Ammonia nitrogen, also known as ammonium nitrogen, refers to nitrogen (N) that exists in the form of free ammonia (NH3 dissolved in water) and ammonium ions (NH4+, ammonium salts). The composition of the two depends on the pH value and water temperature of the water. When the pH is high, the proportion of free ammonia (NH3 dissolved in water) is high, and when the pH is low, the proportion of ammonium salt (NH4+) is high; When the water temperature is high, the proportion of ammonium salts is high, and when the water temperature is low, the proportion of free ammonia is high.

Iodine ions and mercury ions react with ammonia under strong alkaline conditions to form reddish brown colloidal compounds, which exhibit strong absorption at wavelengths around 420nm. The amount of red brown colloidal compounds generated is proportional to the absorption value of their solution, and the content of ammonia nitrogen can be determined by testing the absorption value of the reaction solution.

According to the detection principle, the main methods for determining ammonia nitrogen include Nessler's reagent spectrophotometry, salicylic acid spectrophotometry, distillation neutralization titration, ammonia gas sensing electrode method, ammonium ion selective electrode method, conductivity method, and flow injection method.

There are currently three main national standards for determining ammonia nitrogen in water quality:

HJ 535-2009 Measurement of Ammonia Nitrogen in Water Quality - Nessler's Reagent Spectrometric Method

HJ 536-2009 Measurement of Ammonia Nitrogen in Water Quality Salicylic Acid spectrophotometric Method

HJ 537-2009 Measurement of Ammonia Nitrogen in Water Quality Distillation Neutralization Titration Method

Lianhua Ammonia Nitrogen Test KitSave method:Lianhua Ammonia Nitrogen Reagent LH-N2N3-100：The reagent should be stored under dry, cool, dark, and low temperature conditions. When the storage conditions are met, the warranty period for solid reagents is 6 months, and the warranty period for liquid reagents is 3 months. Lianhua COD reagent LH-DE (recommended to be stored in the refrigerator compartment) and Lianhua total nitrogen reagent LH-NT-100 are also the same.

Accurately weigh ammonium chloride (NH4Cl) 0.3819 dried at 100 ℃ for 2 hours gDissolve in water, transfer to a 1000mL volumetric flask and dilute to the mark with ammonia free solution, shake well. This solution contains 0.1mg of ammonia nitrogen per milliliter, which is 100mg/L.

Lianhua Ammonia Nitrogen Reagent LH-N2N3-100 of themWater samples should be collected in polyethylene or glass bottles and analyzed as soon as possible. If storage is required, sulfuric acid should be added to acidify the water sample to pH<2. It can be stored for 7 days at 2 ℃~5 ℃. When using, the pH should be adjusted to neutral or weakly alkaline.

Precautions for ammonia nitrogen experiment operation​

① The 10ml water sample must be accurately transferred, and if possible, a precision pipette (large belly pipette) can be used for transfer.

② The experimental utensils need to be cleaned thoroughly.

③ Add N3 first and then N2, do not add them in the wrong order.

④ After standing for 10 minutes, immediately compare the color, and the experimental process should be compact.

⑤ Use a 10mm glass colorimetric dish for color comparison.