Table of Contents
What factors affect the Rf values?
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.
How do you increase Rf value?
Either choose a different eluent (solvent) or adjust the solvent ratio by increasing the percentage of the nonpolar solvent relative to the polar solvent in the eluent. The reverse holds true for the Rf of a spot that you want to be larger, i.e., the spot to be further up on the plate.
Do Rf values have to be exact?
Rf values are therefore not exactly reproducible from one experiment to another, even if an effort is made to carry them under the exact same conditions. When comparing two or more substances, they must be run simultaneously on the same plate or the comparison is invalid.
Does the Rf value always stay the same?
The Rf value for a particular substance is always the same if the same solvent and stationary phase are used. R f values vary from 0 (the substance is not attracted to the mobile phase) to 1 (the substance is not attracted to the stationary phase).
How can I improve my TLC experiment?
Resolution in thin-layer chromatography (TLC) can be improved by reducing the size of the sample spot and increasing the separation between the developed spots.
What is a good retention factor?
Well, the largest gain in resolution is achieved when the retention factor value is between 1 and 5. If the k value is lower than 1, analytes may be eluting with other sample components or with the solvent. K values above 5 only provide minimal increases in resolution.
How can I increase my TLC separation?
You must know the nature of your compounds. If they are alkaloids then adding few drops of diethylamine in your solvent system will help you get better separation. you can re-run the TLC and will see the spot getting separated. Thereafter you can run the column and gradually increase the polarity.
Why should all Rf values be 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.
How do you increase chromatography results?
In liquid chromatography, the easiest way to increase a solute’s retention factor is to use a mobile phase that is a weaker solvent. When the mobile phase has a lower solvent strength, solutes spend proportionally more time in the stationary phase and take longer to elute.