What happens if the spots are made too large

Answer: The spots would dissolve into the reservoir of eluting solvent. The Rf value is defined as the ratio of the distance moved by the solute i. 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 addition, tentative identification of the unknown compound can be made through TLC analysis. The silica gel manufacturer coats the silica gel on the TLC plate with a material that fluoresces illuminates green under ultraviolet UV light more specifically nm light.

To be UV - active compounds must possess a certain degree of conjugation, most commonly aromatic compounds. If the solvent is of too low a polarity the components will not move enough, and again separation will not occur Rf's will be too small.

Note that the spotting solvent is simply used as a vehicle to transfer the material to be analyzed to the TLC plate. Once the transfer is made the spotting solvent evaporates.

By capillary action, the solvent will immediately start rising up the TLC plate. As soon as it comes into contact with the spots , it will cause the less polar components of the mixture to start moving.

What happens when the spots are made too large when preparing a TLC plate for development? If the spot too large it may cause the shape of the final spot become skewed and elongates. Allow the solvent to climb up the TLC plate , and remove the plate when the solvent nearly reaches the top. Quickly, before the solvent evaporates, mark the solvent front.

TLC can be used to monitor the progress of a reaction, identify compounds present in a given substance. TLC is also used to separate the identical compounds in a mixture. Many standard methods in industrial chemistry, environmental toxicology, food chemistry, water, inorganic and pesticide analysis, dye purity, cosmetics, plant materials, and herbal analysis rely upon TLC as the preferred approach. Non polar compounds are travel faster on silica gel.

Silica gel is generally used stationary phase and the empirical formula is SiO2. Begin typing your search term above and press enter to search. Press ESC to cancel. Ben Davis February 19, Why do you use a pencil rather than a pen to mark the spotting line on a TLC plate? Why is it important to use only a pencil to mark the starting line of the chromatogram? Why is it necessary to use a pencil instead of a pen or a marker?

Why do you have to use a pencil and not a pen when marking the baseline and any labels on the chromatography paper? What happens if the spots are made too large when preparing a TLC plate for development? How long should you run a TLC plate for? What would happen if you spotted too much sample on the TLC plate?

Does a higher Rf value mean more polar? Why silica gel is used in TLC? What does TLC tell you about purity? What is TLC used for? What are the advantages of TLC? Why do we use TLC? What is TLC principle? What is TLC plate? Place a melting point capillary and in the dark blue part of the Bunsen burner flame. Hold it there until it softens and starts to sag. Quickly remove the capillary from the flame and pull on both ends to about times its original length.

If you pull the capillary inside the flame, you will have a "piece of art", but not a good spotter. Allow the capillary to cool down, and then break it in the middle. Make sure that you break off the closed end on one of them. Do not use gloves when you pull capillaries. You will have much better control without them! The thin end of the spotter is placed in the dilute solution; the solution will rise up in the capillary capillary forces.

Touch the plate briefly at the start line. Allow the solvent to evaporate and spot at the same place again. This way you will get a concentrated and small spot. The spots should be far enough away from the edges and from each other as well. If possible, you should spot the compound or mixture together with the starting materials and possible intermediates on the plate. They will serve as internal reference since every TLC plate is slightly different. The solvent level has to be below the starting line of the TLC, otherwise the spots will dissolve away.

The lower edge of the plate is then dipped in a solvent. Non-polar solvents will force non-polar compounds to the top of the plate, because the compounds dissolve well and do not interact with the polar stationary phase.

Take the plate out and mark the solvent front immediately.