LTH Electronics MTD75, Operation Manual

Page: 48 / 266

Connections
- 46 - MTD75 Operation Guide
Connections
For gel filled, non-flow electrodes the storage boot may become dried out during storage.
This can result in evaporation of the water inside the electrode causing high impedance in
the reference cell. If allowed to fully dry out the operation of the electrode will be
irreversibly damaged. For electrodes in storage it is recommended that every three to four
months the following procedure is carried out:
Remove the black storage boot or transit cover at the end of the electrode. Re-wet the fibre
pack inside the storage boot with 3.8 Molar Potassium Chloride (KCl) saturated solution or if
this is not available use a quantity of 4pH buffer solution. Note do not use deionised water.
Re-seal the storage boot or transit cover.
For electrodes with soaker bottles ensure that the electrode is stored upright in the soaker
bottle, and replace the bottle solution with 3.8 Molar Potassium Chloride (KCl) saturated
solution approximately every 6 months.
Depending on the issue the following glass body pH electrode maintenance procedures
can be carried out:
Initial Cleaning – Wash the electrode with a solution of liquid detergent and warm water by
gently scrubbing with a soft tooth brush or wet tissue. Follow this by thoroughly rinsing
the electrode in deionised water or clean tap water.
Inorganic Scale Deposits – Dissolve the deposit by immersing the electrode bulb only in a
solution of dilute (10%) Hydrochloric Acid for a few minutes.
Follow the supplier’s data
sheet when handling acids and dispose of as instructed by your local authority
regulations
.
Organic Oil or Grease Films – Wash the electrode with a solution of liquid detergent and
warm water by gently scrubbing with a soft toothbrush or wet tissue. Follow this by
soaking the pH electrode for between 10 and 30 minutes in a 3.8 Molar KCl solution.
Plugged or Dry Wick – Remove contaminate with one of the above cleaning procedures.
Then soak the electrode in an 80°C, 3.8 Molar KCl solution for 30 minutes. Before allowing
the electrode to cool in the same solution to promote flow of internal electrolyte through
the liquid junction.