Why do I see more peaks than I expect with flash column chromatography?

Are you observing more chromatographic peaks than you expect compared to TLC or other assessment data?  Well, it could be that your method is separating some isomers or, it could be that there is an actual method issue.

In this post I will discuss what could cause a method issue and suggest some ideas as to how to fix it. Continue reading Why do I see more peaks than I expect with flash column chromatography?

Using pH to optimize reversed-phase flash chromatography separations

I have previously posted on the topic of normal-phase optimization by evaluating different solvent blends or mixtures. I have also touched on reversed-phase method development as well suggesting chemists use HPLC to optimize their purification.

In this post, I will look at the impact modifying mobile phase pH can have on reversed-phase separations.

Continue reading Using pH to optimize reversed-phase flash chromatography separations

How do I remove an annoying MS TIC background?

Have you ever run flash column chromatography with mass detection (Flash-MS) and observed the total ion current or TIC increase during the purification only to find that there was no discernible compound contributing to the effect?

In this post I discuss how I came across this issue and the solution I found to work.

Continue reading How do I remove an annoying MS TIC background?

Why is my UV baseline changing during flash column chromatography?

A baseline that rises or drops when using flash chromatography with a UV detector can be a problem, especially if you are trying to collect compounds with poor detectability or that exist in low quantities.

In this post I will talk about the causes and solutions for a rising (or even dropping) baseline. Continue reading Why is my UV baseline changing during flash column chromatography?

Using TLC to Scout Flash Chromatography Solvents

TLC is the tool most used for normal-phase flash chromatography method development. For many chemists, a solvent system of hexane (or heptane) + ethyl acetate is the first, and sometimes only, solvent system evaluated. Though often useful, ethyl acetate may not always provide the optimal purification conditions. Continue reading Using TLC to Scout Flash Chromatography Solvents