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Understanding solution‐state noncovalent interactions between xenobiotics and natural organic matter using 19 F/ 1 H heteronuclear saturation transfer difference nuclear magnetic resonance spectroscopy
Author(s) -
Longstaffe James G.,
Simpson André J.
Publication year - 2011
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.560
Subject(s) - heteronuclear molecule , saturation (graph theory) , chemistry , spectroscopy , analytical chemistry (journal) , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , physics , stereochemistry , environmental chemistry , mathematics , combinatorics , quantum mechanics
A combination of forward and reverse heteronuclear ( 19 F/ 1 H) saturation transfer difference (STD) nuclear magnetic resonance (NMR) spectroscopic techniques were applied to characterize the noncovalent interactions between perfluorinated aromatic xenobiotics and dissolved humic acid. These NMR techniques produce detailed molecular‐level descriptions of weak noncovalent associations between components in complex environmental mixtures, allowing the mechanisms underlying these interactions to be explored; 19 F observed heteronuclear STD (H‐STD) is used to describe the average molecular orientation of the xenobiotics during their interactions with humic acid, whereas 1 H observed reverse‐heteronuclear STD (RH‐STD) is used to both identify and quantify preferences exhibited by xenobiotics for interactions at different types of humic acid moieties. First, by using H‐STD, it is shown that selected aromatic organofluorides orient with their nonfluorine functional groups (OH, NH 2 , and COOH) directed away from humic acid during the interactions, suggesting that these functional groups are not specifically involved. Second, the RH‐STD experiment is shown to be sensitive to subtle differences in preferred interaction sites in humic acid and is used here to demonstrate preferential interactions at aromatic humic acid sites for selected aromatic xenobiotics, C 10 F 7 OH, and C 6 F 4 X 2 , (where X = F, OH, NH 2 , NO 2 , or COOH), that can be predicted from the electrostatic potential density maps of the xenobiotic. Environ. Toxicol. Chem. 2011; 30:1745–1753. © 2011 SETAC