Using a “dry” loading technique with flash chromatography typically improves compound purity and overall separation quality compared to liquid loading. The reasons for this I have prophesized previously and include:
How does flow rate impact my flash column chromatography separation? This is the kind of question I frequently get. After all, we all know that flow rates that are too high or too low can result in bad prep HPLC chromatography. Well, this is not necessarily true in flash chromatography.
In chromatography there are three inter-related variables which impact your separation and are represented on the chromatographer’s triangle.
Getting the most benefit from your crude sample purification with column chromatography or flash chromatography involves optimizing many variables. In previous posts I have talked about selecting the best solvents, their ratios, and maximizing load based on TLC Rf data. These are all important chromatography-generated variables but now I would like to share some tips on actual technique differences and their impact on purification performance.
As the popularity of prep-scale, reversed-phase flash chromatography increases, so does the frequency that I get asked this question, "How do I determine loading capacity in reversed-phase flash chromatography?"
In the world of HPLC, loading capacity isn’t normally a concern as it is primarily an analytical technique. In the synthetic organic chemistry world, most purification is performed with silica gel where flash column purification methods are developed and loading capacity estimated from TLC data. However, when normal-phase flash does not work and reversed-phase flash is needed, the question of how to determine reversed-phase loading capacity comes up.
Method transfer from reversed-phase TLC (thin layer chromatography) to reversed-phase flash column chromatography can be very challenging. Because of this, I often recommend using HPLC for reversed-phase flash chromatography method development. This really is a straight-forward process if you start with the right HPLC column and know a little about your HPLC system's detector.
In this post, I will share some tips on how to develop a reversed-phase flash purification method using HPLC.
In order to perform flash chromatography consistently, the equipment you use must be properly maintained by following some “best practices”. These best practices include using clean solvents (I typically use ACS grade), volatile organic modifiers, and quality columns.