Non-essential metals such as Aluminium are well-known by their toxic properties. Aluminium often is related with neurodegenerative diseases such as Alzheimer's disease and Parkinson dementia. Genotoxic and cytotoxic effects of Al compounds have been reported for AlCI3, a very common Al salt used in this work as the metal source. Sodium cacodylate (NaCac, pKa 6.27) was used as ligand. This compound is widely used as weak buffer due to its apparently low reactivity. Despite the low solubility of the Aluminium compound up to pH = 4, the reaction with sodium cacodylate yielded a (Al/NaCac)3+ complex soluble over a wide pH range (0 to 11) and metal concentration (up to 7E-3 M). 1H-NMR, 27Al-NMR and potentiometry were used to study the complex formation. 1H-NMR performed on free Sodium cacodylate at different pH yielded pKa values of 1.32 and 6.11. Kinetic experiments performed by 1H-NMR proved that the reaction between Al3+ and cacodylate occurs in the first 5 min. In addition, 1H-NMR at different pH reflects the trend of the complex formation: the higher the pH the less complex amount is formed. 27Al-NMR confirms the complex formation. With Al3+ solutions within pH =1-6 only one peak appeared, ascribed to Al(H2O)63+. The same experiments performed with 1: l complex, gave way to three behaviours: for pH = 1 and 2 only Al(H2O)63+ appears, for pH = 3 and 4 two additional peaks appeared at 2.5 and 4 ppm, showing two additional complexes. Finally, above this pH all the peaks disappear, yielding peaks almost negligible at 60ppms, which are usually assigned to formation of Al-mers. For CM/CL > 10 ratio, the solubility decreased strongly, but complexes with different stoichiometries have been obtained which precipitate at pH > 4.

New aspects to the reactivity of Al: Formation of Al3+/NaCaC complex

SECCO, FERNANDO;BIVER, TARITA;
2013

Abstract

Non-essential metals such as Aluminium are well-known by their toxic properties. Aluminium often is related with neurodegenerative diseases such as Alzheimer's disease and Parkinson dementia. Genotoxic and cytotoxic effects of Al compounds have been reported for AlCI3, a very common Al salt used in this work as the metal source. Sodium cacodylate (NaCac, pKa 6.27) was used as ligand. This compound is widely used as weak buffer due to its apparently low reactivity. Despite the low solubility of the Aluminium compound up to pH = 4, the reaction with sodium cacodylate yielded a (Al/NaCac)3+ complex soluble over a wide pH range (0 to 11) and metal concentration (up to 7E-3 M). 1H-NMR, 27Al-NMR and potentiometry were used to study the complex formation. 1H-NMR performed on free Sodium cacodylate at different pH yielded pKa values of 1.32 and 6.11. Kinetic experiments performed by 1H-NMR proved that the reaction between Al3+ and cacodylate occurs in the first 5 min. In addition, 1H-NMR at different pH reflects the trend of the complex formation: the higher the pH the less complex amount is formed. 27Al-NMR confirms the complex formation. With Al3+ solutions within pH =1-6 only one peak appeared, ascribed to Al(H2O)63+. The same experiments performed with 1: l complex, gave way to three behaviours: for pH = 1 and 2 only Al(H2O)63+ appears, for pH = 3 and 4 two additional peaks appeared at 2.5 and 4 ppm, showing two additional complexes. Finally, above this pH all the peaks disappear, yielding peaks almost negligible at 60ppms, which are usually assigned to formation of Al-mers. For CM/CL > 10 ratio, the solubility decreased strongly, but complexes with different stoichiometries have been obtained which precipitate at pH > 4.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/237967
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