Determination of Nitrite Nitrogen

Aim
To determine the nitrite nitrogen of the given sample of water.

Principle
The nitrite concentration is determined through the formation of a reddish-purple azo dye produced at pH 2.0–2.5 by the coupling of diazotised sulphanilic acid with N-(1-naphthyl)-ethylenediamine dihydrochloride.

Apparatus

1. Spectrophotometer

Reagents (click to check the preparation of reagents)

1. Sulphanilamide reagent
2. N-(1-naphthyl)-ethylenediamine dihydrochloride solution
3. Hydrochloric acid (1+3)
4. Stock nitrite solution
5. Standard nitrite solution

Procedure

1. To 50 ml clear sample neutralised to pH 7, add 1ml sulphanilamide solution.
2. Allow the reagent to react for a period of 2–8 minute.
3. Then add 0.1ml of 1-naphthyl ethylenediamine solutions and mix immediately.
4. Measure the absorbance of the solution after 10 minute at 543 nm at 1 cm light path.
5. Prepare standard calibration curve as in any other case.
6. By noting the absorbance of an unknown sample, the concentration of nitrate can be determined

Calculation

Nitrite N in mg/L =	mg Nitrite N
	mL of sample

Observation
The observation is presented in Tables A and B respectively

Table A: Observation for calibration

Table B:


Results