Investigation of poly(styrene-divinylbenzene-vinylsulfonic acid) as retentive and electroosmotic flow generating phase in open-tubular electrochromatography

•Open-tubular columns with poly(styrene-divinylbenzene-sulfonic acid) were manufactured.•High vinylsulfonic acid ratio's are beneficial for the performance in CEC.•Optimum plate heights corresponding with the capillary inner radius were reached.•Elevated temperatures are beneficial for the performance in OTCEC.•Temperature gradients expedite the analysis while preserving the performance.

In this work, a new sulfonated polystyrene based porous layer was synthesized on the wall of a capillary by a single step in situ polymerization process. To obtain a capillary suited for electrochromatography, vinylsulfonic acid (VSA) was, next to divinylbenzene (DVB), copolymerized to induce charges for the electroosmotic flow (EOF) generation. The VSA ratio in the monomer mixture and the polymerization time were optimized while the chromatographic characteristics of the obtained open tubular columns were investigated in electrochromatography. To allow unambiguous study of only chromatographic processes, evaluations were performed with a mixture of sufficiently retained and electrophoretically neutral parabens. Comparison of SEM pictures and chromatograms revealed that the polymerization time had a great influence on the polymer layer morphology and on the chromatographic performance. An increase in the VSA ratio, led to an increase in the mobile phase velocity but simultaneously lowered paraben retention. The novel optimized stationary phase could generate a stable and significant electro-osmotic flow (EOF) of 1.1 mm/s over a wide pH range which could be produced in a reproducible manner. Minimal plate heights of 10 μm, equivalent to the capillary internal diameter, were obtained. The open-tubular character of this optimized porous layer column allowed successful analyses at elevated temperature, resulting in a maximum efficiency of 85,500 plates for a 75 cm capillary and linear velocities up to 1.4 mm/s. Finally, a thermal gradient was successfully applied, leading to artificial sharpened peaks with a peak capacity of 55 in a 20 min time span.