2.3. Preparation of the electrodes
Carbon paste electrode is prepared by mixing appropriate
conducting graphite powder and paraffin oil as pasting liquid with a
mortar. The mixturewas packed in a plastic syringe tube (internal radius:
2.4 mm). The electric contact was established by a copper wire
through the back of the electrode. The surface of electrodewas polished
on a clean paper until a smooth surface was observed.