The acid base behavior of phytate has been studied (at t = 25 °C by potentiometry, ISE-H+ glass electrode) in NaNO3aq at different ionic strengths (0.1 ≤ I/mol L- 1 ≤ 1.0). The interactions with copper(II) were investigated in the same experimental conditions in different metal to ligand (Phy) ratios (1:1 ≤ Cu2+:Phy ≤ 4:1), by using both ISE-H+ and ISE-Cu2+ electrodes. Phytate acid base behavior in sodium nitrate is very similar to that in sodium chloride, previously investigated. In the experimental conditions adopted, the formation of three CuiHjPhy(12-2i-j)- species is observed: the mononuclear CuH4Phy6- and CuH5Phy5-, and the dinuclear Cu2H5Phy3-. Analysis of complex formation constants at different ionic strengths reveals that both ISE-H+ and ISE-Cu2+ electrodes gave, within the experimental error, analogous values. Dependence of complex formation constants on ionic strength was modeled by EDH (Extended Debye-Hückel) and SIT (Specific ion Interaction Theory) equations. The sequestering ability of phytate toward copper(II) has been evaluated by the calculation of pL50 (the total ligand concentration, as - log CL, able to bind 50% of metal cation), an empirical parameter already proposed for an objective "quantification" of this ability. A thorough analysis of literature data on phytate-copper(II) complexes has been performed.

Speciation of phytate ion in aqueous solution. Protonation constants and copper(II) interactions in NaNO3aq at different ionic strengths.

CREA, PASQUALE;DE STEFANO, Concetta;MILEA, Demetrio;PORCINO, NUNZIATINA;SAMMARTANO, Silvio
2007-01-01

Abstract

The acid base behavior of phytate has been studied (at t = 25 °C by potentiometry, ISE-H+ glass electrode) in NaNO3aq at different ionic strengths (0.1 ≤ I/mol L- 1 ≤ 1.0). The interactions with copper(II) were investigated in the same experimental conditions in different metal to ligand (Phy) ratios (1:1 ≤ Cu2+:Phy ≤ 4:1), by using both ISE-H+ and ISE-Cu2+ electrodes. Phytate acid base behavior in sodium nitrate is very similar to that in sodium chloride, previously investigated. In the experimental conditions adopted, the formation of three CuiHjPhy(12-2i-j)- species is observed: the mononuclear CuH4Phy6- and CuH5Phy5-, and the dinuclear Cu2H5Phy3-. Analysis of complex formation constants at different ionic strengths reveals that both ISE-H+ and ISE-Cu2+ electrodes gave, within the experimental error, analogous values. Dependence of complex formation constants on ionic strength was modeled by EDH (Extended Debye-Hückel) and SIT (Specific ion Interaction Theory) equations. The sequestering ability of phytate toward copper(II) has been evaluated by the calculation of pL50 (the total ligand concentration, as - log CL, able to bind 50% of metal cation), an empirical parameter already proposed for an objective "quantification" of this ability. A thorough analysis of literature data on phytate-copper(II) complexes has been performed.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/1684201
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