A. Exclusion

B. Ion-exchange

C. Adsorption

D. Absorption

Correct Answer: C. Adsorption

Gas-solid chromatography separates analytes through physical adsorption onto solid stationary phases like silica or activated carbon, where molecules temporarily bind to the surface before desorbing.​

Option Analysis

A. Exclusion
Size exclusion chromatography uses porous materials to separate by molecular size. Gas-solid chromatography employs non-porous adsorbents for surface interactions, not steric exclusion.​

B. Ion-exchange
Ion-exchange chromatography uses charged resins to exchange ions based on electrostatic attraction. Gas-solid lacks ionic sites and operates via neutral surface adsorption.​

C. Adsorption (Correct)
The defining principle: gaseous analytes adsorb onto solid surfaces (alumina, molecular sieves) with varying strengths, causing differential retention times. Ideal for permanent gases and light hydrocarbons.

D. Absorption
Absorption involves bulk phase dissolution (gas into liquid/solid matrix). Gas-solid chromatography uses surface phenomena only, not volume penetration.​

Gas-solid chromatography is adsorption chromatography as per basic principle, separating gases via surface interactions—key for analytical chemistry in GATE Life Sciences.

Adsorption Mechanism

Volatile analytes adsorb reversibly onto solid stationary phases (silica, carbon). Stronger adsorption = longer retention. Carrier gas (helium/nitrogen) desorbs components sequentially.​

Principle Comparison

GATE Applications

Used for permanent gas analysis (O₂, N₂, CO₂) in biochemical research. Tests fundamental chromatography classification knowledge.