DESENVOLVIMENTO E APLICAÇÃO DA MICROEXTRAÇÃO LÍQUIDO-LÍQUIDO DISPERSIVA REVERSA PARA A DETERMINAÇÃO DE METAIS EM DERIVADOS DO PETRÓLEO POR ICP OES

Abstract

Metals and metalloids are present in matrices of petrochemical origin in the form of organometallic compounds, chelates, organic salts and inorganic salts. The determination of metallic species in petrochemical industry products is essential to assess the quality of these products, as they can cause serious environmental and human health problems. Due to the complexity of petroleum-derived products, using sample preparation procedures that allow the determination of the elements of interest safely and with satisfactory precision and accuracy is essential in chemical analysis. In this sense, the objective of this work was to develop and apply a non-destructive, simple and miniaturized sample preparation procedure based on reverse dispersive liquid-liquid microextraction (R-DLLME) for the joint determination of Ca, Cd, Cu, Fe, K, Mg, Mn, Ni, Pb and Zn in matrices derived from the petrochemical industry employing inductively coupled plasma optical emission spectrometry (ICP OES). For this, some variables inherent to the R-DLLME were optimized with the aid of multivariate statistical analysis applying a complete factorial design 24 followed by the Doehlert matrix. The R-DLLME variables were evaluated using certified reference material containing the selected elements in mineral oil. In the optimized R-DLLME procedure, masses of ≈5.0 g of sample, 1600 µL of the extraction solution in the proportion of 3.75% (v/v) of HNO3:isopropyl alcohol [3:1 (v/v)], heating bath at 80 °C for 10 min, 60 s of vortexing, 3 min of sonication at 54 ºC and 15 min of centrifugation at 3500 rpm were used. The volume of the aqueous phase obtained was adjusted to 15 mL with ultrapure water. Regarding the instrumental parameters, %RSD below 8.57%, linear correlation coefficients above 0.9985 and quantification limits below 119.61 µg L-1 were obtained. Addition and recovery tests were performed and the results obtained comprised between 69.42 and 98.36% with %RSD < 6.39%. The methodology was applied to samples of aviation gasoline (Avgas), diesel oil (B8), regular gasoline, jet fuel (JET-A1), lubricating oil and petroleum jelly and the element contents ranged from 0.1106±0.0064 to 671.9432±11.6848 mg kg-1 Ca, 0.0387±0.0023 to 0.0865±0.0026 mg kg-1 K and 0.0983±0.0008 to 244.8969±9.4325 mg kg-1 Pb. The samples of JET-A1 and Avgas complied with ANP Resolutions 856/2021 and 5/2009, respectively, while for the other samples there are no limits for the determined metals. The relative simplicity of the R-DLLME procedure can be a viable alternative in routine analysis.