Rechloriding & Storing Grass Ag/AgCl Electrodes

Introduction

The Silver/Silver Chloride electrode has been shown to possess superior characteristics to that of unchlorided silver electrodes when used for recording low level AC and DC potentials. Chlorided silver electrodes present less low frequency "noise" than either gold or silver electrodes. The Grass Silver/Silver Chloride electrodes are constructed of pure silver and then chlorided to provide the stability and low noise characteristics. The chloriding process changes the shiny silver appearance to the dark gray color.

It should also be noted that the silver-silver chloride electrode is photo sensitive, changing it's potential slightly when exposed to light. Therefore, if these electrodes are used during photic stimulation studies, they may need to be shaded or covered to prevent light artifact.

Since the chloriding process deposits chloride ions on the silver surface, care must be taken during handling and storage to avoid scratching or abrading the electrode surface, which will remove part of the chloride surface. If this happens, it is possible to rechloride the electrode.
 
Rechloriding the Electrode
1. Thoroughly clean the silver surface electrodes of tarnish and dirt. Scouring powder or silver cleaner may be used.
2. Place the electrode in an opaque non-metallic container with 5% salt (NaCl) solution.
3. Connect the electrode to be chlorided in the (+) positive terminal of a 1.5 volt battery and the other electrode to the (-) negative terminal. Use a 100 ohm resister in series with the electrode.
4. The chloriding electrode darkens, while the other bubbles. Continue until the darkened surface is evenly coated.
 
Storing the Ag/AgCl Electrodes
To preserve the chlorided surface when not in use, it is recommended that the electrodes be stored in a salt solution, such as a sterile saline solution. If desired, it is possible to add 0.1% Zepherin Chloride as an anti-bacterial agent.