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Abstract This paper describes a detailed study on the determination of Cu, Ni, Pb, and V in ethanol-containing Brazilian commercial gasoline by graphite furnace atomic absorption spectrometry (GF AAS) after application of the novel extraction induced by microemulsion breaking (EIMB) for the extraction of analytes from the sample. EIMB is based on the formation and breaking of microemulsions with the sample and an extractant acid solution (typically HNO 3 solution) in the presence of a dispersant agent (typically a short-chain alcohol). After microemulsion breaking, the following two phases are formed: (i) a top phase containing the remaining gasoline and (ii) a bottom phase containing the extracted metals in a medium composed of water, the dispersant agent, and ethanol, which was already present in the Brazilian gasoline. The bottom phase is collected and used for metal quantification by GF AAS. Several parameters that could affect the performance of the method were evaluated. Under optimized conditions, the microemulsion was prepared by mixing 4.6 mL of the sample with 0.35 mL of 1-propanol and 0.05 mL of a 3.5 mol L−1HNO 3 solution. The microemulsion was shaken for 5 min at 110 rpm to enhance the extraction and was then disrupted by the addition of 0.40 mL of a 3.5 mol L−1 HNO 3 solution. The bottom phase formed under these conditions was taken for metal determination by GF AAS. The limits of detection of the method for Cu, Ni, Pb and were 0.7, 0.1, 0.8 and 1.6 μg L−1, respectively. The method was applied in the analysis of five Brazilian gasoline samples, which presented concentrations of Cu, Ni, Pb, and V in the range of 7.1–63 μg L−1, 1.6–2.8 μg L−1, 5.3–9.7 μg L−1, and 24–44 μg L−1, respectively. Recovery tests were performed to assess the accuracy of the proposed method, with observed satisfactory recovery percentages of 87–116%. Graphical abstract Unlabelled Image Highlights • Novel extraction approach is proposed for Cu, Ni, Pb and V determination in gasoline. • Extraction is based on the transference of the analytes to an alcohol/water phase. • Microemulsions were obtained by mixing the sample with 1-propanol and HNO 3 solution. • Microemulsions were disrupted by addition of 0.4 mL of a 3.5 mol L−1 HNO 3 solution. • The experimental procedure was simple, fast and required minimum sample handling. [ABSTRACT FROM AUTHOR]

In this work, we present the development of a method for the determination of acetate and formate in vegetable oils by ion chromatography with conductometric detection following their extraction from samples using a diluted KOH solution. The extraction procedure was optimized using a multivariate approach. The application of a 2 4 full factorial design showed that the mass of sample, extraction time, and KOH concentration presented significant influence on the extraction of both acetate and formate, whereas the temperature presented little influence on the process. As a result, we set the extraction temperature at 22 °C and performed the multivariate optimization of the other variables using a Doehlert design. The optimum conditions were: 4.8 g of sample, 8 mmol L −1 KOH solution and 19 min extraction time. Six samples of vegetable oils (soybean, corn, canola, sunflower and olive) were analyzed and recovery tests provided recovery percentages in the range of 82–118%. [ABSTRACT FROM AUTHOR]

In this work, a polyurethane foam (PUF) functionalized with phenylfluorone (PUF-PF) was packed in a minicolumn and used as an on-line preconcentration system for cadmium and copper determination in water samples. The experimental conditions (both chemical and physical) were optimized to achieve the highest sensitivity. A study of possible ion interference on the retention of cadmium and copper was also performed. The enrichment factors obtained were 14 and 16 for copper and cadmium, respectively, using a preconcentration time of 1 min. The proposed system allowed the determination of metals with limits of detection (3 σ ) of 0.8 and 0.3 μg L − 1 for Cu(II) and Cd(II), respectively. The precision of the procedures was also calculated as 7.6% for Cu(II) (at 25 μg L − 1 ) and 4.0% for Cd(II) (at 10 μg L − 1 ). The limits of quantification obtained were 2.6 and 0.8 μg L − 1 for Cu(II) and Cd(II), respectively. Cadmium and copper contents in water samples (from rivers and swimming pools) were determined by applying the proposed procedure. In these samples, recovery tests were conducted in order to evaluate the accuracy of the method; the recovery percentages varied between 83 and 109%. [ABSTRACT FROM AUTHOR]

This work reports, for the first time, a detailed investigation on the effect of experimental parameters that affect the extraction induced by emulsion breaking. In this study, we evaluated the influence of the type (Triton X-100, Triton X-114, Tween 20 and sodium dodecylsulfate) and concentration of the surfactant employed as emulsifying agent, as well as the type (HCl or HNO 3 ) and concentration of the mineral acid employed for the extraction of As, Cr, Cu, Mn, Pb and V of spiked mineral oil. The metals were added to the mineral oil in the form of organometallic compounds. In all cases, the emulsion breakdown was induced by heating at 90 °C in a thermostatic bath and the extracts were analyzed by graphite furnace atomic absorption spectrometry (GF AAS). The time required to achieve emulsion breakdown and the extraction efficiency were taken as responses for evaluation. The obtained results showed that the extraction of metals was more efficient when Triton X-100 or Triton X-114 were employed in the preparation of the emulsions. Both HCl and HNO 3 provided quantitative extraction of the analytes when combined with these surfactants, except in the case of As, in which the extraction efficiencies were in the range of 22–60%. However, the emulsions prepared with HCl needed longer times to be broken down. Samples of mineral oils (new and used) from vacuum pumps were analyzed and the results compared with those obtained with the model sample. Only As and V could not be determined in the real samples. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach for the extraction of Hg from Brazilian gasoline samples: extraction induced by microemulsion breaking (EIMB). In this approach, a microemulsion is formed by mixing the sample with n-propanol and HCl. Afterwards, the microemulsion is destabilized by the addition of water and the two phases are separated: (i) the top phase, containing the residual gasoline and (ii) the bottom phase, containing the extracted analyte in a medium containing water, n-propanol and the ethanol originally present in the gasoline sample. The bottom phase is then collected and the Hg is measured by cold vapor atomic absorption spectrometry (CV-AAS). This model study used Brazilian gasoline samples spiked with Hg (organometallic compound) to optimize the process. Under the optimum extraction conditions, the microemulsion was prepared by mixing 8.7 mL of sample with 1.2 mL of n-propanol and 0.1 mL of a 10 mol L −1 HCl solution. Emulsion breaking was induced by adding 300 µL of deionized water and the bottom phase was collected for the measurement of Hg. Six samples of Brazilian gasoline were spiked with Hg in the organometallic form and recovery percentages in the range of 88–109% were observed. [ABSTRACT FROM AUTHOR]

Reference methods for quality control of vaccines usually require treatment of the samples before analysis. These procedures are expensive, time-consuming, unhealthy and require careful manipulation of the sample, making them a potential source of analytical errors. This work proposes a novel method for the quality control of thermostabilizer samples of the yellow fever vaccine employing attenuated total reflectance Fourier transform infrared spectrometry (ATR–FTIR). The main advantage of the proposed method is the possibility of direct determination of the analytes (sodium glutamate and sorbitol) without any pretreatment of the samples. Operational parameters of the FTIR technique, such as the number of accumulated scans and nominal resolution, were evaluated. The best conditions for sodium glutamate were achieved when 64 scans were accumulated using a nominal resolution of 4 cm −1 . The measurements for sodium glutamate were performed at 1347 cm − 1 (baseline correction between 1322 and 1369 cm −1 ). In the case of sorbitol, the measurements were done at 890 cm −1 (baseline correction between 825 and 910 cm −1 ) using a nominal resolution of 2 cm −1 with 32 accumulated scans. In both cases, the quantitative variable was the band height. Recovery tests were performed in order to evaluate the accuracy of the method and recovery percentages in the range 93–106% were obtained. Also, the methods were compared with reference methods and no statistical differences were observed. The limits of detection and quantification for sodium glutamate were 0.20 and 0.62% (m/v), respectively, whereas for sorbitol they were 1 and 3.3% (m/v), respectively. [ABSTRACT FROM AUTHOR]

This present work proposes a new approach for diesel oil preparation for metals determination by ICP-MS. The proposed methodology is based on the extraction of the elements of interest into an aqueous phase employing the extraction induced by emulsion breaking procedure. In this approach, the diesel oil was emulsified with an acid surfactant (Triton X-114) solution in order to form a stable water-in-oil emulsion. Further, the emulsion was broken by centrifugation for 60 min at 3200 rpm, yielding two separated phases: (i) the upper organic phase, containing the diesel oil mixed with the surfactant and (ii) the lower acidic aqueous phase, containing the elements of interest that were extracted from oil. Then, the lower phase was collected, diluted and the analytes were determined by ICP-MS using the internal standardization method. The optimization of the methodology was carried out by analyzing the effect of several parameters that could affect the extraction efficiency such as the concentrations of HNO3 and Triton X-114 in the solution used for emulsification (and extraction), the extraction and collection times and the calibration strategy. The limits of detection and quantification for the elements of interest (Al, Cu, Mn, Ni, Sn and V) were in the range of 26–88 ng L−1 and 86–295 ng L−1, respectively. The accuracy of the methodology was tested by the analysis of spiked samples, since there are no certified samples of diesel oil available in the market. The recovery percentages were in the range of 84–113%. The developed methodology was successfully applied in the metals determination in five commercial diesel oils of different brands. [ABSTRACT FROM AUTHOR]

Abstract: This present work reports the development and evaluation of a method for the direct determination of manganese in waters extracted during petroleum exploitation by Electrothermal Atomic Absorption Spectrometry (ET AAS) using Ir–W as permanent modifier. These waters, usually called produced waters, contain a wide range of organic and inorganic substances and are characterized by their high salinity. In order to achieve suitable experimental conditions for the method application, studies about the effect of operational variables (chemical modifier, pyrolysis and atomization temperatures) were performed, as well as the establishment of convenient calibration strategy. The best results were verified when the temperatures of pyrolysis and atomization were 1000°C and 2300°C, respectively, and using Ir–W as permanent modifier. The results showed that manganese can be determined by the standard addition method or employing external calibration with standard solutions prepared in the same salinity of the samples (with NaCl). Three real samples with salinities varying between 74 and 84‰ were successfully analyzed by the developed procedure. The limits of detection and quantification were 0.24 and 0.80μgL−1, respectively, in purified water, and 0.34 and 1.1μgL−1, respectively, in 0.4molL−1 NaCl medium (approximately 23‰ salinity). [Copyright &y& Elsevier]

Abstract: The present work reports the development of a method for the determination of lead in aviation gasoline samples by electrothermal atomic absorption spectrometry (ETAAS). The samples were emulsified before injecting into the spectrometer in order to avoid the high instability observed in the signals when the samples were injected directly without any treatment. Stable detergent emulsions were obtained by mixing 1mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4mL of aviation gasoline. These emulsions generated constant integrated absorbance signals for 5h at least. Several parameters related to the emulsion formation (Triton X-100 and HNO3 concentrations) and temperature program (pyrolysis and atomization temperatures and heating rate and the final temperature of the drying step) were evaluated. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion influenced the sensitivity of the lead measurements as well as the heating rate utilized in the drying step. The use of a chemical modifier was necessary, being that the Pd conventional modifier presented better performance than the permanent Ir modifier. The limits of detection and quantification derived for the methodology were 1.2 and 4.0μg L−1. Six samples of aviation gasoline were analyzed and the lead concentrations varied between 11.6 and 64.2μg L−1. A recovery test was performed in order to attest the accuracy of the procedure and recovery percentages between 88 and 112% were observed. [Copyright &y& Elsevier]

Abstract: This paper describes the extraction/pre-concentration of Zn from diesel oil and its determination by Flame Atomic Absorption Spectrometry (FAAS), proposed as a novel approach for these kinds of analyses and the multivariate optimization of the proposed procedure. The extraction of Zn is based on the emulsification of an aqueous solution containing Triton X-114 and HNO3 with diesel oil samples followed by breaking of the emulsion by heating. The aqueous phase obtained after the emulsion breaking was collected and used for Zn quantification by FAAS. The methodology was optimized using a Doehlert design and the system variables were the concentrations of surfactant and HNO3 in the solution employed in the emulsification and the temperature used in the emulsion breaking. The ratio between absorbance and the time required to break the emulsions was taken as response. Two sets of experiments, using different emulsifier agents, were run: the first one using Triton X-100 and the second one using Triton X-114. At optimized conditions, the emulsions were prepared by mixing 10mL of diesel oil with 2mL of a solution containing 5% w/v of Triton X-114 and 15% v/v of HNO3 and broken by heating at 80°C. The proposed analytical procedure was applied in the analysis of six real samples of diesel oil and a recovery test was carried out by spiking the samples with known amounts of Zn (25 and 50μgL−1), added as organometallic oiled standard. Recovery percentages achieved in this test were between 92 and 109%. [Copyright &y& Elsevier]

Abstract: This paper reports the development of a method for the determination of copper and iron in jet fuels employing the electrothermal atomic absorption spectrometry (ETAAS). In order to allow the direct determination of the analytes, the samples were injected into the graphite furnace as detergent emulsions in order to avoid their volatilization during analysis. The results obtained in this work indicated that a stable emulsion can be formed by mixing 1mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4mL of jet fuel. The injection of emulsions provided integrated absorbance signals with suitable sensitivity and precision for 300min at least. The addition of chemical modifier was not necessary because background values were always very low, allowing the use of pyrolysis temperature around 1000°C for both analytes. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion had remarkable influence on the sensitivity as well as the heating rate employed in the drying step. Under the best conditions established in the present work, limits of detection of 0.50 and 0.46μgL−1 were observed for copper when oil-based and aqueous standards were added to the emulsions for calibration, respectively. For iron, the limits of detection were 0.88 and 0.90μgL−1 for oil-based and aqueous standards, respectively. The method was applied in the determination of Cu and Fe in five samples of jet fuels and a recovery test was performed, producing recovery percentages between 95% and 105%. [Copyright &y& Elsevier]

Abstract: Partial least squares Fourier-transform infrared (PLS-FTIR) models were developed for the quality assessment of estuarine sediments through the evaluation of several physico-chemical parameters. Models were based on the chemometric treatment of attenuated total reflection (ATR) spectra directly obtained from samples previously lyophilized and sieved through a lower than 63μm grid. Spectra were scanned from 3997 to 523cm−1, averaging 36 scans per spectrum with a nominal resolution of 8cm−1. Models were built using reference data obtained for sediment samples collected from Ria de Arousa estuary. Hierarchical cluster classification of sediment ATR spectra was employed for the establishment of the independent calibration and validation sample sets. Several parameters, like trace element content (Sn, Pb, Cd, As, Sb and total Cr and also acid soluble, reducible and oxidizable Cr fractions), elemental composition (carbon (C), nitrogen (N) and hydrogen (H) content), pH, redox potential (Eh), together with the amount of fulvic and humic acids, were evaluated. Residual predictive deviation (RPD) values ranging from 1.79 to 2.28 were obtained for all trace elements with the exception of Pb, which exhibited a RPD value of 1.5, similar to those obtained for the different extractable fractions of Cr. Regarding the elemental analysis, excellent RPD values were also obtained for C and N, but for H only adequate values for screening purposes were achieved. Prediction errors for pH and Eh were 0.13units and 30mV, respectively, thus indicating the good prediction capabilities of the method. For humic substances, excellent results were obtained for humic acids when compared with fulvic ones. In short, direct ART-FTIR measurements on solid sediments allow a rapid screening of many components of sediments and quantitative data of the main physico-chemical parameters. [Copyright &y& Elsevier]

Abstract: This paper reports the multivariate optimization of a liquid–liquid extraction procedure for the determination of 15 EPA-polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography with fluorescence detection. A Doehlert design was used to find optimum conditions for the procedure through Response Surface Methodology. Three variables (total volume of hexane, number of extraction steps and duration of such steps) were elected as factors in the optimization study. A principal component analysis (PCA) was run with optimized data, resulting in four groups of PAHs, ordered according to their molecular weight. Final working conditions were established in order to achieve a more robust methodology in relation to all fifteen PAHs under study. Best results could be observed when 77mL of hexane were divided in four consecutive extraction steps with 18min each. These experimental conditions were applied in the analysis of a spiked river water sample, and the recoveries varied between 80.9 and 106%, with an average value of 97.1±6.8%. The application of the methodology to river water showed that the method has a good average precision for the studied PAHs. [Copyright &y& Elsevier]

In this work the re-fixation of mobilized copper (Cu) that was released from a deactivated pilot Cu ore dressing plant in the tropical rain forest at Southeastern Amazon (Carajás) was studied. Samples of top soils, decay leaf litter deposited on soils, roots and leaves of standing biomass were taken for the determination of Cu concentration in order to evaluate the distribution of it between different environmental compartments. In the sampling points near to the now extinct plant, total Cu concentrations in the soil reached an average value of 2140μgg−1 above the natural level of about 40μgg−1, being that bioavailable Cu estimated by DTPA method varied from 1. 9 to 20. 7% of this total. From the data was possible to calculate that the soil compartment is able to hold around 10kgCu/m2 of ground. Roots of the standing biomass in that area hold around 17gCu/m2, while the Cu content in leaves showed to be largely independent of the Cu level in the soil. Copper in the leaves was estimated as around 1g/m2 of ground area. In turn, the decay leaf litter deposited on soil can hold about 1. 6gCu/m2. The terrestrial system surrounding the abandoned pilot plant demonstrated great buffer capacity to retain mobile Cu released by anthropogenic activities in the area. [Copyright &y& Elsevier]

Abstract: The present work reports the development of a methodology for the direct determination of vanadium in high saline waters derived from offshore petroleum exploration employing electrothermal atomic absorption spectrometry. Such waters, usually called produced waters, present complex composition containing various organic and inorganic substances. In order to attain best conditions (highest sensitivity besides lowest background) for the methodology, studies about the effects of several variables (evaluation of pyrolysis and atomization temperatures, type of chemical modifier, concentration of modifier and pyrolysis time) and the convenient calibration strategy were performed. Best conditions were reached with the addition of 10μg of NH4H2PO4 as chemical modifier employing pyrolysis (during 10s) and atomization temperatures of 1500 and 2700°C, respectively. Obtained results indicated that, in this kind of sample, vanadium can be determined by standard addition method or employing an external calibration approach with standard solutions prepared in 0.8moll−1 NaCl medium. In order to evaluate possible matrix interferences, a recovery test was performed with five spiked samples of produced waters. The limit of detection, limit of quantification and relative standard deviation in 0.8moll−1 NaCl medium were also calculated and the derived values were 1.9μgl−1, 6.3μgl−1 and 5.6% (at 10μgl−1 level), respectively. [Copyright &y& Elsevier]

Abstract: This paper reports the development of a new strategy for low-level determination of copper in water samples by using a flow-injection system coupled to solid-phase extraction (SPE) using flame atomic absorption spectrometry (F AAS) as detector. In order to preconcentrate copper from samples, a minicolumn packed with a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis-(4-vinyl-phenyl)-methyl]-pyrrolidine-1-carboxylic acid ethyl ester was used and the synthesis procedure is described. System operation is based on the on-line retention of Cu(II) ions at pH 9.0±0.2 in a such minicolumn with posterior analyte elution with 2moll−1 HCl directly to the F AAS nebulizer. The influence of several chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) variables that could affect the performance of this system were investigated as well as the possible interferents. At optimized conditions, for 2min of preconcentration time (13.2ml of sample volume), the system achieved a detection limit of 1.1μgl−1, a R.S.D. 1% at 20μggl−1 and an analytical throughput of 25h−1, whereas for 4min of preconcentration time (26.4ml of sample volume), a detection limit of 0.93μgl−1, a R.S.D. 5.3% at 5μgl−1 and a sampling frequency of 13h−1 were reported. [Copyright &y& Elsevier]

This paper reports the development of a new approach for total phenol distillation using a focussed microwave oven, aiming its determination in petroleum refinery effluents and sour waters. In the procedure, 25 ml of sample is distilled during 15 min at 210 W power. At these conditions, recoveries as high as 95% are obtained, making possible the determination of total phenol in the samples without any interference and in a time significantly lower than that required by the reference method. In the course of the research, the influence of the distilled volume was investigated and a Doehlert matrix was employed for the multivariate optimization of the irradiation power and time. Quantification of phenol was spectrophotometrically performed in a FIA system, exploring classical reaction of phenol with 4-amineantipyrine and ferricyanide. Aqueous standards solutions of phenol could be directly injected in the FIA system for calibration purposes, making the procedure very simple and low time-consuming. A detection limit of 10 μg l−1 was achieved as well as a quantification limit of 33 μg l−1, becoming the procedure very suitable to be applied in the control of total phenols in effluents from petroleum industry. [Copyright &y& Elsevier]

This paper reports the determination of arsenic and antimony in naphtha by employing electrothermal atomic absorption spectrometry (ETAAS) as the analytical technique. In order to promote the direct determination of the analytes in the very volatile naphtha, the formation of a microemulsion with different surfactants (Triton X-100 and Brij-35) and different chemical modification strategies were tested. The results indicated that Triton X-100 is the best emulsification agent for naphtha in both As and Sb determination when it is employed at a concentration of 1% w/v in the microemulsion. Under these conditions, the microemulsion was stabile for at least 2 h. By using Brij-35 it was possible to achieve good stability only in the first 15 min. Among all chemical modification approaches investigated (Ir permanent modifier, W-Ir permanent modifier, and Pd modifier), the Ir permanent modifier provided better sensitivity for both analytes and allowed a higher pyrolysis temperature, which decreased the background signals at lower levels. Under the best conditions established in this work, an RSD of 4.6% (20 μg L-1) and a detection limit of 2.7 μg L-1 were observed for arsenic. For antimony, an RSD of 4.0% (20 μg L-1) and a detection limit of 2.5 μg L-1 were obtained. The accuracy of the procedure was assessed by analyzing spiked samples of naphtha from different origins. [ABSTRACT FROM AUTHOR]

An on-line automated flow injection system with microwave-assisted sample digestion was used to perform silicate rock dissolution in acid medium for iron determination. For this purpose, a continuous flow system was built up by using an automatic flow injection analysis (FIA) system coupled to a flame atomic absorption spectrometer (FAAS), including a focused microwave oven unit. Inside the microwave cavity was inserted a polytetrafluoroethylene (PTFE) reactor coil (300 cm length and 0.8 mm i.d.) where the dissolution takes place. Chemical and flow variables as well as iron determination parameters were studied. In the flow system, a slurry of the rock sample (50 mg in 200 ml of acid mixture HF+HCl+HNO3) is pumped through the reaction coil and the microwaves are turned on. After elapsed the time required to complete the sample dissolution, the mixture is pumped again in order to fill the sampling loop (500 μl). Then, by changing the valve position, a water carrier stream pushes the sample solution through the flame atomic absorption spectrometer nebulizer. To achieve an accurate determination of the rock certified materials, the slurry sample was irradiated during 210 s at 90 W power. Working in that condition, a detection limit of 0.80 μg ml−1 (which corresponds to an Fe2O3 content of 0.46%) and an analytical throughput of 10 h−1 were achieved. The relative standard deviation (R.S.D.) of the method varied between 1 and 11% when applied to the rock certified materials. [Copyright &y& Elsevier]

This paper reports the development of a methodology for the determination of arsenic in petroleum refinery aqueous streams containing large amounts of unknown volatile organic compounds, employing electrothermal atomic absorption spectrometry with polarized Zeeman-effect background correction. In order to make the procedure applicable, the influence of chemical modification and the drying step was examined. Also, pyrolysis and atomization temperatures and the amount of nitric acid added to the sample were optimized using a multivariate approach based on Doehlert matrix. Obtained results indicate that, in this kind of sample, arsenic must be determined by standard addition procedure with a careful control of the drying step temperature and ramp pattern. In order to evaluate the accuracy of the procedure, a test was performed in six spiked samples of petroleum refinery aqueous streams and the relative errors verified in the analysis of such samples (added As between 12.5 and 190 μg l−1) ranged from −7.2 to +16.7%. The detection limit and the relative standard deviation were also calculated and the values are 68 pg and 7.5% (at 12.5 μg l−1 level), respectively. [Copyright &y& Elsevier]

This paper reports a new strategy for flow injection spectrophotometric Cu (II) determination in petroleum refinery wastewaters, exploring its reaction with sodium diethyldithiocarbamate (DDTC), without solvent extraction step, thus avoiding the use of harmful organic solvents. The influence of several chemical and flow variables was studied as well as the possible interferences. Under optimized conditions, the flow system was able to process 63 samples per hour, with a detection limit of 23 ng ml−1 and a RSD of 2.1% at the 0.2 μg ml−1 level. In order to attest the accuracy of the methodology, seven samples of effluents were analyzed by the proposed method and the results were compared with that obtained by FAAS. It was observed that the physical interferences verified in the FAAS procedure, which only permits its use by the standard addition method, were not present in the FIA procedure. The results obtained by FIA method were not statistically different from that obtained by FAAS-standard addition method. Also, the analysis of three spiked samples provided recovery percentages between 93 and 103%. [Copyright &y& Elsevier]

An electrothermal atomic absorption spectrometry (ETAAS) with polarized Zeeman background correction was used for determining selenium in petroleum refinery aqueous streams containing large amounts of volatile unknown organic compounds. Some parameters that might affect the measurement were investigated such as the amount of matrix modifier added, the temperature program and the calibration mode employed. Obtained results indicate that, in this kind of sample, selenium must be determined by standard addition procedure with a careful control of the dry step temperature and ramp pattern. Also, the results show that 2.5 μg of Pd must be added as matrix modifier to stabilize the analyte in the range of 2–20 ng Se. In order to evaluate the accuracy of the procedure, selenium was determined in 18 samples by ETAAS and hydride generation atomic absorption spectrometry (HGAAS) (as reference methodology). In both techniques the results agreed well. [Copyright &y& Elsevier]

The purpose of this study was to demonstrate the feasibility of determining metals (Cr, Mn, Zn, Fe, and Cu) in commercial dietary supplements using microwave-induced plasma optical emission spectrometry (MIP OES) after fast ultrasound-assisted extraction. Various parameters affecting the extraction process, such as the nature and concentration of the extractant solution, sonication time, and sample mass, were evaluated. Under the optimal conditions, it was possible to quantitatively extract metals from the samples by sonicating 1.0 g of the supplement dispersed throughout 25 mL of a 1.0 mol L−1 HNO3 for only 5 min. The developed method was applied to determine the analytes in four dietary supplements available in the Brazilian market. The results obtained with the extraction method were compared with the values obtained when the samples were completely mineralized with concentrated HNO3 in a microwave oven. There were no statistical differences between the developed and reference methods when the paired Student's t-test was applied with a 95% confidence level. The application of ultrasound-assisted extraction was demonstrated to be advantageous compared to total sample digestion. This approach allowed the use of a higher mass of the sample, thereby enhancing the analytical capability of the method. Furthermore, employing less severe conditions, such as lower energy and a diluted acid solution, simplified and reduced the cost of the procedure compared to mineralization. [ABSTRACT FROM AUTHOR]

This study reports a simple and efficient method for the simultaneous determination of Cd, Mn, Pb, and Sb at trace levels in gasoline samples by discrete sample introduction in inductively coupled plasma mass spectrometry (ICP-MS), employing the extraction induced by microemulsion breaking as a sample preparation method. In this work, a microemulsion was formed by mixing 0.7 mL of the gasoline sample with 0.28 mL of ethanol and 0.02 mL of 7 mol L−1 HNO 3 solution. Afterwards, 0.1 mL of ultrapure water was added to induce microemulsion breaking. This lead to the formation of two different phases: (i) a top organic phase and (ii) a bottom aqueous phase that contained acid, ethanol and the extracted analytes. After that, 20 μL of the bottom phase (extract) was collected, and the analyte concentrations were determined by discrete sample introduction in ICP-MS. Calibration curves with 20 μg L−1 of Rh as an internal standard were set up to each analyte in the range from 1 up to 10 μg L−1, wherein the standard solutions were prepared in the matrix-matched extract (70:25:5, ethanol: deionized water: 7 mol L−1 HNO 3 solution). The optimization of the EIMB conditions was carried out by analyzing the effects of the parameters that could affect the extraction efficiency, such as the relation between the nature of the alcohol and the proportion of the volumes of the microemulsion constituents (sample, HNO 3 and alcohol), acid concentration, and the water volume used for the microemulsion breaking. The following limits of detection relative to the amount of sample were obtained: 0.03 (Cd), 0.49 (Mn), 0.07 (Pb) and 0.02 (Sb), all of them in μg L−1. The accuracy of the method was evaluated by the analysis of spiked samples, because no certified gasoline reference material is available. The average recoveries achieved for every analyte ranged from 96% to 114%. The developed methodology was successfully applied to the determination of these metals in five commercial gasoline samples. Image 1 • Extraction of Cd, Mn, Pb and Sb was achieved using a microemulsion breaking. • Quantification was carried out with a segmented flow injection ICP-MS system. • Samples of Spanish gasoline were analyzed using the developed method. [ABSTRACT FROM AUTHOR]

Permethrin is a synthetic pyrethroid insecticide that is largely used in the impregnation of fabrics employed for different purposes. This paper reports a detailed study on the conditions for its extraction from fabrics and for its determination by ultra-high performance liquid chromatography with diode array detection (UHPLC-DAD). Several parameters that could affect the extraction efficiency of permethrin were evaluated, such as the extraction time, agitating mode (mechanical or ultrasound-assisted), solvent type (methanol or acetonitrile), concentration, and volume. Under optimized conditions, the extraction was performed for 10 min using a 2 × 2 cm piece of impregnated fabric and 5 mL of pure methanol. The flask containing the sample and the solvent was shaken mechanically using a horizontal roller mixer. The accuracy of the method was assessed by a recovery test, which presented satisfactory results ranging from 86.8% to 95.2%. The method was employed in the analysis of nine samples of commercial fabrics of different colors and grammages that were impregnated with permethrin. The concentration of permethrin found in these samples varied between 25.6 ± 4.2 and 934 ± 119 mg m−2. [ABSTRACT FROM AUTHOR]

A composite electrode based on acrylonitrile‐butadiene‐styrene and graphite chemically modified with a bismuth film (AGCE‐BiF) was applied for the simultaneous determination of Cd2+ and Pb2+ in gasoline samples. Extraction induced by microemulsion breaking (EIMB) was used for the first time in the preparation of the samples for electroanalysis. AGCE‐BiF was characterized by SEM, AFM, CV, and SWASV. The sensor showed an increase in sensitivity via in situ modification with bismuth film. The LOD was 4 μg L−1 for Cd2+ and 2 μg L−1 for Pb2+. The results showed satisfactory recoveries and precision, being statistically compatible to those obtained with FAAS. [ABSTRACT FROM AUTHOR]

The present work proposes a simple method for direct determination of Cu and Mn in commercial fruit juices and nectars by graphite furnace atomic absorption spectrometry (GF AAS). We analyzed samples of different flavors (orange, mango, passion fruit, peach, and grape) and brands of Brazilian commercial fruit juices and nectars. We also carried out a study to define a suitable temperature program and to optimize the calibration conditions. It was possible to determine Cu and Mn in the samples just after a simple dilution of samples with a 0.70 mol L−1 HNO3 solution, except in the case of grape juice. We compared the results obtained with the proposed method to those obtained after a traditional treatment based on acid digestion in a microwave oven, and no significant differences were observed (except for grape juice). The accuracy of the method was assessed through a recovery test, which provided recovery percentages in the range of 81–117%. Precision was always better than 8%, and the limits of quantification for Cu and Mn were 6 μg L−1 and 9 μg L−1, respectively. We analyzed twenty-two samples, and the concentrations of Cu and Mn were in the range of 24.1–321 μg L−1 and 116–3296 μg L−1, respectively. Statistical analysis using a two-way analysis of variance (ANOVA) at 95% confidence level showed that flavor and brand impacted on the concentration of the analytes in the samples. Among the samples analyzed, the grape juice presented the highest concentrations of both Cu and Mn. [ABSTRACT FROM AUTHOR]

• A sampling device was developed for passive sampling of organic solar filters. • Acetonitrile was employed as acceptor phase inside the semipermeable membrane device. • The solar filters were quantified in the extracts by HPLC-DAD. • Six solar filters were collected from swimming pool waters. Sunscreens are used to protect skin against ultraviolet radiation, avoiding the damages that can be caused by it. However, in vitro and in vivo studies report that some organic substances employed as sunscreens can alter the biological effects of several hormones. Therefore, a methodology for passive sampling using a semipermeable membrane device (SPMD) was developed for the extraction and preconcentration of some organic compounds employed in sunscreen formulations, such as benzophenone (BZP), 2-hydroxy-4-methoxybenzophenone (BZP-3), 3-(4-methylbenzylidene)-camphor (4-MBC), 2-ethylhexyl-4-methoxycinnamate (4-MCN), 2-ethylhexyl salicylate (EHS), and homomethyl salicylate (HMS), from swimming pool waters where exposure to these substances is unintended. The determination of these analytes in the acceptor phase was performed using high performance liquid chromatography with diode array detection (HPLC-DAD). The optimization of the methodology included the evaluation of several variables, such as type and volume of acceptor phase, dimensions and time of exposure of the SPMD, sample pH, and volume. The optimum conditions for the collection of the solar filters were achieved with an 8-cm device filled with 3.0 mL of acetonitrile and without adjustment of the sample pH, which was approximately 5.8. The collection time was 24 h. Afterwards, some parameters of merit of the developed method were determined. The working range for BZP, BZP-3, 4-MBC, 4-MCN, EHS, and HMS was established as 25–500 μg L–1. The methodological limits of detection and quantification for these analytes were 0.2–1.0 μg L–1 and 0.7–3.1 μg L–1, respectively. Quantification of the analytes was performed on four samples collected from different swimming pools. Recovery tests were performed with the samples spiked with 100 μg L–1 of each substance, and recovery percentages in the range of 75–116% were obtained. The performance of the SPMD was also verified through the determination of BZP-3, EHS, and HMS in a swimming pool water sample intentionally contaminated with a commercial sunscreen. [ABSTRACT FROM AUTHOR]

Producing solar fuels through semiconductor‐based photocatalytic water splitting is one of the main options for worldwide employment of non‐fossil energy sources. Nonetheless, the relatively low efficiency of the known photocatalysts, the high prices of composing elements, and the costly preparation methods render expensive devices that would not be economically competitive with fossil energy sources. Herein, we present a facile method for the preparation of both round hematite (Fe2O3) nanoparticles, with average diameter of (56±7) nm, and of niobium‐doped hematite nanoparticles with similar size and morphology. Thin films of these nanoparticles were assembled through electrophoretic deposition, resulting in homogeneous photoanodes with nanometer thickness that can split water, under simulated solar irradiation, to produce oxygen in a photoelectrochemical cell. The optimization of the film composition and thickness resulted in the improvement of the photocurrent from 352.3 to 1,342.5 μA cm−2 at 1.23 V vs RHE for the pristine hematite and Nb‐doped hematite, respectively, both with thickness of (499±63) nm. This enhancement in the oxidation reaction yield is a clear consequence of the improvement of charge carriers transport along the nanoparticle structure due to niobium doping and adequate light absorption/charge transfer balance of the photoelectrode under operation. [ABSTRACT FROM AUTHOR]

In this work, a separation/preconcentration method is proposed for the determination of Cd(II) and Pb(II) in swimming pool waters, using ammonium pyrrolidine dithiocarbamate (APDC) as a complexing agent and unloaded polyurethane foam (PUF) as a sorbent. The proposed method was optimized, and the defined optimal conditions were a pH of 7, 30 min of shaking time, 400 mg of PUF, and 0.5% (m/v) of the APDC solution. The release of Cd(II) and Pb(II) from the solid phase was achieved through the total digestion of PUF using a microwave-assisted acid approach with a 10.5 mol·L−1 HNO3 solution. The methodology was applied to four samples of swimming pool water for the determination of Cd(II) and Pb(II) using graphite furnace atomic absorption spectrometry (GF AAS). The limits of detection and quantification obtained were 0.02 and 0.06 μg·L−1 for Cd(II) and 0.5 e 1.8 μg·L−1 for Pb(II), respectively. We analyzed four samples of swimming pool waters, finding Cd concentrations between 0.22 and 1.37 μg·L−1. On the other hand, only one sample presented Pb concentration above the limit of quantification (11.4 μg·L−1). Recovery tests were performed by spiking the samples with known concentrations of the analytes, and recovery percentages between 82% and 105% were obtained. [ABSTRACT FROM AUTHOR]

The goal of this work was to propose a novel method for the solid-phase extraction of the herbicides diquat (DQT2+) and difenzoquat (DFQT+) from aqueous medium using polymeric Amberlite XAD-2 and XAD-4 resins in the presence of sodium dodecylsulfate (SDS). The addition of SDS to the medium was of fundamental importance in order to allow the formation of a negatively charged surface able to sorb the cationic solutes. Several factors that could influence the sorption process, such as SDS concentration in the medium, sorbent mass, pH, ionic strength, and initial concentration of the solutes were investigated. Kinetic studies were also performed to model the system and to identify the mechanisms that operate the sorption process of the herbicides. SDS concentration in the medium presented remarkable influence on the extraction efficiency, achieving maximum values when the ratios [SDS]/[herbicide] were approximately 90, for XAD-2, and 22 and 11 for DQT2+ and DFQT+, respectively, for XAD-4. The sorption process followed a pseudo second-order kinetic in all cases studied. It was also found that an intraparticle diffusion process controlled exclusively the sorption of the herbicides by the Amberlite XAD-2 and XAD-4 resins in the first 15 min, becoming less active with time. [ABSTRACT FROM AUTHOR]

This work proposes a novel method to determine the Cd(II) and Cr(III) content in commercial sugar samples. It is based on the extraction of the analytes (as ammonium pyrrolidine dithiocarbamate complexes) into a semipermeable membrane device (SPMD) filled with CHCl 3. After extraction, the SPMD was deployed and opened, and the analytes were recovered from the organic phase by back extraction with a 4.2 mol L−1 HNO 3 solution. The analytes present in the acid extract were measured with graphite furnace atomic absorption spectrometry. Under optimized conditions, the limit of quantification of the method was 1.2 and 3.1 ng g−1 for Cd(II) and Cr(III), respectively. Twelve samples of different types of sugar were analyzed. In addition, a recovery test was performed to evaluate the accuracy of the method. The recovery percentage was 90 %–102 % for Cd(II) and 85.2 %–103 % for Cr(III). • A method was developed for the determination of Cd and Cr in commercial sugar, based on a membrane-mediated extraction. • The semipermeable membrane device used for the extraction of Cd(II) and Cr(III) was assembled with chloroform as an internal phase. • The analytes were extracted in the form of ammonium pyrrolidinedithiocarbamate (APDC) complexes. • Analytes were back extracted from chloroform to an HNO 3 solution before their determination by GF AAS. • The developed method was able to determine very low concentrations of Cd and Cr in different types of sugar. [ABSTRACT FROM AUTHOR]

The present work proposes a method for the direct determination of Al, Cu, Cr, Fe and Ni in Brazilian carbonated soft drinks by electrothermal atomic absorption spectrometry (ETAAS). Samples of different flavors packed in containers made of different materials (polyterephthalate ethylene and glass bottles, and aluminum and steel cans) were analyzed. The method was optimized by building up pyrolysis and atomization curves in sample medium and by evaluating the calibration approach. Under optimized conditions, recoveries in the range of 92–104% were obtained in the evaluation of method accuracy. The limits of quantification for Al, Cu, Cr, Fe and Ni were 2.3, 0.93, 0.17, 0.90 and 1.2 μg L −1 , respectively. Also, the impact of the material used in the packaging and flavor on the concentrations of each metal in the samples was evaluated. It was proved that neither flavor nor packaging material affected the concentrations of Al and Fe in the samples. On the other hand, the packaging material influenced the concentration of Cu, Cr and Ni, and only the flavor affected the concentration of Cu in the samples. These conclusions were based on the data obtained from the application of a two-way ANOVA evaluation at 95% confidence level. [ABSTRACT FROM AUTHOR]

This work reports the development of a novel extraction method for total Hg determination in oil samples. After extracting Hg from samples it was quantified in the extracts by cold vapor atomic absorption spectrometry (CV-AAS), employing a laboratory-made gas–liquid separator (GLS) and NaBH 4 as reducing agent. The extraction of Hg from samples was carried out by extraction induced by emulsion breaking (EIEB), which is based on the formation and breaking of water-in-oil emulsion between the oil samples and an extractant solution containing an emulsifying agent (surfactant) and nitric acid. Operational parameters of the GLS were evaluated in order to set the best performance of the measurement system. In these studies it was proven that the volume of sample and the concentration of HCl added to the sample extracts had significant influence on Hg response. The best conditions were achieved by adding 0.5 mL of a 0.3 mol L −1 HCl solution on 1 mL of sample extract. The extraction conditions were also optimized. The highest efficiency was observed when 4 mL of a solution containing 2.5% triton X-100 and 15% v/v HNO 3 were employed for the extraction of Hg contained in 20 mL of sample. Emulsion breaking was performed by heating at 80 °C and took approximately 20 min. The limit of quantification of the method was 1.9 µg L −1 and recovery percentages between 80% and 103% were observed when spiked samples (2 and 10 µg L −1 ) of diesel oil, biodiesel and mineral oil were analyzed. [ABSTRACT FROM AUTHOR]

[Display omitted] • We developed a HPLC-DAD method for the determination of cocaine adulterants in Brazilian Real banknotes. • Acetaminophen, levamisole, caffeine, lidocaine, cocaine, diltiazem and phenacetin were determined in the samples. • The substances were extracted from samples by mechanical agitation with with acetonitrile. • We analyzed 158 banknotes and only one did not presente any of the target substances. Cocaine is a tropane alkaloid extracted from coca leaves, a common bush found in Andean regions of South America. Many medicines are added to the final product to increase the profits, keeping similar or higher effects than cocaine alone. Stimulants, anesthetics, and sedatives are the most found adulterants. The goal of this work was to propose a novel analytical methodology to determine cocaine and the main medicines found in street cocaine in Real banknotes using high-performance liquid chromatography with diode array detection (HPLC-DAD). Under optimized conditions, the target substances were extracted with acetonitrile, and the cleanup of the obtained extracts was carried out by separating the fatty layer at low temperature (–20 °C). The volume of extract was reduced under nitrogen flow and adjusted to 2.5 mL with a solution containing 95% (v/v) of phosphate buffer (10 mmol L−1, pH = 2.5) and 5% (v/v) of acetonitrile. Under these conditions, it was possible to identify and quantify cocaine and its adulterants in the samples, with limits of quantification of 0.29, 0.012, 0.16, 0.22, 0.026, 0.078, and 0.14 µg per banknote for acetaminophen, levamisole, caffeine, lidocaine, cocaine, diltiazem, and phenacetin, respectively. We analyzed 158 samples, and only one did not present any of the tested substances. Higher amounts of the tested substances were verified in banknotes of lower value. [ABSTRACT FROM AUTHOR]

Abstract: This work reports the optimization of a method, based on the extraction induced by emulsion breaking, for the determination of trace concentrations of Cr and Mn in edible oils by electrothermal atomic absorption spectrometry (ETAAS). In the method, a water-in-oil emulsion was prepared by mixing the oil sample with an acid solution (HNO3) of Triton X-114 to allow the intense contact between the sample and the extractant acid solution. Afterwards, the emulsion was broken by heating and the acid aqueous phase deposited in the bottom of the flask was collected for the determination of the metals of interest. The method was optimized by studying the influence of several parameters such as the concentration of HNO3 and the emulsifier agent (Triton X-100 and Triton X-114) in the extractant solution. The best results were verified when the procedure was performed with 5mL of the sample and 1mL of the extractant solution containing 15%m/v of Triton X-114 and 2.8molL−1 of HNO3. Also, the fastest emulsion breaking was verified when the emulsions were heated at 90°C. In these conditions, the emulsions were broken in approximately 10min. The quantification of Cr and Mn in the extracts was carried out by external calibration with aqueous standard solutions, which simplified the procedure. The limits of detection for the determination of Cr and Mn in the oil samples were 66 and 36ngL−1, respectively, and the limits of quantification were 219 and 120ngL−1, respectively. The developed method was applied in the determination of Cr and Mn in twelve samples of edible oils produced with different oleaginous. Recovery tests were performed to attest the accuracy of the method, being observed recovery percentages in the range of 86–115%. [Copyright &y& Elsevier]

Abstract: This paper reports the use of polyurethane foam (PUF) as solid support for diffuse reflectance spectrophotometric determination of Malachite Green (MG), a well known cationic dye used as biocide in the aquaculture industry, using sodium dodecylsulfate (SDS) as a counter ion. The method was based on the formation of an ionic-pair between the dye and the anionic surfactant SDS, which was sorbed onto PUF surface, where the diffuse reflectance was measured at 635nm. Several parameters that could affect the performance of the system were evaluated. As expected, the SDS concentration presented strong influence on the analytical signal because the PUF was able to retain only the ionic-pair. The pH influenced the analytical signal, which was more intense in the acidic/neutral range, while the ionic strength only influenced the kinetic of the MG (as MG–SDS ionic-pair) sorption. The methodology was employed in the determination of MG in river waters and a recovery test was performed to test the accuracy of the procedure. Recovery percentages between 98.7 and 107% were observed when 60 or 80μgL−1 of MG were added to the samples. [Copyright &y& Elsevier]

This work reports a study about the adsorption of Rhodamine B (RB) by unloaded polyether type polyurethane foam (PUF) in a medium containing sodium dodecylsulfate (SDS). The adsorption process was based on the formation of an ionic-pair between RB and SDS, which presented high affinity by PUF. Adsorption was characterized in relation to equilibrium, kinetic, and thermodynamic aspects and the results obtained showed that the ratio between the SDS and RB concentrations played an important role on the adsorption efficiency. A maximum adsorption capacity of 6.85 × 10-6 mol RB g-1 was observed at established experimental conditions. The adsorption process was spontaneous (negative ΔG) and presented an endothermic characteristic (positive ΔH). Also, its rate was regulated by an intraparticle diffusion process. Sequential extraction experiments were carried out by changing PUF plugs in 30 and 60 min time intervals, resulting in removal rates higher than 95%. [ABSTRACT FROM AUTHOR]

This paper reports the development of a new procedure for the adsorption of four cationic dyes (Rhodamine B, Methylene Blue, Crystal Violet and Malachite Green) from aqueous medium employing polyurethane foam (PUF) loaded with sodium dodecylsulfate (SDS) as solid phase. PUF loading process was based on the stirring of 200mg PUF cylinders with acidic solutions containing SDS. The conditions for loading were optimized by response surface methodology (RSM) using a Doehlert design with three variables that were SDS and HCl concentrations and stirring time. Results obtained in the optimization process showed that the stirring time is not a relevant parameter in the PUF loading, evidencing that the transport of SDS from solution to PUF surface is fast. On the other hand, both SDS and HCl concentrations were important parameters causing significant variation in the efficiency of the resulting solid phase for the removal of dyes from solution. At optimized conditions, SDS and HCl concentrations were 4.0×10¿4 and 0.90molL¿1, respectively. The influence of stirring time was evaluated by univariate methodology. A 20min stirring time was established in order to make the PUF loading process fast and robust without losing efficiency. The procedure was tested for the removal of the four cationic dyes from aqueous solutions and removal efficiencies always better than 90% were achieved for the two concentrations tested (2.0×10¿5 and 1.0×10¿4 molL¿1). [Copyright &y& Elsevier]

Abstract: This work presents a detailed study about the adsorption of Methylene Blue (MB) onto polyether type polyurethane foam (PUF). The adsorption process is based on the formation of a hydrophobic ionic-pair between cationic dye MB and dodecylsulfate anion (SDS), which present high affinity by PUF. Set-up employed in the study was built up by adjusting a 200mg cylinder of PUF to the arm of an overhead stirrer. The system was characterized in relation to equilibrium, kinetic and thermodynamic aspects and it was modeled by employing Langmuir and Freundlich isotherms. Obtained results showed that the ratio between SDS and MB concentrations plays an important role on the adsorption process. According to Langmuir isotherm, a maximum adsorption capacity of 7.20×10−5 molMBg−1 was achieved when optimized operational conditions were employed. The adsorption rate seems to be regulated by an intraparticle diffusion mechanism. Adsorption process was spontaneous (negative ΔG) at ambient temperature and presented an endothermic characteristic (positive ΔH). Sequential extraction experiments were carried out by changing PUF plugs in 30min time intervals and around 96% of the MB present in solution could be removed through consecutive extractions with six 200mg PUF cylinders. [Copyright &y& Elsevier]

Abstract: This work reports the evaluation of the combined use of Pd and HF as chemical modifiers for the direct determination of total chromium in waters derived from petroleum exploration employing electrothermal atomic absorption spectrometry (ET AAS). Such waters, usually called as produced waters, have complex composition presenting a number of organic and inorganic substances. When obtained from offshore operations they also present high salinity. In order establish conditions for chromium measurement pyrolysis and atomization curves were built up in different media and employing Pd and HF as chemical modifiers. Also, a detailed study about calibration strategy was performed. At best conditions, pyrolysis and atomization temperatures were 1200 °C and 2600 °C, respectively, and 10 μL of a 500 mg L−1 Pd solution was added together with 10 μL of a 50% (v/v) HF solution on 20 μL of sample. Obtained results indicate that, in this kind of sample, chromium can be determined by standard addition method or employing external calibration with standard solutions prepared in 0.8 mol L−1 NaCl medium. In order to evaluate the accuracy of the procedure, a recovery test was performed with seven spiked samples of produced waters. The detection limit, quantification limit and the relative standard deviation in 0.8 mol L−1 NaCl were also calculated and the values found were 0.45 μg L−1, 1.5 μg L−1 and 6.0% (at 2.5 μg L−1 level), respectively. [Copyright &y& Elsevier]

Abstract: This work proposes a new procedure for on-line electro-oxidative leaching and spectrophotometric determination of uranium in ore samples. By associating a conventional flow injection system, used for uranium determination with Arsenazo III, with an on-line system for electro-oxidative leaching, a fully integrated system was assembled. The systems were integrated after achieving optimum conditions for uranium determination and leaching. According to the results obtained in the present work, a current density of 280mAcm−2 generated enough hypochlorite ions in the electrolyte solution (3.6molL−1 HCl+2% (w/v) NaCl) to promote quantitative oxidation of U(IV) to U(VI) thus improving the extraction efficiency. The slurry density did not significantly affect the performance of the system and the increasing temperature resulted in a decrease in extraction efficiency. This methodology was applied in the determination of U3O8 in four ore samples and the results obtained agreed with those obtained by ICP-MS after conventional wet acid digestion of the samples. [Copyright &y& Elsevier]

Abstract: In this work, a flow injection system with spectrophotometric detection was developed for the determination of lithium in pharmaceutical formulations used in the treatment of bipolar disorder. Reaction between Quinizarine (1,4-dihydroxyanthraquinone) and Li(I) ion in alkaline medium containing dimethylsulfoxide (DMSO) was explored for this purpose. The flow system was optimized regarding to its chemical (DMSO, Quinizarine and NaOH concentrations and sample pH) and physical parameters (sample loop volume, carrier flow rate and reactor length) in order to establish better conditions in terms of sensitivity and sampling frequency. The results obtained showed that the concentration of DMSO in the reagent solution presents remarkable influence on the magnitude of analytical signal. Chemical species that could be found in the formulations such as Na(I), K(I), Mg(II), Ca(II), Ti(IV), Cl−, CO3 2− e sodium dodecylsulfate were tested as possible interfering ions. Among them, only non-monovalent cations presented noticeable interference on lithium signal. However, they were not found in concentrations high enough to cause interference in the determination of lithium in the samples. Sample preparation was performed by sonicating a slurry prepared by dispersing 100mg of powdered sample in 15mL of 0.10molL−1 HCl solution. Results obtained by developed methodology were not statistically different from those obtained by flame emission spectrometry. In the optimized conditions the method presented a linear range of 5–40mgL−1 and a relative standard deviation of 3.6% at 5mgL−1 Li concentration. Detection and quantification limits were 0.54 and 1.8mgL−1, respectively. Sampling frequency, calculated as the time interval passed between two consecutive injections, was 60 samples per hour. The methodology was successfully applied in the determination of lithium in three commercial samples. [Copyright &y& Elsevier]

Abstract: This paper reports the development of a reversed flow injection system for the spectrophotometric determination of Sb(III) and total Sb in antileishmanial drugs. The analytical system is based on the selective reaction between Sb(III) and bromopyrogallol red (BPR) with the decrease of the absorbance at 555nm. Total Sb concentration was determined after reduction of all Sb(V) to Sb(III) with KI and ascorbic acid. The influence of system variables (chemical and flow type) and the possible interference of high amounts of Sb(V) on Sb(III) was studied as well as the suitable conditions for preparation of samples. It was verified that the use of Triton X-100 enhanced the sensitivity of the methodology and that the previous sonication of the samples was fundamental to achieve accurate results. Under optimized conditions the reversed FIA system was able to process 63 samples per hour with a detection limit of 29ngml−1 and a R.S.D. of 3.8% (0.25μgml−1 level). Real samples of commercial antileishmanial drugs were analyzed, being observed no statistical difference between the results obtained by the developed system and FAAS or manual methodology in relation to total Sb concentration. [Copyright &y& Elsevier]

This paper reports the development of a microwave-assisted procedure for leaching of copper, iron, manganese, and zinc from multivitamin/multimineral supplements by use of dilute acid before determination by flame atomic absorption spectrometry (FAAS). A Doehlert design was used to find optimum conditions for the procedure by use of response-surface methodology. Three variables (acid concentration in the leaching solution, irradiation time, and irradiation power) were used as factors in the optimization study for two acids, HCl and HNO3. Final working conditions were established as a compromise between the optimum values for each analyte, taking into consideration the robustness of the procedure. The best leaching results were obtained with HNO3 and the acid concentration, irradiation time, and irradiation power used were 0.70 mol L−1, 15 min and 360 W, respectively. The accuracy of the optimized procedure was evaluated by comparison with a well-established closed-vessel microwave dissolution technique. [ABSTRACT FROM AUTHOR]

Abstract: This work presents the development of a methodology for the determination of Cu, Fe, Mn and Zn in samples of multivitamin/multimineral tablets, by flame atomic absorption spectrometry (FAAS), after extraction of the analytes with diluted hydrochloric acid solution. Several parameters that could influence the extraction process such as acid extraction solution concentration and nature, mixing mode (ultrasonic or magnetic stirring), extraction time and sample composition were evaluated. The obtained results showed that Fe, Mn and Zn were easily extracted with 1mol/L HCl solution after 5min of mixing with either ultrasonic or magnetic stirring for all studied samples. On the other hand, Cu extraction appeared to be more complex since it could only be extracted at the same conditions for silicate-free samples. For samples containing silicates the time of contact between solid sample and extraction solution presented remarkable influence, being necessary up to 12h to achieve quantitative recovery with 1mol/L HCl solution. The developed methodology was applied in the determination of Cu, Fe, Mn and Zn in seven commercially available multivitamin/multimineral tablets. The results obtained with the developed method were compared with those obtained after total digestion of samples using a closed-vessel microwave oven device. [Copyright &y& Elsevier]

Abstract: The present work reports the development of a methodology for the direct determination of lead in high saline waters derived from petroleum exploration employing electrothermal atomic absorption spectrometry with permanent Ir–W and HF as modifiers. These waters, so-called produced waters, have complex composition containing several types of organic and inorganic substances. In order to attain best conditions (highest analytical signal besides lowest background) for the methodology studies about the effect of several variables and the convenient calibration strategy were performed. Also, the efficiency of other modification approaches was evaluated. At best conditions, pyrolysis and atomization temperature were 800 and 2200°C, respectively, when the modifiers cited above were utilized. Obtained results indicate that, in this kind of sample, lead can be determined by standard addition method or employing external calibration with standard solutions prepared in 0.8moll−1 NaCl medium. In order to evaluate the accuracy of the procedure, a recovery test was performed with six spiked samples of produced waters. The detection limit, quantification limit and the relative standard deviation in 0.8moll−1 NaCl were also calculated and the values are 1.5μgl−1, 5.0μgl−1 and 5.0% (at 10μgl−1 level), respectively. [Copyright &y& Elsevier]

This paper presents a study about the sorption of the cadmium–diethyldithiocarbamate [Cd(II)–DDTC] complex onto polyurethane foam (PUF). It was observed that the maximum sorption of Cd(II) (80 or 150 µg L−1) was verified at pH 6.8 in the presence of 4.5 × 10−5 mol L−1 DDTC. The shaking time needed to achieve the equilibrium was 40 min. From these data, a kinetic characterization was performed by applying three models, which revealed that a film-diffusion process was a rate-determining mechanism. Results also indicated that an ether-like solvent extraction was the sorption mechanism. The investigation of many metallic ions as concomitants showed that the sorption by foam is relatively selective and it can be enhanced by using a suitable masking agent or incrementing the foam mass. [ABSTRACT FROM AUTHOR]

• A fast and simple approach for Cu and Ni extraction from vegetable oils is proposed in this work. • An efficient extraction of the analytes was achieved by disruption of a three-component solution. • The three-component solutions were formed by mixing the oil with 1-octanol and HNO 3 solution. • GF AAS was employed for metals determination in the extracts. In this work, we propose a novel approach for extracting Cu and Ni from vegetable oils (which can be expanded to other metals). The method is based on the transference of the analytes to an aqueous acid phase due to the disruption of a three-component solution. The extraction was carried out in two steps. In the first step, a three-component solution was prepared comprising the sample, 1-octanol, and HNO 3 solution. Next, the homogeneous system was disrupted by adding 1.0 mL of deionized water, and two phases were formed. The aqueous extract deposited in the bottom of the flask was collected with a micropipette, and Cu and Ni were determined by graphite furnace atomic absorption spectrometry (GF AAS). The developed method presented limits of quantification (LOQ) of 0.25 and 0.17 ng g−1 for Cu and Ni, respectively, and was successfully applied in the analysis of eleven oil samples from different origins. [ABSTRACT FROM AUTHOR]

This work reports the development of a flow injection analysis (FIA) system for online magnetic preconcentration and determination of Cd(II) in water by flame atomic absorption spectrometry (F AAS). Magnetic nanoparticles of Fe 3 O 4 , functionalized with l -glutamine (GlnMNP), were synthesized and used as a support for Cd(II) retention and preconcentration. Each measurement cycle was performed through online complexation of Cd(II) by l -glutamine attached to Fe 3 O 4 magnetic nanoparticles at pH 10.5, followed by their retention in a coil due to the action of a cylindrical permanent magnet. Subsequently, the retained magnetic nanoparticles containing Cd(II) were dissolved with an acid solution (4 mol L−1 HCl solution), releasing Cd(II) for transportation to the detector. The main chemical and flow parameters that affected the performance of the system were optimized. Under optimum experimental conditions, the limits of detection and quantification were 2 and 5 μg L−1, respectively, and a relative standard deviation of 6.5% (at 50 μg L−1, n = 10) was observed. The FIA system allowed the injection of 24 samples per hour and presented an enrichment factor of four. The method was applied in the analysis of river and pond water samples. The pond water sample was irradiated with ultraviolet light prior to the analysis, in order to eliminate the organic matter. Accuracy of the method was assessed by recovery tests, which provided recovery percentages between 82 and 111%. The developed method was also compared to the direct determination by graphite furnace atomic absorption spectrometry (GF AAS). In this case, the results were not statistical different at 95% confidence level when the Student's t -test was applied. Image 1 • A FIA system Cd(II) was developed for Cd(II) preconcentration from water. • The preconcentration of Cd(II) was based on the magnetic retention of Fe 3 O 4 nanoparticles functionalized with l -glutamine. • A new column was prepared in each measurement cycle, avoiding the increase in the internal pressure of the system. • The proposed method was able to determine Cd(II) in natural water samples. [ABSTRACT FROM AUTHOR]