Abstract
The aim of the work was to extract and identify ethylenediaminetetra‐acetic acid (EDTA) and 1,2‐diaminocyclohexanetetra‐acetic acid (CDTA) or their iron chelates from plant material. Methods were investigated for concentrating these substances and for separating them from the salts, sugars and coloured material that occur in aqueous plant extracts so that identifications can be made by paper chromatography.
A new technique for the quantitative analysis of EDTA and CDTA is described, the principle of which is the sequestering of the metal from highly‐coloured metal complexes.
At pH 2 the chelating agents are retained on columns of cation‐exchange resin and can be eluted with dilute ammonia. Before ion‐exchange chromatography any iron present is precipitated with NaOH in the presence of excess calcium ions.
The iron chelates are completely adsorbed from aqueous solutions on columns of activated charcoal; salts and sugars are eluted with water and 5% aqueous ethanol, the iron chelates with 25% or 50% ethanol.
EDTA and CDTA, or their iron chelates, can be separated by paper chromatography using a 4:1 w/v phenol‐water solvent. The chelating agents are located by staining with nickel dimethylglyoxime and the iron chelates by viewing under ultra‐violet light. When the chelating agents are labelled with ^14^C the positions are found by radio‐assay of the chromatogram in a windowless 4π counter.