Detailed NMR investigation of cyclodextrin-perfluorinated surfactant interactions in aqueous media

Perfluorochemicals (PFCs) are contaminants of serious concern because of their toxicological properties, widespread presence in drinking water sources, and incredible stability in the environment. To assess the potential application of alpha-, beta-, and gamma-cyclodextrins for PFC remediation, we investigated their complexation with linear fluorinated carboxylic acids, sulfonates, and a sulfonamide with carbon backbones ranging from C4-C9. F-19 Nuclear Magnetic Resonance (NMR) spectroscopy studies demonstrated beta-CD formed the strongest complexes with these PFCs. The polar head group had a modest influence, but for PFCs with backbones longer than six carbons, strong association constants are observed for 1:1 (K-1:1 similar to 10(5) M-1) and 2:1 (K-2:1 similar to 10(3) M-1) beta-CD:PFC complexes. Excess beta-CD can be used to complex 99.5% of the longer chain PFCs. Competition studies with adamantane-carboxylic acid and phenol confirmed the nature and persistence of the beta-CD:PFC complex. Detailed analyses of the individual NMR chemical shifts and Job plots indicate the favored positions of the beta-CD along the PFC chain. Solution pH, ionic strength, and the presence of humic acid have modest influence on the 13-CD:PFC complexes. The strong encapsulation of PFCs by (beta-CD under a variety of water quality conditions demonstrates the tremendous potential of CD-based materials for the environmental remediation of PFCs. (C) 2017 Elsevier B.V. All rights reserved.