Enrichment for reducing the detection limits for the analysis of mineral oil in fatty foods

A German draft for a regulation requires that there must be no migration of mineral oil aromatic hydrocarbons (MOAH) from recycled paperboard into food. The Federal Institute for Risk Assessment (BfR) is requested to establish the detection limit. It was previously shown that the detection limit of the commonly used methods is below 0.1 mg/kg for the majority of the foods, but substantially higher in fatty products because of limited capacity of the liquid chromatographic preseparation to retain fat, interference by olefins and, if also the mineral oil saturated hydrocarbons (MOSH) should be analyzed, the natural paraffins primarily consisting of odd-numbered n-alkanes. A method is described for the enrichment of the MOSH and MOAH conceived as an auxiliary tool for fatty foods analyzed by the conventional methods, such as on-line HPLC–GC. In a double bed liquid chromatographic column, the lower packing consists of a mixture of activated aluminum oxide, silica gel with silver nitrate and activated silica gel, the upper of activated silica gel. The technical detection limit in edible oils is below 0.3 mg/kg, which translates to less than 0.1 mg/kg in the dry foods packed in recycled paperboard. The distinction between migrated mineral oil and that present before packaging often presupposes the availability of the food prior to packaging.