title: Evaluation of copper speciation in model solutions of humic acid by mini-columns packed with Chelex-100 and new chelating agents: application to speciation of selected heavy metals in environmental water samples.
abstract: A solid-phase extraction procedure using mini-columns packed with Chelex-100 and two new chelating agents based on poly(vinyl chloride) functionalized with 3-ferrocenyl-3-hydroxydithioacrylic acid and N,N'-[1,1'-dithiobis(ethylene)]-bis(salicylideneimine) (H(2)sales) loaded on microcrystalline naphthalene, is reported. The columns were used to separate labile copper fractions in model solutions and in real samples with subsequent determination using electrothermal atomic absorption spectrometry (ETAAS). Various model solutions containing 20 microg L(-1) of Cu(2+) and 0.0, 0.2, 2.0 and 20.0 mg L(-1) of humic acid, respectively, and buffered to pH 6.0, 7.0 and 8.0 were considered. Results showed a decrease in labile copper fraction with increase in humic acid concentration. Application of the procedure to speciation of Cu, Ni, Zn and Pb in various environmental water samples yielded labile fractions in the range of 1.67-55.75% against a total dissolved fraction of 44.08-69.77%. Comparison of the three chelating agents showed that H(2)sales had a weaker metal chelating strength than Chelex-100, but PVC-FSSH had comparable chelating strength to Chelex-100.
authors.affiliation: Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya. kiptoojac@yahoo.com
authors.forename: Jackson K
authors.initials: JK
authors.lastname: Kiptoo
authors.forename: J Catherine
authors.initials: JC
authors.lastname: Ngila
authors.forename: Ned D
authors.initials: ND
authors.lastname: Silavwe
mesh_terms: D002614:Chelating Agents; D003300:Copper / Q000737:chemistry / Q000302:isolation & purification*; D052918:Environmental Restoration and Remediation / Q000379:methods; D006812:Humic Substances / Q000032:analysis*; D007474:Ion Exchange; D019216:Metals, Heavy; D011143:Polyvinyl Chloride; D012117:Resins, Synthetic; D052616:Solid Phase Extraction / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D002614:Chelating Agents; D006812:Humic Substances; D019216:Metals, Heavy; D012117:Resins, Synthetic; D014874:Water Pollutants, Chemical; C024997:Chelex 100; D003300:Copper; D011143:Polyvinyl Chloride