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Science Reviews 2000 Ltd, Chemical Speciation and Bioavailability, 2(15), p. 29-36

DOI: 10.3184/095422903782775235

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Speciation of phytate ion in aqueous solution. Non covalent interactions with biogenic polyamines

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

The noncovalent interactions of phytate (Phy12−) with biogenic amines were studied potentiometrically in aqueous solution, at t=25°C. Several species are formed in the different H+-Phy12−-amine (A) systems, which have the general formula Ap(Phy)Hq(12-q)−, with p≤3 and 6≤q≤10. The stability of these species is strictly dependent on the charges involved in the formation equilibria. For the equilibrium pHiAi++Hj(Phy)(12-j)−=Ap(Phy)Hq(12-q)−, (q=pi+j) we found the relationship logK=aζ (ζ is the charge product of reactants), where a=0.35(0.03, valid for all the amines; this roughly indicates an average free energy contribution per bond −ΔG0=4.0±0.2 kJ mol−1. A slightly more sophisticated equation is also proposed for predicting the stability of these species. Owing to the quite high (partially protonated) phytate charge, the stability of Ap(Phy)Hq(12-q)− species is quite high, making phytate a strong amine sequestering agent in a wide pH range.