Issue 10, 2018

Phytate–molybdate(vi) interactions in NaCl(aq) at different ionic strengths: unusual behaviour of the 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). Under 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 in 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 rather than at high pH, as demonstrated by the analysis of the pL0.5 values calculated for this system under 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.

Graphical abstract: Phytate–molybdate(vi) interactions in NaCl(aq) at different ionic strengths: unusual behaviour of the protonated species

Supplementary files

Article information

Article type
Paper
Submitted
28 Nov 2017
Accepted
12 Jan 2018
First published
12 Jan 2018

New J. Chem., 2018,42, 7671-7679

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

F. Crea, C. De Stefano, D. Milea and S. Sammartano, New J. Chem., 2018, 42, 7671 DOI: 10.1039/C7NJ04651K

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