Spectroscopic Determination of Metals in Palm Oils from Different Stages of the Technological Process

Abstract

Magnesium, calcium, copper, iron, and lead in palm oils ( Elaeis guineensis ) at various stages of the refining process were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion. The mean concentrations of Mg, Ca, Cu, Fe, and Pb in the studied palm oils varied from 20.7 to 7090.1 μg kg(-1), from 193.9 to 8077.9 μg kg(-1), from 29.7 to 463.0 μg kg(-1), from 115.2 to 415.9 μg kg(-1), and from 1.7 to 16.0 μg kg(-1), respectively, which are below the Polish legal requirements. The comparable precisions for the proposed ICP-MS (RSD = 0.81-5.99%) and standard GFAAS (RSD = 1.18-5.26%) methods demonstrate the benefit of the ICP-MS method in the routine analysis of metal ions in palm oils. There are significant, positive correlations between Ca and Mg, between Ca and Cu, between Fe and Pb, between Cu and Fe, between Cu and Mg, and between Cu and Pb in palm oils determined by two analytical methods (r = 0.8798-0.9817, p < 0.05). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used for discrimination of the quality of the analyzed palm oils based on main and trace metal contents determined by the proposed ICP-MS and the standard GFAAS methods. Two main groups were identified by HCA, whereas the classification and characterization of the studied palm oils within each of groups on the basis of metal ions amounts were obtained from PCA. The chemometric analyses demonstrated that crude palm oil had the highest level of the determined metals concentrations. Also, the analyzed metals in palm oils from different steps of the refining process were grouped using HCA to assess the effectiveness of technological processes for their removal.