Pirkle-type chiral stationary phase on core-shell and fully porous particles: Are superficially porous particles always the better choice toward ultrafast high-performance enantioseparations?

- Novel Pirkle-type Whelk-O1 core-shell chiral stationary phase was prepared.
- Difficulty of efficiently packing polar core-shell particles is reported.
- Effect of surface coverage on adsorption-desorption kinetics is pointed out.
- Kinetic characterization of new stationary phase in normal phase mode is described.
- Separation of enantiomers in less than 1 s was achieved.

Pirkle-type Whelk-O1 chiral stationary phase (CSP) was prepared on 2.6 μm superficially porous particles (SPPs). The chromatographic behavior of columns packed with this new CSP was compared with that of columns packed respectively with 1.8 and 2.5 μm Whelk-O1 fully porous particles (FPPs). In the comparison, both thermodynamic and kinetic aspects were considered. Contrary to initial expectations, chiral columns packed with 2.6 μm SPPs were quasi-comparable to those packed with 2.5 μm FPPs, apparently due to larger contributions to band broadening from both eddy dispersion and, especially for the second eluted enantiomer, adsorption-desorption kinetics. These findings raise the question if SPPs, in spite of the undeniable advantages of their morphology to speed up mass transfer, are always the best choice for high-efficient ultrafast chiral separations. The last part of the work focuses on the use of short columns (10 mm long) and very high flow rates to realize the separation of the enantiomers of trans-stilbene oxide (TSO) in normal phase mode in less than 1 s.