title: Evaluation of the binding of iron(II) to humic substances derived from a compost sample by a colorimetric method using ferrozine.
abstract: In evaluating the quality of composts that include humic substances (HSs), the binding of iron(II) (conditional binding constants and binding capacities) are an important criteria. To determine the binding ability, it is necessary to determine the concentrations of free Fe(2+) and Fe(II)-HS complex species present. In the present study, we describe a colorimetric method for determining free Fe(2+) species using ferrozine in an aqueous solution of Fe(2+) and HS. It was found that the colored species in the Fe(2+) and HS mixture represented only free Fe(2+) species. Two water soluble fractions of HS, humic (HA) and fulvic (FA) acids, were isolated from a compost sample, and the conditional binding constants and binding capacities were estimated by colorimetric titration. Differences in the binding of Fe(II) to HA and FA are discussed, based on their structural features, which were characterized by acidic functional group analysis, elemental analysis and solid-state CP-MAS (13)C NMR spectral data.
authors.affiliation: College of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan. mitsuo@komed.c.u-tokyo.ac.jp
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nishida
authors.forename: Keishi
authors.initials: K
authors.lastname: Otsuka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Komai
authors.forename: Masami
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D001578:Benzopyrans / Q000737:chemistry; D002244:Carbon / Q000032:analysis; D003124:Colorimetry / Q000379:methods*; D004602:Elements; D005297:Ferrozine / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D017186:Titrimetry
chemical_list: D001578:Benzopyrans; D004602:Elements; D006812:Humic Substances; D005297:Ferrozine; D002244:Carbon; D007501:Iron; C005023:fulvic acid