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

Area of Science:

• Analytical Chemistry
• Materials Science
• Microfluidics

Background:

• Development of portable and disposable instruments for on-site chemical analysis is crucial.
• Reversed-phase electrochromatography (RPEC) offers high separation efficiency but requires robust stationary phases.
• Microfluidic devices provide miniaturization advantages for analytical instrumentation.

Purpose of the Study:

• To synthesize and characterize a lauryl methacrylate monolith for RPEC applications.
• To evaluate the electrochromatographic performance of the monolith in a microfluidic device.
• To assess the feasibility of direct droplet injection for simplified operation.

Main Methods:

• Synthesis of a lauryl methacrylate monolith within a cyclic olefin copolymer microdevice.
• Capillary-based evaluation of electroosmotic flow (EOF) mobility, retention, and efficiency.
• Optimization of photopolymerization time for monolith properties.
• On-chip RPEC separation of polycyclic aromatic hydrocarbons (PAHs).
• Comparison of direct droplet injection versus conventional dynamic injection.

Main Results:

• The monolithic bed demonstrated good run-to-run, column-to-column, and batch-to-batch reproducibility (RSD < 9%).
• Optimized photopolymerization time (10 min) yielded a robust, retentive, and efficient system.
• On-chip RPEC separations of PAHs achieved plate heights as low as 15 μm.
• Direct injection from a 2 μL droplet was evaluated as a simplified alternative to dynamic injection.

Conclusions:

• A lauryl methacrylate monolith is suitable for RPEC in microdevices, offering portability and disposability.
• The optimized monolith provides reproducible and efficient separations for neutral compounds like PAHs.
• The developed system shows promise for simplified on-site analysis, potentially utilizing direct injection methods.