2-Isopropylthioxanthone (2-ITX) in food and food packaging materials on the German market

Abstract

To elucidate the occurrence of the photo-initiator, 2-isopropylthioxanthone (2-ITX), more than 100 food products on the German market, packed in cartons, plastic cups and foils, were investigated. For this, a rapid method to detect 2-ITX in food packaging materials was established. In case of positive findings, the accompanying foodstuffs were analysed in a subsequent step using different extraction methods, depending on the fat content of the food. Determination of the photo-initiator was done by high-performance liquid chromatography with diode array and fluorescence detection (HPLC–DAD/FLD). Recoveries ranged between 94 and 106% for non-fatty (RSD ≤ 1.1) and between 80 and 105% for fatty foods (RSD ≤ 8.5). The limit of detection and limit of quantification were determined to 2 and 5 µg l⁻¹. 2-ITX was detected in 36 of 137 packages (26%) and significant migration occurred in 75% of the packaging materials tested positive. The levels of 2-ITX ranged up to 357 µg kg⁻¹ in orange juice.

Keywords:

• 2-Isopropylthioxanthone
• 2-ITX
• 2,4-diethylthioxanthone
• 2,4-DTX
• HPLC
• UV-curing inks
• photo-initiator
• juice
• dairy products
• baby food

Acknowledgements

We wish to thank Ms Pechstein, Ms Drewnik and Ms Moser for the skilful technical assistance, Mr. Dr. Weißhaar and Mr. Altkofer for valuable discussions and IGM Resins for providing 2-ITX.