Considering that the tolerance limits of interfering species are
established at the concentration required to cause no more than
a ±10% error in the recovery of Mn(II) at 50 μg L−1, Table 1 reveals
that Pb(II) affected the stripping signal of Mn(II) when exceeding
100-fold the Mn(II) concentration. It is important to emphasize
that Cu(II), Ni(II) and Zn(II) cannot be accumulated at a bare
glassy-carbon surface for further stripping determinations using
either cathodic or anodic sweeps [24]. However, Pb(II) can be oxidized
to PbO2,which can be deposited at the electrode surface [25] and then
this fact may be the explanation for the strong negative interference
of Pb(II).