Tlc which is more polar

Likewise, the polarity of the molecules can affect how far the spots travel, depending on the type of solvent used. Polar molecules will be more strongly attracted to polar solvents, and so would move further if a polar solvent was used as opposed to a non-polar solvent.

The distance that spots move can be compared to the overall distance the solvent has moved and comparisons and measurements made. Watch this video to see the correct procedure to investigate pigments in leaves using thin layer chromatography. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search.

If the points are non-polar, I don't see how making the eluent more polar will make them travel faster. Anybody care to explain? Most likely you are using "normal phase" TLC plates.

The stationary phase is silica gel, which has free hydroxyl groups making it a polar surface. In TLC, there is a competition for the plate between the analytes and the eluent. As you make the eluent more polar, the eluent will interact more with the plate leaving the analytes to be carried with the mobile phase. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? First, the TLC plate is prepared. The unknown solid is applied as a solution by dissolving it in a solvent. Some solution is drawn up into a micropipette, then applied to the adsorbent near one end of the TLC plate baseline by allowing the solution to wick out onto the adsorbent.

This process is generally referred to as "spotting your TLC plate". The chromatogram is then developed by placing the TLC plate into a TLC chamber a beaker containing the mobile phase, i. The eluent will travel up the adsorbent by capillary action to the top of the TLC plate known as the solvent front , carrying the sample with it. This process is generally referred to as "running your TLC plate".

Depending on the relative polarity of the sample and the eluent, the sample either adsorbs to the solid phase or is eluted by the mobile phase eluent. If the eluent is very polar relative to your compound, it will dissolve your sample and the sample will move with the mobile phase. Overall, the eluent and your sample will compete for a space an active site on the adsorbent stationary phase coated on the TLC plate. The more polar compound will win this competition and adhere adsorb to the adsorbent, while the rest of the mixture will move.

The more polar the compound, the more it will adhere to the adsorbent and the smaller the distance it will travel from the baseline, and the lower its Rf value.

Eluent : the solvent or mixture of solvents mobile phase used to develop a TLC chromatogram plate. Elution : the overall process of developing a TLC plate. Rf retention or retardation factor : is a measure of the distance travelled by the compound spot in relation to the distance travelled by the eluent. A desirable Rf value lies between 0. First a TLC plate is prepared by spotting the purified unknown and an authentic sample of each possible compound.

Then the TLC plate is developed. For the next step co-spotting , an authentic sample of the compound closest in Rf value to the unknown is chosen. TLC co-spotting of a second plate allows for preliminary identification of your compound. Three spots are applied to the adsorbent on the baseline of the TLC plate: the purified unknown, an authentic sample, and a co-spot of unknown and authentic sample. If the developed TLC plate shows only one row of spots, it can be concluded that the unknown has been purifed, and that the unknown is possibly the same compound as the authentic sample.

However, because Rf values are relative, not absolute, some compounds may have very similar Rf values. A mixed melting point measurement is needed to unambiguously identify the unknown compound.

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 progress of a reaction can be monitored by Thin Layer Chromatography. At various times during the experiment, a TLC plate is spotted three times, then developed and viewed under UV light: - At position 1 is an authentic sample of the starting compound. The reaction has gone to completion, when the TLC plate shows that there is no more starting material left in the reaction mixture. Earl N.

Meyer wanted to determine the purity of the benzoic acid which he had obtained from Chemical Recycling. He decided to check the purity by chromatographic analysis using a silica gel TLC plate. On the TLC plate he marked the baseline with a pencil, indicating the spotting position with a tick.

Earl dissolved about 20 mg of the benzoic acid in 1 ml of methanol. Then he dipped a micropipette into the solution and lightly touched the TLC plate at the tick marked on the baseline. Next, Earl prepared the developing chamber. He cut a filter paper to line a ml beaker. He then prepared the eluent: 10 ml of a mixture of dichloromethane and methanol in a ratio of 10 : 1. He added the eluent to the beaker, swirling it onto the filter paper to completely wet it. Earl placed the TLC plate in the developing chamber using tweezers and watched the eluent travel up the plate by capillary action.

When the eluent was near the top of the plate, he used tweezers to remove the plate from the chamber, taking care to immediately mark the solvent front with a pencil.