p becomes equal to 1, 2, and 3 for the given chelating agent concentration. The pKI and pKz of glutamic acid are 4.3 and 9.7, respectively (6). Thereby, and from Figure 2, the leadglutamate complex species and electrode reactions a t pH between 5.0 and 7.2 may be expressed as
+ + Ilg = + HCPb(HG)t + 2e + Hy Pb(Hg) + 2HCPb(HG)f 2e Pb(Hg)
[G-]
