Analysis of NOx in Ambient Air

8/2/2019 Analysis of NOx in Ambient Air

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Envirotech Centre for Research & Development

New Delhi


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Dissolve 4.0 gm Sodium hydroxide

+

1.0 gm Sodium arsenite

And make upto 1000ml with distilled water


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Sulfanilamide Solution

Dissolve 20.0 gm Sulfanilamide

+50 ml of 85% phosphoric acid


(This solution is stable for one month, if kept in refrigerator)


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Hydrogen peroxide Solution

Dilute 0.2 ml of 30% H2O2 solution


(This solution is stable for one month, if kept inrefrigerator & protected for light.)


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N-(1-Napthyl)-ethyenediamine di-hydrochloride (NEDA) Solution

Dissolve 0.5 gm of NEDA


(This solution is stable for one month, if kept inrefrigerator & protected for light.)


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Stock Sodium nitrite solution(1000ug NO2/ml)

Dissolve 1.5 gm of Sodium nitrite


The amount of Sodium nitrite to be used, if the assay percent isless than 100%, is calculated by

G=1.5/A

Where G= Amount of Sodium nitrite in gm1.5= Gravimetric conversion factorA= Assay percentage (should be greater than 97%)(This solution is stable for six weeks, if kept in refrigerator.)


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Working Sodium nitrite solution

Solution A (10ug NO2/ml)

Dilute 5 ml of Stock Sodium nitrite solution


Solution B (1.0ug NO2/ml)

Dilute 25 ml of Solution A

And make upto 250ml with absorbing solution

(Prepare freshly)


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VolumetricFlask50mlBlank

50mlSample1

50mlSample2

50mlSample3

50mlSample4

50mlSample5

Working

NaNO2

Solution B

0 ml 1ml 3ml 5ml 7ml 9ml

AbsorbingMedia

10ml 9ml 7ml 5ml 3ml 1ml

H2O2 Sol. 1ml 1ml 1ml 1ml 1ml 1ml

Sulfanilami

de Sol.

10ml 10ml 10ml 10ml 10ml 10ml

NEDA Sol. 1.4ml 1.4ml 1.4ml 1.4ml 1.4ml 1.4ml

Make upto 50ml with distill water, Mix thoroughly , After 10 minutes measure

absorbance of each flask at 540nm wavelength


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Plot calibration curve with absorbanceversus concentration of NO2


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Volumetric Flask 50mlFor Blank 50mlFor sample

Exposed absorbing Media 0 ml 10ml

Absorbing Media 10ml 0ml

H2O2 Sol. 1ml 1ml

Sulfanilamide Sol. 10ml 10ml

NEDA Sol. 1.4ml 1.4ml

Make upto 50ml with distill water, Mix thoroughly , After 10 minutes measure

absorbance of each flask at 540nm wavelength


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Total volume of air passed through Noximpinger (V, in liter)

Avg. Flow Rate (lpm) X Time (minute)


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Concentration (ug NO2/m3)=

C x A x 1000 x DV x B x 0.82

Where:C= NO2 Curve value

A= Absorbing reagent taken for sampling, mlV= Volume of sampled air

B= Volume taken for sample analysis, mlD= Dilution factor1000 for conversion from liter to m30.82= sampling efficiency

Analysis of NOx in Ambient Air

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