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| Section: Plant Protocol » Environmental Science Methodology |
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| Determination of Nitrite Nitrogen |
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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
- Spectrophotometer
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Reagents (» click to check the preparation of reagents)
- Sulphanilamide reagent
- N-(1-naphthyl)-ethylenediamine dihydrochloride solution
- Hydrochloric acid (1+3)
- Stock nitrite solution
- Standard nitrite solution
Procedure
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To 50 ml clear sample neutralised to pH 7, add 1ml sulphanilamide solution.
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Allow the reagent to react for a period of 2–8 minute.
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Then add 0.1ml of 1-naphthyl ethylenediamine solutions and mix immediately.
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Measure the absorbance of the solution after 10 minute at 543 nm at 1 cm light path.
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Prepare standard calibration curve as in any other case.
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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 |
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Observation
The observation is presented in Tables A and B respectively
Table A: Observation for calibration
Table B:
Results
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