Cleaning and Polishing Voltammetric Electrodes
Resist the temptation tend to over-polish the electrodes. In most cases the electrode remains clean after the experiment, or could be washed clean with suitable organic solvent to remove greasy organic materials, or dilute acid or base (0.1 mol/L HCl, HNO3, NaOH) to remove inorganics. Protein deposits can be hydrolysed with an appropriate commercial enzyme-based cleaner.
Mercury films on platinum or glassy carbon substrates can be removed by gently wiping the electrode tip with lab tissue (dispose of tissue in mercury waste container) any residual mercury can be removed by holding the electrode at an oxidizing potential (eg +1 V) in dilute acid solution.
Only if there is an intractable coating electrodeposited on the electrode, or after extended use, will the electrode need any polishing at all. Polishing should only be done if there is visually obvious surface contamination (use a magnifying glass) or where a trial cyclic voltammogram in clean solvent indicates that there has been surface contamination. Standard maintenance polishing should use 0.05 micron (or less) polishing powder, only a badly scratched electrode, or one with an extremely intractable coating would need to use 0.3 micron (or larger) powder.
While automatic polishing machines might be useful if large numbers of electrode have to be polishes on a regular basis, hand polishing is more usual in a research or teaching lab.
When hand polishing grip the electrode low down (near its tip) and hold it in a vertical position while making figure-8 motions on the polishing pad. After each three or four of the figure-8 motions turn the electrode through 90 degrees in your grip and repeat polishing. This ensures even wear on the electrode.
If you have previously used glass body electrodes then be aware that PEEK or Teflon body electrodes need significantly less downwards pressure to be applied while polishing. Also 0.25 or larger micron powders will cause extensive abrasion of the electrode surface which then takes a lot more polishing with 0.05 micron alumina powder to obtain a mirror smooth finish.
Materials
Suitable polishing materials can be obtained from Buehler Inc, http://www.buehler.com/consumable Some Buehler products suitable for polishing are:
MetaDi II Diamond Paste, Monocrystalline Synthetic Diamond 1 micron, 5g Cat #40-6244 Use for extreme abrasive cleaning. MetaDi II Diamond Paste, Monocrystalline Synthetic Diamond 0.25 micron, 5g Cat #40-6241 Use for heavy duty abrasive cleaning. Buehler Nylon polishing pads, PSA backed 4″ (102mm) diameter Cat #69-3106 (QTY 100)
For routine or final polishing:
MasterPrep Alumina Polishing Suspension 0.05 micron, 6 oz, Cat #63-6377-006 MicroCloth polishing pads PSA backed 4″ (102mm) diameter Cat #69-3108 (QTY 20)
These polishing pads have a pressure sensitive adhesive (PSA) backing and can be affixed to a glass plate to ensure a flat surface. Only a very small amount of powder is added to the polishing pads. Local lapidary supply companies may have equivalent products.
After polishing, use the figure-8 motion on a clean MicroCloth polishing pad (no powder) to remove any adherent material.
eDAQ PEEK body working electrodes will withstand sonication but only immerse the tips of the electrode. Do NOT immerse the electrical contacts.
In short:
1. Only polish when absolutely necessary. 2. Use only light downwards pressure when polishing. When polishing manually grip the electrode at its base (ie the end where it is being polished) 3. Only use 0.05 micron powder for routine polishing. 4. Only use 0.3 or larger powders if absolutely necessary for very contaminated electrodes.
== ET069 and ET072 Leakless Reference Electrodes
The tip of these reference electrodes can become fouled with use. The tip of the ET072 can be washed or lightly polished (like a working electrode) to remove intractable adhering material, and in extreme cases you can even use a scalpel, or razor blade, to shave a thin slice from the tip, which exposes fresh polymer junction.
