What is considered the best way to store a pH probe?

Storing a pH probe in a 3 to 3.5 Molar Potassium chloride (KCl) solution is considered the best practice because this specific solution helps maintain the calibration and performance of the probe. The KCl solution provides the necessary ionic strength and maintains the hydration of the glass membrane of the pH electrode, which is crucial for accurate pH measurements. If a pH probe is not kept hydrated, the glass membrane can dry out and become less sensitive or even damaged, leading to inaccurate readings.

Using distilled water is not ideal for storing pH probes, as it lacks the proper ionic concentration needed to preserve the probe’s sensitivity and performance over time. A saline solution, while somewhat effective, does not provide the same level of stabilization as KCl; salt concentration can vary and affect the probe's accuracy. Storing a probe in a dry environment is detrimental, as it will cause the glass membrane to dry out, leading to deterioration and reduced functionality. Therefore, the KCl solution is the most reliable method for ensuring the longevity and efficacy of the pH probe.