Welcome to the Biotage Flash Purification Blogs.

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

    February 11, 2020 at 3:13 PM / by Bob Bickler posted in Gradient, Solvents, Troubleshooting, Media

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    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).

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

    February 11, 2020 at 3:12 PM / by Bob Bickler posted in Gradient, Normal phase, Optimization, Solvents, Mass-directed purification

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    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. 

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    Why do I see more peaks than I expect with flash column chromatography?

    January 8, 2020 at 3:23 PM / by Bob Bickler posted in Chromatography, Gradient, Normal phase, Solvents, Troubleshooting

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    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.

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

    November 21, 2019 at 3:59 PM / by Bob Bickler posted in Amine, Chromatography, Gradient, Normal phase, Optimization, Polar, Solvents, Troubleshooting, TLC

    4 Comments

    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.

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    How does mobile phase organic solvent choice impact reversed-phase flash column chromatography?

    November 21, 2019 at 3:45 PM / by Bob Bickler posted in Gradient, Optimization, Polar, Solvents, TLC

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    Organic and medicinal chemists frequently utilize flash chromatography to purify their reaction mixtures. Normal-phase flash chromatography is most often used but may not the best methodology, especially when the compounds are quite polar and/or ionizable.

    For these molecules, reversed-phase flash chromatography is preferred but often is not used due to an uncertainty regarding the best solvent choices and the reversed-phase mechanism.  In this post, I will discuss how organic solvent choice in reversed-phase chromatography can influence the chromatographic separation.

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    How many times can I reuse my flash chromatography column?

    November 21, 2019 at 3:40 PM / by Bob Bickler posted in Gradient, Normal phase, Optimization, Polar, Solvents, Troubleshooting

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    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.

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    The Step Gradient Explained

    November 1, 2019 at 9:37 PM / by Greg Saunders posted in Gradient, Selekt

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    Up to six compounds can be easily separated with an automated step-gradient optimizer embedded in modern flash chromatography systems.

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    What is a Chromatography Gradient?

    October 2, 2019 at 3:27 PM / by Bob Bickler posted in Gradient, Optimization

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    Gradients, used in chromatographic methods, assist with chemical separation and elution. They begin with “weak” elution conditions and end with “strong” elution conditions.

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    How do I Create an Efficient Gradient Flash Chromatography Method?

    September 20, 2019 at 2:58 PM / by Bob Bickler posted in Gradient, Optimization

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    For most organic and medicinal chemists flash chromatography is just another step in the synthesis work flow - react, analyze, purify, react, analyze, purify... until the final product is made. The desired product of each reaction, and the mixture of other species present are, of course, different with each cycle.  Separating the desired compound efficiently without a lot of hassle is something I have written about in this post as well as in others in this series.

    In this post, I've written about how that TLC (thin layer chromatography) plate you use for monitoring your reaction can be used to create reliable, efficient, effective gradients.

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    How to Choose Between Linear Gradients and Step Gradients for Flash Chromatography

    April 12, 2019 at 12:51 PM / by Bob Bickler posted in Gradient, Optimization

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    Varying the concentrations of mobile phase solvents during  flash purification chromatography enhances the ability of the technique to effectively isolate the desired compound from reaction by-products and unconsumed reagents.  Choosing how these concentrations will be varied over time has a significant effect on the purity and recovery of desired compounds.

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    The three reasons you should be using step gradients for flash column chromatography

    March 5, 2019 at 9:34 PM / by Bob Bickler posted in Chromatography, Gradient, Normal phase

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    For most synthesis and natural product chemists, flash chromatography is the primary tool for purification and isolation of compounds of interest. Purification methods include flash system defaulted linear gradients (e.g. 0-100%), active gradient modification (on-the-fly) during purification, and unique method creation based one either the chemist’s experience or TLC data (typically a linear gradient).

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