Theoretical Speciation of Ethylenediamine-N-(o-hydroxyphenylacetic)-N‘-(p-hydroxyphenylacetic) Acid (o,p-EDDHA) in Agronomic Conditions

The presence of ethylenediamine-N-(o-hydroxyphenylacetic)-N‘-(p-hydroxyphenylacetic) acid (o,p-EDDHA) as the second largest component in commercial EDDHA iron chelates has recently been demonstrated. Here is reported the speciation of o,p-EDDHA by the application of a novel methodology through the d...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2003-08, Vol.51 (18), p.5391-5399
Main Authors: Yunta, Felipe, García-Marco, Sonia, Lucena, Juan J
Format: Article
Language:English
Subjects:
Agriculture
Calcium - chemistry
Copper - chemistry
Drug Stability
Ethylenediamines - analysis
Ethylenediamines - chemistry
Ferric Compounds - chemistry
Hydrogen-Ion Concentration
Iron Chelating Agents - chemistry
Magnesium - chemistry
Magnetic Resonance Spectroscopy
Spectrophotometry
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Summary:The presence of ethylenediamine-N-(o-hydroxyphenylacetic)-N‘-(p-hydroxyphenylacetic) acid (o,p-EDDHA) as the second largest component in commercial EDDHA iron chelates has recently been demonstrated. Here is reported the speciation of o,p-EDDHA by the application of a novel methodology through the determination of the complexing capacity, protonation, and Ca2+, Mg2+, Cu2+, and Fe3+ stability constants. The pM values and species distribution in solution, hydroponic, and soil conditions were obtained. Due to the para position of one phenol group in o,p-EDDHA, the protonation constants and Ca and Mg stability constants have different values from those of o,o-EDDHA and p,p-EDDHA regioisomers. o,p-EDDHA/Fe3+ stability constants are higher than those of EDTA/Fe3+ but lower than those of o,o-EDDHA/Fe3+. The sequence obtained for pFe is o,o-EDDHA/Fe3+ ≥ o,p-EDDHA/Fe3+ > EDTA/Fe3+. o,p-EDDHA/Fe3+ can be used as an iron chelate in hydroponic conditions. Also, it can be used in soils with limited Cu availability. Keywords: o,p-EDDHA; o,o-EDDHA; iron chelates; fertilizers; formation constants; stability; speciation
ISSN:0021-8561
1520-5118
DOI:10.1021/jf034304r