Principle of column chromatography

In column chromatography, the compound that is less strongly adsorbed on the stationary phase moves faster and hence elutes first.

Since A eluted first, compound A is less strongly adsorbed than B.

Therefore, B is more strongly adsorbed on the stationary phase.

Relation with $R_f$ value

In general, comparing with thin layer chromatography (same stationary phase/solvent system):

• Stronger adsorption $\Rightarrow$ compound moves less
• Hence it has lower $R_f$

So if B is more strongly adsorbed, then B has low $R_f$.

Match with options

• A: high $R_f$, weaker adsorption $\rightarrow$ incorrect
• B: high $R_f$, stronger adsorption $\rightarrow$ incorrect because stronger adsorption gives low $R_f$
• C: low $R_f$, weaker adsorption $\rightarrow$ incorrect
• D: low $R_f$, stronger adsorption $\rightarrow$ correct

Final answer

$\boxed{\text{D: low } R_f, \text{ stronger adsorption}}$