Environmental behaviour of a pesticide metabolite, the AMPA. Sequestration of Ca 2+ , Mg 2+ , Cu 2+ , Zn 2+ and Al 3 .

The chelating and sequestering ability of a glyphosate metabolite, the aminomethylphosphonic acid (AMPA) towards bi- and trivalent metal cations, such as Ca ²⁺ , Mg ²⁺ , Zn ²⁺ , Cu ²⁺ and Al ³⁺ , were investigated in aqueous solutions of NaCl, in an ionic strength range of 0.1 ≤ I/mol dm ^-3  ≤ 1.0 and at constant temperature of T = 298.15 ± 0.15 K. The investigations on the acid-base properties and complexing ability were performed, by means of potentiometry, in conditions of different c _M :c _AMPA molar ratios and pH values. The formation of insoluble species was experimentally observed in the M ⁿ⁺ /AMPA ^2- systems, and the solid phases were characterized by means of X-Ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and InfraRed Attenuated Total Reflection spectroscopy (IR-ATR). The dependence on ionic strength of the stability constants of the M ⁿ⁺ /AMPA ^2- complexes species, determined at different ionic strengths, was modelled by the Debye-Hückel type equation. The sequestering ability of AMPA toward the investigated metal cations was evaluated by pL _0.5 parameter.
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