title: Demetalation of Fe, Mn, and Cu chelates and complexes: application to the NMR analysis of micronutrient fertilizers.
abstract: The application of nuclear magnetic resonance (NMR) for the quality control of fertilizers based on Fe(3+), Mn(2+), and Cu(2+) chelates and complexes is precluded by the strong paramagnetism of metals. Recently, a method based on the use of ferrocyanide has been described to remove iron from commercial iron chelates based on the o,o-EDDHA [ethylenediamine-N,N'bis(2-hydroxyphenylacetic)acid] chelating agent for their analysis and quantification by NMR. The present work extended that procedure to other paramagnetic ions, manganese and copper, and other chelating, EDTA (ethylenediaminetetraacetic acid), IDHA [N-(1,2-dicarboxyethyl)-d,l-aspartic acid], and complexing agents, gluconate and heptagluconate. Results showed that the removal of the paramagnetic ions was complete, allowing us to obtain (1)H NMR spectra characterized by narrow peaks. The quantification of the ligands by NMR and high-performance liquid chromatography showed that their complete recovery was granted. The NMR analysis enabled detection and quantification of unknown impurities without the need of pure compounds as internal standards.
authors.affiliation: Departamento de Química Agrícola, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: López-Rayo
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Lucena
authors.forename: Luca
authors.initials: L
authors.lastname: Laghi
authors.forename: Mauro A
authors.initials: MA
authors.lastname: Cremonini
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D003300:Copper / Q000032:analysis / Q000302:isolation & purification*; D004492:Edetic Acid / Q000737:chemistry; D005308:Fertilizers / Q000032:analysis*; D007501:Iron / Q000302:isolation & purification*; D007502:Iron Chelating Agents / Q000032:analysis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D002614:Chelating Agents; D005308:Fertilizers; D007502:Iron Chelating Agents; D008345:Manganese; D003300:Copper; D004492:Edetic Acid; D007501:Iron