Dynamic reversed-phase liquid-liquid microextraction for the determination of Cd, Cr, Mn, and Ni in vegetable oils by energy dispersive X-ray fluorescence spectrometry

Dynamic reversed-phase liquid-liquid microextraction (RP-LLME) is proposed to prepare vegetable oil samples for posterior determination of cadmium, chromium, manganese, and nickel by energy dispersive X-ray fluorescence (EDXRF) spectrometry. The microextraction procedure was based on a dynamic system in which the sample flowed through the acceptor phase in an extraction chamber. After extraction, the rich phase was deposited on filter paper and subjected to metal determination by EDXRF. The following parameters were optimized: type and concentration of the acceptor phase, sample flow rate, and extraction time. Nitric acid 0.1 mol L−1, a sample flow rate of 10 mL min−1, and an extraction time of 15 min were employed in the recommended procedure. Under these conditions, limits of quantification of 6, 7, 8, and 11 μg kg−1 were obtained for Cd, Cr, Mn, and Ni, respectively. The preconcentration factors obtained were 100 (Cd), 65 (Cr), 82 (Mn), and 74 (Ni). The developed method was applied to determine Cd, Cr, Mn, and Ni vegetable oil samples.