Chemistry A-Level
Rf value
What Rf value means in Chemistry A-Level, as defined for AQA.
Definitions of Rf value
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Reference: AQA
The distance travelled by the spot divided by the distance travelled by the solvent front, both measured from the pencil baseline with the spot measured to its centre.
A value that is high when a substance is highly soluble in the mobile phase but weakly retained by the stationary phase and so travels further.
Distance moved by spot divided by distance moved by solvent front, compared to known standard values to identify an amino acid.
The distance a spot travels relative to the solvent front on a thin-layer plate, carrying no unit.
Topics that use Rf value
- Chromatography (A-level only) (AQA A-Level)
- Proteins (A-level only) (AQA A-Level)
Related terms
- adsorption
- building peptides
- comparison with standards
- condensation
- fragmentation fingerprint
- gas chromatography
- gas chromatography with mass spectrometry
- hydrogen bonding
Using Rf value in the exam
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