Similar peaks have been seen before [28]: the diffusion of Ag into Hg is kinetically slower than that of Hg into Ag, which causes a gradual ageing of the amalgam electrode, which is the cause of gradually shifting of these waves, which was found to cause inter-ference with the Pb determination when an aged electrode was used repeatedly with a long deposition time.
The current of the negative-going scan returned to that of the forward scan near −0.4 V. This potential was selected as plating potential for Hg, as at this point the plating current should be m