Determination of Cr and Pb in edible vegetable oils by coupling of extraction induced by emulsion breaking with dispersive liquid-liquid microextraction followed by flame atomic absorption spectrometry detection

Abstract

This study presents an efficient method for the determination of chromium and lead in various edible vegetable oils by combination of extraction induced by emulsion breaking (EIEB) and dispersive liquid-liquid microextraction (DLLME) followed by flame atomic absorption spectrometry (FAAS) detection. The technique relies on the formation of a water-in-oil emulsion, achieved by introducing an extraction phase containing 20% (w/v) Triton X-100 and 1% (v/v) nitric acid. The metal ions were extracted to the aqueous phase through centrifugation of the resulting emulsion. Subsequently, the collected aqueous phase was mixed with dithizone, and the pH of solution was adjusted at 8 and 9 for Cr and Pb, respectively. Finally, DLLME was applied to concentrate the extracted metal ions, which were then quantified using FAAS. Various factors affecting the extraction efficiency of selected the metal ions were optimized using one-variable-at-a-time method. The estimated limit of quantifications were 5.0 µg/kg and 2.0 µg/kg for lead and chromium, respectively. The standard addition method was used to construct the calibration curves. The calculated relative recoveries for the spiked oil samples ranged from 94.0% to 98.0% for chromium, and from 92.0% to 96.4% for lead. The results showed that the proposed technique offers a simple and efficient analytical methods for the determination of lead and chromium in oil samples.