Quick Answer: What Happens If The Spots Are Made Too Large When Preparing A TLC Plate For Development?

Why silica gel is used in TLC?

Silica gel is by far the most widely used adsorbent and remains the dominant stationary phase for TLC.

The surface of silica gel with the highest concentration of geminal and associated silanols is favored most for the chromatography of basic compounds because these silanols are less acidic..

How many spots should a pure product show on a TLC plate under UV light?

one spotA 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.

What does a high RF value mean?

A high Rf (Ie 0.92) would refer to a substance that is very non-polar. Ie that substance moved a 92% of the entire distance the solvent traveled. A low Rf value (0.10) would refer to a substance that is very polar. IE that substance was only able to move 10% of the entire distance the solvent traveled. Term.

What happens if a TLC plate is allowed to develop too long?

Chemicals move up a TLC plate along with the solvent being used to develop the plate. … This means that if left long enough, the chemicals will all merge together at the top of the plate, eliminating any separation that you could have seen on the plate.

Is it possible to distinguish two spots that have the same Rf value?

5- Yes, it is possible to distinguish two spots that have the same Rf value but represent different compounds.

Which solvent system gave the best results?

Which solvent system gave the best results? The 75% hexane and 25% ethyl acetate gave the best results.

What problem will result if too much sample is applied to the TLC plate?

If the TLC plate runs samples which are too concentrated, the spots will be streaked and/or run together. If this happens, you will have to start over with a more dilute sample to spot and run on a TLC plate.

What will be the appearance of a TLC plate of a solvent of too low polarity?

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.

What does the RF value tell you?

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.

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

The solvent level has to be below the starting line of the TLC, otherwise the spots will dissolve away. … 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.

What are the limitations of TLC?

Disadvantages of TLC include application to only nonvolatile compounds, limited resolution capability (separation numbers or peak capacities of 10–50), and the absence of fully automated systems, although the individual steps of the technique can be automated.

What happens if the spot line and positions are marked on the plate with a ballpoint pen when preparing a TLC plate for development?

What happens if the spot line and positions are marked on the plate with a ballpoint pen when preparing a TLC plate for development? Ballpoint pen ink consists of organic compounds that will move with the development solvent and cause additional spots to appear on the plate.

What happens if the solvent line reaches the top of your TLC plate?

When the solvent has reached the top of the plate, the plate is removed from the developing chamber, dried, and the separated components of the mixture are visualized. If the compounds are colored, visualization is straightforward. Usually the compounds are not colored, so a UV lamp is used to visualize the plates.

What happens if the spots are made too small when preparing a TLC plate for development?

2What happens if the spots are made too small when preparing a TLC plate for development? -If the spots are made too small when preparing a TLC plate for development, it will be very difficult to observe the results or there will be no spots at the end of the process.

What would the result be if the spots are too concentrated in a TLC experiment?

Streaking: If the sample spot is too concentrated, the substance will travel up the stationary phase as a streak rather than a single separated spot. In other words, the solvent can not handle the concentrated sample and in result, moves as much of the substance as it can up the stationary phase.

How long should you run a TLC plate for?

Question: How Long Should You Run A TLC Plate For? Until The Solvent Front Is About Half Way Up. Until The Solvent Front Is At The Top Of The Plate. 2 Minutes.

Why is it important the ink dots are not submerged in the solvent?

It is important that the solvent level is below the line with the spots on it. … 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.

Can RF values be greater than 1?

Long Answer: Rf is the “Retardation Factor”, which is the ratio of the distance traveled by a compound in a mobile phase compared with the distance traveled by the front of the mobile phase itself. It is always greater than or equal to zero, and less than or equal to 1.