Total ammonia nitrogen (TAN) is a measure of the total amount of ammonia nitrogen present in a sample, including both ammonium ion and ammonia gas. Ammonia exists in two forms in water: ionized and unionized. The primary difference between ionized and unionized ammonia is their chemical state, which can affect their behavior and toxicity. Only a fraction of the TAN exists as toxic (un-ionized) ammonia, and a balance exists between it and the nontoxic ionized ammonia based on pH and temperature.Unionized ammonia is more toxic to aquatic life than ionized ammonia.
Principle of analysis:
Water sample is treated in an alkaline citrate medium with sodium hypochlorite and phenol in the presence of sodium nitroprusside which acts as a catalyzer and colour intensifier. The blue indophenol colour formed with ammonia is measured spectrophotometrically at 640nm. APHA(2017,ISBN:9780875532875).
TAN(Conc_std_sol, A_s, A_b, A_st)Total Ammonia Nitrogen (TAN) (in micro gm/L)
Concentration of standard solution
Mean absorbance of samples
Mean absorbance of blanks
Mean absorbance of standards
APHA, 2017. Standard methods for examination of water and wastewater, 23rd edn. APHA, AWWA, WPCF, Washington