Comprehensive two‐dimensional GC after HPLC preseparation for the characterization of aromatic hydrocarbons of mineral oil origin in contaminated sunflower oil

Abstract

Many foods are contaminated with mineral oil at concentrations in the order of or above 10 mg/kg. Often, these mineral oils are of technical grade and contain around 20-30% aromatic hydrocarbons, as previously shown by an on-line HPLC-GC-flame ionization detection method for determining in foods the sum of the mineral oil aromatic hydrocarbons (ranging from 1 to at least 5 aromatic rings). Now, a comprehensive two-dimensional GC (GC x GC) method was added for characterizing these aromatics by ring number and degree of alkylation. In contrast to the polycyclic aromatic hydrocarbons originating from pyrolysis, mineral oil aromatic hydrocarbons are highly alkylated and form extremely complex mixtures. Through MS and addition of standards, sectors in the GC x GC plots were allocated to 1 to 5 ring aromatics in order to estimate the relative abundance of each group. The quantitative composition is approximated by integration of 2nd dimension chromatograms laid as a grid over the three-dimensional hump of unresolved hydrocarbons of the GC x GC-flame ionization detection plot. The procedure is applied to Ukrainian sunflower oils contaminated with mineral oil.