Category: User Tips

Flash column chromatography equilibration speed – how fast can you go?

Equilibrating silica flash chromatography columns is something I always do.  There are chemists who see this as an unnecessary, time-and-solvent-wasting step.  Because getting consistent, predictable results is a priority, I equilibrate to remove the variability that can be caused by heat generated as solvent initially contacts the silica. Consistency is really important when running flash column chromatography because re-runs are time consuming and may put your compound at risk.

In this post, I examine the role of equilibration speed and duration to show its impact, or lack there of, on purification performance.
Continue reading Flash column chromatography equilibration speed – how fast can you go?

How does solvent choice impact reversed-phase flash chromatography separations?

I have recently posted on how solvent choice influences the separation of hard to resolve compounds using normal-phase flash chromatography. As a chemist with an inquiring mind, I thought I would expand my research beyond normal-phase and see what happens in reversed-phase.

In this post, I share my results. 

Continue reading How does solvent choice impact reversed-phase flash chromatography separations?

How can I rapidly remediate THC from CBD in my hemp extract using flash column chromatography?

Tetrahydrocannabinol, aka THC, is a hallucinogen found in cannabis and, to a lesser degree, in hemp.  Though THC is legal in some locations in the US and Canada, there is a growing market for its non-hallucinogenic cousin, cannabidiol (CBD), which has purported medical benefits.

The problem with isolating CBD from cannabis and hemp is contamination from THC, which is typically present at a moderate to high percentage. In this post, I will provide some insight into rapidly purifying CBD to remove THC. Continue reading How can I rapidly remediate THC from CBD in my hemp extract using flash column chromatography?

How many times can I reuse my flash chromatography column?

Flash chromatography – a purification tool for both organic chemists and natural product researchers.  This tool is essential when you need to remove impurities from your targeted product, or products, in order to get them pure.  To reduce the costs associated with flash chromatography, some chemists try reusing the same column over and over, not always with success.

A question I am frequently asked is “how many times can I reuse my flash column?” Although I have previously addressed this topic, I feel it is worth another look. In this post, I will attempt to address this question by providing a bit more science behind the cartridge reuse question.

Continue reading How many times can I reuse my flash chromatography column?

How can I modify my flash chromatography method to separate chemically similar compounds?

The challenges organic, medicinal, and natural product chemists face are many: from designing reactions, to optimizing synthesis, work-up / extraction, and purification / isolation of the desired compound or compounds. Among those issues related to purification / isolation is the common problem of separating compounds with similar chemistry that either co-elute or separate poorly.

In this post I will discuss some tips on how to “resolve” this issue (yes, pun intended).

Continue reading How can I modify my flash chromatography method to separate chemically similar compounds?

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?

How does solvent choice impact flash column chromatography performance?

Selectivity and solvent strength are the most important factors that determine success or failure of a chromatographic separation. These two independent dynamics apply to both normal- and reversed-phase chromatography and should be optimized, especially when high fraction purity is needed.

In this post I will discuss the impact that elution solvent choice has on both normal- and reversed-phase purification. Continue reading How does solvent choice impact flash column chromatography performance?

Pushing flash column chromatography loading limits

A question I hear a lot from chemists is “how much can I load”. The answer is always “it depends on your separation quality”.  At that point I begin asking about the TLC data and purification goals. Purification goal setting should be your first step and the question to answer is – what do I need this purification to achieve? Is the goal high purity, high yield, or some combination.  Remember, you will typically sacrifice purity for high yield and yield for high purity so optimization is an important consideration.

In this post I will discuss the results of a study I conducted where I continually increased the crude sample load until my target compound purity fell below specific targeted levels to understand the real loading limitation. Continue reading Pushing flash column chromatography loading limits