Testing Unknown Substances with TLC

[thE3nigma]

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?

 

[chemisttree]

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...

 

[Borek]

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.

 

[thE3nigma]

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.

 

[chemisttree]

Was one of those two molecules an alkene and the other an alcohol (cyclohexene and cyclohexanol, for example)?

 

[thE3nigma]

no, the molecules he drew were TEMPO and 4-hydroxy-TEMPO.