Semipacked separation columns with monolayer protected gold stationary phases for microgas chromatography

Semi-packed columns (SPC), as a new class of gas chromatography columns, offer several advantages like increased surface area and sample capacity compared to open columns and the elimination of the differential flows observed in multicapillary columns. We present herein for the first time SPCs with monolayer protected gold stationary phases by utilizing the ability of octadecanethiol (C₁₈H₃₇SH) to self-assemble on deposited gold layers. We employed two selective gold deposition approaches followed by thiol functionalization; 1) our previously reported high-yield double-doped self-patterned process and 2) e-beam evaporation of gold followed by the lift-off process. By utilizing both schemes, we produced 1m-long, 250μm-deep, 190μm-wide semipacked columns with circular micropillars of 20 μm-diameters and 20 μm-post spacing. Both approaches afford the separation of complex gas mixtures with wide range of boiling points. However, the shadowing effect inherent in e-beam evaporation specifically for high-aspect-ratio structures results in incomplete gold coverage and limits its application in separation columns with microposts.