Toward enantioselective nano ultrahigh-performance liquid chromatography with Whelk-O1 chiral stationary phase

In this study, a Whelk-O1 chiral stationary phase immobilized on 2.5 μm silica particles was employed in nanoLC. Two nanocolumns (180 and 250 mm long, 75 μm id) with a single polymeric organic monolithic outlet frit were packed under high-pressure ultrasonic-assisted packing procedure. The monolithic outlet frit was prepared by thermal polymerization of methacrylate-based monomers affording high-mechanical stability and high-pressure resistance. Very efficient enantioseparations with more than 70 000 plates/m were achieved in normal phase mode by eluting (+/-) acenaphthenol. Nanocolumns were also tested in RP mode by using on-line MS detection with nano-spray ESI ion source. Kinetic performances of columns in RP mode were comparable to those in normal phase-conditions.