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

      October 4, 2019 at 6:30 PM / by Bob Bickler posted in cartridge, chromatography, Developments, flash column, Flash Theory, gradient, isolera, Mass Detection, normal phase, reversed-phase gradient, selectivity, SNAP cartridge, solvent strength, solvents, terpene, terpenoid, User Tips

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      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. 

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      Using TLC to Scout Flash Chromatography Solvents

      September 20, 2019 at 3:06 PM / by Bob Bickler posted in Flash Theory, solvents, tlc, method development

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      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.

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      How do I determine loading capacity in reverse phase flash column chromatography?

      July 10, 2019 at 3:01 PM / by Bob Bickler posted in Developments, Flash Theory

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      As the popularity of prep-scale, reversed-phase flash chromatography increases, so does the frequency that I get asked this question, "How do I determine loading capacity in reversed-phase flash chromatography?"

      In the world of HPLC, loading capacity isn’t normally a concern as it is primarily an analytical technique.  In the synthetic organic chemistry world, most purification is performed with silica gel where flash column purification methods are developed and loading capacity estimated from TLC data.  However, when normal-phase flash does not work and reversed-phase flash is needed, the question of how to determine reversed-phase loading capacity comes up.

      In this post I will attempt to provide some guidelines to help you understand and determine reversed-phase flash chromatography loading capacity.

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

      June 13, 2019 at 4:59 PM / by Bob Bickler posted in Developments, Flash Theory

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      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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      How to Optimize TLC to Enhance Purification by Flash Chromatography

      June 13, 2019 at 4:53 PM / by Bob Bickler posted in Flash Theory

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      In this article I discuss the optimization of solvent ratios to generate ideal Rf (retention factor) values on TLC plates.  Then I show how maximizing efficiency of flash chromatography achieves higher loading with rapid and reliable isolation of compounds, reduced solvent use and improved separation.

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