Binding of glyphosate by open-chain polyammonium cations

Interaction of glyphosate (N-(phosphonomethyl)-glycine) with six polyamines (ethylendiamine, cadaverine, putrescine, triethyleneterramine, spermine, a nd tetraethylenepentamine) was studied potentiometrically. Several species of different stoichiometry are formed in the various systems, according to the general formation reaction AH(i)(i+) + H-j(glp)((i - 3)) = A(glp)H-i+j( (i + j - 3)) (where A = amine and glp = glyphosate). The complex species fo rmed are always A(glp)H-r((r -3)) with r = 1...(n + 2) (n = maximum degree of protonation of amines). The stability of various complexes is a linear f unction of charges involved in the formation reaction, and can be expressed as logK(ij) = 0.9(+/-0.2)zeta (where zeta = i[3 - j]). From the temperatur e dependence of formation constants, Delta H-0 (and T Delta S-0) values hav e been obtained. Formation percentages of mixed glyphosate-polyammonium cat ion complexes are relevant also in low concentration conditions, and this m eans that these species may play a significant role in the speciation of na tural fluids containing the reactants.