title: Examination of molecular interaction sites of acetanilides with organic matter surrogates using nuclear magnetic resonance techniques.
abstract: The dynamics of acetanilide pesticide interactions with organic matter (OM) surrogates were examined using nuclear magnetic resonance (NMR) spectroscopy. Differences in the relative changes in (13)C and (1)H spin-lattice relaxation times (T(1)) were measured at multiple molecular sites of metolachlor and the probe compound acetanilide to identify interaction sites and/or surfaces between the molecules and dissolved and colloidal OM surrogates. The decrease in T(1) at specific sites of acetanilide molecules was a function of the OM used and its concentration. High-affinity interactions at nonaromatic sites of metolachlor and acetanilide were observed with cellulose, chitin, and collagen, but interactions with lignin occurred with less site specificity and involved both aromatic and nonaromatic sites of the molecules. Changes in relaxation were compared to calculated and experimentally determined binding coefficients (K(oc)). The T(1) relaxation of the aromatic sites of acetanilides showed better relations with K(oc) than the nonaromatic sites. This study shows that NMR relaxation measurements can identify the high-affinity molecular interaction sites of acetanilides to OM surrogates.
authors.affiliation: Department of Civil and Environmental Engineering, University of Maryland, College Park 20742, USA.
authors.forename: Shalini
authors.initials: S
authors.lastname: Jayasundera
authors.forename: Walter F
authors.initials: WF
authors.lastname: Schmidt
authors.forename: Cathleen J
authors.initials: CJ
authors.lastname: Hapeman
authors.forename: Alba
authors.initials: A
authors.lastname: Torrents
mesh_terms: D000081:Acetamides / Q000737:chemistry; D000083:Acetanilides / Q000737:chemistry*; D001665:Binding Sites; D002482:Cellulose / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002686:Chitin / Q000737:chemistry; D003094:Collagen / Q000737:chemistry; D008031:Lignin / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular
chemical_list: D000081:Acetamides; D000083:Acetanilides; D002686:Chitin; D002482:Cellulose; D008031:Lignin; D003094:Collagen; C051786:metolachlor