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Chemistry In Pictures

Chemistry in Pictures: How the TLC got its spots

by Manny I. Fox Morone
July 31, 2023

A thin-layer chromatography plate covered in about 100 irregular brown spots.
Credit: Mudiganti Sastry/Neuland Laboratories

Organic chemists often talk about spots in the context of thin-layer chromatography (TLC) plates. Usually they’re referring to the tiny blobs that climb from the bottom to the top of a TLC plate as a mixture separates into its components, each one representing a different compound. But in this case, Mudiganti Sastry, deputy director at Neuland Laboratories in Hyderabad, Telangana, India, got more spots than he bargained for when he dipped this TLC plate in a 2,4-dinitrophenylhydrazine (DNP) solution, a technique used to better visualize spots containing aldehyde compounds. He initially saw just a couple of spots and was able to conclude that the aldehyde was no longer present in the reaction mixture, so he left the plate out for a while and started doing something else. When he came back to his bench, he was surprised to find that the DNP had created all these spots after reacting with something else on the plate. Sastry says the pattern reminds him of an Indian leopard, but he isn’t quite sure what created the spots or why they didn’t show up immediately.

Submitted by Mudiganti Sastry/Neuland Laboratories

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