When should I use dry loading instead of liquid loading with flash column chromatography?

Many microwave assisted organic synthesis (MAOS) reactions use polar solvents such as alcohols, DMF, DMSO, because they absorb and transfer microwave energy very efficiently.  However, the downside of using polar, microwave absorbing solvents is that they can interfere with the flash chromatography that follows it injected directly onto a flash cartridge.

In this post, I discuss why dry loading can be advantageous when purifying polar-solvated reaction mixtures.

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Published by

Bob Bickler

Technical Specialist, Biotage

2 thoughts on “When should I use dry loading instead of liquid loading with flash column chromatography?”

  1. Hi Bob. I had an incident recently where I was dry-loading on celite using a competitor’s system and solid-load cartridge (we also have a Biotage system). I developed the method at small scale and it worked fine. The new method promised to increase loading by 4 times and also increased the “column yield” (Qty recovered/Qty loaded). When I scaled up, loading 75 g of crude in about 300 g celite, the solid-load cartridge leaked very badly and I had to stop the run. It was my theory that the plunger seal in the cartridge failed, but co-workers thought that the celite/crude mixture was too dense and caused excessive back-pressure. In my mind, the most common use of celite is as a filtration aid, and so you would think that it would lessen backpressure in a solid-load cartridge, not increase it. Can you comment on this issue and recommend an optimum ratio of celite to crude. Thank You.

    1. Hi John,

      Your ratio seems perfect to me. I always recommend 1:3 to 1:4 crude/sorbent ratios as I have found I get the best results with them. I assume your small scale purification had the same ratio.

      Do you recall if the small-scale and large-scale dry loads had similar density/free-flow characterists (was the small-scale a free-flowing powder and the large-scale clumpy)? If the the dry load was clumpy, it may have impeded flow generating some pressure but I doubt enough to cause your issue. That being the case, I tend to agree with your assessment about poor sealing plunger.

      BTW, are you the John Dolan who wrote for LC-GC?

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