Rapid separation and quantification of trace titanium dioxide with sizes down to 20 nm in environmental waters

Titanium dioxide nanoparticles (TiO₂ NPs) are commonly used in consumer products, leading to their release into the environment and raising concerns about their potential human health risks. Smaller TiO₂ NPs penetrate cell membranes more easily and exhibit stronger bio-toxicity than larger particles. However, methods for analyzing small TiO₂ NPs are limited.

A robust method to identify and quantify TiO₂ NPs with size down to 20 nm within 5 min was developed, based on size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry. To address the issue of column adsorption, salicylaldoxime (SO, 0.1 %) was used to complex ionic Ti and surfactant FL-70 (2 %) was used as the coating agent for TiO₂ NPs in the mobile phase. Work conditions including column type, SO concentration, and FL-70 content were optimized. Consequently, the method successfully separated and quantified TiO₂ NPs and ionic Ti species, with detection limits of 2.23 ng/mL for TiO₂ NPs and 2.10 ng/mL for ionic Ti, meeting most application needs. Spiked recoveries of TiO₂ NPs in environmental water samples ranged from 82.75 % to 95.09 %, verifying the method's practicality.

This method provides a powerful tool for rapid screening of smaller TiO₂ NPs-containing environmental waters. Furthermore, the strategy proposed in this study to overcome column adsorption provides a useful model for the SEC separation and determination of other trace metal nanoparticles.