Determination of Cd(II), Cu(II), Pb(II), and Zn(II) content in commercial vegetable oils using derivative potentiometric stripping analysis

The purpose of this paper was to determine the content of Cd(II), Pb(II), Cu(II), and Zn(II) in commercial peanuts, sunflower, soy, maize, rice, grape-seed and hazelnut oils, using derivative potentiometric stripping analysis (dPSA). Previous reports provided evidence that hydrochloric acid extraction followed by dPSA was well suited for trace metals determination in oils: precision lower than 2.1% (expressed as relative standard deviation of the measurements) and detection limits ranging from 0.4 to 0.9 μg kg−1 were obtained for Cd(II), Cu(II), Pb(II), and Zn(II) in the studied vegetable oils. The optimised method was verified with analysing certified reference materials and the obtained accuracy ranged from 93.5% to 97.0%. The results obtained from analysis of commercial vegetable oils showed that the mean levels of cadmium were lower than 4.90 μg kg−1, the average content of lead ranged from 8.60 to 55.61 μg kg−1, the mean content of copper from 53.80 to 674.45 μg kg−1, and zinc from 51.45 to 555.61 μg kg−1.