Determination of 10 photo-initiator residues in food plastic packaging by gel permeation chromatography extraction coupled with gas chromatography-mass spectrometry

Abstract

An analytical method using gel permeation chromatography (GPC) coupled with gas chromatography-mass spectrometry (GC-MS) was established for the determination of 10 photo-initiators – benzophenone (BP), 2-methyl benzophenone (2-MBP), 1-hydroxycyclohexyl phenyl ketone (Irgacure 184), 3-methyl benzophenone (3-MBP), 4-methyl benzophenone (4-MBP), ethyl 4-dimethylaminobenzoate (EDB), 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651), o-methyl-benzoyl benzoate (OMBB), 2-ethylhexyl-4-dimethylamino benzoate (EHA) and 2-isopropylthioxanthone (ITX) – in plastic food packaging. The plastic samples were treated with ultrasound in cyclohexane/ethyl acetate (1 : 1, v/v). The extract was cleaned up by gel permeation chromatography. The final solution was subjected to GC-MS using an external standard method for quantitation in selected ion monitoring mode. The 10 target photo-initiators showed linear recovery relationships over the concentrations of 0.005 to 0.2 mg L⁻¹, with r² > 0.999. The recoveries from spiked samples (0.07 × 10⁻³, 0.17 × 10⁻³ and 0.33 × 10⁻³ mg dm⁻² of standard) for each of the 10 photo-initiators ranged from 77.0% to 120.6%, with relative standard deviations (RSDs) of 0.5–13.9%. The limits of detection (LOD) were from 0.03 × 10⁻³ mg dm⁻² to 0.12 × 10⁻³ mg dm⁻². The developed extraction method is simple and yields a sufficiently pure test sample, while the analytical method meets the sensitivity and precision requirements for photo-initiator detection. This method could be routinely used to determine the levels of photo-initiator residues in plastic food packaging.