For ion selective electrodes (ISE) what is conditioning, why is it important, and what is the proper way to condition electrodes?

Document ID

Document ID TE6932

Published Date

Published Date 27/05/2017
Question
For ion selective electrodes (ISE) what is conditioning, why is it important, and what is the proper way to condition electrodes?
Summary
Information on conditioning for ISEs.
Answer
There are many differences in ISEs, but one thing that all ISEs have in common is the requirement of conditioning.

Conditioning is a procedure that is done to resensitize the electrodes to the analyte (the ion being measured) after storage before calibration/measurement. Refer to the probe's manual for information on proper storage, but the storage of ISEs between use will desensitize the electrodes requiring that they be conditioned before use. This is most important for new electrodes that are being used for the first time, or for probes that recently had membrane replacements if they have a replaceable membrane. Probes that are not properly conditioned can result in inaccurate calbration; lower standards not reading as well as higher standards due to this loss of sensitivity. And also after calibrating, the electrode can become conditioned with use therefore drifting from the calibration which was performed before the electrode was conditioned. Conditioning can also be very helpful in decreasing stability time allowing for quicker results.

To condition the electrodes let them soak in the lowest standard of the calibration set without ionic strength adjustor (ISA) added. For first use, after long term storage, or after membrane replacement this should be done for 1-2 hours. If after short term storage like over night or over the weekend, a shorter conditioning time of 10-30 minutes should be sufficient. Longer conditioning times may be required for older electrodes.