In our more environmentally aware climate, chemical and pharmaceutical companies now prioritize reducing organic solvent use in chemistry labs. Employees and shareholders alike are pushing their companies to become greener which impacts how chemistry, both synthesis and purification, is performed.
Cannabis entrepreneurs continually seek to differentiate themselves from others in the market. Some focus on THC while others focus on CBD. What I have seen recently after attending some cannabis-specific conferences is a growing interest in isolating/purifying some of the minor, naturally occurring phytocannabinoids such as CBG and CBDV.
Varying the concentrations of mobile phase solvents during flash purification chromatography enhances the ability of the technique to effectively isolate the desired compound from reaction by-products and unconsumed reagents. Choosing how these concentrations will be varied over time has a significant effect on the purity and recovery of desired compounds.
What is the best starting strong solvent %? What is the ending strong solvent %? Should the mobile phase concentrations vary gradually in a linear manner or should they vary step-wise or something else altogether? Most separations are performed once, occasionally a handful of times. Because of this, spending effort optimizing a gradient is just not very productive unless there are aids in choosing the gradient profile that provides an effective purification with minimum effort.
Software in flash chromatography instruments, makes it simple to create a gradient. Now, what should that gradient look like?
In this post I compare isocratic, step, and linear gradients and provide some sage advice on choosing among them.
If you synthesize organic amine compounds, especially heterocyclic, secondary, or tertiary amines, you likely have encountered problems with their chromatography using silica columns. With the amine groups being basic and silica being acidic, there is a natural attraction between the two. This sometimes strong attraction often requires the use of a competing amine in the solvent system. Modification of the mobile phase with the addition of a solvent like triethyl amine can provide a successful purification. Often times the use of an amine-modified stationary phase can provide the needed conditions to avoid the acid-base interaction that can interfere with a successful flash chromatography purification.
In this post I will discuss how amine-functionalized silica can simplify organic amine purification and your life (at least in the lab).
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.
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?”
Equilibrating silica flash chromatography columns is something I always do. There are chemists who see this as an unnecessary, time-and-solvent-wasting step. However, because getting consistent, predictable results is a priority for me, I equilibrate to remove the variability that can be caused by heat generated as solvent initially contacts the silica. Consistency is really important when running flash column chromatography because re-runs are time consuming and may put your compound at risk.
In this post, I examine the role of equilibration speed and duration to show its impact, or lack there of, on purification performance.
Reversed-phase flash chromatography usage is increasing rapidly. In fact, over the past 10 or so years, reversed-phase flash chromatography use has increased a dramatic 650%! This is amazing growth despite the fact that reversed-phase flash columns are considerably more expensive than silica columns and you need to evaporate water from your fractions. So, what’s driving this change in chemists’ modus operandi?
In this post, I will explain why chemists are increasingly using reversed-phase flash chromatography for routine, intermediate, and final compound purification and provide and example as well.