Microemulsion as Sample Preparation for Direct Flame Atomic Absorption Spectrometry (FAAS) Determination of Total Iron in Crude and Refined Vegetable Oils

This work proposed a novel, relatively low-cost and rapid analytical method using microemulsion as sample preparation to determine iron (Fe) in vegetable oils by flame atomic absorption spectrometry technique (FAAS). The vegetable oil microemulsions were obtained by mixing appropriate proportions of the crude and refined vegetable oil, Triton® X-100, 1-propanol and nitric acid 50% (v v-1). Moreover, an external calibration method was established using aqueous Fe standards instead of expensive and unstable organometallic standards. The limits of detection and quantification were 0.40 and 1.3 mg kg-1 of oil, respectively. The accuracy was checked by recovery studies (with recoveries ranging 84-105%) and by Fe determination in digested vegetable oil samples by inductively coupled plasma optical emission spectrometry (ICP OES) as comparative procedure. The proposed analytical method was efficient to determine Fe in crude and refined vegetable oils from various vegetable sources, besides being suitable for routine analyses due to its simplicity.