What are the differences between refillable and gel filled pH electrodes?

Document ID

Document ID TE8267

Published Date

Published Date 07/12/2021
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Question
What are the differences between refillable and gel filled pH electrodes?
Summary
Refillable verses gel filled pH probes.
Answer
Gel filled probes are non-refillable, have a shorter life and warranty, and lower maintenance requirements:
  • The gel filled probe warranty is six months and the average life is about one year.
  • They have a lower cost per probe. 
  • While proper storage and cleaning is important with these electrodes, they do not have all of the maintenance requirements of a refillable probe.

Refillable probes have a longer expected life and warranty, and more maintenance requirements:
  • Refillable probes have a one year warranty, and an average life of two to three years.
  • Refillable probes have a higher cost per probe, but they need to be replaced less often, leading to potential long-term savings.
  • In addition to proper storage and cleaning, these probes have an internal filling solution to maintain. The additional maintenance includes remembering to open the fill hole when in use and closing it again when not in use, adding filling solution to the probe as needed, and occasionally replacing the fill solution completely.

The trade off is expected life vs maintenance requirement. For most applications, either a gel filled probe or a refillable probe can be used, although this is not always the case. The most common example where this does not apply is for low ionic strength (LIS) samples. These samples consume electrolyte at an accelerated rate. Because of the higher electrolyte demand, gel filled probes have a much shorter life and often do not stabilize when used on LIS samples. Consequently, all of the probes recommended for LIS applications are refillable.

See also:
What is the warranty period for Hach pH electrodes?
What is the expected life of Hach electrodes?
When should the filling hole on a refillable electrode be open or plugged?
What is the procedure for replacing the filling solution in a refillable pH probe?
Which combined pH electrode can be used in pure water (low ionic strength water)?
What are the special considerations for measuring pH in low ionic strength samples?
Is the IntelliCAL™ catalog number PHC10101 a good probe to use in low ionic strength samples?

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