Solution for blank and matrix difficulties encountered during phthalate analysis of edible oils by high performance liquid chromatography coupled with tandem mass spectrometry

• Development of HPLC strategy for phthalate analysis of edible oils.
• Mobile phase, injector and sample handling contributed to phthalate contamination.
• HPLC column was used for generating elution delay of mobile phase phthalates.
• DSC−18 SPE provided the most efficient fat removal, freezing was the second best.
• LOQs ranged between 5.5 and 110 μg kg−1.

Worldwide production of phthalates has led to their undesirable presence in the food chain. Particularly edible oils have become an area of growing concern owing to numerous reported occurrences of phthalates. The analytical methods used in this field face difficulties associated mainly with matrix complexity or phthalate contamination which this study has aimed to describe and resolve. The proposed procedure consisting of liquid-liquid extraction, solid phase extraction and high performance liquid chromatography coupled with tandem mass spectrometry allowed us to analyze simultaneously 6 individual phthalates and 2 phthalate isomeric mixtures. DSC−18 SPE phase was selected for cleanup owing to the most efficient co-extract removal (assessed using high resolution mass spectrometry). Several sources of phthalate contamination were identified, however, the mobile phase was the most serious. The key improvement was achieved by equipping a contamination trap, a 50‐mm reverse phase HPLC column, generating a delay between target and mobile phase peaks of the same compounds. RSDs ranging between 2.4 and 16 % confirm good precision and LOQs between 5.5 and 110 μg kg−1 reflect satisfactory blank management. With up to 19 occurrences in 25 analyzed edible oil samples and levels up to 33 mg kg−1, bis(2‐ethylhexyl), diisononyl and diisodecyl phthalates were the most important contaminants.