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. The detectors must be able to detect these compounds as they exit the column.
Step 1: Evaluate the detectors.
A. Thermal Conductivity Detector (TCD): A very common, universal detector for GC. It measures the change in thermal conductivity of the carrier gas caused by the sample components. It is non-destructive.
B. Photo Diode-Array Detector (PDA): This is a type of UV-Vis detector used for High-Performance Liquid Chromatography (HPLC), not GC. It detects compounds in a liquid stream.
C. Flame Ionization Detector (FID): A very common and sensitive detector for GC, especially for organic compounds. It burns the sample components in a hydrogen flame, creating ions that generate a current. It is destructive.
D. Electro chemical detector: These detectors are typically used in liquid chromatography (HPLC) or for specific gas sensors, but are not standard detectors coupled with general-purpose GC systems.
Conclusion: The Thermal Conductivity Detector (A) and the Flame Ionization Detector (C) are two of the most widely used detectors for gas chromatography.