Analysis of engineered nanomaterials (Ag, CeO2 and Fe2O3) in spiked surface waters at environmentally relevant particle concentrations

Frédéric Loosli; Jingjing Wang; Mithun Sikder; Kamelia Afshinnia; Mohammed Baalousha

doi:10.1016/j.scitotenv.2020.136927

Analysis of engineered nanomaterials (Ag, CeO₂ and Fe₂O₃) in spiked surface waters at environmentally relevant particle concentrations

Sci Total Environ. 2020 May 1:715:136927. doi: 10.1016/j.scitotenv.2020.136927. Epub 2020 Jan 25.

Authors

Frédéric Loosli¹, Jingjing Wang², Mithun Sikder², Kamelia Afshinnia², Mohammed Baalousha³

Affiliations

¹ Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, United States. Electronic address: looslifred@gmail.com.
² Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, United States.
³ Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, United States. Electronic address: mbaalous@mailbox.sc.edu.

PMID: 32007892
DOI: 10.1016/j.scitotenv.2020.136927

Abstract

Quantification of engineered nanomaterials (ENMs) concentrations in surface waters remains one of the key challenges in environmental nanoscience and nanotechnology. A promising approach to estimate metal and metal oxide ENM concentrations in complex environmental samples is based on the increase in the elemental ratios of ENM-contaminated samples relative to the corresponding natural background elemental ratios. This contribution evaluated the detection and quantification of Ag, CeO₂, and Fe₂O₃ ENMs spiked in synthetic soft, or in natural river waters using the elemental ratio approach, and evaluated the effect of extractants including sodium hydroxide (NaOH), sodium oxalate (Na₂C₂O₄) and sodium pyrophosphate (Na₄P₂O₇) on the recovery of ENMs from the spiked waters. The extracted ENM concentrations were higher in Na₄P₂O₇-extracted suspensions than in NaOH- and Na₂C₂O₄-extracted suspensions due to the higher efficiency of Na₄P₂O₇ to break up natural and engineered nanomaterial heteroaggregates. The size distributions of the extracted suspensions were determined by asymmetrical flow-field flow fractionation coupled to inductively coupled plasma-mass spectrometer (AF4-ICP-MS). These size distribution analysis demonstrated that Ag ENMs were extracted from the spiked river water as both primary particles and small (<100 nm) aggregates, whereas CeO₂ ENMs were extracted from the spiked river water as aggregates of particles in the size range 0-200 nm. The number particle size distribution of the extracted suspensions confirmed that Ag ENMs were extracted as a mixture of primary and aggregated Ag ENMs. Small Ag ENMs (i.e. <20 nm) were detected by AF4-ICP-MS, but these particles were not detected by single particle (sp)-ICP-MS due to high size detection limit of sp-ICP-MS. This study illustrates that the elemental ratio approach is a promising approach to detect and quantify ENMs in surface waters. This study also illustrates the need for a multi-method approach, including extraction, filtration, AF4-ICP-MS and sp-ICP-MS, to detect, quantify, and characterize ENMs in surface waters.

Keywords: AF4-ICP-MS; Engineered nanomaterial quantification; Nanomaterial characterization; Nanomaterial extraction; sp-ICP-MS, sodium pyrophosphate.