Biomimetic solid phase microextraction as a tool for quantifying organic micropollutants-biopolymer partitioning

Understanding the partitioning behavior of emerging organic micropollutants (OMPs) into naturally occurring biopolymers is critical for assessing their environmental transport, bioavailability, and fate. However, existing methods for quantifying OMP-biopolymer interactions often lack sufficient sensitivity to detect environmentally relevant concentrations and are not well suited to low-molecular-weight biopolymers such as polysaccharides. In this study, we introduce a biomimetic solid phase microextraction (SPME) device coated with alginic acid, a marine polysaccharide derived from brown algae, to measure alginate-water partition coefficients for a chemically diverse set of OMPs.

Partitioning was quantified by calculating partition coefficients (K_{OMP, AA/W}) and fiber constants (fc) of the OMPs in hydrated and dehydrated sorbents to simulate environmentally relevant states. Hydrated sorbents exhibited enhanced partitioning of the targeted probe molecules due to increased porosity and polymeric chain mobility, which facilitate partitioning of OMPs. Partitioning was prominent for molecules with log P < 4. Dehydrated sorbents exhibited significantly lower uptake due to hydrogel shrinkage and pore collapse, except for highly hydrophobic pesticides, which interact more strongly with the exposed polysaccharide backbone in the absence of water.

This work lays the groundwork for using native biopolymer-based SPME devices to interrogate partition phenomena of small molecules and introduces a quantitative method for calculating the partition coefficients of OMPs into natural polysaccharides. These findings provide valuable insight into the physicochemical factors governing OMP interactions with marine algal matrices and have broader relevance to environmental chemical processes, biomedical research, and food science.