Figure 1.

Schematic diagram showing the preparation of the paper-based electrodes. (A) Modification of cellulose substrate by addition of carbon ink on one side, having the platform with two visually different sides. Solution was added with a micropipette through the upper side. (B) Adhesive spraying on the protected working electrode. (C) Overlapping process of the bottom side of the paper electrode (the one with the ink) on the screen-printed card and modification with mercury (II) acetate or bismuth (III) standard solutions.