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Procedure

Polishing on smooth ground glass plates allows the condition of the polishing material to be tightly controlled for optimum cleanliness. In addition, the use of deagglomerated alumina of small particle size (0.05 μm) allows for a more scratch free active electrode surface. The use of particles of even smaller size (0.007 μm fumed silica) should enhance the smoothness and activity. If this does not activate the surface, re-polishing with larger particle size abrasive, such as 0.25 :m diamond, followed by 0.05 :m alumina or 0.007 :m silica.

Materials

  • 1 mm diameter (or larger) GC disk electrode
  • Ag/AgCl reference electrode
  • NANOpureTM deionized water
  • Baikalox agglomerate free alumina, 0.05 μm particle size (Baikowski International, Charlotte, NC) or Buehler 0.05 μm alumina
  • Fumed Silica 0.007 μm particle size (Sigma, St. Louis, MO)
  • Smooth ground glass plate (necessary to prevent scratches during polishing)

How to polish your electrodes

The degree of activation of a GC disk electrode can be evaluated by looking at the difference in the peak potential for the redox couple of ferri/Ferrocyanide, which is expected to be close to 60 mV [9]. First, use a slurry of the 0.05 μm alumina to polish the electrode. You can add several scoops of alumina to a small wash bottle of high purity water, like NanopureTM, and squirt it on a clean ground glass plate. For optimum cleanliness it is wise to use gloves when handling the electrodes. This precaution is necessary so that skin oils do not get onto the electrode. Polish with light pressure following a figure 8 pattern for approximately 30 seconds. The electrode should then be immediately rinsed with water. It is suggested that the stream of water be directed against the surface of the electrode. Only high purity water is used throughout the activation process. In order to remove excess water, touch the outer edge of the electrode with a soft tissue paper like KimwipeTM.

Now check the activation of the electrode in a solution 1 mM ferrocyanide in 1 M KCl. Be sure to degass all solutions with high purity nitrogen or argon before running the experiment. A typical result for an electrode scanned at 100 mV/s is shown in Figure 2. For this electrode ΔEp = 67 mV is very close to the expected result.

Figure 2. Cyclic voltammogram of 1 mM ferrocyanide in 1 M KCl with a freshly polished glassy carbon electrode.

It is recommended that any further polishing of the electrode be done in a slurry of 0.007 μm fumed silica. Thoroughly wash the polishing plate with water, dry with a KimwipeTM and add a small amount of silica onto the polishing plate. Add a small amount of water to make a slurry. The silica should be visibly white on the plate. The electrode can be polished for 30 seconds in a figure 8 pattern, cleaned with pure water and then the outer edge of the electrode barrel be touched with KimwipeTM to remove excess water. If your electrode does not produce satisfactory results, repeat the process.