Experimental and numerical study of band-broadening effects associated with analyte transfer in microfluidic devices for spatial two-dimensional liquid chromatography created by additive manufacturing.

Conventional one-dimensional column-based liquid chromatographic (LC) systems do not offer sufficient separation power for the analysis of complex mixtures. Column-based comprehensive two-dimensional liquid chromatography offers a higher separation power, yet suffers from instrumental complexity and long analysis times. Spatial two-dimensional liquid chromatography can be considered as an alternative to column-based approaches. The peak capacity of the system is ideally the product of the peak capacities of the two dimensions, yet the analysis time remains relatively short due to parallel second-dimension separations. Aspects affecting the separation efficiency of this type of systems include flow distribution to homogeneously distribute the mobile phase for the second-dimension ( ² D) separation, flow confinement during the first-dimension ( ¹ D) separation, and band-broadening effects during analyte transfer from the ¹ D separation channel to the ² D separation area. In this study, the synergy between computational fluid dynamics (CFD) simulations and rapid prototyping was exploited to address band broadening during the ² D development and analyte transfer from ¹ D to ² D. Microfluidic devices for spatial two-dimensional liquid chromatography were designed, simulated, 3D-printed and tested. The effects of presence and thickness of spacers in the ² D separation area were addressed and leaving these out proved to be the most efficient solution regarding band broadening reduction. The presence of a stationary-phase material in the ¹ D channel had a great effect on the analyte transfer from the ¹ D to the ² D and the resulting band broadening. Finally, pressure limit of the fabricated devices and printability are discussed.
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