1. Flame Ionization Detector (FID)

• Principle: Organic compounds are burned in a hydrogen-air flame, producing ions. The resulting current is measured.
• Best for: Organic compounds (hydrocarbons, alcohols, etc.)
• Advantages: High sensitivity, wide linear range, minimal noise
• Limitations: Not suitable for inorganic gases, requires fuel gases

2. Thermal Conductivity Detector (TCD)

• Principle: Measures change in thermal conductivity between carrier gas and analytes.
• Best for: Universal detection (organic and inorganic gases)
• Advantages: Non-destructive, simple, detects inert gases
• Limitations: Lower sensitivity than FID

3. Electron Capture Detector (ECD)

• Principle: Electronegative compounds capture electrons emitted from a radioactive source (Ni-63), reducing current.
• Best for: Halogenated compounds, pesticides, PCBs
• Advantages: Extremely high sensitivity for electronegative compounds
• Limitations: Limited to certain compound types, uses radioactive materials

4. Nitrogen-Phosphorus Detector (NPD)

• Principle: Modified flame detector that selectively responds to nitrogen and phosphorus compounds.
• Best for: Amines, phosphorus-containing pesticides
• Advantages: High sensitivity and selectivity for N and P
• Limitations: Requires special catalyst bead, not universal

5. Mass Spectrometry Detector (GC-MS)

• Principle: Analytes are ionized and fragmented; mass-to-charge ratio of fragments is measured.
• Best for: Qualitative and quantitative identification of complex mixtures
• Advantages: High sensitivity, structural information
• Limitations: Expensive, requires vacuum and advanced operation

6. Photoionization Detector (PID)

• Principle: UV light ionizes compounds; ions are detected as current.
• Best for: Aromatics, ketones, VOCs
• Advantages: Selective and sensitive for certain compound classes
• Limitations: Not universal, depends on ionization potential

📘 Summary Table