Migration studies from paper and board food packaging materials. Part 2. Survey for residues of dialkylamino benzophenone UV-cure ink photoinitiators.

A survey of retail samples was conducted in two phases with 50 general paper and board food contact materials and articles analysed in 1992, and 121 samples, specifically of printed cartonboard, analysed in 1995. Packaging samples were extracted with ethanol containing 0.4% triethylamine. The extracts were analysed using high performance liquid chromatography (HPLC) and the presence of 4,4'-bis (dimethylamino) benzophenone (Michler's ketone, MK) and 4,4'-bis (diethylamino)-benzophenone (DEAB) confirmed using gas chromatography coupled to mass spectroscopy (GC-MS). The limits of detection for MK and DEAB in packaging were 0.05 mg/kg and 0.1-0.2 mg/kg respectively. In the first phase, MK was detected in 24% of the 50 samples at concentrations of 0.06-3.9 mg/kg paper. DEAB was detected in 12% of samples (0.1-0.2 mg/kg). In the second phase, 26% of the 121 cartonboard samples contained detectable MK (0.1-1.6 mg/kg) and 4% contained DEAB (0.2-0.7 mg/kg). Residues of the monoamine 4-(dimethylamino)benzophenone (DMAB) were found in 10% of the 1992 samples (0.1-0.6 mg/ kg). DMAB was not surveyed in 1995. These levels are too low to indicate the use of these cure agents for printing the packages. Rather, the most likely origin is from the use of recycled fibres. For three samples where the highest concentration of MK was detected, the food was analysed by GC-MS after extraction and clean-up. There was no measurable migration of MK at a detection limit of 2 micrograms/kg food. It is concluded, therefore, that the concentrations of MK present in the packaging samples analysed are unlikely to pose a risk to human health.