What is the relationship between ammonium ions and ammonia nitrogen in water?

The online ammonia nitrogen analyzer developed and produced by Delfino includes and ion-selective ammonia nitrogen sensor and an ammonia nitrogen controller. The ammonia nitrogen sensor integrates an ammonium ion electrode, a pH electrode, and a REF electrode, and calculates the value of ammonia nitrogen. Our controller can not only display the value of ammonia nitrogen, but also display the value of ammonium ions, pH value, and temperature.
Sometimes, customers think that the value of ammonia nitrogen must be higher than the value of ammonium ions, but in theory this is not the case.
In chemistry, ammonia nitrogen usually refers to the sum of ammonia(NH3) and ammonium ions(NH4+) dissolved in water.

Ammonia can exist in water in two forms: one is free ammonia, and the other is ammonium ions. When the pH value in water is high, ammonia tends to exist in the form of NH3, while under acidic conditions, it mainly exists in the form of NH4+, so which value is larger depends on the pH and other conditions of the water sample. Ammonium ion NH4+ is the form of ammonia nitrogen(NH3-N) reacting with water molecules in water. It is more stable at lower pH values.
Ammonia nitrogen(NH3-N) is the form of ammonia in water, which is usually more stable at higher pH values and higher temperatures.

NH4⁺+OH^- ? NH₃+H2O

NH₃+H⁺ ? NH₄⁺

In addition, the temperature value has a great influence on ammonia nitrogen. As the temperature rises, the tendency of ammonium ions to convert into ammonia nitrogen increases; as the temperature decrease, the tendency of ammonia nitrogen to convert into ammonium ions increases.
Under neutral or weakly acidic conditions, most ammonia exists in the form of ammonium ions, so the concentration of NH4+ will be higher than NH3-N. However, under alkaline conditions, the concentration of NH3-N may increase significantly.
Therefore, in general, in most natural water bodies or domestic wastewater, the concentration of ammonium ions will be higher than ammonia nitrogen due to the low pH value.

Delfino focuses on the research and development and production of water quality analysis instruments. Its main products include pH ORP analyzer, conductivity analyzer, turbidity analyzer, COD analyzer, dissolved oxygen analyzer, ammonium analyzer, chlorine analyzer, etc. If you are interested in ammonia nitrogen analyzer, please contact us.