Navegando por Autor "Costa, Bruno Elias dos Santos"

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    Desenvolvimento de um método de extração em fase sólida in situ para determinação de Cr(III) em infusão de fitoterápicos
    (Universidade Federal de Goiás, 2019-08-08) Siqueira, Alêssa Gomes; Costa, Bruno Elias dos Santos; http://lattes.cnpq.br/9995122149910490; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Rezende, Hélen Cristine; Coelho, Luciana Melo; Alves, Vanessa Nunes; Costa, Bruno Elias dos Santos
    This work presents the development of an in situ solid phase extraction method (SPE-ISS) for the determination of chromium (III) in herbal infusion samples using flame atomic absorption spectrometry (F AAS). Thus, in order to evaluate the inorganic composition of medicinal plant samples (calendula, chamomile, carqueja, green tea, leather hat, melissa and passiflora) we used the EDXRF (Dispersive Energy X-ray Fluorescence). the presence of plant essential metals in addition to toxic metals. Subsequently, a quantitative analysis of some metal ions was performed in infusion samples prepared from these plants, and Fe(III) was the only one found in considerable concentration, while Pb(II), Cr(III), and Cd(II) presented concentrations below the detection limit of the technique. Therefore, it is necessary to develop extraction and preconcentration methods that allow the determination of Cr(III) simply and safely, even when present in low concentrations. In this work, the SPE-ISS method was optimized by multivariate techniques, and the results showed that the formation of the Cr-PAN complex is favored at pH 9.5, with the complexant at 0.18 mmol L-1 concentration. For optimization of solid phase formation and extraction, factorial design and response surfaces were used, which pointed to the use of CTAB as phase transfer agent, NaClO4 0.26 mol L-1 as ionic pairer and agitation time of 7.5 minutes. Studies of possible interferents indicated negative interference of the metallic ions Al(III), Zn(II), Fe(III) and Ca(II). The analytical performance was evaluated by the parameters, preconcentration factor, detection limit (LD) and limit of quantification (LQ) and the values ​​found were 1.66 μg L-1 and 5,5 μg L-1, respectively. The intra-day and inter-day precision (RPD) was 0.001% and 0.0004%, respectively, being the linear range of the method from 250 to 5000 μg L-1, presenting the potential to determine low chromium concentrations. Finally, the accuracy of the method was evaluated from analysis of certified reference water material (APS-1071), as well as recovery tests on water samples and herbal infusions 77.60 - 116%.
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    Extração seletiva por ponto nuvem para pré-concentração e especiação de arsênio inorgânico em matriz alimentícia empregando espectrometria de absorção atômica eletrotérmica em forno de grafite
    (Universidade Federal de Goiás, 2013-07-29) Costa, Bruno Elias dos Santos; Coelho, Luciana Melo; http://lattes.cnpq.br/0074807107314789; Coelho, Luciana Melo; Tarley, César Ricardo Teixeira; Freitas, Sílvia de Sousa
    In this study, a highly sensitive and selective procedure for determination of arsenate and total arsenic in rice by electrothermal atomic absorption spectrometry after cloud point extraction As(V)-CPE-GF AAS was developed. The procedure is based on complex formation of As (V) ions with molybdate in the presence of 50.0 mmol L-1 sulfuric acid and 0.1 mmol L-1 ascorbic acid. The complex of As (V)-molybdate was extracted into the surfactant-rich phase of 0.06% w/v Triton X-114 solution. The variables affecting complex formation, extraction and phase separation such as complexing agent concentration, reducing agent concentration and electrolyte concentration were optimized using a factorial design and response surface methodology through central composite design (CCD). Under the optimal experimental conditions, the calibration graph was linear in the range of 0.03 – 10.0 μg L-1 for As (V) ions. The detection and quantification limits for As(V) were 0.0099 and 0.0331 μg L-1 respectively, obtaining an enrichment factor of 78.3 and the corresponding value for relative standard deviation (R.S.D) for 10 replicate determinations was below 5%. A two-level full factorial experimental design involving three factors (permanent modifiers, pyrolysis temperature PT and atomization temperature AT) was investigated to estimate the optimum values of the variables affecting the detection. It was demonstrated that iridium modifier and PT x AT interaction were considered in modeling the response surface. Recovery values were obtained between 90.8% and 113.1% for spiked samples. The method was successfully applied to the determination of As (V) and total arsenic in some rice samples.