Chromatography—fundamental principle: which statement best captures the basis of separation in a chromatographic column?

Introduction:
Chromatography separates components based on their differential interactions with a stationary phase and a mobile phase. These interactions cause solutes to migrate at different velocities, producing separation along the column length.

Given Data / Assumptions:

• Stationary phase may be solid or liquid supported on a solid.
• Mobile phase may be a gas or liquid.
• Solute–phase interactions drive retention and migration rates.

Concept / Approach:
Solutes partition between phases according to their affinities, resulting in distinct retention times. The essence is the solute moving at different rates; solvent flow simply transports solutes and is not the basis for differential separation by itself.

Step-by-Step Solution:
Step 1: Recognize that separation arises when solutes have different distribution coefficients between phases.Step 2: Translate that into observable behavior: different solute migration rates (peaks at different times).Step 3: Select the statement emphasizing differential solute movement.

Verification / Alternative check:
Retention factor and selectivity calculations depend on solute distribution, not solvent speed alone, confirming that solute migration differences are primary.

Why Other Options Are Wrong:

• Being captured on adsorbent: Applies to adsorption chromatography specifically, not all modes.
• Different rate of solvent: Solvent velocity is set by flow; not the separation basis.
• Any of the above: Overly broad and includes incorrect statements.
• Distribution phrasing: True in theory, but the best matching option in the original list highlights the consequence—different solute movement rates.

Common Pitfalls:
Confusing the driving theory (partitioning/adsorption) with operational factors (mobile phase flow).

Final Answer:
different rate of movement of the solute in the column