# What is the Rf value biology?

The Rf (retardation factor) value is the ratio of the solute’s distance travelled to the solvent’s distance travelled. The word comes from chromatography when it was discovered that a given component will always travel the same distance in a given solvent under the same conditions.

## How do you calculate Rf value in chromatography?

To calculate an Rf value, divide the distance travelled by the component – in other words, the distance from the starting pencil line to the coloured spot -by the distance travelled by the solvent. Rf values are important because each component has a fixed Rf value under a specific set of conditions.

## What is Rf and its formula?

Retention/retardation factor (Rf) can be calculated by the relative migration values of solute (analyte) and the solvent front. Rf = Migration of analyte / Migration of solvent front. The calculation of the Rf value is basically the calculation of relative affinities of a solute with the stationary and mobile phases.

## 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.

## What is the Rf value in paper chromatography?

In paper chromatography when the conditions are kept constant, a particular compound always travels a fixed percentage of the distance traveled by the solvent front. The ratio of the distance the compound travels to the distance the solvent travels is called the Rf value.

## How do you find the Rf value of an amino acid?

The Rf value can be calculated by measuring the distance of the substance from its starting point in millimeters, as well as the distance the solvent traveled from its starting point in millimeters, then dividing the substance distance by the solvent distance.

## What 2 distances are important when calculating Rf values in chromatography?

For each dye, the Rf value is calculated. To do this, 2 distances are measured: The distance between the baseline and the dye. The distance between the baseline and the solvent front, which is how far the solvent has travelled from the baseline.

## How does Rf value relate to polarity?

The fastest moving spot has the highest Rf value. polar (fastest moving), and the spot with the lowest Rf value is the most polar (slowest moving). Rf values are frequently used to compare a known and an unknown substance to determine if they are the same.

## How do you calculate molecular weight from Rf values?

Use a graphing program, plot the log (MW) as a function of Rf. Generate the equation y = mx + b, and solve for y to determine the MW of the unknown protein. Run the standards and samples on an SDS-PAGE gel. Process the gel with the desired stain and then destain to visualize the protein bands.

## What is chromatography GCSE?

Paper chromatography is used to separate mixtures of soluble substances. These are often coloured substances such as food colourings, inks, dyes or plant pigments.

## Can two compounds have the same Rf value?

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.

## What factors affect Rf values in paper chromatography?

• The solvent system.
• Composition of the mobile phase.
• The working temperature of the system.
• The quality of the paper used.
• The distance through which the solvent runs.
• The quality and nature of solvents used.
• The polarity of components.
• The pH of the solvent or mobile phase.

## What does the Rf value say about the pigments?

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

## Is chlorophyll a or b more polar?

Molecular Structure and Polarity The distinctions between the chlorophylls, which are more polar than β-carotene is slight: chlorophyll a has a methyl group (Y=CH3) in a position where chlorophyll b has an aldehyde (Y=CHO). This makes chlorophyll b slightly more polar than chlorophyll a.

## Why amino acids have different Rf values?

Why do amino acids have different Rf values? Different amino acids have different Rf values because their R groups are chemically different; this gives each amino acid its own unique solubility in the developing solvent and, therefore, its own unique migration distance.

## Which amino acid has highest Rf value?

sessilis, reveals the presence of 5 amino acids with the Rf values: 0.35, 0.43, 0.55, 0.72, and 0.77. The Rf values for standard amino acids cysteine, glycine, aspartic acid, and proline are 0.21, 0.39, 0.37, and 0.40, respectively.

## Do nonpolar compounds have higher Rf?

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).

## How do you calculate the polarity index of a solvent?

One way you could actually calculate a solvent’s polarity is by using its dielectrict constant, which is used to measure how well the solvent can partly cancel the field strenght of the electric field of a particle added to it. The higher the value of a solvent’s dielectric constant, the more polar it will be.

## How do you calculate the Rf of a protein?

The Rf is defined as the migration distance of the protein through the gel divided by the migration distance of the dye front. The distance should be measured from the top of the resolving gel to the band of interest, as illustrated on the gel.

## What is the Rf of aspirin?

The Rf values are 0.70 for salicylic acid and diflunisal, 0.67 for aspirin and methyl salicylate, 0.60 for gentisic acid, 0.57 for p-aminosalicyclic acid, and 0.40 for salicyluric acid.