Monolayer-protected gold nanoparticles as an efficient stationary phase for open tubular gas chromatography using a square capillary: Model for chip-based gas chromatography in square cornered microfabricated channels

The application of a dodecanethiol monolayer-protected gold nanoparticle (MPN) stationary phase within a microchannel environment was explored using a square capillary column as a model for high-speed, microfabricated gas chromatography (μGC). Successful deposition and evaluation of a dodecanethiol MPN phase within a 1.3 m long, 100 μm×100 μm square capillary is reported. The thickness of the MPN phase was evaluated using SEM analysis. An average thickness of 15 nm along the capillary walls was determined. While the film depth along the walls was very uniform, the corner depths were greater with the largest observed depth being 430 nm. Overall, an efficient chromatographic system was obtained with a minimum reduced plate height, hmin, of 1.2 for octane (k=0.22). Characterization of the MPN column was completed using four compound classes (alkanes, alcohols, ketones, and aromatics) that were used to form a seven-component mixture with a 2-s separation. A mixture consisting of a nerve agent simulant in a sample containing analytes that may commonly interfere with detection was also separated in only 2 s, much faster than a similar separation previously reported using a μGC system requiring 50 s. A comparison of the MPN stationary phase to phases employed in previously reported μGC systems is also made. Application of the square capillary MPN column for a high-speed separation as the second column of a comprehensive 2-D gas chromatography system (GC×GC) was also explored.