For most chemists, flash purification is a means to an end. In other words, it is a tool needed to purify and isolate one compound from a mixture of compounds so that the next reaction can occur with reduced by-product formation. Other than choosing between normal– or reversed-phase, there typically is not much thought put into cartridge selection, especially not related to stationary phase media porosity.
For most small molecules, this approach makes sense, but for larger molecules and very lipophilic compounds, factoring for media porosity should be included. In this post, I will discuss the impact media porosity can have on chromatographic performance.
Continue reading How does media pore size impact small-molecule flash column chromatography?
Compounds precipitating during flash chromatography is at best an inconvenience when working up your crude reaction mixture. Precipitation during purification typically happens in the column or in the tubing exiting the cartridge.
In this post, I will propose a strategy that can minimize and perhaps prevent this issue from occurring.
Continue reading How to prevent compound precipitation during flash column chromatography
Have you ever experienced compound tailing or streaking on your TLC plate or flash chromatography results and wondered what in the world is going on here? Well, there can be multiple reasons for this problem including poor mass-transfer kinetics, secondary solute-sorbent interactions, or unstable compound chemistry.
In this post, I will discuss one technique that has been shown to work time and time again to address the issue.
Continue reading When should I use a pH modifier in flash column chromatography gradient?
When it comes to the purification of polar, water-soluble compounds reversed-phase chromatography is the most commonly used approach. However, because of strong stationary phase – mobile phase repulsion forces, the use of highly aqueous (90-100% water) solvent systems has been shown to provide less retention than needed. This issue has led to the development of “aqueous compatible” reversed-phase media.
In this post I explore if these types of phases are actually needed by looking at the separation of some very polar and low log P compounds using a “traditional” C18-bonded silica.
Continue reading Are reversed-phase flash chromatography columns designed for aqueous solvents necessary?