Fractionation and preconcentration of silver nanoparticles at environmentally relevant concentrations through induced eco-corona formation and spICP-MS characterization

The increasing application of nanoparticles (NPs) to different products by the industry has raised concerns regarding their release into environmental matrices. Single-particle inductively coupled plasma mass spectrometry (spICP-MS) is a growing technique based on counting particle events that allow the characterisation and quantification of NPs at environmental concentrations. However, a number concentration (N-NP) of 10(4)-10(5) NPs per mL in the suspension is required. Considering 10 ng L-1 for 80 nm AgNPs, a N-NP of similar to 3500 NPs per mL is expected; thus, a preconcentration step can be an alternative to increase the N-NP. Eco-corona formation with humic acid (HA) and NPs is a well-known environmental process. This work used an induced eco-corona formation to fractionate and preconcentrate NPs in environmental waters. For ultrapure water, 7 times more NPs were detected in the spICP-MS analysis, representing a N-NP of similar to 2.9 x 10(4) NPs per mL, with a concentration factor (CF) similar to 9 times that for both N-NP and mass concentration (similar to 80 ng L-1). Additionally, the size of the AgNPs was maintained after the method without compromising NP characterisation. The method's feasibility was also tested in drinking water, tap water, and river water, and a CF between 7 and 8 times that for N-NP and mass concentration was obtained, demonstrating its applicability despite the matrix composition and pH. The induced eco-corona method can be used to track NPs in environmental waters at concentrations <10 ng L-1; besides the main objective of preconcentrating NPs, making the samples suitable for analysis by spICP-MS was achieved, allowing the NPs' proper size distribution characterization according to spICP-MS theory.