Gas chromatography,instrumentation components,detectors,thermal conductivity detector,flame ionisation,electron capture detector, quantitative estimation,applications, advantages

1. By: Dr. Sucheta Gaikwad

2.  What is “chromatography”
 Principle of gas chromatography
 Theory of operation
 Components in technique
 Detectors
 Advantages
 Applications

3.  1903 - Mikhail Tswett separated plant
pigments using paper chromatography
 liquid-solid chromatography
 1930’s - Schuftan & Eucken use vapor as the
mobile phase
 gas solid chromatography

4.  The separation of mixtures into their constituents by
preferential adsorption by a solid”
 “Chromatography is a physical method of separation
in which the components to be separated are
distributed between two phases, one of the phases
constituting a Staionary phaseof large surface area,
the other being a movingthat percolates through or
along the stationary bed.”

5. It is basically a techq in which moving phase is
gas where compound of vapourised sample are
separated and fractionated as consequence of
partition Between a mobile phase and stationary
phase held in column
sample Partition between phases Separated comp.

6. Gas Chromatography
(Based on Stationary Phase)
Gas liquid
Chrmatography
(GLC)
Gas solid
Chrmatography
(GSC)
Mobile Phase -Gas

7. Gas solid Chrmatography
(GSC)
Gas liquid
Chrmatography
(GlC)
St.phase: Solid granular silica
alumina or carbon
Nonvolatile liduid on
solid support
(diatomaceous earth
particles)
Separation
process:
Adsorption Partition
Applicable for Hydrocarbons Most of organic
iorganic ,compd

9. Flame
Ionization
Detector
Column
Oven
Injection Port
top view
front view

10. Carrier gas
(nitrogen or
helium)
Sample injection
Long Column (30 m)
Detector (flame
ionization
detector or FID)
Hydrogen
Air

11. Properties
 Inert Gas
 Available In Low Cost
 Response Towards Detector
 Helium (He), nitrogen (N2), hydrogen (H2),
and argon (Ar).
 Helium and nitrogen - most commonly used
 Main disadvantage of hydrogen- explosion
hazards
 *low density better---------- Separation
Efficiency

12. Liquid or gas sample always injected by syringe through a
silicone rubber diaphragm in the injection port.

13. Two types of column:
 Capillary column:Fabricated from capillary tubing,verythin,high
efficiency with extremely small sample
 Packed column:Made up of stainless steel or cu tubing,folded
coiled,stable at high temp
 Velocity of a compound through the column depends upon affinity
for the stationary phase
Area under curve is
______ of compound
adsorbed to stationary
phase
Gas phase concentration
Carrier gas
mass

14.  Particle size and surface area
 Rate of flow of carrier gas
 Type of stationary phase
 Column length
 Column diameter
 Column temperature
 Statinary phase: utilised should be thermally
stable,chemically inert,low voltality and good solvent

15. Reuirements
 High sensitivity
 Stable
 Capable of operating at maximum suitable
temperature
 Easy to operate
 An output signal is a linear function of the
concentration of a sample

16.  Thermal Conductivity Detector
 Flame Ionisation Detector
 Electron Capture Detector

17. •Working: Consist of Pt,Gold
or Tungsten wire in whetstone
bridge network
•Detects based on difference
in the thermal conductivity of
carrier gas and separated
sample from column stream
•Thermal conductivity affects
the resistance as a function
of temperature

18. Advantage:
Simple, inexpensive, accurate,
non distructive of sample &
Detects CO2 in flue gas
Dis advantage:
Less sensitive,Can be
increased using He as a carrier
gas

19. Hydrogen
Air
Capillary tube (column)
Platinum jet
Collector
Sintered disk
Teflon insulating ring
Flame
Gas outlet
Coaxial cable to
Analog to Digital
converter
Ions
Why do we need
hydrogen?

20.  Working:Large number of organic compounds
get pyrolysed when introduced in flame and
produce ions.
 These ions are collected towards respective
electrode.
 This changes potential difference between
electrodes resulting current which is measured
by amplifier i.e change in conductivity of
flame when composition of gas mixture
changed

21. Advanages:
Responds to compounds that produce Ions
when burned in an H2-air flame(all organic
compounds) Highly sensitive, Linear
response
DisAdvantages:
Complicated, expensive, distructiveof
sample, functional groups like carbonyl
,halogen, amines not detected

22. Working principle: When gas eluted from column strikes at
cathode a beam of free electrons produce by β emitter it
collects at anode. This generates background signal to detect
gas

23. Avdvantage:
Highly sensitive selective towards
analyte of electronegative functional
groups such as halogens ,peroxides, nitro
etc.Detection and determination of
chlorinated insecticides,Dose not alter
sample
Disadvantage:
Distructive,non linear response

24. W1/2
h

26. 1. Isobutane
2. n-Butane
3. Isopentane
4. n-Pentane
5. 2,3-Dimethylbutane
6. 2-Methylpentane
7. 3-Methylpentane
8. n-Hexane
9. 2,4-Dimethylpentane
10. Benzene
11. 2-Methylhexane
12. 3-Methylhexane
13. 2,2,4-Trimethylpentane
14. n-Heptane
15. 2,5-Dimethylhexane
16. 2,4-Dimethylhexane
17. 2,3,4-Trimethylpentane
18. Toluene
19. 2,3-Dimethylhexane
20. Ethylbenzene
21. m-Xylene
22. p-Xylene
23. o-Xylene

27. Column: Petrocol DH, 100m
x 0.25mm ID, 0.5µm film
Cat. No.: 24160-U
Oven: 35°C (15 min) to
200°C at 2°C/min, hold 5
min
Carrier: helium, 20cm/sec
(set at 35°C)
Det.: FID, 250°C
Inj.: 0.1µL premium
unleaded gasoline, split
(100:1), 250°C
Example Method

28.  Problem: some components of a mixture may
have very high velocities and others
extremely low velocities.
 slow down fast components so they can be
separated
 speed up slow components so analysis
doesn’t take forever

29.  Aromatics (benzene, toluene, ethyl benzene, xylene)
 Flavors and Fragrances
 Air pollutants Permanent gases (H2, N2, O2, Ar, CO2, CO,
CH4)
 Hydrocarbons in petroleum industry
 Analysis of Alcohols in blood
 Pesticides, Herbicides, PCBs, and Dioxins
 Water analysis -dissolved gases
 Fatty acids in oils
 Separation of amino acids
 Determination of formaldehyde and phenols in resins
*Compound must exist as a gas at a temperature that can be
produced by the GC and withstood by the column (up to
450°C)

30.  Both qualitative and quantitative analysis .
 Requires only very small samples with little
preparation
 Good at separating complex mixtures into
components
 Results are rapidly obtained (1 to 100 minutes)
 Very high precision
 Only instrument with the sensitivity to detect volatile
organic mixtures of low concentrations
 Equipment is not very complex (sophisticated oven)
 Method applicable to about 60% of organic
compounds
 Separation of isomers possible

31. Thank you !!!