Stable-bond polymeric reversed-phase/weak anion-exchange mixed-mode stationary phases obtained by simultaneous functionalization and crosslinking of a poly(3-mercaptopropyl)methylsiloxane-film on vinyl silica via thiol-ene double click reaction

• Published in: Journal of Chromatography A 2019-05, Vol.1593, p.110-118
• Main Authors: Bäurer, Stefanie, Zimmermann, Aleksandra, Woiwode, Ulrich, Sánchez-Muñoz, Orlando L., Kramer, Markus, Horak, Jeannie, Lindner, Wolfgang, Bicker, Wolfgang, Lämmerhofer, Michael
• Format: Article
• Language: English
• Subjects: Column bleeding; Mixed mode chromatography; Oligonucleotides; Polymer coating; Thiol-ene click reaction; Zwitterionic stationary phase
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2019.01.078

•New polymeric mixed-mode reversed-phase/weak anion exchangers were synthesized.•Simultaneous ligand and polythiol immobilization by double thiol-ene click reaction.•Oxidation of residual thiols to sulfonic acids afforded a zwitterionic phase.•Complementarity to reversed-phase and hydrophilic interaction chromatography.•Stress tests confirmed enhanced stability of the new polymer bonded phases. A polymeric reversed-phase/weak anion exchange (Poly-RP/WAX) mixed-mode stationary phase has been prepared by coating of a poly(3-mercaptopropyl)methylsiloxane film on vinyl-modified silica (100 Å, 5 μm) and simultaneous in situ functionalization with N-(10-undecenoyl)-3-aminoquinuclidine as well as crosslinking to the vinyl silica surface by solventless thiol-ene double click reaction. Such bonding chemistry showed greatly enhanced stability compared to brush-type analogs with bifunctional siloxane bonding to silica. Solid-state 29Si-CP/MAS NMR confirmed the immobilization of the siloxane layer. pH-Dependent ζ-potential determinations revealed a high anion-exchange capacity over the entire pH range with a maximum around pH 5. Oxidation of residual thiols yielded a zwitterionic Poly-RP/WAX/SCX mixed-mode phase with sulfonic acid endcapping and shifted the still net positive surface charge to lower ζ-potentials. It allowed a faster elution of strongly retained anionic species in particular of multiply negatively charged analytes such as oligonucleotides. Chromatographic tests under RPLC and HILIC elution mode with various test substances documented the multimodal utility and complementarity in retention profiles compared to RP, HILIC and commercial mixed-mode phases.