In past posts I discussed which solvents work best for sample loading in reversed-phase flash chromatography. Recently, I was asked to provide some insight as which solvents are best in normal-phase flash column chromatography.
Liquid loading of samples onto chromatography columns is not always straight-forward. If your sample is dissolved in the mobile phase, that can work but may not be the best choice, especially if running a gradient.
In this post I show you some work I have done that opens up quite a few options for solvents used for loading samples and some surprising results with DMF.
Continue reading Which sample solvents work best with normal-phase flash column chromatography?
It is hard for me to believe but the flash purification blog is a year old. This started as an idea within the technical group here at Biotage to share knowledge of flash column chromatography that we have learned over 30-plus years. Though I was reticent at first, now after only a year its hard to imagine my world without this blog.
Those of you who read this blog regularly are growing in number and each time I post we set a new record for numbers of visitors, thank you. There are certainly some posts that are popular. I’ll spend the rest of this post sharing some details and at the end of the post, I ask that you take a couple of minutes to provide feedback in the form of an on-line survey.
Continue reading Celebrating 1 year of the flash purification blog
Sometimes it feels as if organic chemistry and chromatography are a mixture of art and science. Maybe its because of the necessary creativity needed to address the variety of challenges that we face almost daily. Frankly, its what I find most interesting about this world.
One of the bigger challenges facing chemists is the ability to detect and collect compounds with little or no UV absorption during flash purification. In this post I will talk about a technique that I have found to be quite useful when trying to purify mixtures containing one or more poor absorbers.
Continue reading Detecting the undetectable in flash column chromatography using wavelength focusing
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.
Continue reading How and when to insert an isocratic hold in flash column chromatography
This is an age-old question that has been around a long time, perhaps as long as me (and I have been around a while) – “Does silica dissolve in methanol?” For many years I have heard from organic and medicinal chemists as well as students of organic chemistry that silica is dissolved by methanol when running a DCM/MeOH gradient.
In this post I will share the results of some tests I performed that hopefully will help clarify what is happening to the silica when in contact with methanol.
Continue reading Does methanol really dissolve silica during flash column chromatography?
In many of my previous posts I have used the term column volume, typically abbreviated as CV, as a value used to help determine separation quality and loading capacity. However, I recently was asked a question about this topic from a chemist who understands the column volume concept but wanted to better understand its definition and how it is determined.
In this post I will explain what a column volume is and how it is determined empirically.
Continue reading So, what exactly is a column volume in flash column chromatography and how is it determined?