How should I store my pH electrode?
10 November 2016
10 November 2016
The pH electrode is the most delicate part of any pH meter system, but proper care and maintenance will ensure it stays in good condition and gives fast and accurate results.
Storage of pH electrodes is one area which is often misunderstood, and can easily damage the electrode beyond repair if it is done incorrectly. We’ve taken a look at how pH electrodes should be stored to keep them in top condition.
To understand why storage is important, we first need to look at what is going on at the sensing end of the electrode.
The tip of the electrode comprises of a thin glass membrane, which is permeable to H+ ions and contains the inner buffer. Around this, a hydrated “inner gel layer” forms, and a secondary “outer gel layer” forms when the membrane comes into contact with an aqueous solution.
H+ ions diffuse in or out of the gel layer, depending on the ion concentration in the surrounding solution (this is how the electrode detects pH) – in alkaline solutions, H+ ions diffuse out, while in acidic solutions H+ ions diffuse in.
This is how the electrode detects the pH of a sample, but during storage ions will continue to move in or out of the permeable layer.
If this movement occurs too far in either direction (i.e. too many H+ ions move in or out of the gel layers), the electrode response to samples will be altered causing incorrect results.
This is why storage is important – the long periods of time that the electrode spends in storage (not in use) gives enough time for significant movement of ions.
The technicalities of how the electrode works translate into a few simple rules to keep your pH electrode stored correctly;
The TRUEscience SMART pH system incorporates a dedicated storage stand – this not only helps to keep your work bench tidy, but also ensures the electrode is always returned to a suitable storage solution.
The TRUEscience SMART pH cap in its storage stand – ensuring the electrode is kept in storage solution whenever it is not in useThe small storage tube used in the storage stand means that only a minimum amount of storage solution is used, creating less waste and reducing evaporation of the solution over time.
Remember to change the storage solution regularly – roughly weekly, or sooner if you notice crystallization or discoloration.