Why is my UV baseline changing during flash column chromatography?

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. Continue reading Why is my UV baseline changing during flash column chromatography?

Pesticide remediation of Cannabis oil- Myclobutanil removal by flash chromatography

Myclobutanil is a fungicide of considerable concern to the cannabis industry.  Its removal from extracted cannabinoid oil is the hot topic among processors and extractors.  In today’s post we will present how flash chromatography can be used for the remediation of the pesticide, thereby significantly reducing it from the final product in a single step.

Continue reading Pesticide remediation of Cannabis oil- Myclobutanil removal by flash chromatography

Does mass detection make-up solvent choice matter?

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.

Continue reading Does mass detection make-up solvent choice matter?

In-line scavenging simplifies flash column chromatography reaction mixture purification

I am always grateful for the feedback I get from my blog readers.  Today’s blog is in response for multiple requests for  tips on purifying complex mixtures and suggestions for alternative sample loading techniques.

In this post, I will attempt to address both, to some degree anyway, with a single example using a scavenger resin.

Continue reading In-line scavenging simplifies flash column chromatography reaction mixture purification

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

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.

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

Using adducts and fragments to identify compounds in mass-directed flash chromatography

Over the past several years, automated flash chromatography has evolved to include in-line mass detection.  Typically, these single-quadrupole mass detectors are outfitted with either an atmospheric pressure chemical ionization source (APCI) or an electrospray chemical ionization source (ESI).  While this technical advance in flash chromatography has helped chemists detect and isolate pure compounds with a known molecular weight, verifying the identity of that compound can sometimes be a challenge as the detected mass may not match that which you expect due to fragmentation and/or adduct formation.

In this post I will offer some assistance in determining adducts and fragments.

Continue reading Using adducts and fragments to identify compounds in mass-directed flash chromatography

What impact do buffers have on APCI mass detection?

APCI (atmospheric pressure chemical ionization) and ESI (electrospray ionization) are the two most frequently utilized mass detection tools for automated flash chromatography.  In a previous post, I discussed differences between the two detectors and the compound types best suited for each source.

Because these two sources ionize differently, there are cases when additives are needed in the make-up solvent and cases when they should not.  In this post, I will show the impact that adding a buffer or acid has on APCI detection.

Continue reading What impact do buffers have on APCI mass detection?

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

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

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

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?

In this post I will discuss using normal-phase flash chromatography with aqueous solvents, a form of HILIC (hydrophilic interaction liquid chromatography), to purify those compounds that just will not stick well enough on reversed-phase media. Continue reading Very polar compound purification using aqueous normal-phase flash column chromatography

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

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