Novel extraction induced by emulsion breaking as a tool for the determination of trace concentrations of Cu, Mn and Ni in biodiesel by electrothermal atomic absorption spectrometry

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 2.1 mol L(-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 60 min to achieve maximum extraction. The limits of quantification were below 1 µg L(-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.

Development of a method for total Hg determination in oil samples by cold vapor atomic absorption spectrometry after its extraction induced by emulsion breaking

“…According to data obtained in previous works [31][32][33][34], the extraction process is enhanced in the presence of mineral acids because H þ ions compete with metallic cations for the basic sites present in the organic molecules that form the oil sample. Also, nitric acid is able to break covalent bonds between metals and organic structures (oxidation), allowing the release of metals to the medium in the form of free ions.…”

“…The method employed the extraction induced by emulsion breaking (EIEB) [31][32][33][34], which is based on the formation and breaking of detergent emulsions prepared with the samples and an extractant solution (containing triton X-100 and nitric acid only), to enhance the extraction process. The developed method was applied in the determination of trace concentrations of Hg in diesel, biodiesel and mineral oil samples.…”

Greener procedures for biodiesel quality control

“…91 Four steps are required in this procedure: emulsion formation, mechanical agitation for analyte extraction, heating for emulsion breaking (i.e. Internal standardisation with Co in fast sequential FAAS measurements, 89 optimisation of the heating program in ETAAS, 90 and analyte separation by coldvapour generation 91 were important aspects to make feasible external calibration without matrix effects or spectral interferences. This strategy is especially advantageous due to the preconcentration of the analytes in the extract and the possibility for external calibration by simple dilution of inorganic standards in water.…”

Use of Constrained Mixture Design in the Optimization of a Method Based on Extraction Induced by Emulsion Breaking for the Determination of Ca, Mg, Mn, Fe and Zn from Palm Oil by Flame Atomic Absorption Spectrometry

“…Not only is this interface exchange phenomenon of substances between phases favored by increasing contact area, but also by interaction forces dependent on the nature of this substance (polar or nonpolar). 9 Extraction induced by emulsion breaking 10 has been applied in edible oils for the determination of Cr and Mn by graphite furnace atomic absorption spectrometry (GFAAS), 11 in edible oils from Turkey for the determination of Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn using inductively coupled plasma optical emission spectrometry (ICP OES), 12 trace concentrations of Cu, Mn and Ni in biodiesel by GFAAS, 13 Cu, Fe and Mn in used lubricating oils by flame atomic absorption spectrometry (FAAS), 14 zinc from diesel after multivariate optimization 15 and edible oils by FAAS. 8 This study proposes the application of EIEB for the determination of Ca, Mg, Mn, Fe and Zn from palm oil samples by FAAS.…”