Answer :
Gas chromatography (GC) is a powerful technique used to separate and analyze compounds that can be vaporized without decomposition.
In GC, the mobile phase refers to the carrier gas that moves the sample vapor through the column. When using different detectors, suitable carrier gases must be chosen to ensure efficient detection and separation.
The electron capture detector (ECD) is specifically sensitive to electronegative compounds, such as halogens, nitro groups, and sulfur compounds. Due to its selectivity, it is used in environmental analysis, such as detecting pesticides and chlorinated compounds.
For the electron capture detector to work efficiently, a carrier gas that does not interfere with electron capture is needed. The following options are considered:
- A. Argon (Ar): Argon is an inert gas, but it is not commonly used with ECD as a carrier gas.
- B. Nitrogen (N₂): Nitrogen is a common carrier gas for the ECD because it is inert and has low background signal, making it ideal for good sensitivity and selectivity in electron capture detection.
- C. Helium (He): Although helium is a common carrier gas for other detectors, it is not the best choice for ECD due to a higher background signal compared to nitrogen.
- D. Hydrogen (H₂): Hydrogen is typically used in other types of detectors like Flame Ionization Detector (FID), not with ECD.
Therefore, the most common choice of carrier gas for an ECD in gas chromatography is B. Nitrogen (N₂). This choice is based on its inertness and its ability to provide a low background for sensitive detection of electronegative compounds.
