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Phytate – Molybdate(VI) interactions in NaCl(aq) at different ionic strengths: unusual behaviour of protonated species

Abstract

The complex formation between molybdate(VI) (MoO42-) and phytate [Phy, 1,2,3,4,5,6-hexakis(dihydrogen phosphate) myo-inositol] has been investigated at T = 298.15 K in NaCl(aq) at different ionic strengths (0 < I / mol dm-3 ≤ 1.0). In these experimental conditions, eight (MoO4)(Phy)Hr protonated species are formed, with 2 ≤ r ≤ 9. The corresponding formation constants determined proved to be fairly dependent on ionic strength, and this dependence has been modelled by an Extended Debye-Hückel equation. Furthermore, the stability (in terms of stepwise equilibria) of (MoO4)(Phy)Hr complexes regularly increases with the number of protons of the species, probably due to the formation of intermolecular hydrogen bonds between molybdate and phytate in their protonated forms. This unusual behaviour affects the sequestering ability of phytate towards molybdate, which is higher at low than at high pH, as demonstrated by the analysis of the pL0.5 values calculated for this system in various conditions. Finally, a series of empirical relationships have been proposed, with the aim of defining the speciation and the sequestration of molybdate and phytate in a wide number of systems.

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Publication details

The article was received on 28 Nov 2017, accepted on 12 Jan 2018 and first published on 12 Jan 2018


Article type: Paper
DOI: 10.1039/C7NJ04651K
Citation: New J. Chem., 2018, Accepted Manuscript
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    Phytate – Molybdate(VI) interactions in NaCl(aq) at different ionic strengths: unusual behaviour of protonated species

    F. Crea, C. De Stefano, D. Milea and S. Sammartano, New J. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C7NJ04651K

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