This presentation briefly introduces the analytical techniques for measuring air pollutants like toxic gases, suspended matter and ozone. The analytical methods discussed are a Non-dispersive infrared gas analyzer, Resonance fluorescence, Gravimetric estimation of dust fall and chemical methods for ozone determination. Note: Credit goes to https://www.magadhuniversity.ac.in/download/econtent/pdf/lecture%20MSc%203rd%2018%20april%20-%20Pragati%20Kushwaha.pdf

1. ANALYTICAL METHODS FOR MEASURING AIR
POLLUTANTS
S A R A H A R S H A D
1 9 2 5 1 1 7 0 5 7
S E C T I O N B
A N A L Y T I C A L C H E M I S T R Y
D E P A R T M E N T O F E N V I R O N M E N T A L S C I E N C E
LAHORE COLLEGE FOR WOMEN UNIVERSITY

2. CONTENTS
1. Introduction
2. Toxic gaseous pollutants
3. Suspended Matter
4. Ozone
5. Summary

3. INTRODUCTION
Def: Substances that changes the average qualitative composition of the air and thus has
negative impacts on the living and nonliving components of the environment are called Air
pollutants.
- They can be primary pollutants as well as secondary pollutants.
Examples:
-Toxic Air pollutants include carbon monoxide, sulphur dioxide, nitrogen dioxide, etc.
- Suspended particles and photochemical smog
- Particulate matter

4. TOXIC GASEOUS
POLLUTANTS
Non-dispersive infrared gas analyzer and Resonance
flourescence are used to determine the concentration of
toxic gaseous pollutants

5. NON-DISPERSIVE INFRARED
ANALYZER
Instrumentation:
- Infrared light source
- Motor
- Chopper wheel
- Reference cell
- Sample cell
- Gas inlet and outlet
- CO2/CO filter
- Detector

6. NONDISPERSIVE INFRARED ANALYSER -
WORKING PRINCIPLE
The Non Dispersive Infrared (NDIR) detection
method is based upon the absorption of infrared
radiation at specific wavelengths as it passes
through a volume of sample.

7. NONDISPERSIVE INFRARED ANALYSER -
WORKING
- The impure sample is contained in sample cell while the pure sample
is placed in reference cell
- The IR beam from the source with the help of choppers, passes
through the sample cell and reference cell.
- Intensity of the beam decreases as it passes through the sample cell.
It then strikes at a detector containing sample and a moveable
diaphragm.
- As the portion of the detector containing sample would absorb more
radiation than the other portion, it gets hot quickly.
- The difference in energy level of the two portions causes diaphragm
to move from low temperature to the high temperature.

8. NONDISPERSIVE INFRARED ANALYSER -
WORKING - CONTINUED
- The distension of diaphragm is proportional to the difference in
intensity of the IR.
- The final result is in the form of Calibration Curves.

9. RESONANCE FLUORESCENCE, INTRODUCTION AND
WORKING PRINCIPLE
Definition: This is a sensitive and selective analytical
technique used to detect and quantify the abundance of
atoms and some small molecules.
Principle: This method is based upon the absorption of
photon by the specie of interest and re-emission of
radiation at the same wavelength.

10. RESONANCE FLUORESCENCE, INTRODUCTION AND
WORKING PRINCIPLE
Definition: This is a sensitive and selective analytical
technique used to detect and quantify the abundance of
atoms and some small molecules.
Principle: This method is based upon the absorption of
photon by the specie of interest and re-emission of
radiation at the same wavelength.

11. RESONANCE FLUORESCENCE- DIAGRAM

12. RESONANCE FLUORESCENCE - WORKING
- In this technique, a sample e.g. CO absorb radiations in 150 nm
range from a radio frequency discharge lamp and the
flourescence is detected by the photomultiplier tube.
- The flourescence chamber should maintain a pressure of 7-9
bar to balance interference from CO and oxygen.
- Permeation tubes are used to produce standard mixtures of
gases.
- Sample of pure gas under high pressure is allowed to diffuse
through the caliberated at a defined rate into a diluent gas
stream to give a standard sample of known composition.

13. RESONANCE FLUORESCENCE - CALIBRATION CURVE

14. SUSPENDED MATTER (SM)
Suspended matter is determined by dust buckets.
Introduction:-
It is one of the accepted method to determine the SM by
determing the amount of dust gathered during rainfall or wind for
a given period of time.
- A perforated aluminum box with a grease coated polyethylene
cup placed inside is used. The dust particles adhere to the cup's
sides due to grease.
- The weight of the container is determined by: X= a/πb²
- a is the weight of the dust in milligrams and b is the radius of the
container.

15. SUSPENDED MATTER (SM) - CONTINUED
In order to collect the total dust collected in the polythene
container is washed with a jet of hot,
distilled water the washings are qualitatively filtered in an
evaporating dish. Water is evaporated
from the filtrate by heating the sample is dried by further
heating the dried sample is then washed.
And the amount of water insoluble dust is calculated as follow
Where c is the weight of soluble particulates.
Y = a - c

16. SUSPENDED MATTER (SM) - GRAVIMETRIC
ESTIMATION OF DUST FALL

17. PHOTOCHEMICAL SMOG
Introduction: Ozone, or trioxygen, is an inorganic molecule with the
chemical formula O ₃. It is a pale blue gas with a
distinctively pungent smell. It is an allotrope of oxygen
that is much less stable than the diatomic allotrope O ₂,
breaking down in the lower atmosphere to O ₂
Determination: Ozone can be determined by two methods, a reaction
forming triiodide and then determing the concentration
by spectrophotometery and it can also be determined
by ozonolysis reaction and then by colorimetric
mathods.

18. PHOTOCHEMICAL SMOG - CONTINUED
Formation of triiodide:
For determining the concentration of ozone, polluted air is
bubbled through and acidified solution
of potassium iodide. The reaction results in the formation of
triiodide ions whose concentration is
then can be determined spectrophotometrically.

19. A most significant contribution to the analytical
chemistry of ozone is the ozonolysis reaction for determining ozone in air. 4,4-dimethoxystilbene
as the reagent; the resulting ozonide reaction product cleaves to form anisaldehyde which can
then be determine by colorimetric reaction. The reaction can be modified by using 1,2-di(4-
pyridyl)ethylene as the reagent. And the following reaction will take place.
PHOTOCHEMICAL SMOG - CONTINUED
Ozonolysis:

20. SUMMARY
The air pollutants are primarily produced from physical processes. But some pollutants are
not emitted directly, they appear when primary pollutants react or interact with each other.
• Determination of concentration of pollutant is important to analyze the extent of pollution
in any particular area.
• Toxic gaseous pollutants are one of them and contribute to air pollution in majority. They
are basically emitted from automobiles industries, power plants and factories.
• The analytical methods for measuring concentration of air pollutants include
chromatography, infrared spectroscopy, fluorornetry, spectrophotometry and atomic
absorption spectroscopy.
• The most dominated air pollutant are oxides of sulfur, nitrogen and carbon. Photochemical
smog, suspended matter and greenhouse gases are also contributed to air pollution.
• Some other pollutants such as chlorine, ammonia and hydrogen cyanide can be determined
by Infrared spectroscopy.

21. THANK YOU