When storing the HOBO MX2501 pH logger over an extended period of time, remove the electrode from the logger and place it in the electrode storage bottle with clean, fresh storage solution. (Do not leave the electrode in the logger when not in use for long periods of time!)
Check on the storage solution and the electrode from time to time to make sure that there's no growth on the electrode. And change out the storage solution every four to six weeks, as it can evaporate over time, which would affect the electrolyte inside of the electrode.
It's also a good idea to remove the battery from the logger for extended periods of disuse.Do not keep electrodes stored for more than 7 months.