Infrared photo-initiated fabrication of monolithic porous layer open tubular (monoPLOT) capillary columns for chromatographic applications†

Investigation into the development of a fabrication approach for capillary porous layer open tubular (PLOT) chromatographic columns via infrared (IR) photo-initiated polymerisation and the optimisation of the technique is presented in this work. Polyimide coatings on fused silica capillaries absorb strongly in the visible region of the light spectrum making commonly used ultra-violet and visible light photo-initiated polymerisation methods impossible inside this type of capillary. In addition, polystyrene-based materials, which are commonly used as reversed phases and hydrophobic substrates in both liquid (LC) and gas chromatography (GC) also absorb strongly in the ultra-violet (UV) region making them unsuitable for polymerisation via common photo-initiated methods. However, by using infrared light, photo-polymerisation in polyimide coated capillary was made possible herein. Crucially, selecting a suitable photo-initiator with a high extinction coefficient ensures that the penetration ability of the incident light is greatly reduced thus making the technique highly suited to PLOT column fabrication. The described procedure provides a straight forward method for the photoinitiated fabrication of monoPLOT columns in polyimide coated capillary.