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 determination of the complexing capacity, protonation, and Ca(2+), Mg(2+), Cu(2+), and Fe(3+) 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/Fe(3+) stability constants are higher than those of EDTA/Fe(3+) but lower than those of o,o-EDDHA/Fe(3+). The sequence obtained for pFe is o,o-EDDHA/Fe(3+) >/= o,p-EDDHA/Fe(3+) > EDTA/Fe(3+). o,p-EDDHA/Fe(3+) can be used as an iron chelate in hydroponic conditions. Also, it can be used in soils with limited Cu availability.
Yunta
Felipe
F
Department of Agricultural Chemistry, Universidad Autónoma, 28049 Madrid, Spain.
García-Marco
Sonia
S
Lucena
Juan J
JJ
D000383:Agriculture; D002118:Calcium / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D004355:Drug Stability; D005029:Ethylenediamines / Q000032:analysis / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007502:Iron Chelating Agents / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013053:Spectrophotometry
D005029:Ethylenediamines; D005290:Ferric Compounds; D007502:Iron Chelating Agents; C011813:ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid); D003300:Copper; D008274:Magnesium; D002118:Calcium