Aluminum- and Calcium-Binding Affinities of Some Organic Ligands in Acidic Conditions
The Al- and Ca-binding affinities of organic ligands containing carboxylic and/or phenolic groups were studied at pH 4.5, using an ion-pairing chromatographic technique. The ligands were loaded individually in an anion exchange column and were eluted with a solution containing the pairing ion (Al or Ca). Retention data thus obtained were normalized using data from a NaCl elution (i.e., without the pairing ion) and were used as a measure of binding affinity. At pH 4.5, the Al-binding affinity of the following combinations of α, β- substituent groups was found to decrease in the order: > > > . The Ca-binding affinity, on the other hand, showed a different order: > > > . The binding of Al to ligands containing the important group combinations is responsible for the more effective Al mobilization in the environment, the extent of Al availability in biological systems and the interference of Al on Fe and Ca.
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