Peptides, by nature, are composed of amino acids with potentially ionizable chemical moieties. The ionization state of any of these moieties can significantly impact the peptide’s chromatographic behavior, both in terms of peak shape and retention by the solid support. Peptide purification by reversed-phase chromatography, however, almost exclusively includes an acidic additive to the mobile phase solvents, maintaining the solution at a pH of 2-3 throughout the purification cycle. But have you ever considered trying an alternative additive in the mobile phase to improve your purification results?
In the following post I discuss the impact of mobile phase pH in the purification of oxytocin (CYIQNCPLG-NH2), a 9-amino acid peptide that requires disulfide bond-mediated cyclization for its biological activity.
Continue reading Peptide purification improvements with flash column chromatography by modulating mobile phase pH
For some cannabis-based product developers reversed-phase chromatography has become the analytical tool of choice for determining the extract content profile as well as for purification of specific cannabinoid compounds. However, the extracts often contain many other compounds which reduce load capacity and purity of the product(s) of interest and then require even more extensive clean-up.
In this post I show the results of an orthogonal flash purification approach that first uses normal-phase flash column chromatography to clean up the crude cannabis extract followed by reversed-phase C18 flash chromatography of the isolated target compounds. This orthogonal approach to purification increases the targeted product’s purity.
Continue reading Cannabis extract purification using orthogonal flash column chromatography
Compound detection challenges are, for many chemists, a part of life. In a previous post I discussed how wavelength focusing can help your flash system detect and fractionate compounds with poor chromophores. However, compounds naked to UV-Vis light, such as carbohydrates, are impossible to detect by UV when separating by liquid chromatography.
There are some alternatives, however, and in this post I will discuss the application of evaporative light scattering detection (ELSD) to flash purification.
Continue reading Detecting the undetectable in flash column chromatography, part 2
Many chemists today find they need to synthesize molecules at higher temperatures in order to force difficult reactions to proceed. Solvents such as DMF, DMSO, and NMP are commonly used in these reactions as they facilitate the use of the high reaction temperatures. However, the same attributes that make these chemicals attractive as reaction solvents make compound recovery from them very difficult including flash column chromatography. These high boiling solvents are typically polar and pose a challenge if purification is to be accomplished with normal-phase silica.
In this post I explore some options that enable purification of high boiling point solvated reaction mixtures through simple sample work-up.
Continue reading How do I purify my high boiling solvent reaction mixture using silica flash chromatography?
Have you ever wondered if there was a faster and cheaper way to purify your peptides?
My colleagues and I in the peptide community rely almost exclusively on reversed-phase HPLC for delivery of highly pure peptide products. However, this process is often very time consuming and requires expensive columns and solvents to be successful. Alternatively, peptide purification via reversed-phase flash column chromatography can be used to complete a purification in a fraction of the time and with a fraction of the costs.
Here I will show how I do gradient optimization for peptide purification via reversed-phase flash column chromatography and will highlight the similarities with standard HPLC methodologies.
Continue reading Optimizing a mobile phase gradient for peptide purification using flash column chromatography