Applications
In organic chemistry, reactions are qualitatively monitored with TLC. Spots sampled with a capillary tube are placed on the plate: a spot of starting material, a spot from the reaction mixture, and a "co-spot" with both. A small (3 by 7 cm) TLC plate takes a couple of minutes to run. The analysis is qualitative, and it will show if the starting material has disappeared, i.e. the reaction is complete, if any product has appeared, and how many products are generated (although this might be underestimated due to co-elution). Unfortunately, TLCs from low-temperature reactions may give misleading results, because the sample is warmed to room temperature in the capillary, which can alter the reaction—the warmed sample analyzed by TLC is not the same as what is in the low-temperature flask. One such reaction is the DIBALH reduction of ester to aldehyde.
As an example the chromatography of an extract of green leaves (for example spinach) in 7 stages of development. Carotene elutes quickly and is only visible until step 2. Chlorophyll A and B are halfway in the final step and lutein the first compound staining yellow.
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Step 1
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Step 2
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Step 3
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Step 4
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Step 5
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Step 6
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Step 7
In one study TLC has been applied in the screening of organic reactions for example in the fine-tuning of BINAP synthesis from 2-naphthol. In this method the alcohol and catalyst solution (for instance iron(III) chloride) are placed separately on the base line, then reacted and then instantly analyzed.
Read more about this topic: Thin Layer Chromatography