Desenvolvimento de método analítico colorimétrico para determinação de ferro em azeite de oliva utilizando frasco único

Abstract

In this work, a method was developed for the determination of iron in olive oil samples. The sample preparation, by reversed-phase dispersive liquid-liquid microextraction (RP-DLLME), and the detection by digital imaging, was carried out using the single flask analysis concept. The colorimetric reaction of iron (Fe) with ammonium thiocyanate (SCN) in acidic medium was used in the studies to optimize the procedure and to determine iron in olive oil samples. The following parameters of the procedure, involving the preparation and detection steps, were evaluated: different organic solvents as dispersing agent, acidity of the reaction medium, ratio/proportion between the dispersing/extracting solvent solution, concentration of the SCN ion, agitation time and centrifugation time. After adjusting the variables of the sample preparation and detection step, the following values were established: LQ = 1.13 mg L-1,and obtaining 99.9% of analyte recovery. The developed method was shown to be adequate for the determination of iron in commercial olive oil samples, and as main features it stands out as low-cost, simple to operate, using a single flask for the sample preparation and determination steps of Fe3+, with focus on the principles of green analytical chemistry.