Retardation or retention aspect (Rf) worth is the ratio of street traveled by the analyte to the of the solvent front on a chromatogram.

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The Rf (retardation/retention factor) values can be calculation by making use of the provided procedure using the above experiment.

A all set sample equipment (A+B) is used on the chromatogram record and run with a cell phone phase. Analyte (A) and also (B) separate out due to the fact that of different affinities v mobile step (solvent). The relative measurements are taken for the analytes, the solvent front, and the point where the mixture (A+B) was applied.

For the analyte (A)

Rf = Distance moved by analyte (A) / Distance moved by solvent front

Rf = 2.9 / 4.0

Rf = 0.725

For the analyte (B)

Rf = Distance relocated by analyte (B) / Distance moved by solvent front

Rf = 1.3 / 4.0

Rf = 0.325

So, the Rf values for the analytes (A) and also (B) space 0.725 and also 0.325.

Factors affecting Rf values

There are several factors that affect the Rf values of a certain analyte:

Stationary phaseConcentration the stationary phaseMobile phaseConcentration of mobile phaseTemperature

Same substances (analytes ) have various Rf values if the nature that stationary and also mobile phases is changed, i.e. The affinity determinants are changed. Comparable is the situation when the concentration of this phases is changed. Temperature influence the rate of mobile activity of solvent and likewise the solubilities that analytes in the solvent.

Rf values room independent of the concentration the analytes whatsoever.

Concepts Berg

How to calculation Rf?

Retention/retardation aspect (Rf) can be calculated by the family member migration values of solute (analyte) and the solvent front.

Rf = migration of analyte / hike of solvent front

The calculate of the Rf value is usually the calculate of family member affinities the a solute with the stationary and mobile phases.

How to select the solvent system?

The solvent system for a particular analyte separation via chromatography is chosen based on the polarity the solute (analyte), the stationary phases, and also the temperature. The solvent system is actually the mobile step which must reasonably be either much more or much less polar 보다 the stationary phase, which i do not care the reason for the displacement that the analyte native the application allude to a higher level in obelisk chromatography.

A pure solvent have the right to be supplied with particular polarity for a chromatographic procedure. Back if a collection of continuously enhancing or decreasing polarities is required, a mixture of two or much more solvents might be used with a consistent manner of rise in the concentration the one solvent and also decrease of other.

How to interpret the TLC?

Interpretation that the slim layer chromatography (TLC) is totally based upon the Rf values. The Rf values evaluate the relative polarity, the loved one affinities through stationary and also mobile phases, the loved one molecular weights, and even the concentration the analytes if advanced environments room used.

Why carry out we require the Rf value?

Rf values in chromatography are the straightforward requirement the the totality experiment. These worths tell united state whether the analyte (solute) is much more affinitive v stationary or the cell phone phase. Rf worths evaluate the polarity, loved one masses, and relative solubilities with stationary and mobile phases, etc.

How to uncover the Rf values of aspirin in particular solvents?

Rf worths are uncovered by chromatographic experiments. Aspirin is a polar molecule and also will be an ext soluble in a polar solvent. As the general rule of solubility ‘like disappear like’ suggests. The Rf worths are constantly different for different stationary and mobile phases used. So, one aspirin solution is to it is in run against a polar solvent (mobile phase) when the stationary step is less polar 보다 the mobile one. This will certainly leave aspirin in ~ a specific height offering its Rf value in between 0 and 1.

What room the units for Rf values?

Rf values space unitless together the ratio of comparable quantities is constantly just a number. The solute migration value is contrasted by the solvent former migration value to calculation the Rf worth which provides just a ratio number.

What are the advantages of calculating one Rf value in chromatography?

Chromatography is extremely useful only if there is one account for Rf values. This values give the essential information required, because that which the chromatography is basically performed. Rf values evaluate the polarities, the loved one affinities through stationary and also mobile phases, the loved one molecular weights, and also even the identification of analytes (solutes) room done by the Rf values unless there is no record for that specific solute in those conditions.

Which one is much better in TLC, the greater or the lower Rf value?

The basic property of Rf values is to identify the loved one properties of components of a mixture among each other and also with the stationary and also mobile phases. That doesn’t actually issue if their worths are greater or lower as long as these are much apart native one another.

Rf values have to not be either 0 or 1 because both that these problems are not advantageous in the analytical procedure. An Rf worth of zero way that the complete displacement (migration) of the analyte through the mobile phase (solvent), conversely, the value one refers to no displacement at all.

Is chromatography file polar?

In column chromatography, the chromatography record is made of a cellulose network (like a common paper) having actually capillary activity to move solvent end it. The compound acting together the stationary step is the adsorbed water ~ above cellulose fibers which is a polar compound. So, the chromatographic paper in pillar chromatography is polar. This is likewise the reason why the is dubbed liquid-liquid chromatography.

In thin layer chromatography, the TLC document or sheet is having alumina (AL2O3) or silica (SiO2) pasted over glass or metal sheet, which are polar so a TLC paper is also polar.

What is the principle behind chromatography?

The main principle of color layer analyzer is the family member solubilities the a solitary analyte in various solvents.

Retardation/retention element (Rf) worths drive the whole procedure due to the fact that it is the Rf worths that identify the loved one polarities/solubilities of components in a mixture (solutes) based on the polarities that stationary and also mobile solvents.

The principle of chromatography have the right to thus be, the family member affinities of analytes (solutes) v stationary and also mobile phases.

The principle of family member affinities is further described by the adsorption or resolution of solute on stationary solvent or phase and also then leaving the stationary solvent for a relatively greater solubility in mobile solvent/phase.

In chromatography, if solvent reaches the sheet of the file so how can we recognize the Rf value?

In chromatographic techniques, the solvent prior is commonly not allow to reach the finish of the paper. The advance of chromatogram is stopped before that happens and also is put to dried for more evaluation. But if somehow, the solvent front reaches the leaf of record during chromatography, the value of solvent prior migration is required to be the size of the paper.

What is a great Rf value?

Rf values space the retardation worths in a specific environment for a details analyte (solute). These worths aren’t great or bad. This are simply a proportion of 2 migration distances arising simultaneously, the analyte and also the solvent front. It would be much better for the calculation and identification functions if the Rf values of link of a mixture space not as well close.

Although, if the Rf worths of compound in a mixture space too close, these would not be of much use.

Why is Rf much less than 1?

Rf values are constantly less than one because they space the ratios that migration ranges of solutes (analytes) and solvent fronts. Together a general rule, the solvent front always travels more than the of solute, due to the fact that the solutes have to have some attractive properties v stationary phases. It way that the denominator being higher in value, Rf values will always be in between 0 and 1.

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What is the meaning Rf value?

Rf values are fairly significant because the outcome of many of the chromatographic procedures, especially TLC and also column chromatography rest on these Rf values. That is Rf values that provide the family member properties the analytes choose polarities, molecule weights, six with certain solvents, and even the identification of analytes (solutes) have the right to only be completed through the Rf values library.