Not all microplastics are created equal. Quantifying efficacy bias and validation of density separation methods

Microplastics are now recognised as an important environmental issue. In order to combat the environmental concerns associated with plastics, researchers have endeavoured to determine concentrations of microplastics in various environmental matrices (i.e. water, soil, and sediment) using a variety of methodologies. There is a plethora of different sampling techniques, processing methods, and analytical approaches used in the current literature, so researchers need to establish which are most suitable for their research. Due to the lack of standardisation, detailed reporting is necessary. The absence of such complicates the communication and interpretation of research findings. Therefore, validation studies are necessary to achieve clarity on the most appropriate approaches, along with revealing potential sources of bias. Given that microplastics usually include particles of a range of different polymers that have varying densities, the efficacy of the approach is likely better for some types of microplastics than others; however, such biases and error sources have not been quantified. This validation study compares the efficacy of various salt solutions (NaCl, NaBr, ZnCl2, and NaI) used for density separation for a range of individual polymer types (LDPE, PET, and UPVC). Separating funnel and centrifuge approaches are compared, and associated errors are assessed. As expected, the low-density salt solution (NaCl) gave a low recovery percentage (1 Also see: https://micro2024.sciencesconf.org/559674/document