TLC - thin layer chromatography - basics

A day in the life of a synthetic organic chemist.

TLC is one of the most basic means of analysing a reaction mixture. New reactions are generally monitored every x minutes to check their progression, and TLC functions as a rudimentary way of checking a compound's purity and to compare against other compounds to check what the impurities may be. It also paves the way for follow-up methods such as PLC, column chromatography etc.

TLC works by using a stationary phase, i.e. a powdery solid, through which the compounds may pass at variable speed. They are pulled through the solids by use of an eluent, a mixture of solvents with a specially designed polarity, that pulls the compounds you apply on the TLC paper to varying degrees. Using stronger eluents (more polar mixtures, such as 5% HCOOH in MeOH, to name a very polar one) will pull compounds along more strongly, while weaker eluents (very apolar ones, for example 2% DCM in hex, to name a very apolar one) will make compounds move very little. Different compounds will, due to their varying polarity, move through the stationary phase with different speeds, and through this, separation is achieved, showing you how many compounds are (at least) present in the mixture, and if you have a reference, you can identify if a certain compound is in the mixture or not.

There are many subtleties, tips, tricks and traps to TLC, which despite seemingly a very simple analytical method, will catch the unwary synthetic organic chemist off guard. In the interests of time and accessibility of the information, I didn't cover these aspects.

More to come on subjects related to TLC.

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Tags:

• synthetic
• organic
• chemistry
• TLC
• thin
• layer
• chromatography
• analytical
• reaction
• mixtures
• impurities
• monitoring

[Jovibeatz]

Well explained, thank you!

[cmbatay49]

astig! :)



[Nespithe]

Well explained. Thank you!

[JGalz]

Thank you, this was helpful. I'm excited to do a TLC lab tomorrow!