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What is the Chemistry Behind Reversed-Phase Flash Chromatography?

February 25, 2020 at 4:18 PM / by Bob Bickler


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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What is the Chemistry Behind Normal-Phase Flash Chromatography?

February 11, 2020 at 3:44 PM / by Bob Bickler


Our clientele at Biotage have interesting and diverse backgrounds from highly skilled synthetic chemists, to experts in natural product chemistry, to those who are just beginning they journey with chemistry. What I have learned over my 40+ year career in the “art” of chromatography is that for many of these fine folks there is a lack of understanding about chromatographic principles. This lack of understanding, I believe, is only due to their core study curriculum where separation science is used as a tool during lab work but the principles behind why a mixture’s components separate (or do not separate) perhaps are not effectively explained, understood, or studied.

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When should I choose APCI or ESI for my flash column chromatography?

February 11, 2020 at 3:16 PM / by Bob Bickler


Mass spectrometers today are typically available with either Electrospray Ionization (ESI) or APCI (Atmospheric Pressure Chemical Ionization) sources.  That’s really nice but, how do you know which source will work best when purifying your sample?

In this post I attempt to provide some guidance to selecting the ionization source best suited to your sample types.

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When should I use a pH modifier in flash column chromatography gradient?

February 11, 2020 at 3:15 PM / by Bob Bickler


Have you ever experienced compound tailing or streaking on your TLC plate or flash chromatography results and wondered what in the world is going on here? Well, there can be multiple reasons for this problem including poor mass-transfer kinetics, secondary solute-sorbent interactions, or unstable compound chemistry.

In this post, I will discuss one technique that has been shown to work time and time again to address the issue.

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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


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


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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Flash system UV detectors – similarities and differences

February 4, 2020 at 10:28 AM / by Bob Bickler


Flash purification is a preparative liquid chromatography technique. As such, it incorporates the same types of components as preparative high-pressure liquid chromatography (pHPLC) – pump, gradient mixer, column, UV detector, and fraction collector. Though all flash chromatography systems are purpose-built and essentially work the same, the one area of difference is in the UV detector design and operation.

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