EN 13368-2:2007

Fertilizers - Determination of chelating agents in fertilizers by chromatography - Part 2: Determination of Fe chelated by o,o-EDDHA and o,o-EDDHMA by ion pair chromatography

Publication date:   Sep 28, 2007

Scope

This document specifies a method for the chromatographic determination of the iron chelated by each individual ortho(hydroxy)-ortho(hydroxy) isomer of the chelating agents o,o-EDDHA and o,o-EDDHMA in fertilizers containing one or both of these substances. The method allows the identification and the determination of the total concentration of water soluble iron chelates of these chelating agents. It does not determine the free form of the chelating agents.
NOTE 1 The substances EDDHA (ethylene diamine di(hydroxy phenyl) acetic acid) and EDDHMA (ethylene diamine di(hydroxy methyl phenyl)acetic acid) 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-EDDHMA are positional isomers for the hydroxyl groups allowed by the Regulation (EC) No 2003/2003. 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.
NOTE 2 At present, analytically pure standards only exist for ortho,ortho-EDDHA and ortho,ortho-EDDHMA. All other substances being unavailable as a standard, the influence of their eventual presence in the samples (with respect to the sensitivity and the selectivity of this method) has not been studied.
NOTE 3 The meso and the dl-racemic forms of o,o-EDDHA and o,o-EDDHMA can be determined separately by this method.
This procedure concerns EC fertilizers covered by Regulation (EC) No 2003/2003 [5]. It is applicable to a mass fraction of the metal chelated of at least 0,625 %.