Search

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 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: 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 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 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 work proposes a novel method for the determination of trace concentrations of Cu, Mn and Ni in biodiesel samples by electrothermal atomic absorption spectrometry. In order to overcome problems related to the organic matrix in the direct introduction of the samples, a new extraction approach was investigated. The method was based on the extraction induced by emulsion breaking, in which metals were transferred from the biodiesel to an acid aqueous phase after formation and breaking of a water-in-oil emulsion prepared by mixing the biodiesel sample with an aqueous solution containing surfactant and nitric acid. Several parameters that could influence the performance of the system were evaluated. Quantitative extractions of the analytes were obtained when the extraction was performed using an emulsifier solution containing 2.1molL−1 of HNO3 and 7% m/v of Triton X-100. The extraction time had remarkable influence on the efficiency of the process, being necessary an agitation time of 60min to achieve maximum extraction. The limits of quantification were below 1µgL−1 for the three analytes under study. The accuracy of the method was tested by application of a recovery test (recovery percentages between 89% and 109% were observed) and by comparison with a well-established method, taken as reference. [Copyright &y& Elsevier]