1. Lift the vent hole band up and move it to the lower part of the membrane cap.
2. Unscrew the membrane cap from the electrode body.
3. Dump any residual IFG remaining in the cap or on the electrode body.
4. Rinse the membrane cap with DI water, then with 1-2 mL of new IFG.
5. Complete the IFG change as described in the section Electrode Assembly, from step 5 to step 8.
It is recommended to clean the membrane, when the center pore of the membrane cap is discolored (usually yellow or
brown) or if the slope is lower than 50 % of the nominal value after changing the IFG. This is not actually “cleaning”
the membrane, but rather the removal of extra iodine precipitates by Na2S, Na2S2O3 solution or Ethanol. The
recommended process is as follows:
1. Disconnect the electrode and unscrew the membrane cap discard the IFG, and rinse the membrane cap and
the electrode with clean water.
2. Cover the working electrode (WE) and reference electrode (RE) parts with a paper towel and avoid exposure
to sunlight.
3. Prepare ~ 0.1 M Na2S2O3 or 95% Ethanol and pour ~150 ml in an appropriately sized beaker to allow the
membrane to be submerged.
4. Submerge the membrane cap in the solution completely for overnight. Use parafilm to cover the open of the
beaker during soaking.
5. Clear the cap by DI water and paper, refill IFG and screw onto electrode.
If the membrane cap gets damaged, the electrode reading is fluctuating, or the slope is lower than 30% of the nominal
value after changing the IFG and cleaning the membrane, the membrane cap may need to be replaced. Please make
sure the electrode is not powered during assembly and then follow the instruction below for replacement.
1. Unpack the membrane cap replacement kit and prepare the new membrane cap on a clean surface.
2. Unscrew the old membrane cap and discard it.
3. Rinse the new membrane cap with clean water, then rinse it with 1-2 mL of the IFG.
4. Follow the instructions from step 5 to step 8 as described in the Electrode Assembly section.
If the A420-FCL electrode reading is abnormal or the zero point is not within specifications after a reasonable
polarization time, the working electrode (WE) may not be able to completely polarize. Try to polish the WE again with
the polishing strip. In addition, if a stain or discoloration is visible on the surface of the WE, it should be polished until
the stain is less visible or removed completely. Please refer to Step 4 of Electrode Assembly section to brush the gold
reference electrode (RE) a few times in one direction, and then follow the next steps for electrode assembly.
The A420-FCL electrode can be stored in clean water or stored dry, preferably at normal room temperatures, while not
in use. It is recommended to:
1. Soak the electrode in clean water (IFG in cap) if it will be used within 1 week.
2. Store the electrode dry (IFG in cap) if it will be used within 1 month.
3. Store the electrode dry (without IFG in cap) for longer than 1-month storage.
5.3. Cleaning the Membrane Cap (De-iodine)
5.4. Replacing the Membrane Cap
5.5. Polishing the Working Electrode (WE)
5.6. Storing the Electrode
NOTE: The reference electrode is light sensitive and should be capped or covered during storage
6. Troubleshooting
