title: Characterization of polymer monolithic columns for small-molecule separations using total-pore-blocking conditions.
abstract: This study involves the investigation of the meso- and micropores in polymer monolithic materials and the performance characterization of polymer monoliths for the separation of small molecules. Pore-blocking experiments, that involve the blocking of the stagnant pores with a solvent which is immiscible with the mobile phase, were conducted to determine interstitial volumes of a commercially-available polymer monolithic column. After blocking the meso- and micropores a clear reduction in the column void time was observed. Using this approach, the internal porosity (defined as the sum of the meso- and micropores with respect to the volume of the monolithic material) was determined at 12.5%. Peak-dispersion measurements were conducted by applying reversed-phase (RP) conditions. The high plate-height values for small-molecule separations are mainly attributed to the large eddy-diffusion and mobile-phase mass-transfer contributions to band broadening, related to the inhomogeneous structure and presence of parabolic profiles in the macropores. The C-term contribution of early eluting (retained) compounds was higher than that of the late eluting compounds. This could be attributed to the low zone-retention factors of early-eluting compounds and consequently a large stationary-phase mass-transfer contribution. However, peak-dispersion measurements with blocked meso- and micropores carried out at RP conditions indicated that the Cs-contribution alone is likely not be the main cause of peak broadening. Finally, (1)H spin-spin (T2) relaxometry NMR measurements were conducted with water and ACN in the monolithic material.
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, Brussels, B-1050, Belgium.
authors.forename: Catherine
authors.initials: C
authors.lastname: Stassen
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, Brussels, B-1050, Belgium.
authors.forename: Gert
authors.initials: G
authors.lastname: Desmet
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, Brussels, B-1050, Belgium.
authors.forename: Ken
authors.initials: K
authors.lastname: Broeckhoven
authors.affiliation: Vrije Universiteit Brussel, Physical Chemistry and Polymer Science, Pleinlaan 2, Brussels, B-1050, Belgium.
authors.forename: Luk
authors.initials: L
authors.lastname: Van Lokeren
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, Brussels, B-1050, Belgium. Electronic address: seeltink@vub.ac.be.
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Eeltink
mesh_terms: D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D011108:Polymers; D012997:Solvents; D014867:Water
keywords: Absorption; Column characterization; Gel porosity; Polymer monolith