title: Thermodynamics of adsorption of imidacloprid at constant charge hydrophobic surfaces: physicochemical aspects of bioenvironmental activity.
abstract: Adsorption of the insecticide 1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine (Imidacloprid) on the hanging mercury drop electrode (HMDE) surface was studied by temperature-dependent stripping voltammetry (TD-SV). At near physiological pH, under reducing conditions, the Gibbs free energy of adsorption, DeltaGADS, shows two distinct temperature-dependent regimes. (a) At 0 degrees < T < 10 degrees C a temperature-independent mechanism occurs with a constant DeltaGADS = -40.5 kJ/mol, resulting in strong chemisorption at high surface coverage. For T < 10 degrees C a considerable enthalpy gain is estimated, and this represents the driving force for the adsorption of Imidacloprid onto the electrode surface. (b) At T > 10 degrees C a temperature-dependent mechanism is operative with DeltaGADS/DeltaT = -91.4 J/K mol, resulting in a rapid weakening of adsorption and low surface coverage. On the basis of the present findings we suggest that the strong chemisorption at T < 10 degrees C at physiological pH under reducing conditions is related to the high specific insecticide activity of Imidacloprid in cool-blooded insects as contrasted to its low efficiency in warm-blooded organisms.
authors.affiliation: Department of Environmental & Natural Resources Management, University of Ioannina, Seferi 2, Agrinio, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Giannakopoulos
authors.forename: P
authors.initials: P
authors.lastname: Stivaktakis
authors.forename: Y
authors.initials: Y
authors.lastname: Deligiannakis
mesh_terms: D000327:Adsorption; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D057927:Hydrophobic and Hydrophilic Interactions; D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D007093:Imidazoles; D000073943:Neonicotinoids; D009574:Nitro Compounds; C082359:imidacloprid