Developing an achiral SFC screen

Here at Reach Separations we are not ones to shy away from promoting the benefits of SFC. Both the time and energy savings during post processing and evaporation, and the reduction in organic solvents used, make SFC a greener technique than traditional normal phase methods.
However, we admit that we have mainly used the technique for chiral separations and not explored the benefits for achiral separations. Until recently! Diki has long since returned to the University of Warwick but her project has left a lasting impression on the lab.
Initially aiming high, wishing to produce a database that enabled SMILES structure IN, achiral SFC column OUT proved to be step too far. However, we have developed a screening protocol that enables us to cover the widest range of chemical space with the minimum number of stationary phases.
Diki took 17 commercially available phases and judged the retention of 22 drug-like molecules on each phase. Using retention factor as the only judging criterion a correlation matrix was created looking for any trends between calculated physiochemical properties and retention factors.
A relationship was observed between molecular refractivity and pKa, and retention factor on a given phase. This relationship is summarised in the table below.

From the table it can be seen immediately that many of the columns cover a similar chemical space, this makes it easy to eliminate certain columns from our screen. We have selected the following five columns to make up our achiral screen:

GreenSep Nitro
Acquity UPC2 Torus 1-AA
Acquity UPC2 Torus DEA
Acquity UPC2 BEH 2-EP
Acquity UPC2 BEH

This limits our primary achiral screen to less than 40 minutes. The decrease in screening time means achiral SFC can now be run in conjunction with our standard RP methods for all achiral jobs in the laboratory.

To find out more please see the full article in this month’s ChromSoc magazine.

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