1. Gas Liquid Chromatography
Chapter 4-4
Chromatography
Gas Liquid Chromatography
Principles
Partition of molecules between liquid (stationary phase) and gas (mobile phase)
Dr Gihan Gawish

2. Gas-liquid chromatography (GLC)
The mobile phase is a carrier gas, usually an inert gas such as helium or an uncreative gas such as nitrogen
The stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside glass or metal tubing, called a column.
The instrument is called a gas chromatograph
Dr Gihan Gawish

3. Gas-liquid chromatography (GLC)
In the animation below the red molecules are more soluble in the liquid (or less volatile) than the green molecules.

4. Most Common Stationary Phases of GC
1. Separation of mixture of polar compounds
(polyethylene glycol)
2. Separation of mixtures of non-polar compounds
(polymer of methyl silicone)
Methyl ester of fatty acids
DEGS (diethyl glycol succinct)
Dr Gihan Gawish

5. Gas Chromatography gas system inlet column detector data system
Filters/Traps
Data system H
RESET
Regulators
Syringe/Sampler
Air
Hydrogen
Gas Carrier
Inlets
gas system
inlet
column
detector
data system
Detectors
Column
Dr Gihan Gawish

6. Schematic Diagram of Gas Chromatography
A gas chromatograph is a chemical analysis instrument for separating chemicals in a complex sample.

7. GC analysis
A gas chromatograph uses a flow-through narrow tube known as the column, through which different chemical constituents of a sample pass in a gas stream (carrier gas, mobile phase) at different rates depending on:
Their various chemical and physical properties
Their interaction with a specific column filling, called the stationary phase.
Dr Gihan Gawish

8. GC analysis
As the chemicals exit the end of the column, they are detected and identified electronically.
The function of the stationary phase in the column is to separate different components at a different time (retention time).
Other parameters that can be used to alter the order or time of retention are the carrier gas flow rate, and the temperature and strength of adsorption.
Dr Gihan Gawish

9. Physical Components 1. Auto samplers
The auto sampler provides the means to introduce automatically a sample into the inlets.
Manual insertion of the sample is possible but is no longer common.
Automatic insertion provides better reproducibility and time-optimization.
Dr Gihan Gawish

10. Physical Components
2- The column inlet (or injector) provides the means to introduce a sample into a continuous flow of carrier gas.
The inlet is a piece of hardware attached to the column head.
Dr Gihan Gawish

11. 3. Columns 3-1- Packed columns Two types of columns are used in GC:
Animation
3. Columns
Two types of columns are used in GC:
3-1- Packed columns
They are m in length and have an internal diameter of mm.
The tubing is usually made of stainless steel or glass and contains a packing of solid support material that is coated with a liquid or solid stationary phase.
The nature of the coating material determines what type of materials will be most strongly adsorbed.
Thus numerous columns are available that are designed to separate specific types of compounds.
Dr Gihan Gawish

12. Physical Components 3-1- Capillary Columns
They have a very small internal diameter, on the order of a few tenths of millimeters, and lengths between meters are common.
The inner column walls are coated with the active materials.
Most capillary columns are made of fused- silica with a polyimide outer coating. These columns are flexible, so a very long column can be wound into a small coil.
Dr Gihan Gawish

13. 4.Detector Physical Components
4- Detector is used to monitor the outlet stream from the column; thus,
the time at which each component reaches the outlet
the amount of that component can be determined.
Dr Gihan Gawish

14. Types of Detector in GC
4.1.Flame Ionization Detector (sensitivity 10 µg)
High temperature of hydrogen flame (H2 +O2 + N2) ionizes compounds eluted from column into flame.
The ions collected on collector or electrode and were recorded on recorder due to electric current. -5
Dr Gihan Gawish

15. Types of Detector in GC
4.2.Thermal Conductivity Detector (sensitivity 10 µg)
Measures the changes of thermal conductivity due to the sample (mg).
Dr Gihan Gawish

16. 4.3.Electron Capture Detector (sensitivity 10 µg)
Types of Detector in GC
4.3.Electron Capture Detector (sensitivity 10 µg) -5
which uses a radioactive (electron) source to measure the degree of electron capture.
Sensitive to electronegative groups
• Insensitive to amines, alcohols
Dr Gihan Gawish

17. Types of Detector in GC 4.4. GC-MS Detector
Some gas chromatographs are connected to a mass spectrometer which acts as the detector.
The combination is known as GC-MS.
Dr Gihan Gawish

18. SEMI- QUANTITATIVE ANALYSIS OF FATTY ACIDS
GC-Application
SEMI- QUANTITATIVE ANALYSIS OF FATTY ACIDS
Dr Gihan Gawish

19. TENTATIVE IDENTIFICATION OF UNKNOWN COMPOUNDS
GC-Application
TENTATIVE IDENTIFICATION OF UNKNOWN COMPOUNDS
Dr Gihan Gawish

20. GC-Advantages 1. Very good separation 2. Time (analysis is short)
3. Small sample is needed - ml
4. Good detection system
Quantitatively analyzed
Dr Gihan Gawish

21. DISADVANTAGES OF GAS CHROMATOGRAPHY
Material has to be volatilized by oxidation, acylation and alkylation.
Dr Gihan Gawish

22. Gas Chromatogram of Methyl Esters of Fatty Acids
Dr Gihan Gawish