A gas chromatography–tandem mass spectrometry (GC–MS/MS) method for the detection of six
phthalates in olive oil was developed. A gel permeation chromatography (GPC) clean-up step with cyclohexane:dichoromethane
7:3 as mobile phase was employed to remove the high-molecular mass species
present in oil. Two ionization methodologies, i.e. electron (EI) and isobutane-chemical ionization (CI),
were compared, in MS/MS mode, to achieve better analytical performances. An overall evaluation of all
analytical parameters shows that the EI-MS/MS approach provides satisfactory results and is to be preferred
to CI-MS/MS, at least in the case of the examined analytes. The observed accuracies, ranging from
71.7% to 112.2%, and the RSD values less than 9.7%, confirm the effectiveness of the proposed method in
the assay of phthalate content in such a complex matrix as olive oil. The proposed protocol for the identi-
fication and assay of phthalates in olive oil might be of interest for the implementation of the QS (quality
assurance scheme) for residue monitoring in food safety assessment