The potential of a multi-method platform centred on ICP-MS to provide new insights into the size-resolved quantification of TiO2 particles in food

Abstract

The use of titanium dioxide (TiO₂) as an additive in food has been a subject of ongoing debate in Europe due to its potential toxicity. To inform and support toxicological assessment of this additive, a better understanding of the physicochemical characteristics of TiO₂ added to food is needed. For this reason, recent research efforts have focused on method development for the physicochemical characterisation of TiO₂ in food and, as a raw material, in a regulatory context. Despite the significant progress made so far, more information is needed about the size-resolved quantification of titania nanoparticles in the fraction below 100 nm. Here, we report the development of a multi-method analytical platform for the characterisation of TiO₂ in food. It is based on single particle ICP-MS (spICP-MS), supported by asymmetrical flow field-flow fractionation (AF4) coupled on-line to ICP-MS and multi-angle light scattering (MALS). spICP-MS was optimised to detect TiO₂ with sizes down to 15 nm. This enabled us to detect and quantify a fraction of TiO₂ particles with sizes below 35 nm, which has not been reported in the literature so far. The presence of this size fraction was confirmed by AF4/MALS/ICP-MS in the raw E171 additive. The relative percentage of particles in this fraction (from the total particle number detected) ranged from 48 to 61% in a range of food products purchased from a local grocery store, with a number concentration range of 2.9 10¹⁰–7.13 10¹³ kg⁻¹, depending on the product. These findings will help bridge the gap with regard to lack of data comparability between orthogonal measurement methods and provide further scientific evidence supporting policy makers and regulators.