Size characterization and quantification of E171 titanium dioxide particles in food sauces using spICP-MS

Abstract

A sample preparation method associated to a single particle inductively coupled plasma mass spectrometry (spICP-MS) analysis was developed to ensure a quantitative characterization of TiO2 particles in food sauces. The method was optimized with a fat sauce matrix for which the pristine E171 additive was available. The highest extracted amount of TiO2 particles was obtained using an ultrasound-assisted dispersion in tetramethylammonium hydroxide (TMAH). TEM analysis confirmed these results, showing that these conditions effectively solubilised the fat matrix. The trueness of the method evaluated using a Ti-free mayonnaise spiked with the E171 additive or the NM-100 reference material (NM-100 RM) proved satisfactory with quantitative mass recoveries (>90%). A good agreement in terms of particle sizes was also obtained between those of the spiked mayonnaise and the TiO2 suspensions used for spiking. However, as also shown in the optimization study, the presence of fatty compounds tended to improve particle dispersion. The application of this procedure to E171 labelled food sauces purchased from the EU market showed concentrations of TiO2 particles in the (0.6 – 6) g/kg range with median diameters between 170 and 320 nm. The TiO2 nanoparticle fraction (size < 100 nm) was evaluated between 2% and 12%, depending on the sample. No titanium was detected in the food sauces not labelled E171. Conclusively, the developed method can provide an efficient and reliable analytical approach for TiO2 particles determination in fat food samples which complies with the EU current regulations.