Sample Preparation for Determining Heavy-Metal Contents in Fatty Oils

Abstract

Two methods were compared to select the optimum sample-preparation option for determining the heavy-metal contents in fatty oils. The first (GOST 26929–94) employed extraction of the metal ions from an oil sample by refluxing aqueous HCl solution. The second (European Pharmacopoeia, 8th Ed.) employed complex oxidative thermal destruction of an oil sample followed by processing in a mixture of conc. HNO3 and HCl with completion of the process by adding conc. H2SO4 . The mineralization was carried out at high pressure in sealed Teflon containers with microwave heating. Extraction of metals from the weighed portions of fatty oils by HCl solution provided accurate and satisfactorily reproducible results. This method was shown not to require special apparatus and was expedient for determining metal impurities in fatty oils. Sample preparation using oxidative thermal destruction required the use of expensive equipment and was unsafe.