Testing Unknown Substances with TLC

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In summary, the use of standards in TLC is not a common practice. TLC is mainly used for monitoring reactions and identifying components in a sample. While there are no specific standards, knowing the expected compounds in a sample can aid in identifying spots. In some cases, a standard may be used for comparison, such as in the case of TEMPO and 4-hydroxy-TEMPO.
  • #1
thE3nigma
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What are standards used for in TLC. Are they used so as to compare some unknown substances, and then from that to determine what chemicals/molecules have been separated or are being used?
 
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  • #2
There are none. TLC is an ad hoc system. I only use it to monitor the progress of a reaction or to identify how many components might be in a sample. In the case where I monitor the reaction, the reactants are the standards. The product(s) must be purified individually (usually by flash column) and identified by other techniques.

Rf is not a specific test...
 
  • #3
While there are no standards, if you know what compounds to expect in your sample, you can always put them on the side to help identify spots.
 
  • #4
Borek said:
While there are no standards, if you know what compounds to expect in your sample, you can always put them on the side to help identify spots.

Although my TA never told us what the standard spot was containing, he did draw two molecules that were of same composition but with one having an added -OH group. So I am assuming that the standard was to be used for comparing spots formed.
 
  • #5
Was one of those two molecules an alkene and the other an alcohol (cyclohexene and cyclohexanol, for example)?
 
  • #6
no, the molecules he drew were TEMPO and 4-hydroxy-TEMPO.
 

Related to Testing Unknown Substances with TLC

1. What is TLC and how does it work?

TLC stands for Thin Layer Chromatography, which is a technique used to separate and analyze mixtures of compounds. It works by using a stationary phase (a thin layer of material such as silica gel or alumina) and a mobile phase (a solvent) to separate the components of a mixture based on their different affinities for the two phases.

2. How can TLC be used to identify unknown substances?

TLC can be used to identify unknown substances by comparing the movement of the unknown substance on the TLC plate to the movement of known substances. If the unknown substance has a similar Rf value (retention factor) to a known substance, it is likely the same compound.

3. What factors can affect the results of TLC?

The results of TLC can be affected by factors such as the type of stationary phase used, the composition and pH of the mobile phase, and the temperature and humidity of the environment. The technique also relies on accurate spotting and careful handling of the TLC plate.

4. Can TLC be used to quantify substances?

While TLC is primarily used for qualitative analysis, it can also be used for quantitative analysis by comparing the intensity of the spots on the TLC plate to known standards. However, this method is not as accurate as other quantitative techniques such as HPLC or GC.

5. Are there any safety precautions to take when performing TLC?

Yes, safety precautions should always be taken when performing TLC or any other scientific experiment. This includes wearing appropriate personal protective equipment, working in a well-ventilated area, and following proper handling and disposal procedures for chemicals. It is also important to carefully read and follow the instructions and safety guidelines provided by the manufacturer of the TLC materials being used.

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