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Screening a Selective Chelator Pair for Simultaneous Determination of Iron(II) and Iron(III)

Wang, Tiangen, Peverly, John H.
Soil Science Society of America journal 1998 v.62 no.3 pp. 611-617
soil analysis, water, chemical analysis, iron, chemical speciation, chelating agents, quantitative analysis, accuracy, EDTA (chelating agent), redox reactions
Direct determination of Fe(II) and Fe(III) is a fundamental technology for environmental Fe chemistry research. The key to accurate determination of Fe(II) and Fe(III) in soil, water, and plant samples is to stabilize Fe oxidation states during Fe extraction and analysis, but the goal has only been partially achieved in previous research. In this research, an approach to stabilizing the original oxidation states of Fe during extraction and analysis was studied. The following sequential procedures were conducted: computer simulation → colorimetric tests → Fe(III) reduction resistance tests → metal interference tests → sensitivity tests → determination of optimal pH for Fe extraction. Results indicated that EDTA (ethylenediamine-N,N,N′,N′-tetraacetate, disodium salt) and BPDS (bathophenanthroline disulfonate, disodium salt) were the most effective chelator pair with which to stabilize Fe oxidation states and that they may allow accurate, simultaneous determination of Fe(II) and Fe(III). This research was conducted at the Dep. of Soil, Crop and Atmospheric Sciences, Cornell Univ., Ithaca, NY.