This document discusses air sampling methods and gas chromatography. It begins by describing various air sampling techniques for particulate and gaseous pollutants, including filtration, impingement, precipitation, absorption, adsorption and condensation. It then discusses gas chromatography, explaining the basic components and process. Key aspects covered are the carrier gas, column, stationary phase, detectors and how gas chromatography can be used to qualitatively analyze samples based on retention times and peak detection.

1. AIR SAMPLING METHODS
AND
GAS CHROMATOGRAPHY
SUBMITTED BY :-DEEPAK RAVI
ROLL NO:-162509
ME(I&C) REGULAR 2016-18
SUBMITTED TO :-
Dr. POONAM SYAL
ASSOCIATE PROFESSOR
ELECTRICAL ENGINEERING DEPARTMENT
NITTTR CHANDIGARH

2. CONTENTS
• AIR SAMPLING
• TYPES OF CONTAMINANT
• CONTAMINANT DEFINITIONS
• AIR SAMPLING CALCULATION
• AIR SAMPLING METHOD
• SOME NEW METHODS OF AIR SAMPLING
• RESEARCH PAPER
• REFERENCES

3. AIR SAMPLING
Air pollution sampling : Related to analysis of pollutants in a given
volume of air.
Air sampling: Capturing the contaminant from a known volume of air,
measuring the amount of contaminant captured, and expressing it as a
concentration
The air is passed through a filter medium (normally a paper for solid &
liquid contaminants and a sorbent for gases).
 The volume of air is measured against the amount of contaminant captured.
This gives the concentration, which is expressed either as milligrams per
cubic metre (mg/m3 ) or parts per million (ppm).
The volume of air is calculated by multiplying the flow rate through the
filter medium by the time in minutes.

4. TYPES OF CONTAMINANT
There are three types of contaminant according to their physical properties:
Particulates
 Vapours
 Gases
Particulates can be further subdivided into five types:
 Aerosols
 Dusts
 Fumes
 Smokes
 Mists

5. CONTAMINANT DEFINITIONS
Aerosol : Dispersion of solid particles of microscopic size in air.
Dust: Solid particulate capable of temporary suspension in air.
Fume: Solid particles produced by condensation from the gaseous
phase. Fumes are usually derived from the heating of a solid to its
melting point and the subsequent cooling of the gas produced.

6. CONTINUED….
Smoke: Particles resulting from the incomplete combustion of
organic matter consisting predominantly of carbon and oxides of
carbon.
Mist: Dispersion in air of liquid droplets usually large enough to be
seen by the naked eye.
Vapour: Gaseous phase of a substance that usually exists as a liquid
or solid at normal room temperature and pressure.
Gas: A substance which does not normally exist as a liquid or solid at
normal room temperature and pressure.

7. AIR SAMPLING CALCULATION
An air sample requires three basic measurements:
Amount of pollutant collected
Flow of air through the medium
The run time in minutes.
 Flow×time(in minute)=volume through filter in cubic meter
 Concentration in microgram per cubic meter or in ppm

8. AIR SAMPLING METHODS
• Air pollutant sampling are of two types :-
Air sampling based on the particulate pollutant
Air sampling based on the gaseous and vapor pollutant

9. AIR SAMPLING BASED ON THE
PARTICULATE POLLUTANTS
Air sampling techniques for particulate pollutants
SEDIMENTATION
FILTRATION
IMPINGEMENT
PERCIPITATION
 THERMAL PRECIPITAION
 ELECTROSTATIC PRECIPITATION

10. SEDIMENTATION
• Used to collect settle able particulate that settle out of the atmosphere as a result of
the gravitation force
• Particulate pollutant having
size of 10 mirco meter can be collected
with 99% efficiency
• The sampler consists of simple dust jar
fitted with a funnel
• A liquid is added to collector
to prevent the solids blown out from
the jar by air
• Collected dust is evaporated to dryness
and then weighed in mg
• Sampling period is 30 days

11. FILTRATION
Technique used in the collection of air pollutants of size smaller than
10 micro meter in diameter
The particulates are removed from the air sample by suction apparatus
through a porous filter where particulates are deposited
The glass fiber filter of porous size less than 0.1 micro meter is used
in high volume sampler
Sampling period: 24 hours
Air volume sucked: 2000 cubic meter
Particulate concentration: micro gram per cubic meter

12. CONTINUED……

13. IMPINGEMENT
Based on the inertial technique in which particles are collected from
the high velocity air steam directed toward the obstacles placed across
the path of air stream
Particulates collide with the obstacle and air changes its direction
If the obstacle are adhesive surface then particles are impacted on it
and this is known as dry impingement
If obstacle is wet by any liquid then it is called wet impingement

14. PRECIPITATION
Precipitation are two types---
Thermal precipitation
Electrostatic precipitation
THERMAL PRECIPITATION :- Thermal precipitation is based on
the principle that the particles move towards the lower temperature
region when subjected to a strong temperature gradient
 The temperature gradients are normally of the order of 3000 ° C per
centimeter
 This technique is used to collect the particle of size 0.001 micrometer
with high efficiency

15. CONTINUED…..
ELECTROSTATIC PRECIPITATION:-
 Theses precipitators are an electrically charged to force radioactive
particulates to migrate out the air steam onto a collection surface
 In this precipitators two electrodes are used positive and negative
 When the air stream with particulates pass through the electrodes
particles pick up negative charge and migrate towards inner post of the
precipitators where got discharged and deposited on the positive
electrodes

16. AIR SAMPLING OF THE GASEOUS
POLLUTANTS
ABSORPTION SAMPLING
ADSORPTION SAMPLING
CONDENSATION SAMPLING

17. ABSORPTION SAMPLING
Gaseous pollutants are absorbed in a solvent when both the pollutant
and absorbent are in close contact
Liquid react with the gaseous pollutant to form a non gaseous
pollutant
ALKALINE FOR ACIDIC GASES
ACIDIC SOLUTION FOR ALKALINE GASES
OILS FOR HYDROCARBONS

18. ADSORPTION SAMPLING
Gaseous pollutants are adsorbed on the solid surface of activated
carbon, silica gel, activated alumina and molecular sieve
As the surface area increases the adsorption increases

19. CONDENSATION SAMPLING
The conversion of a vapour or gas to a liquid
Method used to collect the radioactive gases, hydrocarbons and non
reactive vapors
Air pollutant can be trapped by condensation reaction
As the gaseous pollutant pass through the different temperature range
of condensers where the temperature is below the boiling point the
gaseous pollutant will trap in the liquid

20. SOME NEW METHODS OF AIR
SAMPLING
Bubble Sampling
Air drawn into the impinger is forced through a nozzle, which is covered by
a liquid such as high purity water.
The pollutant dissolves in the liquid and is subsequently analysed, usually
by colorimetric techniques.
Sorbent Sampling
Sorbents are normally contained in a small glass tube with sealed ends.
 Air is drawn through the sorbent, which captures molecules of the gas or
vapour to be sampled.
The trapped contaminants are released using solvent washing or heat to a
gas chromatograph (GC) for analysis. One of the best known sorbents is
charcoal.

21. CONTENTS
• CHROMATOGRAPHY
• DIFFERENT TECHNIQUES OF CHROMATOGRAPHY
• GAS CHROMATOGRAPHY
• REQUIREMENT FOR GAS CHROMATOGRAPHY
• BLOCK DIAGRAM OF GAS CHROMATOGRAPHY
• QUALITATIVE ANALYSIS
• ADVANTAGES AND DISADVANTAGES OF GAS
CHROMATOGRAPHY
• MODERN APPROACH

22. CHROMATOGRAPHY
Laboratory technique for the separation of a mixture.
The mixture is dissolved in a fluid called the mobile phase, which carries it
through a structure holding another material called the stationary phase.
 The various constituents of the mixture travel at different speeds, causing
them to separate.
 The separation is based on differential partitioning between the mobile and
stationary phases.
Chromatograph: equipment that enables a sophisticated separation, e.g.
gas chromatographic or liquid chromatographic separation.
Chromatogram: Visual output of the chromatograph.
 In the case of an optimal separation, different peaks or patterns on the
chromatogram correspond to different components of the separated mixture.

23. TECHNIQUES BASED ON
CHROMATOGRAPHIC BED SHAPE
Column chromatography: Separation technique in which the
stationary bed is within a tube.
Planar chromatography: Separation technique in which the
stationary phase is present as or on a plane.
The plane can be a paper, serving as such or impregnated by a
substance as the stationary bed (paper chromatography) or a layer of
solid particles spread on a support such as a glass plate (thin layer
chromatography)

24. TECHNIQUES BASED ON PHYSICAL STATE
OF MOBILE PHASE
Gas chromatography (GC): Also known as gas-liquid
chromatography, (GLC),
a separation technique in which the mobile phase is a gas. Gas
chromatographic separation is always carried out in a column, which
is typically "packed" or "capillary".
Liquid chromatography (LC): Separation technique in which the
mobile phase is a liquid.
carried out either in a column or a plane

25. GAS CHROMATOGRAPHY
Gas chromatography:
Mobile phase a carrier gas, usually an inert gas such as helium or
an nonreactive gas such as nitrogen.
Hydrogen is preferred for improved separations.
The stationary phase is a microscopic layer of liquid or polymer on an
inert solid support, inside a piece of glass or metal tubing called a column.
The instrument used to perform gas chromatography is called a gas
chromatograph.
The gaseous compounds being analysed interact with the walls of the
column, which is coated with a stationary phase. This causes each
compound to elute at a different time, known as the retention time of the
compound.
The comparison of retention times is what gives GC its analytical
usefulness.

26. CONTINUED….
The function of the stationary phase in the column is to separate different
components, causing each one to exit the column at a different
time(retention time).
As the carrier gas sweeps the analytic molecules through the column, this
motion is inhibited by the adsorption of the analytic molecules either onto
the column walls or onto packing materials in the column.
The rate at which the molecules progress along the column depends on the
strength of adsorption, which in turn depends on the type of molecule and
on the stationary phase materials.

27. CONTINUED……
Since each type of molecule has a different rate of progression, the
various components of the analytic mixture are separated as they
progress along the column and reach the end of the column at different
times(retention Time).
Detector: used to monitor the out let stream from the column; thus,
the time at which each component reaches the outlet and the amount of
that component can be determined.
Generally, substances are identified(qualitatively) by the order in
which they emerge(elute) from the column and by the retention time
of the analytic in the column.

28. REQUIREMENT FOR GAS
CHROMATOGHRAPHY
VOLATILITY:-Tendency of a substance to evaporate at normal
temperatures
POLARITY:-Substance comprised of molecules that contain unbalanced
localized charges (dipoles) is a polar substance.
 Polar substances tend to interact with other polar substances and rarely
react to a significant degree with nonpolar substances
When two atoms form a covalent bond, they each share an electron.
Different atoms have different abilities to attract electrons quantified by
their electronegativity values. When one atom in a covalent bond has a
much higher electronegativity than the other, the electron is found closer to
that atom than the weaker one. This creates a dipole effect with a slight
negative charge at the atom the electron favours and a slight positive charge
at the other

29. BLOCK DIAGRAM OF GAS
CHROMATOGRAPHY

30. COMPONENT OF GAS
CHROMATOGRAPH
carrier gas
flow regulator
injector
column
stationary phase
oven
detectors
display device

31. CARRIER GAS
• he(common),
• others:n2,h2
• safety; non-flammability, cost and efficiency are factors for gas
selection
• inertness
• suitable for the detector
• high purity
• easily available

32. FLOW METER
• Deliver the gas with uniform pressure/flowrate
• Flowmeters:-Rotameter

33. INJECTOR
• Transfers the sample into the column.
• Provides the means to introduce a sample into a continuous flow of
carrier gas.
• Injectors are usually heated to ensure sample’s transfer to a gas
phase.
• Volatile liquid or gaseous sample is injected through a septum.

34. COLUMN
Gas chromatography columns : packed and capillary.
Packed columns :A glass or stainless steel coil(typically1-5m total length and
5mm inner diameter), filled with the stationary phase, or a packing coated with
the stationary phase.
Capillary columns: A thin fused-silica (purified silicate glass) capillary
(typically10-100 m in length and 0.5 mm inner diameter) that has the stationary
phase coated on the inner surface.
Provides much higher separation efficiency than packed columns but are more
easily overloaded by too much sample.
The main chemical attribute regarded when choosing a column is the polarity of
the mixture, The polarity of the sample must closely match the polarity of the
column stationary phase to increase resolution and separation while reducing
runtime.

35. TEMPERATURE CONTROL DEVICES
Temperature Control Devices
Preheaters: convert sample into its vapour form, present along with
injecting devices
Thermostatically controlled oven
Temperature maintenance
in a column is highly essential
for efficient separation.

36. STATIONARY PHASES
For every polar sample, polyethylene glycol(thickess
0.25mircometer) is commonly used as the stationary phase.
Stationary Phases must have:
1.Low volatility
2.Thermal stability
3.Chemical inertness

37. SOME STATIONARY PHASE LIST

38. DETECTOR
Placed at the exit of the column.
Employed to detect and provide a quantitative measurement of the
various constituents of the sample
The choice of a particular type of detector is governed by the
following factors:
1. High sensitivity, sufficient enough to provide adequate signal for
even small sample
2. Response should be linear, unaffected by temperature and flowrate.
3. Non distorted shape of peak and non destructive.
4. Detector temperature must not condense the eluted vapours in it.
5. Simple & Inexpensive
6. Applicable to wide range of samples
7. Good reproducibility, rapidity and linearity.

39. COMMONLY USED DETECTOR
Most commonly used types:-
1.Thermal Conductivity Detector TCD
2.Flame Ionization Detector FID
3.Electron Capture Detector ECD
4.Atomic-Emission Detector AED
5.Flame Photometric GC Detector FPD

40. QUALITATIVE ANALYSIS
Chromatographic data is presented as a graph of detector response(y-axis)
against retention time(x-axis), which is called a chromatogram.
This provides a spectrum of peaks for a sample representing the analytics
present in a sample eluting from the column at different times.
The number of components in a sample is determined by the number of
peaks.
The amount of a given component in a sample is determined by the area
under the peaks.
The identity of components can be determined by the given retention
times.

41. ADVANTAGES AND DISADVANTAGES
OF GC
ADVANTAGES:-
High Resolution
Very high sensitivity, detect down to 100 ppm.
Very good precision and accuracy.
Very good separation
Time(analysis is short), fast analysis is possible.
Small sample is needed-ml
Good detection system
Quantitatively analysis
DISADVANTAGES :-
Sample must be volatile
Dirty sample choke the capillary

42. MODERN APPROACH
GCMS:-Gas Chromatography Mass Spectrometry
Mass spectrometry: Analytical technique that ionizes chemical
species and sorts the ions based on their mass-to-charge ratio.
Gas chromatography–mass spectrometry (GC-
MS):Analytical method that combines the features of gas-
chromatography and mass spectrometry to identify different
substances within a test sample.
Applications of GC-MS include drug detection, fire investigation,
environmental analysis, explosives investigation, and identification of
unknown samples

43. GCMS:-GAS CHROMATOGRAPHY MASS
SPECTROMETRY

44. 2014 IEEE International Conference on Liquid Dielectrics, Bled Slovenia, June 30 -
July 3, 2014
Methanol Detection in Transformer Oils using Gas
Chromatography and Ion Trap Mass Spectrometer
S. Y. Matharagel, Q. Liul, E. Davenportl, G. Wilson2, D. Walker3 and Z.D.
Wang The University of Manchester, Manchester, M13 9PL, UK
2The National Grid Company, Warwick, CV34 6DA, UK
3Scottish Power, Blantyre, G72 OHT, UK

45. Continued…..
• Abstract-Paper ageing is an irreversible process, which has made
paper insulation a lifetime determining factor for transformers.
Chemical indicators in oil such as carbon oxide gases and 2-FAL, are
used to indicate the ageing state of paper as it is difficult to obtain
paper samples to measure DP or tensile strength. Methanol amount in
oil was recently found to be an early-ageing indicator for paper. In this
study, a heads pace gas chromatography mass spectrometry setup was
developed to measure methanol in transformer oil. This setup consists
of an auto sampler with a gas tight syringe, a gas chromatography unit
with 60 m VF-624ms column and a quadrupole ion trap type mass
spectrometer unit. Measurement of several laboratory-aged and
service-aged oil samples were conducted with both external standard
and internal standard calibration methods. Higher methanol values
obtained from internal standard method confirmed that it is more
suitable than external standard method.

46. REFERENCES
A text book of environmental chemistry by “BALRAM PANI”
“https://en.wikipedia.org/wiki/Gas_chromatography%E2%80%93mas
s_spectrometry
https://en.wikipedia.org/wiki/Gas_chromatography
https://www.youtube.com/watch?v=p3_WtEYIhTo
https://www.youtube.com/watch?v=gU2st5-T1Go