Simplifying Functional Assays for Partitioning of Nanoparticles in Immiscible Phases

Conventional functional assays (FAs), which are used to describe the behaviors and assess the impacts of engineered nanomaterials (ENMs), have extensive human factor related errors (i.e. extraction process errors due to human laboratory skills), and consume considerable amounts of laboratory material. Consequently, there is a need and opportunity to improve conventional FAs by minimizing the potential for human factor related errors, reducing the usage of ENMs and reagents, and increase experimental reproducibility. The goal of this study was to simplify the conventional FAs and evaluate the feasibility and reproducibility of the simplified FAs. The underlying hypothesis implies that simplified FAs could quickly quantify the partitioning of nanoparticles between immiscible phases with minimum human factor related errors, low usage of ENMs, and high experimental reproducibility. Three different FAs were studied for this project: octanol-water assay, distribution to sediment assay, and cloud point extraction (CPE) assay. Three widely applied ENMs were selected: silver nanoparticles (AgNPs) coated with citrate, magnetite nanoparticles (Fe3O4) capped with polyvinyl pyrrolidone (PVP), and multiwall carbon nanotubes (MWCNTS) dispersed in an organic solution. Removal efficiency was the selected parameter used to describe the distribution of ENMs. Based on the variability and the t-tests on the removal efficiencies of conventional and simplified FAs, it is conclusive that the conventional octanol-water FAs on Fe3O4, the sediment FAs on Fe3O4, and the CPE FAs on MWCNTs and Fe3O4 can be simplified. The conventional octanol-water on AgNPs and the sediment FAs on AgNPs and MWCNTs cannot be simplified. It is inconclusive that the conventional octanol-water FAs on MWCNTs and the CPE FAs on AgNPs can be simplified, due to the uncertain causes and consistency of the differences on the removal efficiencies.