Reference Electrode Impedance Check

Reference Electrode Impedance Check

This procedure can be used to quickly estimate the impedance of your reference electrode. You must have EIS capability in your electrochemistry system to perform this test.

  1. Partially fill a beaker with electrolyte. If you normally use a Luggin capillary, the concentration of this electrolyte should be approximately the same as that of your test solution.

  2. Immerse the tip of your reference electrode into the solution. If you will be using a Luggin capillary place the tip of the Luggin capillary in the solution and place your reference in the Luggin. Make sure you have an unbroken electrolyte path from the tip of the reference to the tip of the Luggin capillary.

  3. Add a high surface area platinum wire or graphite rod counter electrode to the solution.

  4. Connect the reference electrode to the working (and working sense) leads of your potentiostat. Yes, we said the working electrode!

  5. Connect the graphite rod to the reference and counter electrode (and counter sense if applicable) leads.

  6. Set up an EIS scan starting from 5 kHz (or higher) and scanning towards lower frequencies. Make sure that the applied DC potential is zero versus the open circuit potential (Eoc).  A 5 mV AC amplitude should be sufficient.

  7. Start the scan. Make sure that the DC current is less than 10 mA. If it isn’t, shut off the potentiostat as soon as possible.

    CAUTION: Do not allow the test to run if significant DC currents are flowing. Your reference electrode could be damaged if this occurs.

  8. Let the scan run for about a decade in frequency, then halt the scan and turn off the cell. Note the magnitude and phase of the measured impedance.

The measured impedance at high frequency should be resistive (the phase angle should be near zero).
If it is, the impedance magnitude is a good estimate of your reference electrode’s resistance. If the phase angle isn’t near zero, the impedance cannot be trusted.

We have used this test on several electrodes in our lab. It gives reasonable results on our P/N 930-03 SCE with a Vycor frit.

  

 

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Last revised on Thursday, August 30, 2007