Articles
THE EFFECT OF pH AND COMPETING METAL IONS ON THE STABILITY OF THE ISOMERS OF FeEDDHA IN FERTIGATION SOLUTIONS
Article number
559_98
Pages
669 – 674
Language
English
Abstract
The iron chelate etilendiamine-di-o-hydroxiphenilacetateferrate (III) (FeEDDHA), decomposes quickly at low pH values.
This reaction is reversible except when ions that compete with Fe for EDDHA or with EDDHA for iron occur in the solutions.
Till now, all the experiments have studied the influence of a sole competing ion on the reaction.
The joint effect, of all the elements that take part in a nutritive solution, on these reactions is studied in this paper.
As FeEDDHA is constituted by two geometrical isomers (a meso form and a racemic mixture) of different stability constants, in order to stablish the influence of the competing ions on both isomers separately, the research has been made by high-pressure liquid chromatography (HPLC). Our study indicates that the sole addition of the chelate to a solution containing several competing ions at pH 6, destroys 25.3% of the racemic mixture and 75% of the meso isomer.
Percentages are of 33% and 78% respectively if pH is 4.5. When the solution is acidified to pH 1 and re-alkalinised to pH 6, only the 25% of the racemic mixture and the 8% of the meso form remains in solution.
Although over a longer term, a higher chelate recovery would be expected, the situation can be significant in soilless cultures with moving nutritive solution.
The separate addition of FeEDDHA to fertigation solutions is therefore highly recommended.
This reaction is reversible except when ions that compete with Fe for EDDHA or with EDDHA for iron occur in the solutions.
Till now, all the experiments have studied the influence of a sole competing ion on the reaction.
The joint effect, of all the elements that take part in a nutritive solution, on these reactions is studied in this paper.
As FeEDDHA is constituted by two geometrical isomers (a meso form and a racemic mixture) of different stability constants, in order to stablish the influence of the competing ions on both isomers separately, the research has been made by high-pressure liquid chromatography (HPLC). Our study indicates that the sole addition of the chelate to a solution containing several competing ions at pH 6, destroys 25.3% of the racemic mixture and 75% of the meso isomer.
Percentages are of 33% and 78% respectively if pH is 4.5. When the solution is acidified to pH 1 and re-alkalinised to pH 6, only the 25% of the racemic mixture and the 8% of the meso form remains in solution.
Although over a longer term, a higher chelate recovery would be expected, the situation can be significant in soilless cultures with moving nutritive solution.
The separate addition of FeEDDHA to fertigation solutions is therefore highly recommended.
Authors
M.M. Cerdán, M. Juárez, J. Sánchez-Andréu, M.D. Bermúdez, J. Jordà
Keywords
Chelate; Nutritive solution; CuEDDHA, ZnEDDHA, HPLC
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