3.6. Overall considerations
The aim of the study was to explore if nanoparticles in general can migrate out of food packaging polymers into food. Nanoparticulate TiN was chosen as a model substance, because of the sensitive traceability of Ti by ICP-MS and due to its high chemical inertness (Avasarala & Haldar,2010) which supports the expectation that the target migrating species will be particles and not ionic Ti species. The conditions of our migration experiments were chosen to simulate food contact with the food packaging under more severe conditions than in practice. The setup of our migration experiments was shown to meet the requirements for sensitive detection of potentially migrated Ti. Recovery experiments demonstrated that in any used food simulant Ti could be recovered almost completely at sufficient low detection limits. Therefore, it was shown that detection of Ti would be possible when present in the simulant. In all of the food simulants 95% ethanol, 3% acetic acid, isooctane and 0.2% NovaChem solution no release of Ti could be detected at in the applied severe migration experiments for all 3 LDPE test samples. These simulants can be considered as worst case food contact simulating matrices for the migration of TiN nanoparticles. Ethanol at 95% level in water is known to interact with polyolefins, in particular at 60 8C. Isooctane is known to swell LDPE, wherefore the mobility of migrants in the polymer matrix is facilitated. Acetic acid as a small molecule can penetrate into LDPE and may dissolve Ti under the applied contact conditions. The 0.2% NovaChem solution was chosen as food simulant, because its composition of surfactants stabilizes TiN nanoparticles. In another study we used asymmetric flow field-flow fractionation (AF4) with multi angle laser light scattering (MALLS) for the separation and characterization of TiN nano particles. From this study it is known that TiN cannot be measured with AF4/MALLS with low sensitivity due to interactions with instrument components, but the 0.2% NovaChem solution was demonstrated to disperse TiN very well. Since the surfactant solution is suitable to disperse potentially migrated TiN nanoparticles it was chosen in this study as food simulant, but it did not show any release of TiN/Ti under the applied severe test conditions.