Question

When performing a thin layer chromatography procedure, the solvent front moved 10.0 centimeters. The substance of interest moved 4.0 centimeters. What is the Rf for the substance of interest?

Answer 1

Rf or Retention factor for a substance in chromatography is given as the ratio of distance traveled by the solvent front to the distance traveled by the substance of interest in that solvent or solvent-system. Mathematically, it is given as: Rf = (Distance traveled by substance)/(Distance traveled by solvent front).

Thus, being the ratio between two similar quantities, retention factor is a dimensionless quantity and varies strictly between 0 and 1. For a particular substance, in a particular adsorbent and eluent system, the Rf is always constant. Rf increases with incerasing solvent polarity and decreases with decreasing solvent polarity.

Now, in the given case, Rf = (4.0 cm)/(10.0 cm) = 0.40.