How does an Ammonia Ion Selective Electrode (ISE) work?

24 May 2019

How does an Ammonia Ion Selective Electrode (ISE) work?

The TRUEscience Ammonia ion selective electrode is made up of three parts: a flat surface PH electrode, a Teflon membrane located in the end cap and a refillable ammonium chloride solution.

The Teflon membrane is partially permeable and allows gas to pass through. This means that ammonia gas can pass through the membrane and react with the solution, being converted to ammonium by the basic solution. This reaction between the high pH solution and the ammonia gas reduces the pH of the solution surrounding the pH probe, creating a readable voltage directly proportional to the ammonia concentration.

Why use this method to measure ammonia?

While there are some solid state electrodes to detect ammonium, in order to detect ammonia as a gas an electrode containing a solution is used.  This style of electrode also has a greater precision and can detect down to 1 ppb, when using a solid state electrode the detection limit is often closer to <2 ppm.

For more information about testing ammonia please get in touch with our technical team on or phone us on +44 1954 233 144. 

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