The ability to predict the fate of pharmaceuticals released into the environment is crucial in protecting human and ecosystem health. Sorption, the transfer of a chemical from water to solid interface, like soil, is important in determining environmental fate. While well-established predictive models exist for the sorption of non-polar and polar neutral chemicals to soils and sediments, comparable models have not been developed for charged compounds. Anionic pharmaceuticals, the subject of this study, contain -COOH and- OH and sorb to soils via cation bridging, and surface complexation. Mackay and Vasudevan (2012) proposed a model to predict the sorption of charged compounds using probe compounds and scaling factors. This research evaluates the potential for using small simple probe compounds, including 2-naphthoic acid, salicylic acid, and 2,3-dihydroxynaphthalene, to capture soil receptor site densities and the baseline driving force for sorption. By measuring and comparing sorption of six different probe compounds and pharmaceuticals (e.g., ibuprofen, carbenicillin, sulfasalazine) to pure phase minerals and 30 distinct soils, this research shows that probes and scaling factors relevant to primary sorption mechanism (cation bridging or surface complexation) can be leveraged predict anionic pharmaceutical sorption.

Predicting anionic pharmaceutical sorption to soils using probe compounds

ACS Spring 2022

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