How can I perform normal-phase and reversed-phase column chromatography on one flash system?

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. 

Continue reading How can I perform normal-phase and reversed-phase column chromatography on one flash system?

How do particle size and flow rate affect normal-phase flash column chromatography?

Media particle size and solvent flow rate play major roles in chromatographic separations including flash purification.  This is true in both reversed-phase chromatography (aka partition chromatography) as well as normal-phase chromatography.

The roles played are related to the overall compound mass-transfer kinetics and diffusion/dispersion as they migrate through the column.  Smaller particles reduce sample dilution by reducing interstitial volume, while flow rate impacts the ability of molecules to efficiently pass through the porous particles.

In this post, I will show how both particle size and flow rate impact flash chromatography.

Continue reading How do particle size and flow rate affect normal-phase flash column chromatography?