Retardation factor

Retardation factor

In chromatography, a retardation factor (Rf) (also known as retention factor) describes the ratio of time spent in the stationary phase relative to time spent in the mobile phase. It can be mathematically described by the following ratio:

R_f = frac{mbox{migration distance of substance{mbox{migration distance of solvent front

For example, if particular substance in an unknown mixture travels 2.5 cm and the solvent front travels 5.0 cm, the retention factor would be 0.5. An Rf value will always be in the range 0 to 1: if the substance moves at all, it moves along the direction the solvent ("mobile phase") does less, but cannot move further than the solvent does. Rf values are only useful if they are between these two extremes. One can choose a mobile phase with different characteristics (especially polarity) in order to control how far the substance being investigated migrates. An Rf value is characteristic for any given compound (provided that the same stationary and mobile phases are used).

It can provide corroborative evidence as to the identity of a compound. If the identity of a compound is suspected but not yet proven, an authentic sample of the compound, or standard, is spotted and run on a TLC plate side by side (or on top of each other) with the compound in question. Note that this identity check must be performed on a single plate, because it is difficult to duplicate all the factors which influence Rf exactly from experiment to experiment.

ee also

*Paper chromatography
*Thin layer chromatography


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • retardation factor —    The ratio of the average linear velocity of ground water to the velocity of the retarded constituent at C/Co=0.5 [22] …   Lexicon of Cave and Karst Terminology

  • retardation factor — (RF)    The ratio of the distance traveled by the solute spot’s center divided by the distance traveled by the solvent front, both measured from the origin …   Forensic science glossary

  • Retardation — may have different meanings: * Mental retardation * Negative acceleration in mechanics (i.e. rate of decrease of velocity) * Retardation Factor, in the Advection/Dispersion transport equation (ADE) * Retarded potential in electrodynamics …   Wikipedia

  • Factor de crecimiento insulínico tipo 1 — (somatomedina C) HUGO 5464 …   Wikipedia Español

  • gel retardation assay — (= mobility shift assay) Test for interaction between molecules by looking for a change in gel electrophoretic mobility. For example, to assay for levels of a transcription factor, cell extracts are incubated with a radiolabelled oligonucleotide… …   Dictionary of molecular biology

  • analysis — /euh nal euh sis/, n., pl. analyses / seez /. 1. the separating of any material or abstract entity into its constituent elements (opposed to synthesis). 2. this process as a method of studying the nature of something or of determining its… …   Universalium

  • RF — or RF is an abbreviation for: * Roger Federer, 13 time Grand Slam winning and 1 time Olympic champion tennis player * Radio frequency * Randall Flagg * Range Factor, a baseball statistic * rate of flow , as in Volumetric flow rate * Receptive… …   Wikipedia

  • Holocene Epoch — formerly Recent Epoch Latest interval of the Earth s geologic history, dating from 10,000 years ago to the present. The younger of the two epochs that constitute the Quaternary Period, the Holocene follows the last glacial stage of the… …   Universalium

  • Thin layer chromatography — Separation of black ink on a TLC plate Acronym TLC Classification Chromatography Other techniques Related …   Wikipedia

  • Rf, RF — Symbol denoting movement of a substance in paper chromatography relative to the solvent front ( i.e., retardation factor); equal to the migration distance of a substance divided by the migration …   Medical dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”