Aromatic Hydrocarbons of Mineral Oil Origin in Foods: Method for Determining the Total Concentration and First Results

Abstract

An online normal phase high-performance liquid chromatography (HPLC)-gas chromatography (GC)-flame ionization detection (FID) method was developed for the determination of the total concentration of the aromatic hydrocarbons of mineral oil origin with up to at least five rings in edible oils and other foods. For some samples, the olefins in the food matrix were epoxidized to increase their polarity and remove them from the fraction of the aromatic hydrocarbons. This reaction was carefully optimized, because also some aromatics tend to react. To reach a detection limit of around 1 mg kg(-1) in edible oils, an off-line enrichment was introduced. Some foods contained elevated concentrations of white paraffin oils (free of aromatics), but the majority of the mineral oils detected in foods were of technical grade with 20-30% aromatic hydrocarbons. Many foods contained mineral aromatic hydrocarbons in excess of 1 mg kg(-1).

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

“…In the GC-FID chromatogram, a hump of unresolved components is observed, topped by signals from n-alkanes. The GC Â GC plot confirms that the majority of the material (some 70%, as determined by on-line HPLC-GC-FID [4]) consists of paraffins. The aromatics form many identifiable spots (peaks), but also zones of high complexity with fused signals, particularly at the higher elution temperatures.…”

“…Instead of transferring them to GC for the determination of the sum of the MOSH and the MOAH [4], the fraction was collected in an 1.5 mL autosampler vial from the dismounted transfer line and reconcentrated to 20-100 mL (dilution with MTBE). Before use, the autosampler vials were cleaned by heating for 5 h at 350-4001C.…”

“…Technical oils contain aromatic hydrocarbons at concentrations of 10-40% [3], and these are probably more relevant for the risk assessment than the saturated hydrocarbons. In the meantime, an on-line HPLC-GC-flame ionization detection (FID) method has been developed for the determination of the sum of all mineral oil aromatic hydrocarbons (MOAH; ranging from 1 to at least 5 aromatic rings) in edible oils or food extracts [4]. Together with the analysis of the mineral oil saturated hydrocarbons (MOSH), this enabled the characterization of the mineral oil quality in a food.…”

“…The more recent on-line HPLC-GC-FID method [4] was intended for routine analysis and does not separate the MOAH into groups. The edible oil or crude food extract is injected into a 25 cm  2 mm id silica gel HPLC column, which retains the lipids in the upper part and separates the MOAH from the MOSH in the lower.…”

“…The method described in this paper is tied up to that for determining the sum of the MOAH [4] and aims at characterizing the composition of the MOAH: the HPLC fraction of the MOAH is further separated by GC Â GC, with MS for identification and FID for routine analysis and quantitation. Presently, it is performed in off-line mode, but it could easily be converted on-line.…”