Thiago M.B.F. Oliveira
Federal University of Ceará
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Featured researches published by Thiago M.B.F. Oliveira.
Talanta | 2013
Thiago M.B.F. Oliveira; M. Fátima Barroso; Simone Morais; Pedro de Lima-Neto; Adriana N. Correia; Maria Beatriz P.P. Oliveira; Cristina Delerue-Matos
This study focused on the development of a sensitive enzymatic biosensor for the determination of pirimicarb pesticide based on the immobilization of laccase on composite carbon paste electrodes. Multi-walled carbon nanotubes (MWCNTs) paste electrode modified by dispersion of laccase (3%, w/w) within the optimum composite matrix (60:40%, w/w, MWCNTs and paraffin binder) showed the best performance, with excellent electron transfer kinetic and catalytic effects related to the redox process of the substrate 4-aminophenol. No metal or anti-interference membrane was added. Based on the inhibition of laccase activity, pirimicarb can be determined in the range 9.90 × 10(-7) to 1.15 × 10(-5) mol L(-1) using 4-aminophenol as substrate at the optimum pH of 5.0, with acceptable repeatability and reproducibility (relative standard deviations lower than 5%). The limit of detection obtained was 1.8 × 10(-7) mol L(-1) (0.04 mg kg(-1) on a fresh weight vegetable basis). The high activity and catalytic properties of the laccase-based biosensor are retained during ca. one month. The optimized electroanalytical protocol coupled to the QuEChERS methodology were applied to tomato and lettuce samples spiked at three levels; recoveries ranging from 91.0 ± 0.1% to 101.0 ± 0.3% were attained. No significant effects in the pirimicarb electroanalysis were observed by the presence of pro-vitamin A, vitamins B1 and C, and glucose in the vegetable extracts. The proposed biosensor-based pesticide residue methodology fulfills all requisites to be used in implementation of food safety programs.
Bioelectrochemistry | 2014
Thiago M.B.F. Oliveira; M. Fátima Barroso; Simone Morais; Mariana Araújo; Cristina Freire; Pedro de Lima-Neto; Adriana N. Correia; Maria Beatriz P.P. Oliveira; Cristina Delerue-Matos
A bi-enzymatic biosensor (LACC-TYR-AuNPs-CS/GPE) for carbamates was prepared in a single step by electrodeposition of a hybrid film onto a graphene doped carbon paste electrode (GPE). Graphene and the gold nanoparticles (AuNPs) were morphologically characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, dynamic light scattering and laser Doppler velocimetry. The electrodeposited hybrid film was composed of laccase (LACC), tyrosinase (TYR) and AuNPs entrapped in a chitosan (CS) polymeric matrix. Experimental parameters, namely graphene redox state, AuNPs:CS ratio, enzymes concentration, pH and inhibition time were evaluated. LACC-TYR-AuNPs-CS/GPE exhibited an improved Michaelis-Menten kinetic constant (26.9±0.5M) when compared with LACC-AuNPs-CS/GPE (37.8±0.2M) and TYR-AuNPs-CS/GPE (52.3±0.4M). Using 4-aminophenol as substrate at pH5.5, the device presented wide linear ranges, low detection limits (1.68×10(-9)±1.18×10(-10)-2.15×10(-7)±3.41×10(-9)M), high accuracy, sensitivity (1.13×10(6)±8.11×10(4)-2.19×10(8)±2.51×10(7)%inhibitionM(-1)), repeatability (1.2-5.8% RSD), reproducibility (3.2-6.5% RSD) and stability (ca. twenty days) to determine carbaryl, formetanate hydrochloride, propoxur and ziram in citrus fruits based on their inhibitory capacity on the polyphenoloxidases activity. Recoveries at two fortified levels ranged from 93.8±0.3% (lemon) to 97.8±0.3% (orange). Glucose, citric acid and ascorbic acid do not interfere significantly in the electroanalysis. The proposed electroanalytical procedure can be a promising tool for food safety control.
Biosensors and Bioelectronics | 2013
Thiago M.B.F. Oliveira; M. Fátima Barroso; Simone Morais; Mariana Araújo; Cristina Freire; Pedro de Lima-Neto; Adriana N. Correia; Maria Beatriz P.P. Oliveira; Cristina Delerue-Matos
A novel enzymatic biosensor for carbamate pesticides detection was developed through the direct immobilization of Trametes versicolor laccase on graphene doped carbon paste electrode functionalized with Prussian blue films (LACC/PB/GPE). Graphene was prepared by graphite sonication-assisted exfoliation and characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The Prussian blue film electrodeposited onto graphene doped carbon paste electrode allowed considerable reduction of the charge transfer resistance and of the capacitance of the device. The combined effects of pH, enzyme concentration and incubation time on biosensor response were optimized using a 2(3) full-factorial statistical design and response surface methodology. Based on the inhibition of laccase activity and using 4-aminophenol as redox mediator at pH 5.0, LACC/PB/GPE exhibited suitable characteristics in terms of sensitivity, intra- and inter-day repeatability (1.8-3.8% RSD), reproducibility (4.1 and 6.3% RSD), selectivity (13.2% bias at the higher interference:substrate ratios tested), accuracy and stability (ca. twenty days) for quantification of five carbamates widely applied on tomato and potato crops. The attained detection limits ranged between 5.2×10(-9)molL(-1) (0.002mgkg(-1) w/w for ziram) and 1.0×10(-7)molL(-1) (0.022mgkg(-1) w/w for carbofuran). Recovery values for the two tested spiking levels ranged from 90.2±0.1 (carbofuran) to 101.1±0.3% (ziram) for tomato and from 91.0±0.1% (formetanate) to 100.8±0.1% (ziram) for potato samples. The proposed methodology is appropriate to enable testing pesticide levels in food samples to fit with regulations and food inspections.
Analytical Biochemistry | 2011
Thiago M.B.F. Oliveira; Francisco Wirley Paulino Ribeiro; Janete E.S. Soares; Pedro de Lima-Neto; Adriana N. Correia
The electrochemical reduction behavior of dexamethasone at a hanging mercury drop electrode was investigated by cyclic and square-wave adsorptive voltammetries in a Britton-Robinson buffer at pH 2.0. The optimized experimental conditions consisted of a pulse potential frequency of 100 s(-1), a pulse amplitude of 15 mV, and a potential step height of 2 mV, with E(acc)=-0.60V and t(acc)=15s. From these parameters, it was also possible to develop a detailed study about the kinetic and mechanistic events involved in the reduction process. Two well-defined peaks were observed in the cathodic scan, and peak 2 was used to obtain analytical curves. A linear range between 4.98×10(-8) and 6.10×10(-7)mol L(-1), with a detection limit of 2.54×10(-9)mol L(-1) and a quantification limit of 8.47×10(-9)mol L(-1), was observed. Moreover, it was possible to achieve a simple, selective, and versatile methodology adaptable to the quantification of dexamethasone because common excipients used in multicomponent commercial formulations caused no interference. The satisfactory recoveries and the low relative standard deviation data reflected the high accuracy and precision of the proposed method for the determination of dexamethasone in injectable eye drops and elixir samples.
Journal of the Brazilian Chemical Society | 2012
Thiago M.B.F. Oliveira; Francisco Wirley Paulino Ribeiro; Jefferson Melo do Nascimento; Janete E.S. Soares; V. N. Freire; Helena Becker; Pedro de Lima-Neto; Adriana N. Correia
This paper describes an electroanalytical methodology using square-wave adsorptive voltammetry, which has been successfully applied for the direct determination of dexamethasone residues in raw natural waters used for the public supply of the Ceara State, Brazil. The obtained detection limits ranged from 7.47 × 10-9 to 1.80 × 10-8 mol L-1 for the three matrices of raw natural waters evaluated. High percentages of average recovery (98.86% ± 0.72), repeatability (0.32% ± 0.05) and reproducibility (0.91% ± 0.20) were obtained in these samples, reaffirming the sensitivity of the procedure. Energy of the LUMO orbitals and Mulliken’s atomic charges were calculated using the functional BLYP/DNP. The theoretical results allied to the diagnostic criteria of the square-wave voltammetry indicate that the dexamethasone redox mechanism is associated to the quasi-reversible and irreversible reduction process of the ketone groups located at C-20 and C-3, respectively.
Environmental Science and Pollution Research | 2017
Lyliane F. Trigueiro; Larissa M. Silva; Luciana A. B. D. Itto; Thiago M.B.F. Oliveira; Artur J. Motheo; Carlos A. Martínez-Huitle; Janete Jane Fernandes Alves; Suely Souza Leal Castro
The yeast Saccharomyces cerevisiae, a microorganism with cell walls resistant to many types of treatments, was chosen as a model to study electrochemical disinfection process using dimensionally stable anodes (DSA). DSA electrodes with nominal composition of Ti/RuO2TiO2 and Ti/RuO2TiO2IrO2 were evaluated in 0.05xa0molxa0L−1 Na2SO4 containing yeast. The results showed inactivation about of 100xa0% of the microorganisms at Ti/RuO2TiO2 by applying 20 and 60xa0mAxa0cm−2 after 120xa0min of electrolysis, while a complete inactivation at Ti/RuO2IrO2TiO2 electrode was achieved after 180xa0min at 60xa0mAxa0cm−2. When chloride ions were added in the electrolyte solution, 100xa0% of the yeast was inactivated at 20xa0mAxa0cm−2 after 120xa0min of electrolysis, independent of the anode used. In the absence of chloride, the energy consumption (EC) was of 34.80xa0kWhxa0m−3, at 20xa0mAxa0cm−2 by using Ti/RuO2TiO2 anode. Meanwhile, in the presence of chloride, EC was reduced, requiring 30.24 and 30.99xa0kWhxa0m−3 at 20xa0mAxa0cm−2, for Ti/RuO2TiO2 and Ti/RuO2IrO2TiO2 electrodes, respectively, The best performance for cell lysis was obtained in the presence of chloride with EC of 88.80xa0kWhxa0m−3 (Ti/RuO2TiO2) and 91.85xa0kWhxa0m−3 (Ti/RuO2IrO2TiO2) to remove, respectively, 92 and 95xa0% of density yeast. The results clearly showed that yeast, as a model adopted, was efficiently inactivated and lysed by electrolysis disinfection using DSA-type electrodes.
Microchemical Journal | 2013
Thiago M.B.F. Oliveira; Helena Becker; Elisane Longhinotti; Djenaine De Souza; Pedro de Lima-Neto; Adriana N. Correia
Colloids and Surfaces A: Physicochemical and Engineering Aspects | 2013
Bianca Sandrino; Claudenilson S. Clemente; Thiago M.B.F. Oliveira; Francisco Wirley Paulino Ribeiro; Felippe José Pavinatto; Selma Elaine Mazzetto; Pedro de Lima-Neto; Adriana N. Correia; Christiana Andrade Pessoa; Karen Wohnrath
Electrochimica Acta | 2012
Francisco Jonas Nogueira Maia; Claudenilson S. Clemente; Thiago M.B.F. Oliveira; Diego Lomonaco; Túlio Ítalo S. Oliveira; Mayara O. de Almeida; Pedro de Lima-Neto; Adriana N. Correia; Selma Elaine Mazzeto
Electrochimica Acta | 2016
Maycon J.R. Santos; Mateus C. Medeiros; Thiago M.B.F. Oliveira; Crislânia Carla de Oliveira Morais; Selma Elaine Mazzetto; Carlos A. Martínez-Huitle; Suely Souza Leal Castro