Work out chromatography retention factor instantly with clear inputs, formula shown and shareable results.
The retention factor is the distance a spot travels divided by the distance the solvent front travels, so it is always between 0 and 1 and is independent of how long the plate was run. On silica, polar compounds stick to the plate and give low Rf values. Comparing an unknown's Rf to a co-run standard gives a relative retention that survives small changes in plate and solvent.
Retention factor
Rf = distance moved by spot / distance moved by solvent front
Relative retention
relative = Rf(sample) / Rf(standard)
The spot is carried by the solvent, so it cannot outrun the front. An Rf of 1 means the compound is not retained at all.
Around 0.3-0.5 gives the best resolution and is the usual target when choosing a solvent system for a column.