Stepwise a.c. amperometric titration of cadmium and zinc with EGTA.
The theory of d.c. and a.c. amperometric titrations based on complexometric reactions is presented. It is shown that when E(1 2 )(M(I)) > E(1 2 )(M(II)) and log K(M(I)L) < log K(M(II)L), M(I) and M(II) can be sequentially determined by d.c. as well as a.c. amperometric titration. If, on the other hand E(1 2 )(M(I)) > E(1 2 )(M(II)) and log K(M(II)L), a stepwise titration can be performed only by a.c. amperometry. The effect of oxygen on an a.c. amperometric titration is also discussed. The stepwise a.c. amperometric titration of cadmium and zinc with EGTA at pH 6 in the presence of oxygen and an excess of 0.05 M acetate illustrates the theory.
Asplund
J
J
Department of Analytical Chemistry, Abo Akademi, Abo, Finland.