Use of pyrolyzed paper as disposable substrates for voltammetric determination of trace metals

The possibility of using pyrolyzed paper as disposable working electrodes for trace metals determination is reported for the first time. A small piece of pyrolyzed paper (0.7x0.7 cm) was positioned at the bottom side of the electrochemical cell using a rubber O-ring, which defined the electrode area (0.48 cm; 0.18 cm(2)). A large number of electrodes can be obtained from a single piece of standard dimensions (2.5 cmx7.5 cm) of paper, therefore minimizing the cost per unit. The electrochemical performance of the pyrolyzed paper was demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and by the determination of Zn, Cd, and Pb by square-wave anodic stripping voltammetry. The unmodified pyrolyzed paper showed excellent performance for Pb and Cd detection (LOD =0.19 and 0.16 ppb, respectively). In the presence of Bi3+(in-situ film formation), the simultaneous determination of Zn, Cd and Pb was also possible (LOD=0.26, 0.25, and 0.39 ppb, respectively).