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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]

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: 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]

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 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 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]

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 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 reports, for the first time, the determination of Ca and Mg in biodiesel after their extraction from samples using the novel extraction induced by emulsion breaking. The quantification of the analytes in the extracts was performed by flame atomic absorption spectrometry operating at fast sequential mode (FS-FAAS) and using cobalt as internal standard. Several parameters that could affect the extraction efficiency of the method were studied such as the influence of surfactant (Triton X-114) and acid (HNO3) in the extractant solution. Also, operating parameters of the spectrometer (flame stoichiometry and observation height) were evaluated in order to allow sensitive measurements of Ca, Mg and Co in the same conditions. Quantitative extraction of the analytes can be obtained by using 20 mL of biodiesel and 4 mL of a solution containing 2.1 mol L-1 HNO3 and 7.5% m/v Triton X-114. In these conditions, the emulsions can be broken in 10 min of heating at 90 °C. The limits of quantification for Ca and Mg were 0.047 and 0.013 μg mL-1 , respectively. Five samples of soybean-based biodiesel were analyzed and recovery tests were performed, obtaining recovery percentages in the range of 88%-106%. [ABSTRACT FROM AUTHOR]

Abstract: A novel approach is proposed for the sample preparation of used lubricating oils to determine Cu, Fe and Mn by FAAS. The method is based on the extraction induced by emulsion breaking, in which the elements of interest are transferred to an aqueous phase before the measurement by FAAS. In the method, each sample of used lubricating oil was diluted with toluene (20% v/v) and the resulting solution was emulsified with a Triton X-114 solution containing HNO3. Further, the water-in-oil emulsion was broken by centrifugation for 30min at 3500rpm, originating a system with two well-separated phases: (i) the upper phase, containing the used lubricating oil diluted in toluene and (ii) the lower aqueous phase, containing the analytes that were extracted from oil. The lower phase was collected, diluted with water and the analytes were determined by FAAS. The optimization of the methodology was performed by studying the influence of different parameters that could affect the extraction efficiency such as the nature and concentration of the solvent used for sample dilution, the concentrations of HNO3 and Triton X-114 in the solution employed for emulsification and the operational conditions for extraction (extraction, centrifugation and sampling times). The limits of quantification for Cu, Fe and Mn were 2.9, 77 and 8.2ngg−1, respectively. The accuracy of the method was evaluated by comparison with the reference method based on the total digestion of the samples in a closed-vessel microwave oven. There were no statistical differences between the results obtained with the proposed method and the reference one, except for Fe in the cases where its concentration was higher than 80µgg−1. [Copyright &y& Elsevier]

Abstract: This paper reports the development of a new method for the focused ultrasound extraction of Cr and Mn from pharmaceutical formulations and their determination by electrothermal atomic absorption spectrometry (ETAAS). The method was optimized by evaluating the influence of several variables such as the sonication power and time, concentration of HCl in the extractant solution and mass of sample employed in the extraction procedure. The curves of pyrolysis and atomization were constructed for both analytes in order to evaluate the effect of the matrix on the measurement of Cr and Mn. Quantitative extraction of both Cr and Mn was achieved when 25–150mg of the sample were sonicated for 30min at 50% power with 5ml of a 1moll−1 HCl solution. The developed method was successfully applied in the determination of Cr and Mn in samples of pharmaceutical formulations containing different active principles such as ciprofloxacin, cephalexin, azithromycin, amlodipine and methionine. There was no statistical (95% confidence level, paired t-test) difference between the results obtained by the proposed method and the results obtained after total digestion of the samples. [Copyright &y& Elsevier]