Reference Electrode Overview and Care

Posted by gamry on July 7, 2016

Gamry sells the Saturated Calomel and Ag/AgCl Reference Electrodes.  Proper care must be taken to ensure that your electrode continues to take accurate measurements.  The tip of the electrode is a Vycor frit (clear) or electro porous glass (opaque white).  The frit allows ionic transport into the electrode.  In order to operate properly the frit must always be kept wet with electrolyte.  Reference Electrodes can be stored for short periods of time with a rubber cap installed over the frit.  A securely fitted cap can keep a frit in good working condition for about 2 months.  For a better storage method, immerse the tip of the electrode into a beaker of saturated KCl solution.  Electrodes stored in this manner will have a working frit for a very long time.

If a Reference Electrode is suspected to be bad, its potential can be checked against a Lab Master Electrode.  A potential difference of less than 5mV is acceptable.  If the difference is higher, the internal solution of the electrode can be refreshed.  This solution is saturated potassium chloride (KCl).  For optimum potentiostat performance, the impedance of the Reference Electrode must be low.  A high-impedance Reference Electrode will cause problems that range from overloads to potentiostat oscillation.  If your results look very noisy, or your cell is picking up excessive noise when you move around, it is probably a high-impedance reference electrode.  Use our Application Note: Checking the Impedance of Your Reference Electrode, or change to a 2-electrode measurement to see if the noise disappears.

To fix a high impedance reference electrode the frit should first be replaced.  You can download this replacement procedure here:  Care of Vycor Frits.  Gamry sells frit replacement kits that contain 5 replacements and new PTFE sleeves that secure the frit.  Premade filling solution is also available. 

First, cut the PTFE sleeve which secures the frit to the glass body of the electrode.  Slide the rubber filling collar to expose the filling port.

Drain the electrode’s internal solution and run DI water through the body of the electrode.  Completely replacing the internal solution with fresh solution will yield the highest performance.

Make sure the glass tip of the electrode body is completely dry.  Slide a single 4.0mm PTFE sleeve over the electrode tip.  With gloves, or delicate tweezers, pick up a new frit from the kit package and dropped it into the PTFE sleeve.

Using a heat gun or blow dryer, evenly apply heat to the PTFE sleeve.  You will see the sleeve shrink around both the glass electrode tip and the frit.  NOTE: Excessive heat could potentially damage the new frit, use only enough to see the PTFE sleeve shrink to the same diameter as the frit.  Carefully remove the excess PTFE sleeve material with a precision blade after it has cooled back to room temperature.

Replace the internal filling solution (saturated KCl) until it is about 1cm below the filling hole on the electrode body.  Replace the rubber filling collar.  Now, allow the electrode tip to soak in saturated KCl for at least 15 minutes.  Check the impedance of the Reference electrode again to verify its performance.