1 Scope
This document specifies a method for the determination by ion pair chromatography
of the iron chelated by each individual ortho (hydroxy)- ortho (hydroxy) isomer of the chelating agents [o,o] EDDHA, [o,o] EDDHMA and by HBED in
organo-mineral fertilizers, having an organic matrix based on vegetal residues (cocoa
shells, grape residue, soybean residue, …), algae extract, and animal meal (feather,
bones, blood, ...) and containing one or more of these substances, except for [o,o] EDDHMA
and HBED mixes.
The method allows the identification and the determination of the total concentration
of water soluble iron chelates of these chelating agents. Also, after derivatization
with Fe, the soluble amount of the chelating agents can be determined when other micronutrients
beside Fe are present in organo-mineral fertilizers containing [o,o] EDDHA, [o,o] EDDHMA
or HBED.
This method is applicable to a mass fraction of the metal chelated of at least 0,625 %.
NOTE 1 The substances EDDHA and EDDHMA exist as several different isomeric forms. Positional
isomers for the hydroxyl or methyl groups (in ortho, meta, and para positions) as well as stereo isomers ( meso and dl-racemic forms) are known. Both meso and dl-racemic forms of the [ ortho,ortho ] EDDHA and [ ortho,ortho ]. Since para, meta and ortho methyl positional isomers of the EDDHMA present quite similar stability, they could
be grouped: in the method here described the para, meta and ortho methyl positional isomers of the [o,o] EDDHMA are considered together. HBED (N,N'-bis(2-hyd...