Understanding the fate of plastics and the health and environmental risks associated with exposure requires a better understanding of their behavior in natural and applied systems. Tools capable of elucidating the degradation pathways (i.e., identify chemical changes) of the material across the size spectrum from the bulk to micro and nanoplastic (MNP) species should ultimately result in the ability to track their movement through different environmental compartments. In an effort to support current field research on plastic degradation and human health, we will present our workflow and progress towards developing mass spectrometric and spectroscopy methods to characterize the chemical signatures of different plastic controls in the sub-micron size regime. Because no reference materials exist for MNPs, measurement tools with appropriate sensitivity and spatial resolution have high uncertainties, which has limited progress. To improve uncertainty and begin evaluating capacity of current instrumentation, internal controls of known polymer composition milled into distinct size regimes and morphologies were produced through collaborative efforts. The internal controls are useful benchmarks for measurement development tailored to natural samples. Specifically, the control materials are being used to optimize separations using hyphenated flow field flow fractionation and aerosol techniques that bin, fractionate and concentrate samples for the further offline characterization method developments outlined above. Importantly, control material development has been done in parallel with macroplastic samples collected from different sources to ensure applicability to real world samples by comparing suspension properties using light scattering. We will present our initial work to attain similar colloidal behavior between the controls and field samples by modifying surface oxidation and surface chemical functionalization, which improved dispersion and resulted in higher selectivity and recovery. The development of modified controls in appropriate quantities for different spectroscopic and spectrometric methods provides the opportunity to improve identification and quantification for MNPs, especially in the nano size regime.

Progress towards the development of validated measurement methods to characterize and quantify nanoplastics in aqueous media

ACS Spring 2022

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