Nitrite (NO₂⁻) is an intermediate compound in the nitrogen cycle and is commonly found in wastewater due to agricultural runoff, sewage contamination, or incomplete nitrification. The NEDA method is a sensitive and widely used colorimetric method for nitrite determination in water.Nitrite reacts with sulphanilamide in acidic medium to form a diazonium salt. This salt further couples with N-(1-naphthyl) ethylenediamine dihydrochloride (NED) to form a pink-colored azo dye.
The intensity of the colour produced is directly proportional to the nitrite concentration and is measured using a spectrophotometer at 543 nm. Here we take Waste water to test the nitrite.
Chemicals Required To Test Nitrite in Water:
- Sulfanilamide reagent – Dissolve 5g of sulfanilamide in a mixture of 50 ml concentrated hydrochloric acid and dilute to 500 ml with distilled water.Reacts with nitrite in acidic medium to form a diazonium salt.
- N-(1-naphthyl)-ethylenediamine dihydrochloride (NED)– Dissolve 500 mg of NED in 500 distilled ml of water. Replace as soon as a brown colour develops. Couples with the diazonium salt to form a pink-coloured azo dye, whose intensity is proportional to nitrite concentration.
- Hydrochloric Acid-Provides the acidic medium necessary for diazotization of nitrite with sulphanilamide.
- Standard Nitrite Solution-Dissolve 0.6072 of potassium nitrate and make up to 1000 ml (1ml = 100 μg nitrite) distilled water.
- Distilled water-To make the reagent.The conductivity of distilled water should be <5 μS/cm to prevent contamination.
Glassware & Instruments Required for Nitrite Analysis in Water:
- Spectrophotometer(543nm)-Measures how much light is absorbed by the colored solution; higher absorption indicates higher nitrite concentration.
- Volumetric flasks(100ml)– To make up volume to the mark.
- Pipettes(2 ml)-Allows precise addition of small amounts of reagents to the water sample.
Nitrite Testing Procedure of Water Sample:
- Take 50 mL of the water sample in a clean flask.
- Add 2 mL sulfanilamide reagent and mix well.
- Allow to stand for 2–3 minutes for diazotization.
- Add 2 mL NED reagent and mix.
- Allow color to develop for 10 minutes.
- Measure absorbance at 543 nm against a reagent blank.
- Determine nitrite concentration using a standard calibration curve.
Calculation:
Nitrite (mg/L) = Sample Absorbance x 150/ Sample Taken
Purpose of Nitrite Testing in Water Sample:
- Detects Water Contamination-Nitrite (NO₂⁻) indicates contamination from sewage, fertilizers, or industrial waste.
- Monitors Drinking Water Safety-High nitrite levels in water can be harmful.
- Assesses Wastewater Treatment Efficiency-Nitrite testing helps evaluate nitrification and denitrification processes in treatment plants.
Handling Mistakes should avoided during Nitrite testing in Water Sample:
- Use freshly prepared NED reagent.
- Avoid contamination from nitrite-containing glassware.Proper cleaning Process described previously.
- Perform color measurement within recommended time.
- Do not expose reagents to direct sunlight.
- Maintain correct acidic conditions.
Conclusion of Testing of Nitrite in Water:
The NED method is a simple, sensitive, and reliable technique for nitrite estimation in water. It is widely accepted for routine laboratory and field analysis due to its accuracy and ease of operation. By following these method, you can easily test the nitrite of water at laboratory & also manufacturing industry with availability of the equipments & chemicals. If you can’t understand the procedure you can check our real time photo attached with this writing or also you can reach to Pro Research & Testing Laboratory for the advance testing.
Frequently Asked Questions (FAQ)-Nitrite Detection of Water Sample:
Q1. Why is NED used in nitrite testing?
NED forms a colored azo dye with diazotized nitrite, enabling colorimetric measurement.
Q2. Can nitrate interfere in this method?
No, nitrate does not react directly unless reduced to nitrite.
Q3. Which wavelength is used for measurement?
The absorbance is measured at 543 nm.
Q4.What are typical sources of error in laboratory analysis?
Degraded reagent,Incorrect reaction time,Contaminated glassware
Q5. Which method is used to detect nitrite in water sample?
The NEDA method is a sensitive and widely used colorimetric method for nitrite determination in water.
How We Verified This Testing/Research Procedure :
This testing is done under qualified analysts in our lab.Continually monitored by expertise.Repeatedly testing is always done to get accurate result.
Written by
Riya Ghosh (M.Sc. Food Technology, MAKAUT)
Designation – Chemist
Reviewed by
Anwesha Das (M.Sc Microbiology,BU)
Designation – Microbiologist
Verified By
Dr. Jyotirmoy Kumar Dey (Phd,Chemistry)
Designation – Senior/Chief Chemist
Experience – 25 Years +