Optimisation of an extraction/leaching procedure for the characterisation and quantification of titanium dioxide (TiO2) nanoparticles in aquatic environments using SdFFF-ICP-MS and SEM-EDX analyses

Abstract

The quantitative recovery of nanoparticles from environmental samples represents a critical step during the implementation of routine analytical monitoring methods for the reliable quantitative determination of nanomaterials released into aquatic environments at the expected low concentration levels. In this work, several approaches based on different extraction agents have been evaluated with respect to their suitability for the recovery of TiO₂ nanomaterials from fresh sediment samples. Centrifugal-field-flow-fractionation (SdFFF) hyphenated to inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) has been applied to separate the extracted nanoparticles as well as to overcome the known interference problem related to their Ti-specific detection when using ICP-based techniques. SdFFF-ICP-MS/MS method validation included in particular parameters such as particle recovery or stability of the particle size-distribution. Spike recoveries from the optimized colloidal extraction procedure of up to 95 ± 11% have been achieved. In a case study conducted from 2015 to 2016, the developed method was applied to monitor the release of nano-sized TiO₂ materials into a lake environment that is frequently used for recreational activities such as swimming and surfing. The investigated sediment samples show a significant increase of the Ti concentration from 26.2 ± 2.7 mg kg⁻¹ in June 2015 to 40.2 ± 4.6 mg kg⁻¹ in December 2016 originating from TiO₂ particles.