Why must the spot applied to chromatography paper be above the level of the developing solvent?

It is extremely important that the solvent in the developing chamber be lower than the spotos on the plate, because the solvent must be drawn upward through the sample in order to draw the sample along with it. If the sample is dipped in to the solvent, the sample may simply dissolve in the developing solvent.

Why do you use a small spot in chromatography?

In paper chromatography, a starting line in drawn on the paper in pencil (pencil so that it does not dissolve in the solvent and affect the results). Small spots of each sample are placed on the starting line. If a substance is more strongly attracted to the paper than the solvent then it will move a short distance.

How does chromatography work Why does a spot separate into more than one spot?

Saturating the atmosphere in the beaker with vapour stops the solvent from evaporating as it rises up the paper. As the solvent slowly travels up the paper, the different components of the ink mixtures travel at different rates and the mixtures are separated into different colored spots.

Where should the mixture be placed in chromatography?

A spot of the mixture is placed near the bottom of a piece of chromatography paper. The paper is then placed upright in a suitable solvent , such as water. As the solvent soaks up the paper, it carries the mixtures with it. Different components of the mixture will move at different rates.

Why must the spot of the sample be applied to the TLC plate above the level of the developing solvent?

Used to separate volatile components of a mixture with low B.P. Why must the spot be applied to the TLC plate above the level of development solvent? Low B.P. and thus more likely to evaporate off the plate before separation can occur.

Why must the spots be above the solvent level?

In paper chromatography, why must the start line be above the solvent level? The start line above the solvent level allows the solvent to move past the start line, carrying the dissolved samples along with it.

Why is it important to keep the spots applied to TLC slide for chromatography as small as possible?

keeping small spots on your silica plate (or whatever your immobile phase is) will allow for greater resolution between the spots allowing for more accurate Rf calculations and solvent separation/preparation if using to isolate a compound in a mixture.

Does each spot on the developed chromatography paper or plate represent one substance?

Thin Layer Chromatography (TLC) is a separation technique requiring very little sample. 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.

Why is it recommended to spot the analyte on the TLC plate in a position that will not be immersed in eluent solvent?

The reason is that the plate will be immersed in the eluting solvent to effect the separation, and the eluting solvent should not touch the spots when the separation begins.

Why must the spot be applied to the TLC plate above the level of development solvent?