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Chemistry In Pictures

Chemistry in Pictures: Seeing spots

by Manny Morone
October 29, 2019

An NMR tube and apparently blank TLC plate under visible light.
Credit: Liselotte Karulf and Samuel K. Pedersen

This thin-layer chromatography (TLC) plate and NMR tube take on different appearances under various wavelengths of light. This became exceedingly clear to Samuel K. Pederson and Liselotte Karulf, a PhD and master’s student, respectively, at Aarhus University in Troels Skrydstrup’s lab, which researches how to use carbon dioxide to synthesize valuable natural products. After separating a reaction mixture, the researchers examined the TLC plate with visible light (top), but didn’t see any spots. When they switched to so-called short-wave UV light (254 nm wavelength), the TLC plate glowed green because of dyes added during manufacturing, so the chemicals of interest absorbed the UV light and created dark spots (middle). In the case of this reaction, the chemicals were fluorescent enough under long-wave UV light (365 nm wavelength, bottom) to reveal their positions on the TLC plate and to make the mixture in the NMR tube glow blue as well.

An NMR tube fluorescing cyan and a TLC plate with blue and purple spots under long-wave ultraviolet light.
Credit: Liselotte Karulf and Samuel K. Pedersen

Submitted by Liselotte Karulf and Samuel K. Pedersen. Follow the Skrydstryp group on Instagram (@CADIAC_au) and Twitter (@SkrydstrypGroup).

Do science. Take pictures. Win money. You can enter our monthly photo contest here. This photo is part of our #SeparationScene Chromatography Contest sponsored by Restek.

Related C&EN Content:

An NMR tube and green TLC plate with dark spots under short-wave ultraviolet light.
Credit: Liselotte Karulf and Samuel K. Pedersen

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