Quantitative 27Al NMR spectroscopic studies of Al (III) complexes with organic acid ligands and their comparison with GEOCHEM predicted values

Kerven G.L., Larsen P.L., Bell L.C. and Edwards D.G. (1995) Quantitative 27Al NMR spectroscopic studies of Al (III) complexes with organic acid ligands and their comparison with GEOCHEM predicted values. Plant and Soil, 171 1: 35-39. doi:10.1007/BF00009561


Author Kerven G.L.
Larsen P.L.
Bell L.C.
Edwards D.G.
Title Quantitative 27Al NMR spectroscopic studies of Al (III) complexes with organic acid ligands and their comparison with GEOCHEM predicted values
Journal name Plant and Soil   Check publisher's open access policy
ISSN 0032-079X
Publication date 1995-01-01
Sub-type Article (original research)
DOI 10.1007/BF00009561
Volume 171
Issue 1
Start page 35
End page 39
Total pages 5
Publisher Kluwer Academic Publishers
Subject 1111 Nutrition and Dietetics
1110 Nursing
1102 Cardiovascular Medicine and Haematology
1900 Earth and Planetary Sciences
2300 Environmental Science
Abstract The toxic inorganic monomeric forms of aluminium (Al) that limit plant growth have been shown to be effectively detoxified by complexation with organic acid ligands released by breakdown of added organic materials. The binding capacity of these acids is dependent on the degree of dissociation of their carboxyl groups and their ability to form bonds with Al. 27Al NMR spectroscopy provides a non-invasive technique to study the bonding of Al with potential ligands without disturbing the equilibrium of the system. In single ligand systems containing oxalic acid, three 27Al resonance peaks were observed at 6.4, 11.4 and 16.0 ppm downfield from the Al3+ reference peak at 0 ppm. These were assigned to Alox, Alox2 and Alox3 complexes respectively and were observable at pH values down to 3.5. In the presence of the citrate ligand, two 27Al resonance peaks at 6.1 and 11.3 ppm, assigned respectively to the Alcit and Alcit2 complexes, were observed at pH 3.4. At pH 4.3 and an Al:citrate molar ratio of 1:2, the 6.1 ppm peak was not visible, and the second peak further downfield was split into two unresolved peaks at 10.8 and 12.4 ppm indicating the presence of two forms of the Alcit2 complex. Distribution of Al between the various species, based on integration of the resonance peaks and equilibrium calculations carried out using GEOCHEM, is discussed in light of the stability constants present in the database of GEOCHEM version (v.) 1.23 and GEOCHEM-PC v. 2.0. Large discrepancies between the computed values and the NMR measured values indicate the need to incorporate more recent literature values in the database for realistic equilibrium calculations in systems containing organic acid ligands. The potential of using quantitative 27Al NMR measurements to calculate stability constants is discussed.
Keyword aluminium
equilibrium calculations
GEOCHEM
NMR
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import - Archived
 
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