Chip electrochromatography of polycyclic aromatic hydrocarbons on an acrylate-based UV-initiated porous polymer monolith

The first rigorous evaluation of a UV-initiated porous polymer monolith (PP M) as a stationary phase for chip electrochromatography (ChEC) is described . All channels in an offset T-injector-design-chip (25-mum deep by 50-mum w ide channels) were filled by capillary action with an acrylate-based PPM pr ecursor solution and polymerized in situ using 365 nm light for several min utes. Photodefinability of the monolith cast in the channels during the pol ymerization process was also demonstrated by masking off the injection arms during photoinitiation. The chromatographic performance of this chip was c ompared with that of chips completely filled with monolith. The detection w indow was photodefined after polymerization using the detection laser (257 nm doubled argon ion laser) to depolymerize the detection window. A success ful ChEC separation of 10 out of 13 polycyclic aromatic hydrocarbons (PAH) was performed with on-column, off-packing laser-induced fluorescence detect ion at 257 nm. Van Deemter plots for early-, middle-, and late-eluting comp ounds showed the minimum plate height to be 5 mum. The average number of th eoretical plates per meter for the PAH was 200,000. Several factors contrib uted to irreproducible results. Oxygen was observed to dynamically quench t he fluorescence of the sample over time. Improved sealing of the reservoirs solved this problem. A within-chip variability in the retention time of 2- 10% RSD was observed. These results demonstrate the feasibility and reliabi lity of the PPM as a solid reversed-phase for electroosmotic flow-driven ch ip-based chromatography in microscale total analysis systems.