A New Film-Based Passive Sampler for Moderately Hydrophobic Organic Compounds

Passive samplers for moderately hydrophobic organic compounds (MHOCs) (i.e., log K_ow ranging from 2 to 5) are under-developed compared to those that target polar or strongly hydrophobic compounds. The goal of this study was to identify a suitable polymer and develop a robust and sensitive film-based passive sampler for MHOCs in aquatic systems. Poly­(methyl methacrylate) (PMMA) exhibited the highest affinity for fipronil and its three metabolites (i.e., fipronils) (log K_ow 2.4–4.8) as model MHOCs compared with polyethylene and nylon films. In addition, a 30–60 min treatment of PMMA in ethyl ether was found to increase its sorption capacity by a factor of 10. Fipronils and 108 additional compounds (log K_ow 2.4–8.5) reached equilibrium on solvent-treated PMMA within 120 h under mixing conditions and their uptake closely followed first-order kinetics. PMMA-water partition coefficients and K_ow revealed an inverse parabolic relationship, with vertex at log K_ow of 4.21 ± 0.19, suggesting that PMMA was ideal for MHOCs. The PMMA sampler was tested in an urban surface stream, and in spiked sediment. The results demonstrated that PMMA film, after a simple solvent swelling treatment, may be used as an effective passive sampler for determining C_free of MHOCs in aquatic environments.