3D-printing has gained popularity as a fabrication tool in many fields. It is now commonly viewed as not only a prototyping tool, but also as an approach to obtain a final, customized product. Inorganic moulds or housings in which stationary phases have been successfully created include fused silica capillaries and tubes, glass slides, and titanium, while organic housings include cyclic olefin copolymer (COC; chips and tubes) and polypropylene (PP; pipette tips and tubes). 3D-printed metals, such as titanium, provide housing materials with excellent properties and the possibility to localize monolith synthesis or packing channels with stationary phase particles.

Separation and characterization of complex mixtures are of crucial importance in many fields, such as proteomics, metabolomics and lipidomics, which require extremely high separation powers. This growing need is spurring the quest for high peak capacities in separation procedures. Spatial three-dimensional liquid chromatography can offer a solution to achieve peak capacities in the order of a million. A novel way to produce efficient three-dimensional devices for this approach may be established through the use of 3D-printing technologies.

Here, we will demonstrate the creation of stationary phases in different types of material housings. RPLC separations are achieved by in-situ fabrication of porous polymer monoliths, directly within the 3D-printed PP channels by fused-deposition modeling (FDM). Two approaches were used for thermal monolith fabrication, viz. (i) a two-step modification reaction for a standard polypropylene filament using a short reaction time with AIBN as the crosslinker, which was followed by a second polymerization step to generate the monolith using thermal initiation; (ii) a silanization step, followed by a one-pot approach for a glass-reinforced polypropylene wall.

Furthermore, a second printed device for 2D separations is being developed that will be 3D-printed in glass. Here, the aim is to study ion exchange (IEX) as a spatial first-dimension separation and reversed-phase liquid chromatography (RPLC) as the second dimension. RPLC separations are achieved by in-situ creation of polymer monoliths localized in the devices, directly within the 3D-printed channels.

Peter Schoenmakers

Appearances