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Chemistry In Pictures

Chemistry in Pictures: Spectrum of impurity

by Manny I. Fox Morone
July 27, 2023


Under an ultraviolet light, fluorescent pink, yellow, purple, and green bands of color squiggle wildly across a preparatory thin-layer chromatography plate.
Credit: Anna Poryvai

Anna Poryvai, a postdoc at the Swiss Federal Institute of Technology (EPFL), suggested that a student in her lab synthesize a fluorescent dye intermediate. To purify the intermediate, the student learned how to run a preparative thin-layer chromatography (prep-TLC) plate, and this was the result.

Lavender, pink, and purple bands of color squiggle wildly across a white preparatory thin-layer chromatography plate.
Credit: Anna Poryvai

Prep-TLC works best when a mixture runs up the plate forming straight, horizontal bands, each band containing a different compound from the reaction mixture that travels at its own speed. Unfortunately, the separation didn’t happen so cleanly, leaving behind these squiggly bands that started to overlap on their way up the TLC plate. The various fluorescent compounds look striking under ultraviolet light (above) and don’t look too shabby under visible light either (below).

Poryvai says they were still able to salvage some product, which they used to make other fluorescent dyes for cell tracking and labeling. But a substantial part of this product could not be neatly scratched off and had to be left on the plate.

Submitted by Anna Poryvai. Follow @PoryvaiAnna on Twitter.

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