The association equilibria of PHQ and PHQ–coordinated with some transition metal cations such as: Al(III), Ca(II), Cd(II), Co(II), Cu(II), Fe(III), Mg(II), Ni(II), Pb(II) and Zn(II) ions were studied using potentiometric technique. The association constant (Ka) of PHQ was calculated from the average number of protons attached per repeating unit in the PHQ matrix (nA) at different pH values. This value of pKa which formed was found to be 7.75.
The titration curves revealed that the metal ion replaces protons and coordinates to the polymer matrix. In addition, the use of such titration curves could be computed of the formation constants (log ) of the different species exist at equilibrium. The formation constant (log ) for different molar ratios of species such as 1 : 2, 1 : 1 and 2 : 1 for metal : polymer matrix, in solution were computed and the results were discussed. The value of and PL for the metal ions under investigation were calculated at different pH values. The Formation Constant (log ) of the coordinated polymer based on PHQ–Metal ion were computed using – PL system. Mathematical calculations of differential change of ( ) gave a sharp signal for calculations of formation constant. From there are partial formation constant ( log 1, log 2 and log 3 ) which indicate to the protonation degree. The analyses of potentiometric data helped us to determine each value of the formation constant and/or partial formation constant for the metal ions such as: Al(III), Ca(II), Cd(II), Cu(II), Co(II), Fe(III), Mg(II), Ni(II), Pb(II) and Zn(II) coordinated with PHQ matrix .