VORTEX-ASSISTED REVERSE PHASE DISPERSIVE LIQUID-LIQUID MICROEXTRACTION FOR IRON AND MAGNESIUM DETERMINATION IN VEGETABLE OILS BY F AAS

The samples preparation represents a determinant step in the performance of analytical methods for metals determination in complex samples, especially, vegetable oils. An alternative procedure to conventional acid digestion is the reverse-phase dispersive liquid-liquid microextraction (RP-DLLME), which is based on the separation of analytes by partition between two immiscible phases. In this procedure, the extraction and preconcentration of the metals is performed using an aqueous extractive solvent and an organic dispersing solvent. The present work uses the vortex-assisted RP-DLLME for the determination of Fe and Mg in vegetable oils samples by F AAS. Parameters such as: type and amount of solvent dispersant, solvent extraction concentration and ultrasound time were optimized. Under optimized conditions, 5 g of the samples were weighed and heated (95 ± 5 ° C) for 10 min, to reduce de sample viscosity. Then, 1 mL of the dispersing solvent mixture (Propanol and 1% HNO3 1:1 v/v ratio) was added, maintained in vortex for 20 seconds and submitted in ultrasound bath for 10 min. Subsequently, the supernatant was separated by centrifugation and the concentrations of Fe and Mg in the extractive phase were determined by FAAS. The calibration ranges were 0.05-0.50 μg g-1 for Fe and 0.01-0.10 μg g-1 for Mg. The LOD and LOQ values ranged from 95 ng g-1 and 318 ng g-1 for Fe and 2 ng g-1 and 8 ng g-1 for Mg. The method was applied for Fe and Mg determination in vegetable oil samples from different sources and the obtained concentrations were in μg g-1 range for both analytes. The method is shown to be precise, simple and can be routinely performed for analytes determination in vegetable oils.