کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5372263 | 1388871 | 2006 | 9 صفحه PDF | دانلود رایگان |
The formation and stability of Mg2+ and Ca2+-phytate complexes was studied potentiometrically using an ISE-H+ electrode. Measurements were performed at 10 °C and 25 °C in NaClaq in the ionic strength range 0.1 â¤Â I â¤Â 0.75 mol Lâ 1. For both magnesium and calcium systems, the formation of ten MiPhyHj(12â2iâj)â species was observed in the range 3 â¤Â pH â¤Â 7 with i = 1, 2, 3 and j = 3, 4, 5 (and i = 3, j = 2). These species are quite stable; here we report for example some quantitative data for the species CaiPhyH3(9â2i)â, i = 1, 2, 3 (equilibrium iCa2+ + HjPhy(12âj)â = CaiPhyHj(12âjâ2i)â: Kij) at I = 0.25 mol Lâ 1 and t = 25 °C: logK13 = 3.42, logK23 = 6.47 and logK33 = 9.41. The speciation of the Ca2+-phytate system was also checked by ISE-Ca2+ measurements. Dependence on ionic strength was modeled using a simple Debye-Hückel type equation and formation constants were calculated at infinite dilution. The stability constants of complexes formed at pH > 7 were estimated using an empirical predictive equation. The sequestering ability of phytate towards Mg2+ and Ca2+ was calculated in different experimental conditions and compared with those of other chelating agents.
Journal: Biophysical Chemistry - Volume 124, Issue 1, 20 October 2006, Pages 18-26