Welcome to the Biotage Flash Purification Blogs.

    What is the maximum volume I can load on my reversed-phase flash column?

    May 19, 2021 at 2:11 PM / by Bob Bickler posted in Reversed-phase, Solvents, loading capacity

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    With all forms of chromatography there are limitations relating to sample load – both mass and volume. These are independent variables which, for the best results, should be investigated separately. In this post, I will address the impact of increasing solvent volume on flash chromatographic separations.

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    Does flash column equilibration volume impact purification results?

    April 20, 2021 at 3:21 PM / by Bob Bickler posted in Chromatography Fundamentals, Solvents, Sfär, Selekt, purification, equilibration

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    Chemists using silica columns for normal-phase flash chromatography typically equilibrate their columns prior to loading their samples. Companies manufacturing automated flash purification systems often have the equilibration volume and flow rate pre-programmed and tied to a column size. Some of these flash system companies allow equilibration volume to be edited while others have the volume fixed.  Is one of these options better than the others? In this post I discuss how equilibration volume impacts flash chromatography results.

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    Can Flash Chromatography be Green? Part 1

    January 4, 2021 at 2:30 PM / by Bob Bickler posted in Amine, Chromatography Fundamentals, Solvents, Green, Media and Resin

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    The term “Green Chemistry” has become a major part of the science community’s lexicon. When I think about green chemistry and its relationship to flash column chromatography I think of two specific areas where it applies...

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    Using pH to optimize reversed-phase flash chromatography separations

    December 8, 2020 at 8:51 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Solvents, Media and Resin, Detector

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    I have previously posted on the topic of normal-phase optimization by evaluating different solvent blends or mixtures. I have also touched on reversed-phase method development as well suggesting chemists use HPLC to optimize their purification.

    In this post, I will look at the impact modifying mobile phase pH can have on reversed-phase separations.

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    Does mass detection make-up solvent choice matter?

    December 7, 2020 at 4:18 PM / by Bob Bickler posted in Solvents, mass detection

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    An interesting question, at least to me. Depending on the detector brand, some mass spectrometer manufacturers recommend acetonitrile while others recommend methanol. Is there a real difference between these solvents?

    In this post I look at how acetonitrile and methanol compare when used with an APCI source.

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    When should I add acid to my detector make-up solvent when using mass-directed flash chromatography?

    November 20, 2020 at 2:57 PM / by Bob Bickler posted in Amine, Chromatography Fundamentals, Reversed-phase, Solvents

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    Increasingly, organic and medicinal chemistry labs use mass-directed flash chromatography to isolate synthesized compounds. Mass-directed flash chromatography benefits are many, including collecting only the targeted molecule(s) in the reaction mixture. This approach simplifies compound purification since you know what you have made and it's associated mass.

    However, there are mass detection nuances that can be challenging. One of these is to know when an acid should be added to the mass detector’s make-up solvent to protonate targeted molecules. In this post, I will provide some insight on this topic.

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    Why is my UV baseline changing during flash column chromatography?

    November 6, 2020 at 8:15 AM / by Bob Bickler posted in Chromatography Fundamentals, Solvents, Media and Resin

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    A baseline that rises or drops when using flash chromatography with a UV detector can be a problem, especially if you are trying to collect compounds with poor detectability or that exist in low quantities.

    In this post I will talk about the causes and solutions for a rising (or even dropping) baseline.

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    Ionizable compound purification using reversed-phase flash column chromatography

    October 16, 2020 at 4:54 PM / by Bob Bickler posted in Chromatography Fundamentals, Solvents, Media and Resin

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    With most chromatographic purifications, only two solvents are needed to adequately separate compounds from each other. Unfortunately, there are instances where the separation is either poor or cannot be accomplished with “normal” elution conditions such as those with ionic or very polar organic molecules.

    In this post I offer some solutions to this issue.

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    How best to extract reaction products from high boiling solvents

    September 22, 2020 at 2:23 PM / by Bob Bickler posted in Solvents, Workflow, Extraction method optimization

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    Organic chemistry syntheses often use polar, high boiling point solvents to facilitate high temperature reactions. However, these solvents also can complicate down-stream compound purification, either by evaporation, crystallization, or even flash chromatography.

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    5 Steps to successful flash chromatography

    April 20, 2020 at 10:15 AM / by Bob Bickler posted in Amine, Chromatography Fundamentals, Reversed-phase, Solvents, Media and Resin, Loading Techniques, Normal Phase, Pillar Page

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    The bane of organic synthesis for most chemists is purification rather than synthesis. Synthetic reaction mixtures are rarely devoid of impurities so some type of purification is necessary.  Most often flash chromatography is used but for many chemists, it is less well understood than their chemical reaction and provides some level of anxiety.

    In this post, I will summarize the five most important steps to creating a successful flash chromatography method and thus the anxiety associated with it.

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    Understanding silica – why matching TLC and flash silica is important for good flash column chromatography

    April 15, 2020 at 12:00 PM / by Bob Bickler posted in Chromatography Fundamentals, Solvents, Sfär, Media and Resin, Normal Phase

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    Recently, I posted an article explaining why high performance TLC plates are not needed for method development for high-performance flash chromatography.  Based on some excellent feedback, I see a need to discuss silica chemistry and its impact on chromatography.

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    How and when to insert an isocratic hold in flash column chromatography

    April 13, 2020 at 7:00 PM / by Bob Bickler posted in Chromatography Fundamentals, Solvents

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    For many chemists using generic linear gradients and even gradients based on TLC the purification results often are not selective enough to separate all of the compounds in their mix.  This is especially true if your target has a closely eluting impurity. One method used to try and increase resolution is the use of an isocratic hold or gradient pause during purification.

    In this post I examine the use of the isocratic hold to determine how well it works and when/if it should be inserted into a gradient method.

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    How does an alkaline pH affect normal-phase flash chromatography separations?

    April 7, 2020 at 6:25 PM / by Bob Bickler posted in Amine, Chromatography Fundamentals, Solvents, Sfär, Normal Phase, Isolera

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    The products of organic synthesis are designed with specific functional groups in order to possess desired properties. Depending on the compound’s functionality, it can be neutral, acidic, or basic as determined by a compound measurement called pKa or acid dissociation constant. Compounds with low pKa are typically acidic while those with high pKa tend to be basic. Compounds with a pKa near 7 are deemed neutral.

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    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 Chromatography Fundamentals, Reversed-phase, Solvents, Sfär, Selekt, Media and Resin, Normal Phase

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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 Chromatography Fundamentals, Solvents, Troubleshooting and Optimization, Normal Phase, Isolera

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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 Fundamentals, Solvents, Troubleshooting and Optimization, Normal Phase, Isolera

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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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