisted mainly of the anatase phase of TiO2, and XPS results indicated that this oxide is free of Al and any other alloying element.
    No preview · Article · Aug 2014 · Materials Science and Engineering C
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    Ricardo F. Brocenschi · Romeu C. Rocha-Filho · Boris Duran · Greg M. Swain
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    ABSTRACT: We report on the use of flow injection analysis with amperometric detection (FIA-EC) to evaluate the potential of using diamond electrodes for the analysis of three estrogenic compounds: estrone, 17-β-estradiol, and estriol. Amperometric detection was performed using a cathodically pretreated boron-doped diamond electrode that offered low background current, relatively low limits of detection, and good response reproducibility and stability. For all three compounds, response linearity was observed over the concentration range tested, 0.10 to 3.0μmolL(-1), the sensitivity was ca. 10mALmol(-1), and the minimum concentration detection (S/N≥3) was 0.10μmolL(-1) (~27μgL(-1)). The response variability with multiple injections was ca. 10% (RSD) over 20 injections. For estrone, the oxidation reaction on diamond does not proceed through an adsorbed state like it does on glassy carbon. After an initial current attenuation, the diamond electrode exhibited a stable response (oxidation current) for 3 days of continuous use, indicative of minimal surface contamination or fouling by reaction intermediates and products. The method for estrone was assessed using spiked city tap and local river water. Estrone recoveries in spiked city and river water samples presented standard deviations of less than 10%. In summary, the FIA-EC method with a diamond electrode enables sensitive, reproducible, stable, quick, and inexpensive determination of estrogenic compounds in water samples.
    Full-text · Article · Aug 2014 · Talanta
  • José M. Aquino · Romeu C. Rocha-Filho · Nerilso Bocchi · Sonia R. Biaggio
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    ABSTRACT: Hybrid thermal heating induced by a microwave oven was unprecedentedly used to successfully attain rapid and facile crystallization into the anatase phase of amorphous TiO2 nanotubes grown on a Ti substrate. Amorphous TiO2 nanotubes were obtained by anodic oxidation of a Ti foil either in aqueous or organic medium. Afterward, these TiO2 nanotubes were thermally treated by hybrid heating in a common commercial microwave oven. The as-grown amorphous nanotubes were characterized by SEM and XRD, whereas the evolution of the nanotubes crystallization with thermal treatment time was followed by XRD. The crystallization into the anatase phase of the amorphous TiO2 nanotubes occurred after only 2 or 3 min of hybrid thermal treatment, which is very short and convenient as compared with several hours that are needed when conventional thermal treatment is used.
    No preview · Article · Jul 2014 · Materials Letters
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    ABSTRACT: A square-wave voltammetry method for the determination of hydroxychloroquine (HCQ) in pharmaceutical and synthetic urine samples with a cathodically pretreated (CPT) boron-doped diamond (BDD) electrode was successfully developed. Using cyclic voltammetry, the HCQ oxidation was shown to be a one-electron diffusion-controlled process. The obtained SWVanalytical curve (I-pa/mu a = 0.033 + 1.24 [HCQ/mu mol L-1)]) for HCQ determination (using 0.1 mol L-1 H2SO4 as supporting electrolyte) presented a linear response from 0.1 to 1.9 mu mol L-1, with a detection limit of 0.06 mu mol L-1, the best value attained yet with an unmodified electrode. The proposed method was successfully applied in the determination of HCQ in pharmaceutical (tablets) samples, with results similar at a 95% confidence level to those obtained using a reference spectrophotometric method. Additionally, adequate recovery results were obtained for the determination of HCQ in doped synthetic urine samples. The novel proposed method is inexpensive and fast, with no need of sample pretreatment. (c) 2014 Elsevier B.V. All rights reserved.
    Full-text · Article · Apr 2014 · Journal of electroanalytical chemistry
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    ABSTRACT: Oxidation of anthraquinonic dye Acid Blue 62 by electrolysis with conductive-diamond electrodes is studied in this work. COD, TOC, and color have been selected to monitor the degradation of the molecule as a function of several operating inputs (current density, pH, temperature, and NaCl concentration). Results show that the electrochemical oxidation of this model of large molecules follows a first order kinetics in all the conditions assessed, and it does not depend on the pH and temperature. The occurrence of chloride ions in wastewaters increases the rate of color and COD removal as a consequence of the mediated oxidation promoted by the chlorinated oxidizing species. However, chloride occurrence does not have an influence on the mineralization rate. First-order kinetic-constants for color depletion (attack to chromophores groups), oxidation (COD removal), and mineralization (TOC removal) were found to depend on the current density and to increase significantly with its value. A single model was proposed to explain these changes in terms of the mediated oxidation processes. Rate of mineralization remained very close to that expected for a purely mass transfer-controlled process. This was explained assuming that mediated oxidation does not have a significant influence on the mineralization in spite it has some effect on intermediate oxidation stages. The efficiency of the oxidation was found to depend mainly on the concentration of COD being negligible the effect of the other inputs assessed except for the occurrence of chloride ions. Opposite, the efficiency of mineralization depends on concentration of TOC and current density and it did not depend on the chloride occurrence. This observation was found to have an important influence on the power required to remove a given percentage of the initial TOC or COD. To decrease COD efficiently, the occurrence of chloride in the solution is very important, while to remove TOC efficiently, it is more important to work at low current densities and chloride effect is negligible. Energy consumption could be decreased by folds using the proper conditions.
    No preview · Article · Mar 2014 · Environmental Science and Pollution Research
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    ABSTRACT: The Direct Black 22 dye was electrooxidized at 30 mA cm(-2) in a flow cell using a BDD or beta-PbO2 anode, varying pH (3, 7, 11), temperature (10, 25, 45 degrees C), and [NaCl] (0 or 1.5 g L-1). In the presence of NaCl, decolorization rates were similar for all conditions investigated, but much higher than predicted through a theoretical model assuming mass-transport control; similar behavior was observed for COD removal (at pH 7, 25 degrees C), independently of the anode. With no NaCl, COD removals were also higher than predicted with a theoretical model, which suggests the existence of distinct dye degradation pathways.
    Preview · Article · Jan 2014 · Química Nova
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    ABSTRACT: Boron-doped diamond (BDD) films are excellent electrode materials, whose electrochemical activity for some analytes can be tuned by controlling their surface termination, most commonly either to predominantly hydrogen or oxygen. This tuning can be accomplished by e.g. suitable cathodic or anodic electrochemical pretreatments. Recently, it has been shown that amorphous carbon nitride (a-CNx) films may present electrochemical characteristics similar to those of BDD, including the influence of surface termination on their electrochemical activity toward some analytes. In this work, we report for the first time a complete electroanalytical method using an a-CNx electrode. Thus, an a-CNx film deposited on a stainless steel foil by DC magnetron sputtering is proposed as an alternative electrode for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) in synthetic biological samples by square-wave voltammetry. The obtained results are compared with those attained using a BDD electrode. For both electrodes, a same anodic pretreatment in 0.1molL(-1) KOH was necessary to attain an adequate and equivalent separation of the DA and AA oxidation potential peaks of about 330mV. The detection limits obtained for the simultaneous determination of these analytes using the a-CNx electrode were 0.0656μmolL(-1) for DA and 1.05μmolL(-1) for AA, whereas with the BDD electrode these values were 0.283μmolL(-1) and 0.968μmolL(-1), respectively. Furthermore, the results obtained in the analysis of the analytes in synthetic biological samples were satisfactory, attesting the potential application of the a-CNx electrode in electroanalysis.
    Full-text · Article · Oct 2013 · Analytica chimica acta

Publication Stats

2k Citations
287.98 Total Impact Points

Institutions

  • 1987-2016
    • Universidade Federal de São Carlos
      • • Departamento de Química (DQ)
      • • Centro de Ciências Exatas e de Tecnologia (CCET)
      São Carlos do Pinhal, São Paulo, Brazil
  • 2005
    • The Electrochemical Society
      Society Hill, New Jersey, United States