If you use a Bluelab pH Pen or Probe, KCl Storage Solution is one of the simplest and most important parts of probe care. It keeps the probe hydrated and helps protect the internal reference system, so your pH readings stay stable, and your probe lasts longer.
What is KCl storage solution?
KCl is the chemical symbol for Potassium Chloride, and for the context of pH measurement, it is the solution used for storage and hydration of pH Pens and probes.
The Bluelab pH Probe KCl Storage Solution is specifically designed and formulated for use with your Bluelab pH Pens and pH Probes. Although it plays a simple role, it is a crucial element for keeping your Probe in optimal condition when it’s not in use.
The pH Probe shouldn't be stored dry. The chemistry of the KCl solution is the same as the internal reference solution of your pH Probe, using other types of solutions could cause an osmotic reaction.
Why can't I just use RO/distilled water?
It’s a common question, but RO (Reverse Osmosis) and distilled water isn’t suitable for storing a pH Probe. pH Probes are designed to be stored in a potassium chloride (KCl) solution, which keeps the reference junction hydrated and the internal reference chemistry stable. It is also the same solution that the reference in the pH cell contains, so when you store the probe in KCl your surrounding it with the same type of solution that is already inside the probe. When a probe is stored in RO or distilled water, potassium chloride can diffuse out through the junction, reducing the ionic strength around the reference system and destabilising the probe’s reference potential.
In addition, if the probe is left in water that isn’t sealed, evaporation can expose the bulb and junction, allowing them to dry out and further impact performance.
Bluelab recommends Bluelab pH Probe KCl Storage Solution because it is specifically formulated and tested for use with our sensors. Using the correct storage solution helps keep your probe in the right condition between measurements.
During normal use, small amounts of KCl solution slowly migrate through the reference junction. Storing the probe in KCl Storage Solution helps maintain the correct environment at the junction and supports stable performance between measurements. KCl is used because it’s the same solution contained inside the reference of the pH cell, helping keep conditions consistent and the probe properly hydrated.
Storing a probe in water or other unsuitable liquids can compromise the reference system, which may lead to:
- Contamination of the probe’s internal reference solution
- Reduced measurement accuracy
- Slower stabilisation/response times
- Premature probe failure
Note: De-ionised, pure, distilled or RO (reverse osmosis) water should never be used to store or hydrate a pH Pen or Probe. De-ionised, distilled, or RO water is especially problematic because it has very low ionic strength and can draw electrons out of the probe, accelerating instability and potential damage.
How often should you use KCl storage solution?
For best performance from your Bluelab pH Pen or pH probe, we recommend:
-
After each use: Add enough KCl Storage Solution to the storage cap to keep the probe tip hydrated before you store it.
- Once a week: check for evaporation and top off as needed (something along these lines) pH probes sit for months or years in the same KCl.
Note: If you observe mold growth (which is quite common) empty and rinse the storage cap and add fresh KCl solution.
This helps keep the probe hydrated, supports stable readings, and ensures it’s ready to use whenever you need it.
The bottom line
Your pH probe is a precise, complex tool that requires proper care to perform at its best and to provide accurate readings for optimal plant health. This means it matters how you store it.
Using the correct KCl Storage Solution in the right way will:
- Maintain accuracy
- Extend lifespan
- Prevent contamination
So, if you want reliable pH readings and consistent plant health, proper storage isn't optional; it is essential.
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