title: Influence of suspended clay minerals and humic matter on the solid phase extraction efficiency of selected pesticides from water.
abstract: The purpose of this investigation was to determine the influence of humic acids (HA) and Ca-montmorillonite (CaM) on the solid-phase extraction (SPE) efficiency of atrazine, alachlor and alpha-cypermethrin from water samples at various pH-values. The nature and intensity of binding of the studied pesticides to CaM were determined by X-ray diffraction analysis and termogravimetric analysis (TGA) test. The studied pesticides eluted from discs were analysed by thin-layer chromatography (TLC). The effects of CaM and humic acid were generally pH-dependent and acted independently in extraction efficiency influence. Lower recovery of pesticides was observed at higher pH values when CaM was > or =0.1 g and was attributed to greater dispersion of clay, increased surface area and subsequent adsorption. Concentrations of dissolved organic carbon (DOC) in humic acid had less effect on the extraction efficiency when water was at pH 8 compared to water at pH 2, which was probably due to greater nonpolar interactions of the pesticides to the charge-neutralized humic acid molecule.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Croatia. dmutavdz@fkit.hr
authors.forename: Dragana
authors.initials: D
authors.lastname: Mutavdzić
authors.forename: Ivan
authors.initials: I
authors.lastname: Brnardić
authors.forename: Marija
authors.initials: M
authors.lastname: Kastelan-Macan
mesh_terms: D000081:Acetamides / Q000032:analysis / Q000302:isolation & purification; D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D001280:Atrazine / Q000032:analysis / Q000302:isolation & purification; D001546:Bentonite / Q000737:chemistry*; D002855:Chromatography, Thin Layer; D000077215:Clay; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000737:chemistry*; D010575:Pesticides / Q000737:chemistry*; D011722:Pyrethrins / Q000032:analysis / Q000302:isolation & purification; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification
chemical_list: D000081:Acetamides; D000538:Aluminum Silicates; D006812:Humic Substances; D008903:Minerals; D010575:Pesticides; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; D001546:Bentonite; C017160:cypermethrin; C000188:alachlor; D001280:Atrazine; D000077215:Clay