Olive Oil Quality Analysis and the Detection of Adulterations by GC-MS With Cold EI

Abstract

Olive oil is widely consumed for its nutritional and health benefits, yet its high market value makes it vulnerable to adulteration and mislabeling. Current analytical approaches for assessing olive oil quality and authenticity rely largely on indirect analyses, such as fatty acid methyl ester (FAME) profiles, peroxide values, or UV absorbance, and do not account for olive oil's triglycerides content. In this manuscript, we demonstrate the application of gas chromatography–mass spectrometry (GC-MS) with cold electron ionization (Cold EI) for the direct analysis of olive oil based on its glyceride profiling. Cold EI employs a supersonic molecular beam interface with a contact-free fly-through ion source, providing vibrational cooling that enhances the abundance of molecular ions. This enables direct GC-MS analysis of all glycerides and acids without derivatization, with total analysis time of 19 min. We analyzed multiple commercial olive oil brands, certified reference material, and intentionally adulterated samples containing canola and/or sunflower oil. The resulting mass chromatograms and triglyceride molecular ion patterns allowed clear discrimination between pure olive oil, adulterated oils, and degraded (oxidized) samples. Adulteration at the 30% level was detected through distinct hybrid triglyceride patterns, although aging effects were uniquely identified by increased diglyceride and free fatty acid signals. High sensitivity was demonstrated by the confident detection of olive oil at trace levels down to 100 pg on-column using selective ion monitoring. These results establish GC-MS with Cold EI as a rapid, sensitive, and highly informative technique for ensuring the authenticity, quality, and consumer safety of olive oil.