Table of Contents
- 1 Does Rf value depend on temperature?
- 2 What do the Rf values determine?
- 3 How does temperature affect chromatography?
- 4 Why do Rf values change with different solvents?
- 5 How do you increase Rf values?
- 6 What does the Rf value mean in chromatography?
- 7 What is the relationship between structure and Rf value?
Does Rf value depend on temperature?
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.
What do the Rf values determine?
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.
How does temperature affect chromatography?
Chromatography is a series of equilibrium reactions where the analytes are either dissolved in the mobile phase or adsorbed to the stationary phase of the column. The higher the temperature, the faster the exchange of the analytes between the mobile phase and the stationary phase.
What factors affect Rf values in paper chromatography?
Factors affecting Rf value 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.
Why do Rf values differ?
The larger an Rf of a compound, the larger the distance it travels on the TLC plate. When comparing two different compounds run under identical chromatography conditions, the compound with the larger Rf is less polar because it interacts less strongly with the polar adsorbent on the TLC plate.
Why do Rf values change with different solvents?
The eluting power of solvents increases with polarity. 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 increase Rf values?
Rf values increase with increasing solvent polarity as substance are more attracted to the solvent and therefore move with it.
What does the Rf value mean in chromatography?
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. Keeping this in view, what does Rf value mean in chromatography?
Why are Rf values always between 0 and 1?
Due the fact that the solvent front is always larger from the distance travelled by the solute, Rf values are always between 0 – one extreme where solute remains fixed at its origin and 1 – the other extreme where the solute is so soluble that it moves as far as the solvent.
What does the Rf value tell you in TLC?
The Rf value is defined as the ratio of the distance moved by the solute (i.e. the dye or pigment under test) and the distance moved by the the solvent (known as the Solvent front) along the paper, where both distances are measured from the common Origin or Application Baseline, that is the point where the sample is
What is the relationship between structure and Rf value?
What is the relationship between structure and RF value? It is a measure of how strongly the substituents are attached (adsorp) to the stationary phase. The stronger the adsorption, the lower is the Rf value. By the way, Rf can be calculated by dividing the distance covered by the substituent with distance covered by the mobile phase.