Gas Chromatography—Why Is Helium Commonly Chosen as Carrier Gas? Compared with nitrogen and hydrogen, why is helium frequently preferred as the carrier gas in many GC applications?

Introduction / Context:
The choice of carrier gas in GC affects efficiency, analysis speed, safety, and detector compatibility. Helium, nitrogen, and hydrogen are common options; each has trade-offs. Understanding why helium is widely used clarifies method robustness and safety.

Given Data / Assumptions:

• Typical capillary GC with temperature programming.
• Standard detectors (FID, TCD, MS) are considered.
• Safety and chromatographic performance are both important.

Concept / Approach:
Helium is inert and non-flammable, reducing side reactions and safety risks (versus hydrogen). Its diffusivity and viscosity yield a Van Deemter curve with a relatively flat minimum at practical linear velocities, enabling faster runs with good efficiency compared with nitrogen. It also works well with many detectors, especially MS (vacuum compatibility) and TCD, yielding stable baselines.

Step-by-Step Solution:

Verification / Alternative check:
Method translations between gases show helium and hydrogen enable faster analysis than nitrogen; helium remains preferred where hydrogen’s flammability is a concern.

Why Other Options Are Wrong:

• Each single reason (a–c) is true but incomplete; option (e) is frivolous and not scientific.

Common Pitfalls:
Ignoring safety protocols for hydrogen; while it can outperform helium in speed, flammability demands strict controls.

Final Answer:
All of the above