Toxicity and fate assessment are key elements in the evaluation of the environmental, health and safety risks of engineered nanomaterials (ENMs). While significant effort and resources have been devoted to the toxicological evaluation of many ENMs, including nanoscale TiO2, obtaining conclusive and reproducible results continues to be a challenge. This can be traced in part to the lack of standardized dispersion protocols and the inconsistent application of dispersion procedures in relevant biological and environmental matrices. In order to address these issues, the National Institute of Standards and Technology (NIST) jointly with the Center for the Environmental Implications of Nanotechnology (CEINT) have developed a series of standardized and validated protocols for the dispersion of ENMs from a powdered material source for both human health and environmental testing applications. These protocols have been developed and validated using NIST Standard Reference Material (SRM) 1898. SRM 1898 consists of a widely studied and industrially relevant TiO2 nanomaterial with broad commercial penetration and a production history dating back several decades.
While the procedures detailed in this series focus on the dispersion of SRM 1898 in specific aqueous media, it is believed that the adopted characterization, optimization and validation approaches can be more generally applied to the preparation of ENM dispersions in any relevant matrix. For this reason, and to allow for broader applicability, experimental details and discussions regarding the characterization, process optimization and validation steps adopted for the development of the dispersion method are detailed in a separate publication.