Biochemical Techniques and Instrumentation

2.6.5. Retention factor

Once the spots of compounds are visible, the "R_f value" or "retention factor" of each spot can be determined by dividing the distance travelled by the compound by the total distance travelled by the solvent.

$$Rf\ value = {Distance\ moved\ by\ solute\ or\ compound \over Distance\ moved\ by\ solvent}$$

This value is constant for a particular compound under standard conditions. The compounds are then identified based on reference compounds separated alongside the sample.