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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
And make upto 1000ml with distilled water
(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
And make upto 250ml with distilled water
(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
And make upto 500ml with distilled water
(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
And make upto 1000ml with distilled water
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
And make upto 500ml with distilled water
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