Interferent substances in the MOSH-MOAH analytics: Causes, examples, consequences and solutions

The analysis of mineral oil saturated and aromatic hydrocarbons (MOSH-MOAH) in edible oils and fats is a well-recognized analytical challenge. The reasons are multiple: matrix variety, analyte composition, relatively complex sample treatment, challenging results interpretation, and a problem with selectivity due to a broad variety of co-eluting interfering substances. In certain cases, the use of a compound characterization approach is recommended, due to the huge uncertainty on the values obtained by the official quantitative methodology by LC-GC-FID, and the high chance of false negative/positive results. Complex analytical approaches based on GCxGC-MS can help to clarify the composition of the MOSH and MOAH fractions, which has a direct impact on the identification of co-eluting substances non-related to mineral oil contaminants, and hence on the certainty of the quantitative results. In this work we aim to review the most common interference substances in the MOSH-MOAH analytics, and to share the fruits of our efforts on identifying unknown substances by on-line LC-GCxGC-TOF-MS/FID, with a special emphasis on the MOAH fraction.