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This Technical Specification specifies a method for the chromatographic determination of the amount of iron chelated by each of the individual isomers of the chelating agent ortho para EDDHA (o,p-EDDHA) in fertilizers. The method allows the identification of this chelating agent and the determination of the water soluble fraction of iron chelated by this chelating agent. The method is not applicable for the determination of the amount of free chelating agent. NOTE 1 This method has been shown to be also suitable for the determination of the amount of iron chelated by each of the individual isomers of the chelating agent ortho ortho EDDHA (o,o-EDDHA) in fertilizers. NOTE 2 o,o-EDDHA and o,p-EDDHA are abbreviations used in this standard for the sake of simplicity. For complete names see Annex A. NOTE 3 The substances o,o-EDDHA and o,p-EDDHA both exist as different stereoisomers. For o,o-EDDHA a meso form and a d/l pair (the racemic isomers) exist, for o,p-EDDHA two different d/l pairs exist. All four stereoisomers are observed separately in this method. NOTE 4 Presently, an analytically pure standard only exists for o,o-EDDHA. The method for o,p-EDDHA has been developed with an o,p-EDDHA standard containing an uncertain concentration of o,p-EDDHA.