Emprego da microextração líquido-líquido dispersiva em fase reversa (RP-DLLME) e identificação de metais em óleo diesel nos postos de combustível do municípios Medianeira

Abstract

S10 fuel is a hydrocarbon from the oil refining process. Its use in Brazil is mandatory in combustion vehicles, which use diesel as fuel, manufactured from the year 2013. In order to avoid aggravation of pollution problems, CONAMA instituted a maximum limit for the presence of certain metals in S10 fuel (Sodium + Potassium is 5 mg·kg-1, and Calcium + Magnesium is 5 mg·kg-1), also avoiding the blocking of pre- and postcombustion filter elements. There are some known techniques for detecting metals in oily substances. To analyze the fuels, the reversed-phase liquid-liquid dispersive micro extraction technique (RP-DLLME) was used, a method that presents in its stages several factors that show it to be more practical, including the low use of reagents, of solutions, the reduced cost of the reagents used, the minimization of generated waste and the Detection Limits (LD) and Quantification Limits (LQ) are below those required by ABNT standards. The F AAS (Flame Atomic Absorption Spectrometry) is an excellent device for detecting trace metals such as Na, Ca, K and Mg. The method still dispenses with the use of toxic reagents such as Xylene. Samples are prepared by separating them into 10 g aliquots, followed by heating in a water bath for 20 minutes at 70° C, after which 1 mL of solvent will be added in the proportion of 20% of extracting solvent (HNO3 1.0 mol·L-1) and 80% of dispersing solvent (Isopropanol), followed by 10 minutes of centrifugation at 3600 revolutions per minute (RPM). After centrifugation, the liquid separates into two phases. The excess of the organic phase (top) is removed and then the aqueous phase is subtracted, transferring it to a flask where its volume is made up to 5 mL of HNO3 (0.5% v/v). Subsequently, the aliquots are analyzed in F AAS. The method was applied to 7 different samples of diesel S10, being considered viable for the determination of Na, K, Ca and Mg, meeting the requirements of the International Law, which determines maximum limits of 5 mg·kg-1 for the sum of Na and K and the same limit for the sum of Ca and Mg.