Luciana Melo Coelho

Universidade Federal de Goiás, Goianá, Goiás, Brazil

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Publications (15)22.11 Total impact

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    ABSTRACT: A highly sensitive and selective procedure for the determination of arsenate and total arsenic in food by electrothermal atomic absorption spectrometry after cloud point extraction (ETAAS/CPE) was developed. The procedure is based on the formation of a complex of As(V) ions with molybdate in the presence of 50.0mmolL(-1) sulfuric acid. The complex was extracted into the surfactant-rich phase of 0.06% (w/v) Triton X-114. The variables affecting the complex formation, extraction and phase separation were optimized using factorial designs. Under the optimal conditions, the calibration graph was linear in the range of 0.05-10.0μgL(-1). The detection and quantification limits were 10 and 33ngL(-1), respectively and the corresponding value for the relative standard deviation for 10 replicates was below 5%. Recovery values of between 90.8% and 113.1% were obtained for spiked samples. The accuracy of the method was evaluated by comparison with the results obtained for the analysis of a rice flour sample (certified material IRMM-804) and no significant difference at the 95% confidence level was observed. The method was successfully applied to the determination of As(V) and total arsenic in rice samples. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Food Chemistry 07/2015; 178. DOI:10.1016/j.foodchem.2015.01.014 · 3.26 Impact Factor
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    01/2015; 2(1). DOI:10.2478/sampre-2014-0004
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    ABSTRACT: This review provides an overview and discusses different analytical strategies that minimize or eliminate the preparation of samples for speciation of organic and inorganic species of As, Cr and Se in samples of biological interest. These metals are important for the human body and the presence of various chemical forms of metals determines its essentiality and toxicity, thus speciation comes as an important tool for the study of biological samples. However, speciation requires a reduction in the steps of sample preparation, allowing a sample investigation in its most native form in order to reduce the changes in chemical species. The strategies proposed for speciation of these metals include: solid phase extraction, point cloud extraction, suspension and direct analysis. Selected methods proposed for the speciation of organic and inorganic species of As, Cr and Se were reviewed including their main figures of merit, advantages and disadvantages
    01/2014; 2(1). DOI:10.2478/sampre-2014-0001
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    ABSTRACT: A solid phase extraction method was developed for the direct determination of nickel in alcoholic beverages. This method is based on the adsorption of nickel onto the peel of Citrus reticulata (mandarin orange). The solution pH, amount of adsorbent, sample and eluent flow rates, eluent concentration and matrix effects were investigated using multivariate optimization strategies. Desorption studies were carried out with 1 mol L-1 HCl. The optimum extraction conditions were obtained using a sample pH of 6.0, sample flow rate of 4.3 mL min-1, 50 mg of sorbent mass and 1.0 mol L-1 HCl at a flow rate of 2.0 mL min-1 used as eluent. The preconcentration factor, precision, limit of detection (LOD), limit of quantification (LOQ), consumption index and sample throughput were estimated as 12, 0.9% (30.0 µg L-1, n = 7), 3.1 µg L-1, 10.3 µg L-1, 0.85 mL and 15 samples per h, respectively. The method was applied to sugar cane spirit and whisky samples and the results for recovery tests were higher than 99%.
    Journal of the Brazilian Chemical Society 06/2013; 24(6):1072-1078. DOI:10.5935/0103-5053.20130138 · 1.25 Impact Factor
  • Bioresources 05/2013; 8(3). DOI:10.15376/biores.8.3.3309-3321 · 1.55 Impact Factor
  • Bioresources 01/2013; 8(2). DOI:10.15376/biores.8.2.2738-2751 · 1.55 Impact Factor
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    Applied Bioremediation - Active and Passive Approache, Edited by Yogesh B. Patil; Prakash Rao, 01/2013: chapter Bioremediation of Waters Contaminated with Heavy Metals Using Moringa oleifera Seeds as Biosorbent: pages 225-253;
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    ABSTRACT: Metal contaminants are generally removed from effluents by chemical and physical processes which are often associated with disadvantages such as the use of toxic reagents, generation of toxic waste and high costs. Hence, new techniques have been developed, among them the study of natural adsorbents, for instance, the use of Moringa oleifera seeds. The potential of M. oleifera seeds for nickel removal in aqueous systems was investigated. The seeds utilized were obtained from plants grown in Uberlândia/Brazil. After being dried and pulverized, the seeds were treated with 0.1 mol/L NaOH. Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analyses were used for the characterization of the material. Using the optimized methodology (50 mL of 4.0 mg/L Ni(II), pH range of 4.0-6.0, agitation time of 5 min and adsorption mass of 2.0 g) more than 90% of Ni(II) could be removed from water samples. The sorption data were fitted satisfactorily by the Langmuir adsorption model. Evaluation applying the Langmuir equation gave the monolayer sorption capacity as 29.6 mg/g. The results indicate that this material could be employed in the extraction of nickel, considering its ease of use, low cost and environmental viability, which make it highly attractive for application in developing countries.
    Water Science & Technology 03/2012; 65(8):1435-40. DOI:10.2166/wst.2012.026 · 1.21 Impact Factor
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    ABSTRACT: A three-step sequential extraction procedure recommended by the European Standards, Measurements and Testing (SM&T) Program, formerly the Community Bureau of Reference (BCR), was applied to the chemical speciation of heavy metals (Cu, Pb, Cr and Zn) in sediments from different populated zones of Uberlândia City (MG State, Brazil). To obtain a mass balance, a fourth step, i.e., digestion and analysis of the residue, was performed using a microwave-assisted acid digestion procedure. The highest metallic elements concentrations were observed at one of the sampling points which receive discharge from an urban area and an industrial zone. All metals, except Zn, were present at higher concentrations in the residual fractions (strongly associated with the crystalline structures of the minerals) indicating that Cu, Pb and Cr were less mobile and potentially less bioavailable in these sediments. In sediments from industrial and urban discharge zones the mobility sequence of the heavy metals studied was Pb > Zn > Cu > Cr. The highest Pb concentrations were found in the residual fractions at the sampling point located in the tributary stream that drains the industrial district (102 mg kg-1), indicating that this metallic element was strongly bound to the sediments. Therefore, under the contamination and toxicological point of view, Pb has no impact to the environment and consequently to the human health. The sum of the four fractions (acid-soluble + reducible + oxidizable + residual) was in good agreement with the total content, which verifies the accuracy of the microwave extraction procedure in conjunction with the FAAS analytical method.
    Journal of the Brazilian Chemical Society 11/2011; 22(11):2094-2100. DOI:10.1590/S0103-50532011001100011 · 1.25 Impact Factor
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    ABSTRACT: Recebido em 3/5/10; aceito em 21/12/10; publicado na web em 25/3/11 USE OF (Dypterix alata) BARU ALMONDS FOR Ni(II) REMOVAL FROM ETHANOL FUEL. The present work describes the sorption potential of Dypterix alata (baru) for removal of Ni(II) in hydrous ethanol. Infrared spectroscopy was used for elucidating possible functional groups responsible for uptaking Ni(II). Sorption studies using Ni(II) standard solutions were carried out in batch experiments as functions of extraction time and pH solution. The Ni(II) was quantified before and after the removal experiments using Flame Atomic Absorption Spectrometry. Furthermore, based on adsorption studies and adsorption isotherms applied to the Langmuir and Freundlich models, it was possible to verify that D. alata presents a high adsorption capacity. The results show that D. alata can be used for removing Ni(II) in ethanol solutions.
    Química Nova 01/2011; 34(6). DOI:10.1590/S0100-40422011000600002 · 0.66 Impact Factor
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    ABSTRACT: In the present paper a procedure for simultaneous preconcentration of Cd, Cu, and Pb using cloud point extraction (CPE) and multielemental sequential determination by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) is proposed. This preconcentration procedure is based on the metals extraction into micellar media of octylphenoxypolythoxyethanol (Triton X-114) after their reaction with 1-(2-pyridylazo)-2-naphtol (PAN). A Box-Behnken design was used to optimize the variables (pH, buffer concentration and volume of NaCl) involved in the extraction procedure. Enrichment factors were calculated as the ratio between the slopes of calibration equations with and without the preconcentration procedure in the TS-FF-AAS, with values of 59, 25, and 21 respectively for Cd, Cu, and Pb. Limits of detection (LOD) (3sb, n ¼ 10) were also calculated as 0.025, 0.38, and 0.43 mg L21 to Cd, Cu, and Pb, respectively. The precision (repeatability) expressed as relative standard deviation (RSD, n ¼ 10) for reference standards of 10.0 and 20.0 mg L21 were 6.1 and 4.5% for Cd, 7.2 and 3.4% for Cu and 5.2 and 8.7% for Pb. The accuracy was confirmed through the analysis of certified reference material (NIST 1643d, Trace elements in water). The developed procedure was also applied to Cd, Cu, and Pb determinations in mineral water samples.
    Separation Science and Technology 10/2008; 43:1-13. DOI:10.1080/01496390701870630 · 1.20 Impact Factor
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    ABSTRACT: A method using bi-directional electrostacking (BDES) in a flow system is presented for As preconcentration and speciation analysis. Some parameters such as electrostacking time and applied voltage, support buffers and their concentrations were investigated. Boric acid plus sodium hydroxide at 0.1mol/l concentration was selected as support buffer to improve the pre-concentration factor (PF) for As(V). An analytical range from 2.0 to 50.0mugl(-1), and 0.35mugl(-1) as limit of detection, when applied 750V for 20min, were achieved. Under these conditions, a pre-concentration factor of 4.8 was obtained. The proposed method was applied to determine As(V) in mineral water and natural water samples (river, fountain and gold mine) from Ouro Preto city. Recoveries from 93.5 to 106.4% were achieved at 10mugl(-1) added As level (R.S.D.s between 3 and 7%). Potassium permanganate (10mgl(-1)) was used for oxidising As species in order to determine total As, being established the concentration of As(III) from the difference between total As and As(V).
    Talanta 02/2007; 71(1):353-8. DOI:10.1016/j.talanta.2006.04.007 · 3.51 Impact Factor
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    Luciana Melo Coelho, Marco Aurélio Zezzi Arruda
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    ABSTRACT: This paper describes a micelle-mediated phase separation in the presence of electrolyte as a preconcentration method for cadmium determination by flame atomic absorption spectrometry (FAAS). Cadmium was complexed with ammonium O,O-diethyldithiophosphate (DDTP) in an acidic medium (0.32 mol l− 1 HCl) using Triton X-114 as surfactant and quantitatively extracted into a small volume (about 20 μl) of the surfactant-rich phase after centrifugation. The chemical variables that affect the cloud point extraction, such as complexing time (0–20 min), Triton X114 concentration (0.043–0.87% w/v) and complexing agent concentration (0.01–0.1 mol l− 1), were investigated. The cloud point is formed in the presence of NaCl at room temperature (25 °C), and the electrolyte concentration (0.5–5% w/v) was also investigated. Under optimized conditions, only 8 ml of sample was used in the presence of 0.043% w/v Triton X-114 and 1% (w/v) NaCl. This method permitted limits of detection and quantification of 0.9 μg l− 1 and 2.9 μg l− 1 Cd, respectively, and a linear calibration range from 3 to 400 μg l− 1 Cd. The proposed method was applied to Cd determination in physiological solutions (containing 0.9% (w/v) of NaCl), mineral water, lake water and cigarette samples (tobacco).
    Spectrochimica Acta Part B Atomic Spectroscopy 06/2005; DOI:10.1016/j.sab.2005.02.016 · 3.15 Impact Factor
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    ABSTRACT: Arsenic compounds including arsenous acid (As(III)), arsenic acid (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were separated by high-performance liquid chromatography (HPLC) and detected by inductively coupled plasma mass spectrometry (ICP-MS). A Hamilton PRX-100 anionic-exchange column and a pH 8.5 K(2)HPO(4)/KH(2)PO(4) 5.0x10(-3)molL(-1) mobile phase were used to achieve arsenic speciation. The separation of arsenic species provided peaks of As(III) at 2.75min, DMA at 3.33min, MMA at 5.17min and As(V) at 12.5min. The detection limits, defined as three times the standard deviation of the lowest standard measurements, were found to be 0.2, 0.2, 0.3 and 0.5ngmL(-1) for As(III), DMA, MMA and As(V), respectively. The relative standard deviation values for a solution containing 5.0mugL(-1) of As(III), DMA, MMA and As(V) were 1.2, 2.1, 2.5 and 3.0%, respectively. This analytical procedure was applied to the speciation of arsenic compounds in drinking (soft drink, beer, juice) samples. The validation of the procedure was achieved through the analysis of arsenic compounds in water and sediment certified reference materials.
    Talanta 06/2005; 66(4):818-22. DOI:10.1016/j.talanta.2004.11.037 · 3.51 Impact Factor
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    ABSTRACT: RESUMO As intervenções de natureza humana em uma bacia hidrográfica podem interferir na qualidade das águas e restringir seus usos. Dessa forma, o objetivo deste trabalho foi avaliar a qualidade da água do Córrego Fundo, localizada no Município de Catalão, na região Sudeste do Estado de Goiás, analisando potenciais ecológicos e de ação antrópica. As amostras de água e de solos foram coletadas durante onze meses, e as análises químicas foram realizadas. Os resultados das amostras de água foram comparados com os valores recomendados pela legislação (CONAMA 357/2005) para verificar a qualidade da água. O objetivo de analisar o solo foi identificar quais elementos estão presentes nessas amostras que podem interferir na qualidade da água. Na região de estudo, foi observado que o uso da terra é predominantemente para pastagens, além de pequenos plantios de milho, arroz e feijão. Destaca-se também o plantio de eucaliptos e atividade de mineração. Algumas amostras de água apresentaram desconformidade com a Legislação para os compostos inorgânicos, sendo alumínio (Al), ferro (Fe), fósforo (P), manganês (Mn) e nitrogênio (N) (Córrego Mata Preta); Al, Pb, Fe, P, Mn e N (Córrego Vargem Grande e Macaúba); Al, Pb, Fe, bário (Ba), P, Mn N (Córrego Garimpo jusante) e Al, Pb, P e N (Córrego Fundo). O ferro foi encontrado em quase todas as amostras analisadas (água e solo). A presença de elementos como Ba, N, Mn P encontrados nos valores maiores que permitidos pela Legislação deve-se a geologia e a intensa adubação do solo na região. Palavras-chave: qualidade de água, Resolução CONAMA, Microbacia do Córrego Fundo ABSTRACT Evaluation of surface water quality of "Córrego Fundo" Watershed -Catalão (GO). The interventions of human nature in a watershed can affect water quality and restrict their use. Thus, the goal of this study was to evaluate the water quality of the Córrego Fundo, located in the city of Catalão, in the southeastern region of the State of Goiás, analyzing the environmental and anthropogenic potentials. Samples of water and soil were collected for eleven months and the chemical analyses were performed. The results of water samples were compared with the values recommended by the legislation (CONAMA 357/2005) to verify the quality of water. The purpose of analyzing the soil is to identify which elements are present in these samples that can interfere with water quality. The region examined was observed that the use of land was predominantly for pasture also low growing of corn, rice and beans. In this region there is also the planting of eucalyptus and mining activity. Some water samples showed disagreement with the legislation for inorganic compounds such as aluminum (Al), iron (Fe), phosphorus (P), manganese (Mn) and nitrogen (N) (Córrego Mata Preta), Al, Fe, P and Mn (Córrego Vargem Grande and Macaúba), Fe, barium (Ba), P, Mn and N (Córrego Garimpo downstream) and Al, Fe, P and N (Córrego Fundo). The iron was found in almost all samples analyzed (water and soil). The presence of elements such as Ba, N, Mn, P found in levels higher than allowed by law is due to geology activities and intensive fertilization of the soil in the region.