What is Gas Chromatography?
Gas Chromatography (GC) is a powerful analytical technique used to separate,
identify, and quantify volatile compounds in a mixture. It is widely used in
chemical industries, pharmaceuticals, environmental testing, and food
analysis.
In GC, the sample is vaporized and carried by an inert gas through a column
coated with a stationary phase. Different compounds travel at different
speeds, leading to separation.
Principle of Gas Chromatography
The separation in GC is based on:
Volatility of compounds
Interaction with stationary phase
Boiling point differences
👉 Compounds that are more volatile travel faster
👉 Compounds with stronger interaction move slower
Gas Chromatography Animation
Injector
Detector
Components of Gas Chromatography
1. Carrier Gas
Inert gas like Helium (He), Nitrogen (N₂), or Hydrogen (H₂)
Acts as the mobile phase
2. Injector
Introduces the sample into the system
Converts liquid sample into vapor
3. Column
Heart of GC system
Types:
Packed column
Capillary column
4. Oven
Maintains temperature for separation
Can operate in isothermal or temperature programming mode
5. Detector
Common detectors include:
Flame Ionization Detector (FID)
Thermal Conductivity Detector (TCD)
Electron Capture Detector (ECD)
Working Process of Gas Chromatography
Sample is injected into injector
It vaporizes instantly
Carrier gas carries it through column
Compounds separate based on interaction
Detector detects components
Chromatogram is generated
What is a Chromatogram?
A chromatogram is a graphical representation of detector response vs time.
X-axis: Retention Time
Y-axis: Detector Signal
Each peak represents a compound.
Real-Time Chromatogram Plotting
Detector signal vs Retention Time (tR)
Applications of Gas Chromatography
Environmental analysis (air pollutants)
Pharmaceutical quality control
Food safety testing
Petrochemical analysis
Forensic science
Advantages of GC
High sensitivity
Excellent separation efficiency
Fast analysis
Accurate quantification
Limitations of GC
Only for volatile compounds
Requires sample preparation
Expensive instrumentation