What does a high RF value mean in paper chromatography?
The retention factor (Rƒ) may be defined as the ratio of the distance traveled by the solute to the distance traveled by the solvent. It is used in chromatography to quantify the amount of retardation of a sample in a stationary phase relative to a mobile phase.
Definition. Rf = distance traveled by substance/distance traveled by solvent front. A high Rf (Ie 0.92) would refer to a substance that is very non-polar. Ie that substance moved a 92% of the entire distance the solvent traveled. A low Rf value (0.10) would refer to a substance that is very polar.
- Retention time (RT) is a measure of the time taken for a solute to pass through a chromatography column. It is calculated as the time from injection to detection. The RT for a compound is not fixed as many factors can influence it even if the same GC and column are used.
- Rf values. The Rf value of a particular compound is always the same - if the chromatography has been carried out in the same way. This allows industry to use chromatography to identify compounds in mixtures.
- Radio frequency
A small Rf indicates that the moving molecules are not very soluble in the hydrophobic (non-polar) solvent; they are larger and/or have a greater affinity for the hydrophillic paper (they have more polar groups) than molecules with a larger Rf.
- A small Rf indicates that the moving molecules are not very soluble in the hydrophobic (non-polar) solvent; they are larger and/or have a greater affinity for the hydrophillic paper (they have more polar groups) than molecules with a larger Rf.
- Beta carotene is carried the furthest because it is highly soluble in the solvent and because it forms no hydrogen bonds with the chromatography paper fibers. Chlorophylls are bound more tightly to the paper than the other two, so they travel the shortest distance.
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RF value (in chromatography) The distance travelled by a given component divided by the distance travelled by the solvent front. For a given system at a known temperature, it is a characteristic of the component and can be used to identify components.
- The stronger a compound is bound to the adsorbent , the slower it moves up the TLC plate. Non-polar compounds move up the plate most rapidly (higher Rf value), whereas polar substances travel up the TLC plate slowly or not at all (lower Rf value).
- Thus, simple paper chromatography can be used to identify substances both qualitatively (by color) and quantitatively by its characteristic Rf value. If distance from the origin to solvent front is 6 cm, calculate the Rf factor for the 4 pigments illustrated above. Start with the pigment that rose the highest (5.5 cm).
- Radio frequency
Updated: 25th September 2018