For chemists, flash chromatography is part of their everyday synthesis workflow. For most syntheses, crude reaction mixtures are purified by normal-phase (aka adsorption) chromatography. There are times, however, where the crude mixture’s complexity and polarity make normal-phase chromatography very challenging. For these situations, reversed-phase (aka partition) chromatography may be a preferred option.
But, if you have only one flash system available, can you, should you, and how do you efficiently switch from non-polar, normal-phase solvents to polar, reversed-phase solvents – and back again without issues? In this post I'll attempt to shed some light on the topic.