Single-Particle ICP-MS Method for the Determination of TiO2 Nano- and Submicrometric Particles in Biological Tissues

Titanium dioxide (TiO2) nano- and submicrometric particles’ widespread use in different sectors raised concerns about human and environmental exposure. The validation of analytical methods is essential to ensure reliability in risk assessment studies. In this study, a single-particle inductively coupled plasma mass spectrometry (spICP-MS) method was validated for the detection, quantification, and dimensional characterization of TiO2 particles in biological tissues. Tissue samples collected after exposure to TiO2 particles underwent mild acidic digestion using a HNO3/H2O2 mixture to achieve complete matrix decomposition while preserving particle integrity. The resulting digests were analyzed by ICP-MS operated in single-particle mode to quantify and size TiO2 particles. Method validation was conducted according to ISO/IEC 17025:2017 and included linearity, repeatability, recovery, and detection limit assessments. The limit of detection for TiO2 particles was 0.04 µg/g, and 55.7 nm was the size the detection limit. Repeatability was within 0.5–11.5% for both TiO2 mass concentrations and particle size determination. The validated method was applied to tissues from inhalation-exposed subjects, showing TiO2 levels of 80 ± 20 µg TiO2/g and particle number concentrations of 5.0 × 105 ± 1.2 × 105 part. TiO2/mg. Detected TiO2 particles’ mean diameter ranged from 230 to 330 nm. The developed and validated spICP-MS method provides robust and sensitive quantification of TiO2 particles in biological matrices, supporting its use in human biomonitoring and exposure assessment studies.