Characterization of TiO2 Nanoparticles in Food Additives by Asymmetric-Flow Field-Flow Fractionation Coupled to Inductively Coupled Plasma-Mass Spectrometry-a Pilot Study

This study aims at the optimization of a novel analytical approach for the characterization of TiO2 nanoparticles (NPs) in food additives by asymmetric-flow field-flow fractionation (AF4) in tandem with inductively coupled plasma-mass spectrometry (ICP-MS). For this purpose, the influence of pH, ionic strength, and of various surfactants on the zeta potential (ZP) of both NPs and the AF4 membrane was assessed. Results show that the ionic strength has a considerable influence on the membrane ZP and consequently on the NPs' recovery from the AF4 membrane during their separation. Therefore, ZP of the membrane can be controlled by varying the ionic strength of the analyzed NP suspension to obtain the same electrostatic charge as the NPs and hence minimizing their adsorption on the membrane. It was also confirmed that the nature of the surfactant affects mostly NP dispersion quality than on the recovery rate. Among the surfactant investigated, ultrapure water and FL-70 provided the lowest measured gyration diameter despite the presence of aggregates. Additional parameters such as the use of different phases for the NP dispersion and eluent composition could be taken into consideration for future experiments.