The concept of "Rf value" is commonly associated with which chromatographic technique?
Column chromatography
Thin-layer chromatography (TLC)
Gas chromatography (GC)
High-performance liquid chromatography (HPLC)
The concept of "Rf value" (retardation factor) is commonly associated with thin-layer chromatography (TLC), not column chromatography.
Hence option 2 is correct.