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 is the result of applying too much sample in chromatography?
Applying too much sample may result in
large, diffuse bands of chemical moving up the plate
, making it difficult to accurately measure the distance the chemical has been transported.
What happens if you add too much compound to a TLC plate?
3) What could happen if you spot too much of a compound on the TLC plate? Answer:
The spot would show trailing
.
What would be the result of applying too much compound to a TLC plate quizlet?
What will be the result of applying too much compound to a TLC plate?
The spots of various components will overlap to the point where the number of different components cannot be ascertained resulting in erroneous conclusions about separation
and/ or the purity of the sample.
What affect will there be on the TLC experiment if too much compound mixture is used in making the spotting solution?
Do not put spots too close together on the spotting line
, or too close to the edge. o This will cause the spots to streak together, or to be cut off by edge. Too much sample= streaking (the compounds will overlap, thus skewing the results).
Can two compounds have the same Rf value?
The larger an Rf of a compound, the larger the distance it travels on the TLC plate. … If two substances have the same Rf value,
they are likely (but not necessarily) the same compound
. If they have different Rf values, they are definitely different compounds.
What is the problem if the solvent level is too high?
If a development solvent of too high a polarity is used,
all components in the mixture will move along with the solvent and no separation will be observed
(Rf's will be too large). 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).
Why must the spot be applied to the TLC plate above the level of development 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
.
What would happen to the Rf values of the spots if you ran the TLC of A and B in the 50 50 hexane acetone solvent system?
What would happen to the Rf values of the spots if you ran the TLC of A and B in the 50:50 hexane: acetone solvent system? The Rf values of the spots (if the TLC was ran in the more polar solvent system 50:50 hexane: acetone)
would increase for both A and B
.
What would be the consequences of immersing the initial spots in your filter paper with your developing solvent?
If the spots were immersed they would
dissolve in the solvent and be pulled down into the solvent itself
. … The solvent rises up the paper by CAPILLARITY. The solvent flows through the paper, over and past the mixture of substances.
What will be the appearance of a TLC plate if a solvent of too high polarity is used?
Some components may have such similar polarities that they appear under one spot after development. If a development solvent of too high a polarity is used,
all components in the mixture will move along with the solvent and no separation will be observed
(Rf's will be too large).
What should the spots placed at least 5mm from the edge of the plate?
The lanes should not be placed too close to the edge (keep at least 5mm away from each edge), as it is not unusual for
solvent
to travel slightly “fast” at the edge where capillary action of the solvent is greater (Figure 2.24).
What would you expect to observe after plate development and visualization as a result of the following errors in the use of TLC?
What would you expect to observe after plate development and visualization as a result of the following errors in the use of TLC: (A)
the solvent level in the developing chamber is higher than the spotted sample
. The compound will be dissolved away; hence no spots will be seen.
What happens if the spots are made too small when preparing a TLC plate for development?
What happens if spots are made too small when preparing a TLC plate for development? What happens if spots are made too large when preparing a TLC plate for development? Why must the spots be above the level of development solvent in chamber?
They will dissolve in the development solvent if they were submerged
.
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.
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.
