How do I Choose the Right Column Size for Purification by Flash Chromatography?

In all my years of working with medicinal and organic chemists, I have found that choosing how many grams of silica to use for purification by flash chromatography is something frequently guessed at. Getting the size of the column right is awfully important because using too few grams of silica will doom your purification to failure and using more an optimal mass of the stationary phase means the purification  consumes excess silica, solvents, and a chemist’s time. To determine the optimal amount of silica for a purification, I rely on a factor called ΔCV (delta Column Volume) to identify the best loading capacity on any cartridge. I have also found that ΔCV this is a better loading capacity predictor for flash purification than ΔRf.

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Published by

Bob Bickler

Technical Specialist, Biotage

7 thoughts on “How do I Choose the Right Column Size for Purification by Flash Chromatography?”

  1. Hi, Our lab has been using Biotage catridges for a while now. I want to know what is the upper limit in terms of loading a sample (in gm quantities) in say a 10g catridge. I cannot find such information in the brochure we received. is it 100mg?

    1. Hi Aswin,

      A cartridge’s loading capacity is going to be based on several factors…
      1. Separation quality (TLC of your sample with various solvent blends can help you find the best solvent pairing to maximize the separation). TLC data will also help you determine the cartridge’s loading capacity for your sample.
      2. Purification goal or goals. If you need maximum purity then you may need to reduce the amount of compound injected. If you need to purify more material but can sacrifice purity then you can load more if you need both yield and purity move up to a larger cartridge or consider a step gradient (can usually double the loading capacity).

      The rule-of thumb is 1% of the media mass but I would rather optimize the separation to maximize purity and load then make the 1% load assumption.

  2. What an interesting blog ! Great job & interesting topics, I’m looking forward to your new posting.
    Hope this blog has a long life and, particulary, frequent updates…

    1. Thank you, Valerie, for your kind response. I just posted another topic on Tuesday on choosing between linear and step gradients. There are more scheduled throughout the year.

      Best regards,

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