International validation of the determination of saturated hydrocarbon mineral oil in vegetable oils

An interlaboratory study was conducted in 2014 to evaluate a method for determining mineral oil saturated hydrocarbons in vegetable oils and fats. Samples were dissolved in an apolar solvent and subjected to a purification on silica gel impregnated with silver nitrate. The final extract was analyzed using gas chromatography with a flame ionization detection. Quantification was performed using internal standardization. Six samples were assayed for mineral oil saturated hydrocarbons by 21 collaborating laboratories from nine countries. Sample matrices included olive, olive pomace, sunflower, soybean, and rapeseed oils. Comparing two types of integration of the unresolved complex mixture area, it was decided to recommend in the test method the integration of the natural hydrocarbons only considering the highest peaks of n-alkanes. Repeatability (RSDr) ranged from 3.7 to 10.5% and reproducibility (RSDR) ranged from 10.3 to 25.7% for samples containing greater than 35 mg/kg of mineral oil saturated hydrocarbons. The method provides acceptable results for quantification of mineral oil saturated hydrocarbons in edible oils, from 50 to 1000 mg/kg.