Issue 5, 2022

Quantification and classification of engineered, incidental, and natural cerium-containing particles by spICP-TOFMS

Abstract

Cerium containing nanoparticles (Ce-NPs) from geogenic and anthropogenic sources are frequently found in the environment, and the ability to determine the origins of Ce-NPs relies on the presence of other rare earth elements (REEs), such as La. In this study, we develop a scheme to classify individual natural, incidental, and engineered Ce-containing particles using spICP-TOFMS. Well-characterized CeO2 engineered particles (Ce-ENPs), incidental particles (Ce-INPs) from ferrocerium mischmetal, and natural particles (Ce-NNPs) from ground minerals (bastnaesite and parisite) are used as a model particle system. Based on mixtures of these three Ce-NP types, we demonstrate that the measured signals of Ce, La, and Nd in Ce-NNPs follow Poisson statistics and have conserved element ratios. The Ce-INPs we measure have similar Ce : La mass ratios to those of the Ce-NNPs, and Ce : Nd mass ratios can be used to distinguish these two Ce-NP types. Based on this, we develop particle-type-specific detection limits (LD,sp) for the measurement of La and Nd in Ce-NNPs. Our approach establishes LD,sp values with defined confidence intervals to control false-positive particle-type assignments, and allows us to accurately classify engineered, incidental, and natural Ce-NPs down to effective spherical diameters of 32, 35, and 45 nm, respectively. In pure Ce-NNP suspensions, this approach accurately classifies 68% of all detected Ce-NPs with <4% false assignments. For ternary mixtures of Ce-ENPs, INPs, and NNPs, we classify 56% to 76% of all detected Ce-NPs. We demonstrate a linear response with increasing concentrations of Ce-INPs and Ce-ENPs across approximately three orders of magnitude and can classify particles down to ratios of ∼1 : 50 for anthropogenic : natural Ce-NPs.

Graphical abstract: Quantification and classification of engineered, incidental, and natural cerium-containing particles by spICP-TOFMS

Supplementary files

Article information

Article type
Paper
Submitted
12 Nov 2021
Accepted
08 Mär 2022
First published
18 Mär 2022
This article is Open Access
Creative Commons BY license

Environ. Sci.: Nano, 2022,9, 1627-1638

Quantification and classification of engineered, incidental, and natural cerium-containing particles by spICP-TOFMS

S. E. Szakas, R. Lancaster, R. Kaegi and A. Gundlach-Graham, Environ. Sci.: Nano, 2022, 9, 1627 DOI: 10.1039/D1EN01039E

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