Ionizable compound purification using reversed-phase flash column chromatography

With most chromatographic purifications, only two solvents are needed to adequately separate compounds from each other. Unfortunately, there are instances where the separation is either poor or cannot be accomplished with “normal” elution conditions such as those with ionic or very polar organic molecules.

In this post I offer some solutions to this issue.

Continue reading Ionizable compound purification using reversed-phase flash column chromatography

How do I purify ionizable organic amine compounds using flash column chromatography?

For most organic reaction mixture purifications the process is fairly straightforward. Use hexane/ethyl acetate or, for polar compounds, DCM/MeOH.  But what do you do if this doesn’t work and your compounds are basic organic amines?

In this post, I re-examine the options available to achieve an acceptable organic amine purification when typical separation methods are insufficient. Continue reading How do I purify ionizable organic amine compounds using flash column chromatography?

What do I do if a 2-solvent gradient will not separate my sample?

Usually, a 2-solvent or binary gradient will separate your desired compound from the by-products and impurities. Sometimes though, you can encounter a mixture in which some compounds co-elute and are not separable with any binary gradient you try.

I encountered this situation recently while trying to purify a lavender essential oil and have dedicated this post to how I solved the problem.  Continue reading What do I do if a 2-solvent gradient will not separate my sample?

Does a longer flash column really provide better purification?

This is an interesting question that I am asked from time to time. There does seem to be two camps in which chemists reside – one believing longer and thinner columns provide better separations and the other preferring shorter and fatter columns to do the same chromatography.

Which is right? That is a question I will try to answer based on my own data. Continue reading Does a longer flash column really provide better purification?

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?

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?