UV-curable inks, coatings, and adhesives are being increasingly used in food packaging
systems. When exposed to UV energy, UV-photoinitiators (PI’s) present in the formulations produce
free radicals which catalyze polymerization of monomers and pre-polymers into resins. In addition
to photopolymerization, other free radical reactions occur in these systems resulting in the formation
of chemically varied photolytic decomposition products, many of which are low molecular weight
chemical species with high migration potential. This research conducted model experiments in
which 24 commonly used PI’s were exposed to UV-energy at the typical upper limit of commercial
UV-printing press conditions. UV-irradiated PI’s were analyzed by gas chromatography-mass
spectrometry (GC-MS) and electrospray-mass spectrometry (ESI-MS) in order to identify photolytic
decomposition products. Subsequently, migration studies of 258 UV-cure food packaging samples
were conducted using GC-MS; PI’s and photolytic decomposition products were found in nearly all
samples analyzed. One hundred-thirteen photolytic decomposition products were identified. Eighteen
intact PI’s and 21 photolytic decomposition products were observed as migrants from the 258 samples
analyzed, and these were evaluated for frequency of occurrence and migratory concentration range.
The most commonly observed PI’s were 2-hydroxy-2-methylpropiophenone and benzophenone.
The most commonly observed photolytic decomposition products were 2,4,6-trimethylbenzaldehyde
and 1-phenyl-2-butanone. This compilation of PI photolytic decomposition data and associated
migration data will aid industry in identifying and tracing non-intentionally added substances (NIAS)
in food packaging materials.