The widespread use of nanotechnology in food raises health concerns, particularly regarding titanium dioxide (nano)particles (TiO₂ NPs, known as E171), which was recently banned in foodstuffs within Europe. This regulatory shift underscores the need for reliable analytical methods to detect and characterize TiO₂ NPs in food matrices (size, number, and mass concentrations). Therefore, the aim of this ongoing work is to evaluate suitable approaches for their digestion, as well as their extraction and stabilization for further analysis by single particle inductively coupled plasma mass spectrometry (sp-ICP-MS).

Three representative test materials (RTMs, JRC Repository) and a certified reference material (NIST 1898) were used as standards, while confectionery products (n = 7) from a Swiss retailer were selected as samples. Total titanium (Ti) content was measured using ICP-MS/MS in total mode for initial sample screening and to assess the digestion capacity of various acid mixtures. sp-ICP-MS was used to determine the mass and number concentrations of TiO₂ NPs in confectionery products. Dynamic light scattering (DLS) was used to assess NP stability in various dispersions prepared with ultrapure water, PVP (2%), SDS (0.03%), BSA (0.05%), and a buffered solution (0.036 mol L⁻¹ NaNO₃, pH 3.5).

Digestion capacity of TiO₂ NPs varied with acid composition, with an HNO₃/HBF₄ mixture achieving superior recovery compared to other acid mixtures. Zeta potential (ZP) measurements showed good colloidal stability (ZP < -30 mV), but high Z-average sizes revealed agglomeration, particularly in PVP and the buffered solution. TiO₂ NPs could then be characterized using sp-ICP-MS in all RTMs and two confectionery samples with high total Ti content, revealing a large proportion of particles below 100 nm. However, low recoveries highlight the need to address agglomeration and NP losses. Future work will focus on validating sp-ICP-MS across food samples and optimizing stabilization strategies to improve NP dispersion and reduce agglomeration.