TLC Rf & Eluent Advisor
Compute the retardation factor (Rf) from your spot and solvent-front distances, then get a suggestion for adjusting eluent polarity toward the ideal 0.3–0.5 window.
How to use this tool
Turn your TLC plate measurements into an Rf value and get a hint on whether to adjust the solvent. Measure two distances from the baseline, pick your plate type, and read off the result.
What to enter
- Solvent front distance: baseline to the solvent front, in mm.
- Spot distance: baseline to the centre of the spot, in mm. Use the same units for both, only the ratio matters.
- Stationary phase: normal phase (silica/alumina) or reversed phase (C18); this sets which way to push polarity to move Rf.
Reading the result
You get the Rf (a number from 0 to 1), a bar showing how far up the plate the spot ran, and advice on changing eluent polarity to bring Rf into the ideal 0.3–0.5 band where close-running spots resolve best.
Worked example
A spot 20 mm from the baseline with the solvent front at 50 mm gives Rf = 0.40, right in the ideal 0.3–0.5 window.
Plate measurements
Result
Methodology
Rf = (distance travelled by the spot) ÷ (distance travelled by the solvent front), measured from the baseline. It is dimensionless and ranges 0–1. A good separation usually keeps the spot of interest in the 0.3–0.5 band, where neighbouring components resolve best.
Adjusting the eluent
- Normal phase (silica): a more polar eluent raises Rf; a less polar eluent lowers it.
- Reversed phase (C18): the opposite, a more polar eluent lowers Rf.
- Change the polar modifier in small steps (e.g. 5–10% ethyl acetate in hexane at a time).
Known limits
- Rf is reproducible only under identical plate, solvent, chamber-saturation and temperature conditions. Always co-spot a reference.