In this work, the mineral composition of fresh bovine milk obtained from the milk-producing areas... more In this work, the mineral composition of fresh bovine milk obtained from the milk-producing areas of the Brazilian State of Sergipe was examined. A dry-ashed digestion method and the ICP OES technique were used for the quantification of mineral elements (eg, Ca, Mg, K, Na, P, Sr ...
In this study, mechanical mixtures of sugarcane bagasse and iron salts (nitrate, acetate, or a mi... more In this study, mechanical mixtures of sugarcane bagasse and iron salts (nitrate, acetate, or a mixture of both) were subjected to thermal decomposition for producing iron oxide and carbonaceous composite materials, which were evaluated as adsorbents for removing dyes from water using methylene blue (MB) as a model system. Aiming to optimize the conditions for obtaining composite adsorbents, the Box-Behnken design (BBD) was used to study the effects of mass sugarcane bagasse/mass iron salt, type of mixture of sugarcane bagasse/iron salt, and temperature on the response to be obtained (adsorption capacity, qe) before the execution of the adsorption tests. The synthesized composites were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The relationship between the characteristics of different materials, based on the processing of statistical data and the results of the adsorption tests, helped...
The elemental/centesimal composition of dried fruits and capsules containing Goji berries (Lycium... more The elemental/centesimal composition of dried fruits and capsules containing Goji berries (Lycium barbarum L.) was evaluated by ICP OES after two digestion procedures. Furthermore, phenolic acid compounds and flavonoids were quantified by HPLC-UV-DAD. Precision, accuracy, LOD and LOQ were evaluated. The samples showed similar contents of proteins, lipids and carbohydrates. The metal contents in the samples were found at different levels (minimum-maximum, in mg kg), as follows: Ca (181.1-200.2); Cu (1.703-2.145); Fe (7.420-7.852); K (81.78-83.59); Mg (92.58-95.12); Mn (1.630-2.570); Na (587.9-590.7); P (3.124-3.360); Se (2.812-3.345); V (0.055-0.062) and Zn (2.325-2.610). Al, As, Ba Cd, Co, Ni, P, Pb, Sb, Sn and Sr showed values below the LOD. Accuracy was assessed by analysis of tomato leaves (NIST 1573a). Eight bioactive phenolic compounds (caffeic, chlorogenic, ellagic, ferulic, gallic, p-coumaric, syringic and vanillic acids) and two flavonoids [(+)-catequin and rutin] were deter...
This study deals with the development of a separation and quantification method by high performan... more This study deals with the development of a separation and quantification method by high performance liquid chromatography with a diode array detector (HPLC- DAD), for the determination of phenolic acids and methylxanthines in tea (Camellia Sinensis) samples. Six phenolic acids (Gallic, trans-cinnamic, caffeic, ferulic and p-coumaric acids) and two methylxanthines (caffeine, theobromine) were studied, according to the principles of green chemistry, with the goal of comparing teas with different processing level. After development and validation of separation and extraction methods was applied to 11 extracts obtained by infusions of green and black tea samples in commercial areas of the city of Salvador-BA, showing feasible and efficient. Was employed multivariate data analysis and the Tukey test to correlate the chromatographic profile with the different samples. Principal component and analysis and hierarchical cluster analysis were used for the chromatographic analysis, allowing the visualization of two groups, formed by green and black tea samples.
Doehlert design and desirability function were used in the optimization of an ultrasound assisted... more Doehlert design and desirability function were used in the optimization of an ultrasound assisted dissolution method of fish fillet samples with tetramethyl ammonium hydroxide (TMAH) for the determination of Ca, Fe, Zn and Mg by flame atomic absorption spectrometry. The variables values after optimization were 620 μL (volume of TMAH), 25 min (sonication time) and 46 °C (bath temperature). The quantification limits for Ca, Mg, Fe and Zn were 56, 107, 23 and 2.9 μg g, respectively. Accuracy was evaluated by comparing the results generated from the analysis of the samples treated by the proposed method and by wet digestion. Additionally, accuracy for Fe and Zn was assessed by the analysis of certified reference materials Tort-3 (Lobster hepatopancreas), ERM-CE 278 (mussel tissue) and Dolt-4 (Fish liver). There were no significant differences between the results obtained at a 95% confidence level when results were evaluated by t-test application.
A method using reversed-phase high-performance liquid chromatography with diode array detection (... more A method using reversed-phase high-performance liquid chromatography with diode array detection (HPLC-DAD) was applied after extraction with acidified methanol, to determine 12 bioactive phenolic compounds in the peel and pulp of the mango fruit (Mangifera indica L.) cultivated in the Bahia, state of Brazil. The proposed methodology was previously fully validated and proven successful in the analysis of methanolic extracts of lyophilized samples. The limits of quantification ranged between 0.78 and 3.14 mg L and the individual recovery values obtained for the spiked samples ranged from 80% to 120%. The results were evaluated using PCA and ANN. The results indicate that the fruits are rich in polyphenols, mainly: ellagic acid, gallic acid, rutin and catechin, which contribute to their greater use as functional foods, natural antioxidants and in the pharmaceutical industry, as well as other applications.
In this work, an analytical method was proposed for the simultaneous determination of mercury and... more In this work, an analytical method was proposed for the simultaneous determination of mercury and selenium in fish samples using Atomic Fluorescence Spectrometry (AFS). Multivariate designs were performed to evaluate the variables and optimize the best condition of chemical vapor generation (CVG) and simultaneous determination of mercury and selenium by AFS. Fish samples were prepared via acid digestion in digester block with cold finger reflux system, which ensured that the elements were not lost by volatility. The proposed analytical method was validated, and excellent figures of merit have been achieved, such as detection limits of 0.33 and 9.18 ng g for mercury and selenium, respectively. The method was applied for simultaneous determination of mercury and selenium in canned sardines. Mercury concentrations ranged from 0.057 to 0.203 μg g and selenium concentration from 1.76 to 2.21 μg g, providing a mean molar ratio (Se:Hg) equivalent to 36.
Http Dx Doi Org 10 1080 05704920903435474, Jan 14, 2010
Abstract This article critically overviews the state-of-the-art of slurry sampling as an approach... more Abstract This article critically overviews the state-of-the-art of slurry sampling as an approach for the minimization of sample preparation prior to the determination of metals and metalloids in complex matrices by spectroanalytical techniques. Relevant factors involved ...
... Article | PDF (225 K) | View Record in Scopus | Cited By in Scopus (28). [10] EM de Moraes Fl... more ... Article | PDF (225 K) | View Record in Scopus | Cited By in Scopus (28). [10] EM de Moraes Flores, APF Saidelles, EL de Moraes Flores, MF Mesko, MP Pedroso, VL Dressler, CF Bittencourt and AB da Costa, Microchem. J. 77 (2004), p. 113. ...
The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ion... more The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ions Pb(II) and Cd (II) biosorption from natural waters. The flame atomic absorption spectrometry was used for quantitative determination and study of the ions Pb(II) and Cd(II) adsorption on the solid phase. The Fourier transform infrared spectroscopy (FT IR) was used to investigate the sisal structure and the specific BET surface area was analyzed. The biosorption potential of sisal as biosorbent for the removal of the ions Pb(II) and Cd(II) from aqueous solution was investigate considering the followings parameters: pH, biomass amount and contact time. Langmuir and Freundlich isotherms were used to evaluate adsorption behavior of the ions on this solid phase. The results showed that sisal has a surface area to adsorption of 0.0233 m 2 g − 1 , and the OH and CO functional groups are the main involved in the biosorption. The best interpretation for the experimental data was given by Freundlich isotherm that proposes a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interactions between sorbed molecules. The maximum monolayer biosorption capacity was found to be 1.85 mg g − 1 for Cd (II) and 1.34 mg g − 1 for Pb (II) at pH 7 and 296 K. This phase solid can be used for biosorption of cadmium and lead in polluted natural waters.
Um sistema contendo Amberlite XAD-2 (estireno-divinilbenzeno) carregado com 2-(2tiazolilazo)-5-di... more Um sistema contendo Amberlite XAD-2 (estireno-divinilbenzeno) carregado com 2-(2tiazolilazo)-5-dimetilaminfenol (TAM) é proposto para amostragem em campo, preconcentração e determinação de cádmio (II) e níquel (II) em amostras de águas naturais usando espectrometria de absorção atômica com chama (FAAS). O processo de otimização foi univariado e os seguintes parâmetros foram estudados: efeito de pH, efeito de vazão de amostragem, concentração da solução e vazão de eluente, efeito de outros ions, precisão e exatidão. Na etapa de amostragem, os ions metálicos são retidos na minicoluna sob a forma de TAM complexos. A amostra é percolada com vazão de 3,0 mL min-1 após filtração usando filtro de 0,45 µm. Posteriormente, a minicoluna é incorporada sobre um sistema em fluxo contínuo e os ions metálicos são eluídos com solução de ácido clorídrico de concentração 1,0 mol L-1 diretamente para o sistema de nebulização do espectrômetro. Para níquel, os limites de detecção (LOD) e quantificação (LOQ) foram 12 e 39 ng L-1 , respectivamente. A precisão expressa como desvio padrão relativo (RSD) para 10 determinações independentes foram 5,5% e 7,0% para concentrações de níquel de 10 e 1,0 µg L-1 , respectivamente. O fator de preconcentração, calculado como a relação entre as inclinações de curvas obtidas pelo presente procedimento e pela aspiração direta foi 637 para um volume de amostra de 150 mL. Para cádmio, os LOD e LOQ foram 22 e 72 ng L-1 , respectivamente. A precisão expressa como RSD, foi 6,0% e 6,8% para concentrações de cádmio de 10 e 1,0 µg L-1 , respectivamente. O fator de preconcentração experimental foi 548, também para um volume de amostra de 150 mL. O procedimento foi aplicado para determinação de cádmio e níquel em águas naturais de baixa salinidade, coletadas de lagoas da Cidade de Salvador, Bahia, Brasil. A system containing Amberlite XAD-2 (styrene-divinylbenzene copolymers) loaded with 2-(2thiazolylazo)-5-dimethylaminophenol (TAM) reagent is proposed for field sampling, preconcentration and determination of cadmium (II) and nickel (II) ions in fresh water using flame atomic absorption spectrometry (FAAS). The optimisation process was univariate and the followings parameters were studied: pH effect, effect of sample flow rate, eluent concentration and flow rate, effect of other ions, precision and accuracy as recovery tests. In the sampling step, metal ions are retained in a minicolumn as TAM complexes. The sample is pumped at 3.0 mL min-1 with on-line filtration using a 0.45 µm filter. Afterwards, the minicolumn is incorporated in a flow-injection system and the metal ions eluted with a solution of 1.0 mol L-1 hydrochloric acid into the nebuliserburner system of the spectrometer. For nickel, the limits of detection (LOD) and quantification (LOQ) were 12 and 39 ng L-1 , respectively. The precision expressed as relative standard deviation (RSD) for ten independent determinations was 5.5% and 7.0% for nickel concentrations of 10 and 1.0 µg L-1 , respectively. The experimental preconcentration factor, calculated as the ratio of the slopes of the calibration curves obtained by the present procedure and manual direct aspiration was 637 for a sample volume of 150 mL. For cadmium, the LOD and LOQ are 22 ng L-1 and 72 ng L-1 , respectively. The precision, expressed as RSD was 6.0% and 6.8% for cadmium concentrations of 10 and 1.0 µg L-1 , respectively. The experimental preconcentration factor was 548 also for a sample volume of 150 mL. The procedure was applied for determination of cadmium and nickel in fresh water samples with low saline concentration, collected in lagoons from Salvador City, Bahia, Brazil.
A procedure has been developed for the simultaneous determination of trace amounts of cadmium, co... more A procedure has been developed for the simultaneous determination of trace amounts of cadmium, copper, chromium, nickel and lead in digested vegetable samples. The method involves solid-phase extraction of the metals using a minicolumn of Amberlite XAD-4 modified with dihydroxybenzoic acid (DHB) and detection by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The elution of the metals from minicolumn was performed with 1.0 mol L −1 hydrochloric acid. Variables associated with flow preconcentration system performance, such as pH, buffer concentration, eluent concentration and sampling flow rate, were optimized. The developed procedure provides enrichment factors of 100, 72, 16, 91 and 53, for cadmium, copper, chromium, nickel and lead, respectively. Detection limits (3σ B) were 0.02 (Cd), 0.23 (Cu), 0.58 (Cr), 0.060 (Ni) and 0.54 (Pb) g L −1. The procedure was applied for determination of metals in samples of guarana and cabbage. The accuracy of the method was checked by the analysis of a certified reference material (NIST 1571, Orchard leaves). Results found were in agreement with certified values.
It has been observed in previous work using high-resolution continuum-source atomic absorption sp... more It has been observed in previous work using high-resolution continuum-source atomic absorption spectrometry that up to 50% of the nickel and vanadium in crude oil, most likely non-polar nickel and vanadyl porphyrin complexes, was already lost at pyrolysis temperatures 4400 1C, whereas the rest of the analyte was stable up to at least 1200 1C. In this work we were investigating the use of a chemical modifier in order to avoid these low-temperature losses and also to make possible a differential determination of the volatile analyte fractions. Oil-in-water emulsions, using Triton X-100 as surfactant, were used for easy sample handling. A mass of 20 mg of Pd, introduced into the graphite tube and thermally pretreated prior to the injection of the emulsion, was found to efficiently prevent any low-temperature losses of nickel and vanadium from crude oil samples up to pyrolysis temperatures of 1200 1C and 1450 1C, respectively. The best characteristic mass obtained was m 0 ¼ 16 pg for Ni and m 0 ¼ 33 pg for V. The limits of detection and quantification were 0.02 mg g À1 and 0.065 mg g À1 , respectively, for Ni, and 0.06 mg g À1 and 0.17 mg g À1 , respectively, for V in oil, based on an emulsion of 2 g of oil in 10 mL. The precision expressed as relative standard deviation (n ¼ 9) for a crude oil containing about 5 mg g À1 Ni and 3 mg g À1 V was 2.0% and 3.1% for Ni and V, respectively. The accuracy of the procedure was verified by analyzing the certified reference material NIST SRM 1634c, trace metals in fuel oil, and the research material RM 8505, vanadium in crude oil.
... Fáabio de Souza Dias,1,2 Lucylia Suzart Alves,1 Walter Nei L. dos Santos,3 Jorge MaurıcioDavi... more ... Fáabio de Souza Dias,1,2 Lucylia Suzart Alves,1 Walter Nei L. dos Santos,3 Jorge MaurıcioDavid,2 and Sérgio Luis C ... 1995; Januzzi, Krug, and Arruda 1997; Lücker 1999; Vassileva, Baeten, and Hoening 2001) and ICP mass spectrometry (Maia, Pozebon, and Curtius 2003; Ni ...
In this work, the mineral composition of fresh bovine milk obtained from the milk-producing areas... more In this work, the mineral composition of fresh bovine milk obtained from the milk-producing areas of the Brazilian State of Sergipe was examined. A dry-ashed digestion method and the ICP OES technique were used for the quantification of mineral elements (eg, Ca, Mg, K, Na, P, Sr ...
In this study, mechanical mixtures of sugarcane bagasse and iron salts (nitrate, acetate, or a mi... more In this study, mechanical mixtures of sugarcane bagasse and iron salts (nitrate, acetate, or a mixture of both) were subjected to thermal decomposition for producing iron oxide and carbonaceous composite materials, which were evaluated as adsorbents for removing dyes from water using methylene blue (MB) as a model system. Aiming to optimize the conditions for obtaining composite adsorbents, the Box-Behnken design (BBD) was used to study the effects of mass sugarcane bagasse/mass iron salt, type of mixture of sugarcane bagasse/iron salt, and temperature on the response to be obtained (adsorption capacity, qe) before the execution of the adsorption tests. The synthesized composites were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The relationship between the characteristics of different materials, based on the processing of statistical data and the results of the adsorption tests, helped...
The elemental/centesimal composition of dried fruits and capsules containing Goji berries (Lycium... more The elemental/centesimal composition of dried fruits and capsules containing Goji berries (Lycium barbarum L.) was evaluated by ICP OES after two digestion procedures. Furthermore, phenolic acid compounds and flavonoids were quantified by HPLC-UV-DAD. Precision, accuracy, LOD and LOQ were evaluated. The samples showed similar contents of proteins, lipids and carbohydrates. The metal contents in the samples were found at different levels (minimum-maximum, in mg kg), as follows: Ca (181.1-200.2); Cu (1.703-2.145); Fe (7.420-7.852); K (81.78-83.59); Mg (92.58-95.12); Mn (1.630-2.570); Na (587.9-590.7); P (3.124-3.360); Se (2.812-3.345); V (0.055-0.062) and Zn (2.325-2.610). Al, As, Ba Cd, Co, Ni, P, Pb, Sb, Sn and Sr showed values below the LOD. Accuracy was assessed by analysis of tomato leaves (NIST 1573a). Eight bioactive phenolic compounds (caffeic, chlorogenic, ellagic, ferulic, gallic, p-coumaric, syringic and vanillic acids) and two flavonoids [(+)-catequin and rutin] were deter...
This study deals with the development of a separation and quantification method by high performan... more This study deals with the development of a separation and quantification method by high performance liquid chromatography with a diode array detector (HPLC- DAD), for the determination of phenolic acids and methylxanthines in tea (Camellia Sinensis) samples. Six phenolic acids (Gallic, trans-cinnamic, caffeic, ferulic and p-coumaric acids) and two methylxanthines (caffeine, theobromine) were studied, according to the principles of green chemistry, with the goal of comparing teas with different processing level. After development and validation of separation and extraction methods was applied to 11 extracts obtained by infusions of green and black tea samples in commercial areas of the city of Salvador-BA, showing feasible and efficient. Was employed multivariate data analysis and the Tukey test to correlate the chromatographic profile with the different samples. Principal component and analysis and hierarchical cluster analysis were used for the chromatographic analysis, allowing the visualization of two groups, formed by green and black tea samples.
Doehlert design and desirability function were used in the optimization of an ultrasound assisted... more Doehlert design and desirability function were used in the optimization of an ultrasound assisted dissolution method of fish fillet samples with tetramethyl ammonium hydroxide (TMAH) for the determination of Ca, Fe, Zn and Mg by flame atomic absorption spectrometry. The variables values after optimization were 620 μL (volume of TMAH), 25 min (sonication time) and 46 °C (bath temperature). The quantification limits for Ca, Mg, Fe and Zn were 56, 107, 23 and 2.9 μg g, respectively. Accuracy was evaluated by comparing the results generated from the analysis of the samples treated by the proposed method and by wet digestion. Additionally, accuracy for Fe and Zn was assessed by the analysis of certified reference materials Tort-3 (Lobster hepatopancreas), ERM-CE 278 (mussel tissue) and Dolt-4 (Fish liver). There were no significant differences between the results obtained at a 95% confidence level when results were evaluated by t-test application.
A method using reversed-phase high-performance liquid chromatography with diode array detection (... more A method using reversed-phase high-performance liquid chromatography with diode array detection (HPLC-DAD) was applied after extraction with acidified methanol, to determine 12 bioactive phenolic compounds in the peel and pulp of the mango fruit (Mangifera indica L.) cultivated in the Bahia, state of Brazil. The proposed methodology was previously fully validated and proven successful in the analysis of methanolic extracts of lyophilized samples. The limits of quantification ranged between 0.78 and 3.14 mg L and the individual recovery values obtained for the spiked samples ranged from 80% to 120%. The results were evaluated using PCA and ANN. The results indicate that the fruits are rich in polyphenols, mainly: ellagic acid, gallic acid, rutin and catechin, which contribute to their greater use as functional foods, natural antioxidants and in the pharmaceutical industry, as well as other applications.
In this work, an analytical method was proposed for the simultaneous determination of mercury and... more In this work, an analytical method was proposed for the simultaneous determination of mercury and selenium in fish samples using Atomic Fluorescence Spectrometry (AFS). Multivariate designs were performed to evaluate the variables and optimize the best condition of chemical vapor generation (CVG) and simultaneous determination of mercury and selenium by AFS. Fish samples were prepared via acid digestion in digester block with cold finger reflux system, which ensured that the elements were not lost by volatility. The proposed analytical method was validated, and excellent figures of merit have been achieved, such as detection limits of 0.33 and 9.18 ng g for mercury and selenium, respectively. The method was applied for simultaneous determination of mercury and selenium in canned sardines. Mercury concentrations ranged from 0.057 to 0.203 μg g and selenium concentration from 1.76 to 2.21 μg g, providing a mean molar ratio (Se:Hg) equivalent to 36.
Http Dx Doi Org 10 1080 05704920903435474, Jan 14, 2010
Abstract This article critically overviews the state-of-the-art of slurry sampling as an approach... more Abstract This article critically overviews the state-of-the-art of slurry sampling as an approach for the minimization of sample preparation prior to the determination of metals and metalloids in complex matrices by spectroanalytical techniques. Relevant factors involved ...
... Article | PDF (225 K) | View Record in Scopus | Cited By in Scopus (28). [10] EM de Moraes Fl... more ... Article | PDF (225 K) | View Record in Scopus | Cited By in Scopus (28). [10] EM de Moraes Flores, APF Saidelles, EL de Moraes Flores, MF Mesko, MP Pedroso, VL Dressler, CF Bittencourt and AB da Costa, Microchem. J. 77 (2004), p. 113. ...
The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ion... more The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ions Pb(II) and Cd (II) biosorption from natural waters. The flame atomic absorption spectrometry was used for quantitative determination and study of the ions Pb(II) and Cd(II) adsorption on the solid phase. The Fourier transform infrared spectroscopy (FT IR) was used to investigate the sisal structure and the specific BET surface area was analyzed. The biosorption potential of sisal as biosorbent for the removal of the ions Pb(II) and Cd(II) from aqueous solution was investigate considering the followings parameters: pH, biomass amount and contact time. Langmuir and Freundlich isotherms were used to evaluate adsorption behavior of the ions on this solid phase. The results showed that sisal has a surface area to adsorption of 0.0233 m 2 g − 1 , and the OH and CO functional groups are the main involved in the biosorption. The best interpretation for the experimental data was given by Freundlich isotherm that proposes a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interactions between sorbed molecules. The maximum monolayer biosorption capacity was found to be 1.85 mg g − 1 for Cd (II) and 1.34 mg g − 1 for Pb (II) at pH 7 and 296 K. This phase solid can be used for biosorption of cadmium and lead in polluted natural waters.
Um sistema contendo Amberlite XAD-2 (estireno-divinilbenzeno) carregado com 2-(2tiazolilazo)-5-di... more Um sistema contendo Amberlite XAD-2 (estireno-divinilbenzeno) carregado com 2-(2tiazolilazo)-5-dimetilaminfenol (TAM) é proposto para amostragem em campo, preconcentração e determinação de cádmio (II) e níquel (II) em amostras de águas naturais usando espectrometria de absorção atômica com chama (FAAS). O processo de otimização foi univariado e os seguintes parâmetros foram estudados: efeito de pH, efeito de vazão de amostragem, concentração da solução e vazão de eluente, efeito de outros ions, precisão e exatidão. Na etapa de amostragem, os ions metálicos são retidos na minicoluna sob a forma de TAM complexos. A amostra é percolada com vazão de 3,0 mL min-1 após filtração usando filtro de 0,45 µm. Posteriormente, a minicoluna é incorporada sobre um sistema em fluxo contínuo e os ions metálicos são eluídos com solução de ácido clorídrico de concentração 1,0 mol L-1 diretamente para o sistema de nebulização do espectrômetro. Para níquel, os limites de detecção (LOD) e quantificação (LOQ) foram 12 e 39 ng L-1 , respectivamente. A precisão expressa como desvio padrão relativo (RSD) para 10 determinações independentes foram 5,5% e 7,0% para concentrações de níquel de 10 e 1,0 µg L-1 , respectivamente. O fator de preconcentração, calculado como a relação entre as inclinações de curvas obtidas pelo presente procedimento e pela aspiração direta foi 637 para um volume de amostra de 150 mL. Para cádmio, os LOD e LOQ foram 22 e 72 ng L-1 , respectivamente. A precisão expressa como RSD, foi 6,0% e 6,8% para concentrações de cádmio de 10 e 1,0 µg L-1 , respectivamente. O fator de preconcentração experimental foi 548, também para um volume de amostra de 150 mL. O procedimento foi aplicado para determinação de cádmio e níquel em águas naturais de baixa salinidade, coletadas de lagoas da Cidade de Salvador, Bahia, Brasil. A system containing Amberlite XAD-2 (styrene-divinylbenzene copolymers) loaded with 2-(2thiazolylazo)-5-dimethylaminophenol (TAM) reagent is proposed for field sampling, preconcentration and determination of cadmium (II) and nickel (II) ions in fresh water using flame atomic absorption spectrometry (FAAS). The optimisation process was univariate and the followings parameters were studied: pH effect, effect of sample flow rate, eluent concentration and flow rate, effect of other ions, precision and accuracy as recovery tests. In the sampling step, metal ions are retained in a minicolumn as TAM complexes. The sample is pumped at 3.0 mL min-1 with on-line filtration using a 0.45 µm filter. Afterwards, the minicolumn is incorporated in a flow-injection system and the metal ions eluted with a solution of 1.0 mol L-1 hydrochloric acid into the nebuliserburner system of the spectrometer. For nickel, the limits of detection (LOD) and quantification (LOQ) were 12 and 39 ng L-1 , respectively. The precision expressed as relative standard deviation (RSD) for ten independent determinations was 5.5% and 7.0% for nickel concentrations of 10 and 1.0 µg L-1 , respectively. The experimental preconcentration factor, calculated as the ratio of the slopes of the calibration curves obtained by the present procedure and manual direct aspiration was 637 for a sample volume of 150 mL. For cadmium, the LOD and LOQ are 22 ng L-1 and 72 ng L-1 , respectively. The precision, expressed as RSD was 6.0% and 6.8% for cadmium concentrations of 10 and 1.0 µg L-1 , respectively. The experimental preconcentration factor was 548 also for a sample volume of 150 mL. The procedure was applied for determination of cadmium and nickel in fresh water samples with low saline concentration, collected in lagoons from Salvador City, Bahia, Brazil.
A procedure has been developed for the simultaneous determination of trace amounts of cadmium, co... more A procedure has been developed for the simultaneous determination of trace amounts of cadmium, copper, chromium, nickel and lead in digested vegetable samples. The method involves solid-phase extraction of the metals using a minicolumn of Amberlite XAD-4 modified with dihydroxybenzoic acid (DHB) and detection by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The elution of the metals from minicolumn was performed with 1.0 mol L −1 hydrochloric acid. Variables associated with flow preconcentration system performance, such as pH, buffer concentration, eluent concentration and sampling flow rate, were optimized. The developed procedure provides enrichment factors of 100, 72, 16, 91 and 53, for cadmium, copper, chromium, nickel and lead, respectively. Detection limits (3σ B) were 0.02 (Cd), 0.23 (Cu), 0.58 (Cr), 0.060 (Ni) and 0.54 (Pb) g L −1. The procedure was applied for determination of metals in samples of guarana and cabbage. The accuracy of the method was checked by the analysis of a certified reference material (NIST 1571, Orchard leaves). Results found were in agreement with certified values.
It has been observed in previous work using high-resolution continuum-source atomic absorption sp... more It has been observed in previous work using high-resolution continuum-source atomic absorption spectrometry that up to 50% of the nickel and vanadium in crude oil, most likely non-polar nickel and vanadyl porphyrin complexes, was already lost at pyrolysis temperatures 4400 1C, whereas the rest of the analyte was stable up to at least 1200 1C. In this work we were investigating the use of a chemical modifier in order to avoid these low-temperature losses and also to make possible a differential determination of the volatile analyte fractions. Oil-in-water emulsions, using Triton X-100 as surfactant, were used for easy sample handling. A mass of 20 mg of Pd, introduced into the graphite tube and thermally pretreated prior to the injection of the emulsion, was found to efficiently prevent any low-temperature losses of nickel and vanadium from crude oil samples up to pyrolysis temperatures of 1200 1C and 1450 1C, respectively. The best characteristic mass obtained was m 0 ¼ 16 pg for Ni and m 0 ¼ 33 pg for V. The limits of detection and quantification were 0.02 mg g À1 and 0.065 mg g À1 , respectively, for Ni, and 0.06 mg g À1 and 0.17 mg g À1 , respectively, for V in oil, based on an emulsion of 2 g of oil in 10 mL. The precision expressed as relative standard deviation (n ¼ 9) for a crude oil containing about 5 mg g À1 Ni and 3 mg g À1 V was 2.0% and 3.1% for Ni and V, respectively. The accuracy of the procedure was verified by analyzing the certified reference material NIST SRM 1634c, trace metals in fuel oil, and the research material RM 8505, vanadium in crude oil.
... Fáabio de Souza Dias,1,2 Lucylia Suzart Alves,1 Walter Nei L. dos Santos,3 Jorge MaurıcioDavi... more ... Fáabio de Souza Dias,1,2 Lucylia Suzart Alves,1 Walter Nei L. dos Santos,3 Jorge MaurıcioDavid,2 and Sérgio Luis C ... 1995; Januzzi, Krug, and Arruda 1997; Lücker 1999; Vassileva, Baeten, and Hoening 2001) and ICP mass spectrometry (Maia, Pozebon, and Curtius 2003; Ni ...
Uploads
Papers by Walter Nei Lopes Santos