Gas Chromatography

A complete presentation on gas chromatography, illustrating the basics, operation and different instrumentation components of the whole system.
Kindly comment if this presentation helps you or if you like this.

1. GAS LIQUID CHROMATOGRAPHY

2. • Principles
Partition of molecules between gas (mobile
phase) and liquid (stationary phase).
Gas Liquid Chromatography

3. Most Common Stationary Phases
1.Separation of mixture of polar compounds
Carbowax 20M (polyethylene glycol)
2.Separation of mixtures of non-polar compounds
OV101 or SE-30 (polymer of methylsilicone)
3.Methylester of fatty acids
DEGS (diethylene glycol succinate)

4. Filters/Traps
A
i
r
H
y
d
r
o
g
e
n
G
a
s

C
a
r
r
i
e
r

Column
Gas Chromatography
•gas system
•inlet
•column
•detector
•data system
Data system
Syringe/Sampler
Inlets
Detectors
Regulators
H
RESET

5. Schematic Diagram of Gas Chromatography

6. Detector
• Flame Ionization Detector (Nanogram - ng)
High temperature of hydrogen flame (H
2
+O
2
+ N
2
)
ionizes compounds eluted from column into flame.
The ions collected on collector or electrode and were
recorded on recorder due to electric current.

7. Exhaust
Chimney
Igniter
Hydrogen
Inlet
Column
Effluent
Collector Electrode
Schematic Diagram of Flame Ionization Detector

8. Measures the changes of thermal conductivity due
to the sample (mg). Sample can be recovered.

Thermal Conductivity Detector

9. Thermal Conductivity Detector
Principal: The thermal balance of a heated filament
Electrical power is converted to heat in a filament and
the temperature will climb until heat power loss form
the filament equals the electrical power input.
The filament may loose heat by radiation to a cooler
surface by conduction to the molecules which contact
with the filament.

10. Thermal Conductivity Basics
When the carrier gas is contaminated by
sample , the cooling effect of the
gas changes. The difference in cooling
is used to generate the detector signal.
The TCD is a nondestructive,
concentration sensing detector. A
heated filament is cooled by the flow of
carrier gas.
F
lo
w
F
lo
w

11. When a separated compound elutes from the
column , the thermal conductivity of the mixture
of carrier gas and compound gas is lowered. The
filament in the sample column becomes hotter
than the control column.
The imbalance between control and sample
filament temeprature is measured by a simple
gadget and a signal is recorded
Thermal Conductivity Detector

12. Relative Thermal Conductivity
Compound Relative Thermal Conductivity
Carbon Tetrachloride 0.05
Benzene 0.11
Hexane 0.12
Argon 0.12
Methanol 0.13
Nitrogen 0.17
Helium 1.00
Hydrogen 1.28

13. Thermal Conductivity Detector

14. •Responds to all compounds
•Adequate sensitivity for many compounds
•Good linear range of signal
•Simple construction
•Signal quite stable if carrier gas glow rate, block
temperature, and filament power are effectively controlled
•Nondestructive detection
Thermal Conductivity Detector

15. Electron Capture Detector
Analyses for pesticide, Insecticides, vinyl
chloride, and fluorocarbons in foods.
Most sensitive detector (10
-12
gram)

16. Electron Capture Detector
ECD detects positive ions of carrier gas by the anode electrode.
63
Ni emits b particles.
Ionization : N
2
(Carrier gas) + b (e) = N
2
+
+ 2e. The N
2
+
establish a
“base line”
X (F, Cl and Br) containing sample + b (e)  X
-
Ion recombination: X
-
+ N
2
+
= X + N
2,
The “base line” due to the
N
2
+
will decrease and this decrease constitutes the signal.
The more the halogen containing X compounds in the sample, the
less the N
2
+
in the detector

17. Electron Capture Detector

18. Electron Capture Detector

19. Chromatogram of Compounds from Fermented Cabbage

20. Chromatogram of Orange Juice Compounds

21. Gas Chromatography Application

22. Semi-Quantitative Analysis of Fatty Acids
C
C
C
D
e
t
e
c
t
o
r
R
e
s
p
o
n
s
e
Retention Time
14
16
18
P
e
a
k

A
r
e
a
Sample Concentration (mg/ml)
2
4
6
8
10
0.51.01.52.02.53.0
The content % of C fatty acids =
C
C + C + C
100*
14
181614
= the content % of C fatty acids14
14

23. Tentative Identification of Unknown
Compounds
R
e
s
p
o
n
s
e
GC Retention Time on Carbowax-20 (min)
Mixture of known compounds
Hexane
Octane
Decane
1.6 min = RT
R
e
s
p
o
n
s
e
Unknown compound may be Hexane
1.6 min = RT
Retention Time on Carbowax-20 (min)

24. R
e
s
p
o
n
s
e
GC Retention Time on SE-30
Unknown compound
RT= 4 min on SE-30
R
e
s
p
o
n
s
e
GC Retention Time on SE-30
Hexane
RT= 4.0 min on SE-30
Retention Times

25. Advantages of Gas Chromatography
•Very good separation
•Time (analysis is short)
•Small sample is needed - ml
•Good detection system
•Quantitatively analyzed

26. Disadvantages of Gas Chromatography
Material has to be volatilized at 250C without decomposition.

R C OH CH
3
OH H
2
SO
4
O
R C O CH
3
O
CH
2
O C R
CH O C R
CH
2
O C R
O
O
O
CH
3
OH
O
R C O CH
3
CH
3
ONa
Fatty Acids Methylester
Reflux
+
3
Volatile in Gas
Chromatography
Volatile in Gas
Chromatography
+ +

27. Gas Chromatogram of Methyl Esters of Fatty Acids

28. Effects of OH groups of Carbohydrates
OH
O
OH
OH
HO
CH
2
OH
1
2
3
4
5
6

29. OH
O
OH
OH
HO
CH
2
OH
1
2
3
4
5
6
+ Si
CH3
CH3
CH35Cl
O-Si(CH
3
)
3
O
O-Si(CH
3
)
3
O-Si(CH
3
)
3
(CH
3
)
3
-Si-O
CH
2
O-Si(CH
3
)
3
1
2
3
4
5
6
5HCl+
Derivation of Glucose with Trimethylchlorosilane
Glucose Trimethylchlorosilane

30. Effects of Derivation
•Time consumption
•Side reaction
•Loss of sample

31. Kindly comment if you like this presentation.