Abstract
This work reports the development of a simple and fast method for the spectrophotometric determination of Fe in diesel oil using the classic reaction with 1,10-phenanthroline after its extraction induced by emulsion breaking (EIEB). The extraction parameters of EIEB were optimized (concentration of HNO3 and Triton X-100® in the emulsifying solution) as well as the adjustment of the pH of the final solution, a necessary step to complete the colorimetric reaction. The developed method presented a limit of detection of 0.004 mg L–1 and a limit of quantification of 0.013 mg L–1 and was applied in the analysis of six samples of diesel oil with different specifications. The results were statistically similar to those obtained by graphite furnace atomic absorption spectrometry (GF AAS). A recovery test was also performed by spiking the samples with 1.0 mg L–1 of Fe in the form of an organometallic compound, yielding recovery percentages between 83 and 108%.
Highlights
In Brazil, diesel oil is widely used to push a huge fleet of trucks and buses, which is responsible for the transportation of people and products throughout the country
The reaction between FeII and 1,10-phenanthroline is well-known[31] and largely used for the spectrophotometric determination of Fe in different kinds of samples, some adjustments were needed for its use in the quantification of Fe in the acid extracts from
The following factors were evaluated: (i) the influence of the concentration of ascorbic acid, which was used as a reducing agent to ensure that the presence of all Fe in the solution was as the FeII ion; (ii) the influence of the concentration of 1,10-phenanthroline, which acts as a chromogenic reagent; (iii) the influence of pH since the extension of the reaction between FeII and 1,10-phenanthroline depends on the adjustment of the pH of the medium; and (iv) the influence of the order of the addition of reagents
Summary
In Brazil, diesel oil is widely used to push a huge fleet of trucks and buses, which is responsible for the transportation of people and products throughout the country. The method was based on the introduction of the samples in the form of emulsions, but with the use of diesel oil instead of jet fuel for the preparation of the emulsions In this case, a Varian AA240Z graphite furnace atomic absorption spectrometer (Mulgrave, Australia) equipped with a GTA 120 atomization unit and a Zeeman-effect background corrector was employed for the measurements. The tube containing the emulsion was immediately immersed in a water bath at 85 °C until the breakdown of the emulsion was verified, which took approximately 30 min At this stage, two phases had already formed: (i) an upper phase containing the remaining diesel oil and (ii) a lower phase, which was formed by the aqueous acid solution containing the extracted Fe. After the heating step, the tube was centrifuged for 10 min at 5000 rpm to improve the separation of the phases, which allowed the recovery of 2 mL of aqueous extract.
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