Electrochromatography in cyclic olefin copolymer microchips: a step towards field portable analysis

In order to develop a portable and disposable instrument for on-site analysis of neutral compounds, a lauryl methacrylate monolith has been synthesized into a cyclic olefin copolymer microdevice for reversed-phase electrochromatography purposes. This monolith was tested in capillary to evaluate electrochromatographic performances in terms of electroosmotic flow (EOF) mobility, retention and efficiency prior to its transfer into the microfluidic device. The produced monolithic bed exhibited a good run-to-run repeatability, column-to-column reproducibility and batch-to-batch reproducibility, with relative standard deviation (RSD) values below 9% for EOF mobility, retention factors and heights of theoretical plate. The electrochromatographic performances of the monolith were optimized by reducing irradiation time. Photopolymerization time of 10 min was found to be the best process in order to obtain a robust, retentive and efficient system. The on-chip performances of this monolith were evaluated in detail for the reversed-phase electrochromatographic separation of polycyclic aromatic hydrocarbons, with plate heights reaching down to 15 μm when working at optimal velocity. Aiming at the maximum simplification of instrumental fabrication and operation, a direct injection from a 2 μL droplet was compared with more conventional dynamic injection process.