Question

Which of the following detectors can be coupled with a gas chromatographic system?
A. Thermal conductivity detector
B. Photo diode-array detector
C. Flame ionization detector
D. Electro chemical detector

• A. A and D only
• B. C and D only
• C. A and C only
• D. B and D only

Hint:

For Gas Chromatography, the two workhorse detectors to remember are \textbf{TCD} (Thermal Conductivity Detector - universal, non-destructive) and \textbf{FID} (Flame Ionization Detector - sensitive for organics, destructive).

Answer 1

The Correct Option is C

Gas chromatography (GC) separates volatile compounds in a gas phase. Detectors must identify compounds as they leave the column.
Step 1: Detector Evaluation.
A. Thermal Conductivity Detector (TCD): A common, universal GC detector. It measures changes in the carrier gas's thermal conductivity caused by sample components. It is non-destructive.
B. Photo Diode-Array Detector (PDA): A UV-Vis detector type used in High-Performance Liquid Chromatography (HPLC), not GC. It detects compounds in a liquid stream.
C. Flame Ionization Detector (FID): A common, sensitive GC detector, especially for organic compounds. It burns sample components in a hydrogen flame, creating ions that generate a current. It is destructive.
D. Electro chemical detector: These are typically used in liquid chromatography (HPLC) or specific gas sensors; they are not standard in general-purpose GC systems.
Conclusion: The Thermal Conductivity Detector (A) and the Flame Ionization Detector (C) are widely used GC detectors.