A physical chemistry lens on environmental nanoplastics analysis challenges. Part I: Why isolation is more complex than for microplastics?

Abstract

Nanoplastics (NPs) are emerging pollutants (EPs) which behave so differently to their micron-size counterparts that a new field of scientific interest is rapidly growing on the topic. The presence of these small plastic particles has been reported in a wide range of environments, from oceans to human organs. However, reliable quantitative data is sparse because their isolation from environmental matrices and subsequent detection faces technical limitation. Yet, baseline levels of NPs occurrence are needed to understand their impact on the environment, on the biota at large, as well as on human health. This impact is feared to be more detrimental than that of microplastics, in part due to their high surface area to volume ratio which makes NPs, like other nanoparticles, very reactive. Their small size also means they can pass through living cell membranes and disrupt biological processes. To date, however, there is a lack of reliable information on the concentration and type of NPs present in the different environmental matrices to adequately study and address these issues. Most research has so far focused on micro-plastics whereas the isolation of sub-micron particles, and especially those smaller than 100 nm, remains a significant challenge. This review aims to highlight the current state of the art and the gaps in both knowledge and technology that are to be filled prior to a comprehensive study of NPs. Specifically, a focus on the unique physico-chemical properties of NPs is used to narrow down isolation methods most suited for subsequent NPs detection, identification, and quantification. The expected outcome of this review is to provide researchers outside of the field of colloidal science a mechanistic explanation of the physico-chemical properties of common NPs necessary to achieve their selective capture.