Microextração líquido-líquido dispersiva em fase reversa para determinação de zinco em óleos vegetais por espectrometria de absorção atômica

Abstract

The preparation of samples is an important step in the efficiency of the determination of metals, especially in complex samples such as vegetable oils. The reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) is based on the the separation of analytes by partition between two immiscible phases, ideal for complexes samples. This procedure is based on the extraction and pre-concentration of the metals using an aqueous extractor solvent and an organic dispersor solvent. The aim of this paper was to use the RP-DLLME on the extraction and pre-concentration of Zn in olive oil samples to posterior determination by FAAS. Was evaluated the influence of storage time on the migration of Zn to the product. To extraction and pre-concentration of the analytes were weighed 5g of the samples and heated by 10 minutes, then added of 1mL of the extraction solution mixture (propanol and extraction solution HNO3 1% on the proportion of 1:1), vortex for 20 seconds and kept in ultrasound for 10 min, then the Zn concentration determined by FAAS. The LOQ and LOD values were 8 ng g-1 and 25 ng g-1 and the R2 were > 0,9919, showing being and efficient technique to extraction and pre-concentration of Zn in vegetable oils. The determinations were performed in different brands of olive oil, being that the two brands won’t show and significant increase of zinc concentration in relation to the storage time. However, in one of the samples the concentration varied from 0,19 ug g-1 to 0,82 ug g-1 after 30 days of storage. Therefore, improper storage conditions and the type of packaging material can compromise the quality of the oil.