Can an Rf value be exactly 0?

Can an Rf value be exactly 0?

• A. Yes
• B. No
• C. Sometimes
• D. Not defined

Answer: (B)

Rf is defined as the distance traveled by the substance divided by the distance traveled by the solvent front. Since the solvent front clearly moves a positive distance up the plate, the denominator is nonzero. If a substance did not move from the baseline, the numerator would be zero, giving an Rf of zero. In standard TLC reporting, results are given as positive values up to the solvent front, and a true zero would indicate no migration rather than a usable comparative value. For that reason, an exact zero Rf isn’t treated as a valid, informative result.

Rf is defined as the distance traveled by the substance divided by the distance traveled by the solvent front. Since the solvent front clearly moves a positive distance up the plate, the denominator is nonzero. If a substance did not move from the baseline, the numerator would be zero, giving an Rf of zero. In standard TLC reporting, results are given as positive values up to the solvent front, and a true zero would indicate no migration rather than a usable comparative value. For that reason, an exact zero Rf isn’t treated as a valid, informative result.