How do you calculate the RF value?

Teisha Knewtson asked, updated on April 8th, 2021; Topic: rf value
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The retention factor, or Rf, is defined as the distance traveled by the compound divided by the distance traveled by the solvent.

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In every case, how do you calculate Rf values for TLC?

In thin-layer chromatography, the retention factor (Rf) is used to compare and help identify compounds. The Rf value of a compound is equal to the distance traveled by the compound divided by the distance traveled by the solvent front (both measured from the origin).

In one way or another, can more than one compound have the same Rf value? The larger an Rf of a compound, the larger the distance it travels on the TLC plate. ... If two substances have the same Rf value, they are likely (but not necessarily) the same compound. If they have different Rf values, they are definitely different compounds.

At the same time, what does an RF value tell you?

The Rf values indicate how soluble the particular pigment is in the solvent by how high the pigment moves on the paper. ... Small Rf values tend to indicate larger, less soluble pigments while the highly soluble pigments have an Rf value near to one.

Why is RF less than 1?

By definition, Rf values are always less than 1. An Rf value of 1 or too close to it means that the spot and the solvent front travel close together and is therefore unreliable. This happens when the eluting solvent is too polar for the sample.

18 Related Questions Answered

Why do we calculate Rf values?

R f values can be used to identify unknown chemicals if they can be compared to a range of reference substances. The Rf value for a particular substance is always the same if the same solvent and stationary phase are used.

Do RF values have units?

Rf values do not have units since it is a ration of distances. Because mixture solvents are often applied Rf values are usually written as the following examples: ... Note that mixture compounds with larger proportions are placed first in the mixture sequence.

Does a higher Rf value mean more polar?

In general, the adsorptivity of compounds increases with increased polarity (i.e. the more polar the compound then the stronger it binds to the adsorbent). ... 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).

What factors affect RF values in paper chromatography?

Rf values and reproducibility can be affected by a number of different factors such as layer thickness, moisture on the TLC plate, vessel saturation, temperature, depth of mobile phase, nature of the TLC plate, sample size, and solvent parameters. These effects normally cause an increase in Rf values.

Do all compounds have unique RF values?

Rf or Retention factor is a unique value for each compound under the same conditions. The Rf for a compound is a constant from one experiment to the next only if the chromatography conditions below are also constant: solvent system. adsorbent.

What does a high RF value mean?

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.

What is the RF value of benzoic acid?

0.37

What does a small RF value indicate?

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.

Which pigment has the highest RF value?

PigmentRf value rangeRelative position
Lutein0.22-0.28Below, or almost at the same level of, the highest green
Violaxanthin0.13-0.19Below, or almost at the same level of, the highest green
Neoxanthin0.04-0.09Below, or almost at the same level of, the highest green

What is the maximum and minimum value of RF?

In chromatography, the Rf value represents the ratio between the migration distance of a substance and the migration distance of the solvent front. Rf is a coefficient called retention factor and has values that range between zero and 1.

Is RF value always less than 1?

In paper or thin-layer chromatography, the distance from the baseline of the migrated compound divided by the distance of migration of the solvent (mixture) is the Rf value. This value which is always less than 1 is characteristic of a particular compound within a defined system of chromatography.

Can RF values be less than zero?

Also the r f value will never be less than zero.

What are the 4 types of chromatography?

There are four main types of chromatography. These are Liquid Chromatography, Gas Chromatography, Thin-Layer Chromatography and Paper Chromatography. Liquid Chromatography is used in the world to test water samples to look for pollution in lakes and rivers.

What are the RF values of pigments?

The Rf value varies depending on the solvent used, but the general order of the pigments (from the highest to the lowest Rf value) usually remains the same, because the nonpolar compounds move further than the polar compounds....Explanation.PigmentRf value
Chlorophyll b0.42
Anthocyanins0.32-0.62
Xanthophylls0.15-0.35

What does an RF value of 0 mean?

indicating the molecule did not move up

What does Rf value tell you about purity?

It is primarily used to determine the purity of a compound. A pure solid will show only one spot on a developed TLC plate. In respect to this, what does the RF value tell you? The Rf values indicate how soluble the particular pigment is in the solvent by how high the pigment moves on the paper.

What are good RF values?

The best Rf (retention or retardation factor) lies between 0.3 and 0.7. If you want the Rf of your TLC spot to be smaller, i.e., the spot to be lower down on the plate, you must decrease the eluent polarity.

Which amino acid has the highest RF value?

Chromatography of amino acidsAmino acidRf value
histidine0.11
isoleucine0.72
leucine0.73
lysine0.14