Welcome to the Biotage Flash Purification Blogs.

    How does gradient slope impact flash chromatography loading capacity?

    February 9, 2021 at 1:40 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Troubleshooting and Optimization, Scale-Up

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    For many synthetic chemists the primary purification goal is to isolate as much synthetic product as possible with a minimum of 80% purity. The go-to technique for product isolation is flash purification (flash chromatography), especially for intermediates.

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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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    Can reversed-phase flash column chromatography be greener?

    December 3, 2020 at 7:24 PM / by Bob Bickler posted in Reversed-phase, Green

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    In previous posts I offered some suggestions to improve the “greenness” of normal-phase flash purification.  As the use of reversed-phase flash purification has increased the past few years I thought I would explore how to potentially make it greener too.

    So, with that in mind, let's take a look at the use of acetone in place of acetonitrile as a reversed-phase flash chromatography solvent.

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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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    Can reversed-phase chromatography compound elution volume/time be predicted?

    November 18, 2020 at 9:26 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Method development

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    When developing reversed-phase flash chromatography methods it is important to understand the impact that a change in solvent ratio has on compound retention and, therefore, separation performance. Unlike normal-phase chromatography where you can optimize separations using TLC and a wide variety of solvents and solvent ratios, reversed-phase limits you to 3 to 4 solvents, including water, using either HPLC or small flash columns for method development. Those solvents include:

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    Non-aqueous (or nearly so) reversed-phase flash column chromatography – a nice alternative for purifying lipophilic compounds

    October 23, 2020 at 5:25 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, purification

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    For most organic and medicinal chemists, normal-phase flash chromatography is used to purify and isolate many types of organic compounds, most with some polar functional groups which help them retain on silica. However, some compound mixtures are water insoluble such as lipids, carotenoids, terpenes, tocopherols, polyaromatic and other hydrocarbons with minimal polar functionality.   These lipophilic compounds do not retain well on silica and do not dissolve readily in water making them really difficult to separate.

    In this post I will talk about a technique called non-aqueous reversed-phase chromatography that can be very effective at separating and purifying very lipophilic compounds.

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    How do I convert my HPLC method to flash chromatography?

    July 14, 2020 at 2:00 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, HPLC

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    As synthetic chemistry has evolved, so has flash chromatography. Target molecule synthesis is becoming more complicated and the synthetic products more polar. This shift in compound polarity has changed purification strategy from almost entirely normal-phase flash chromatography using silica to a significant percentage of flash chromatography now being reversed-phase during the past 9 or so years.

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    How do I scale-up my reversed-phase flash chromatography method?

    April 27, 2020 at 2:53 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Scale-Up

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    Scaling up reversed-phase flash chromatography methods is often necessary as reaction scale increases. This is especially true when other non-chromatographic purification techniques do not work or meet purity and/or yield needs.

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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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    How does reversed-phase flash chromatography compare to prep HPLC?

    March 26, 2020 at 2:42 PM / by Bob Bickler posted in Reversed-phase, Green, Sfär, Selekt, HPLC

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    For medicinal chemists, maximizing the synthetic yield of their newly created intermediate compound is their priority. More times than not, flash chromatography is used to purify these intermediate compounds to at least 80% purity. Final compounds, however, not only require high yield but maximum attainable purity, typically in excess of 95%. For this purity level, chemists will either send the reaction mixture to an in-house prep HPLC lab or perform their own preparative HPLC compound purification, if it is available in the lab.

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    What is the Chemistry Behind Reversed-Phase Flash Chromatography?

    February 25, 2020 at 4:18 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Sfär

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    In my previous post, I talked about the "Chemistry Behind Normal-phase Flash Chromatography", the most common form of liquid-solid chromatography. In this post, I focus on reversed-phase flash chromatography and how it differs from normal-phase.

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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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    5 Tips on extending reversed-phase flash chromatography cartridge life

    January 7, 2020 at 8:51 PM / by Bob Bickler posted in Reversed-phase, SPE solid phase extraction

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    With reversed-phase flash column chromatography becoming increasingly popular for routine purification, understanding how to make the cartridges last (since they cost more) is important to know. 

    In this post I will mention a few tips to prolong reversed-phase cartridge life.

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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

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    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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    So, which detector should I use for flash column chromatography?

    January 3, 2020 at 3:38 PM / by Bob Bickler posted in Reversed-phase, Detector, Normal Phase

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    In my role as senior technical specialist at Biotage I am often asked about compound detection options. For most flash chromatography methods, UV is the default detection tool since many compounds do absorb some UV light.

    Diode array UV detectors provide chemists choices in wavelength selection providing the ability to widen or narrow the wavelength range needed to detect specific compounds and enhance their sensitivity.

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    How do I decide between normal- or reversed-phase flash column chromatography?

    December 30, 2019 at 4:49 PM / by Bob Bickler posted in Chromatography Fundamentals, Reversed-phase, Green, Normal Phase, Isolera, HPLC

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    Choosing a good purification strategy is an important for successful crude compound purification. A major factor in your strategy is choosing between normal-phase or reversed-phase chromatography.  How do you choose?

    In this post, I will provide some simple guidance on helping determine which route to take.

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