Fast separation of low molecular weight analytes on structurally optimized polymeric capillary monoliths

The optimization of recently introduced tetrakis(4-vinylbenzyl)silane (TVBS)-derived capillary monoliths to suit the fast separation of small molecules was accomplished by simultaneous changes in both the stoichiometry of the polymerization mixture and in the polymerization temperature. Four types of monoliths were prepared by varying the polymerization temperature within 60 and 65 °C as well as by changing the monomer content between 15.0 and 20.0 wt.%. Changes in the porosity and morphology of the capillary columns were studied applying inverse size exclusion chromatography (ISEC), nitrogen sorption (BET), and scanning electron microscopy (SEM). All monoliths were used for the reversed-phase separation of various sets of low molecular weight analytes such as alkyl benzenes, aryl amines, carboxylic acids, and a mixture of phenols and carbonyl compounds. Comparable efficiency and performance towards the different sets of analytes were observed. With optimized monolith structures, the fast separation of six-alkyl benzenes was accomplished within less than 2 min. This was made possible by a high linear solvent flow (10 mm/s) at low column pressure drops (<15 MPa).