Mineral oils are complex mixtures of saturated (MOSH) and aromatic hydrocarbons (MOAH), mainly alkylated, giving gas chromatographic (GC) traces characterized by the presence of hundreds of unresolved peaks forming one or more "humps" with different molecular weight distribution, depending on the source of contamination. Various foods can be contaminated with mineral oils. Different sources of contamination have been recognized for vegetable oils: environmental contamination, use of lubricating in the extraction plant, storage and transport of he raw matter in jute bags, transport of the oil in ships previously used to transport mineral oils etc.
It is well known that vegetable oils can be contaminated with mineral oils, but almost all published data refers to the analysis of the saturated fraction (MOSH), without checking for the presence of the MOAH. Since MOSH and MOAH have different toxicological relevance, and particularly MOAH are suspected to contain carcinogenic compounds, it is important to quantify them separately.
Recently, both on-line liquid chromatography (LC)-GC flame ionization detection (FID) and off-line solid phase extraction (SPE)-GC-FID approaches have been proposed for MOSH and MOAH determination. A comparison between off-line and on-line approaches for the assessment of these contaminants in vegetable oil and fats is presented and discussed. Sample pre treatment and enrichment is important for accurate determination of the contamination and to reach the required sensitivity when analyzing vegetable oils and fats. The possibility to use alternative approaches such as automated solid phase extraction and micro scale saponification for sample enrichment and purification have been explored. Data on MOSH and MOAH content in a number of samples are reported and discussed. Unambiguous presence of mineral oils in contaminated samples has been confirmed through GC-MS analysis of hopanes (recognized markers for confirming the presence of mineral oil)
