Planar chromatography principle Thin-layer chromatography (TLC) primarily operates via which chromatographic mechanism?

Introduction / Context:TLC is a rapid, inexpensive method for separating small molecules. Recognizing its underlying mechanism informs solvent selection and interpretation of Rf values.

Given Data / Assumptions:

• The plate is coated with a polar adsorbent (silica gel or alumina).
• Mobile phase is a solvent or solvent mixture that ascends by capillarity.
• Analytes distribute between being adsorbed on the surface and moving with the solvent front.

Concept / Approach:TLC relies on adsorption to a solid stationary phase, with competition by the mobile solvent for binding sites. More strongly adsorbed compounds move more slowly, yielding lower Rf values.

Step-by-Step Solution:Identify stationary phase: polar solid (silica/alumina) → adsorption.Consider solvent strength: stronger eluent disrupts adsorption and increases Rf.Select the option that names adsorption chromatography.

Verification / Alternative check:Switching from hexane to ethyl acetate (more polar) typically increases Rf for polar analytes, consistent with adsorption competition.

Why Other Options Are Wrong:Partition chromatography (option a) better fits paper chromatography or certain bonded-phase systems.Electrical mobility (option b) describes electrophoresis, not TLC.None of the above (option d) is incorrect as adsorption is correct.

Common Pitfalls:Assuming TLC is identical to paper chromatography; ignoring how solvent polarity affects adsorption strength.

Final Answer:Adsorption chromatography on a polar solid such as silica or alumina.