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).