Abstract: To assess migration risks of nucleating agents in polypropylene (PP) food contact materials, an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for simultaneous quantification of 9 target compounds. The migration behaviors of nine nucleating agents from polypropylene (PP) food contact materials were systematically investigated in aqueous food simulants (4% acetic acid, 10%, 20%, and 50% ethanol) and oil-based food simulants (95% ethanol, n-hexane, and olive oil). Nine nucleating agents were well separated on a Phenomenex Kinetex Biphenyl column (4.6 mm×100 mm, 2.6 μm) under gradient elution with a mobile phase composed of formic acid, ammonium acetate and acetonitrile. All 9 nucleating agents showed good linearity in the given ranges. Their coefficients of determination r² were all greater than 0.9902. The method limits of detection (LOD) and quantification (LOQ) were determined. For olive oil simulant, LODs were 0.10-20.0 μg/kg and LOQs 0.30-50.0 μg/kg. For other simulants, LODs were 0.06-10.0 μg/L and LOQs 0.20-25.0 μg/L. The recoveries ranged from 81% to 103%, while the relative standard deviations (RSDs) were 2.5%-6.0%. The effects of food simulant type, exposure temperature and contact time on the migration behavior of nucleating agents were systematically investigated using positive samples in this study. The results showed that the target compound 1,3:2,4-bis (3,4-dimethyl) benzylideno sorbitol (DMDBS) exhibited a high migration level in oil-based food simulants. Moreover, the migration amount increased with increasing temperature. The migration process basically reached dynamic equilibrium, while the temperature reached about 60 ℃. The method is simple and highly sensitive. It accurately determines the migration levels of nine nucleating agents in PP materials. The results reveal high-risk migration characteristics of DMDBS in oil and at high temperatures. This study provides key experimental data. It also provides a theoretical basis for assessing the safety of PP food contact materials.

Key words: UPLC-MS/MS, polypropylene, food contact materials, nucleating agent, migration laws