Welcome to the Biotage Flash Purification Blogs.

    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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    When should I use an amine-bonded silica for flash chromatography?

    May 8, 2020 at 8:30 PM / by Bob Bickler posted in Amine, Chromatography Fundamentals, Sfär, Media and Resin, Normal Phase

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    Flash chromatography is a standard part of an organic chemist’s workflow. It is utilized after most reaction steps in order to remove most of the generated by-products and excess reagents.

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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

    6 Comments

    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 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

    6 Comments

    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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    Can I use TLC for reversed-phase flash column chromatography method development?

    January 7, 2020 at 8:49 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Troubleshooting and Optimization, Media and Resin, HPLC

    2 Comments

    I am often asked why reversed-phase TLC data does not translate well to reversed-phase flash column chromatography.  There are several reasons for this and in this post I will attempt to explain the challenges associated with reverse-phase TLC as a method development tool for reversed-phase flash chromatography.

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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 Fundamentals, Solvents, Troubleshooting and Optimization, Green, Media and Resin

    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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    Does particle shape and/or particle size impact flash column chromatography load limits?

    November 21, 2019 at 3:51 PM / by Bob Bickler posted in Chromatography Fundamentals, Media and Resin, Normal Phase, Isolera

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    There are many factors which influence successful flash column chromatography. One of those factors is sample load, which itself is influenced by things like selectivity, efficiency, dissolution solvent, and load technique. Several of these factors I have addressed in previous posts. Of these, selectivity and efficiency are specific to a media's physical and chemical characteristics.

    In this post I will show if particle size and/or particle shape can influence loading capacity.  Additionally, I will show the positive impact that surface area has on flash column chromatography purification.

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    What is the optimal sample to sorbent ratio for dry loading in flash column chromatography?

    November 1, 2019 at 9:32 PM / by Bob Bickler posted in Sfär, Selekt, Media and Resin, Loading Techniques

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    For chemists preferring or needing to dry load their crude sample mixtures to get an acceptable flash purification result, using the right ratio of sample to sorbent can be quite important.  Too much sample and solubility issues can ensue, too little sample and significant band broadening occurs, reducing the separation quality.

    In this post, I propose an acceptable ratio range based on my own experimental data.

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    Flash column equilibration – is it a waste of time or necessary step?

    November 1, 2019 at 9:30 PM / by Bob Bickler posted in Chromatography Fundamentals, Media and Resin, Normal Phase

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    slash column chromatography has been practiced by chemists since the 1970s. That practice requires the silica in the column be properly wetted to remove trapped gasses and ensure uniform flow (remember those days of not letting air into the column?). Today, with automated flash chromatography systems and pre-packed columns as the norm, chemists ask me – do I really need to pre-equilibrate my column?

    In this post I explore the impact on chromatography that equilibration, and lack thereof, has on separation performance.

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    How important is your flash column’s plate count, aka efficiency, to your purification?

    October 29, 2019 at 5:00 PM / by Bob Bickler posted in Chromatography Fundamentals, Media and Resin

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    Plate count is a theoretical number describing the separation efficiency of a chromatography column. In short, it is a measure an eluting compound's bandwidth at the time it elutes from a column, Equation 1.

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    Which sorbents work best for dry loading flash column chromatography samples?

    October 18, 2019 at 10:05 PM / by Bob Bickler posted in Chromatography Fundamentals, Solvents, Media and Resin, Normal Phase

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    For chemists needing to purify natural product extracts or synthesis reaction mixtures flash chromatography is typically the tool of choice. In previous posts I have discussed various ways to optimize the purification to obtain the highest purity compounds with maximum load in minimal time.

    Sometimes, though, chemistry gets in the way in the form of solubility issues. When this happens most often dry loading is recommended for these sample types. In this post I will show the impact various dry load sorbent options have on chromatography.

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    Purifying ionic compounds by flash column chromatography

    October 18, 2019 at 10:00 PM / by Bob Bickler posted in Reversed-phase, Troubleshooting and Optimization, Sfär, Selekt, Media and Resin

    2 Comments

    One of the more challenging purifications is that of water-soluble, ionizable compounds. Typically, normal-phase with silica is not used because of the probable non-reversible interactions, especially between the ionized amines interacting and the ionizable silanols.  With normal-phase out of the purification solution that leaves ion exchange and reversed-phase as chromatographic options.

    In this post I will discuss the use of reversed-phase and the influence pH and buffers have on the chromatography of some ionic, water soluble compounds.

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    Six key factors that impact flash chromatography

    October 18, 2019 at 9:54 PM / by Bob Bickler posted in Chromatography Fundamentals, Solvents, Sfär, Media and Resin, Automation, Cost

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    In this post I will delve into six key factors that impact your purification success in flash column chromatography.

    Previously, I have discussed the use of TLC for solvent scouting and method development and optimization. I have have also talked about cartridge size, particle size, and surface area and their impact on flash purification.  Here I integrate that information into the six factors below.

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

    October 4, 2019 at 6:17 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Synthesis, Workflow, Media and Resin, Loading Techniques

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    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 normal-phase flash chromatography.

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

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    Very polar compound purification using aqueous normal-phase flash column chromatography

    September 20, 2019 at 2:49 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Sfär, Selekt, Media and Resin, Normal Phase

    2 Comments

    Purifying polar organic compounds can be very challenging. In a previous post I have discussed using reversed-phase flash chromatography to retain and purify ionizable and ionic compounds.  My colleague, Dr. Elizabeth Denton, has also posted a blog on purifying very polar peptides as well.  Sometimes, however, despite all your efforts with reversed-phase, success is elusive. When this happens, what do you do?

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