A Method for 3D Modeling of Chemical Separation in Microfabricated Gas Chromatography Columns: Case Studies in Temperature Gradients and Stationary Phase Topologies.

Conventional capillary gas chromatography (GC) columns, which have circular symmetry in cross-section and uniformity in length, are well modeled mathematically by the GC rate theory. However, even after adaptation, the theory has limited applicability to many unconventional properties in microfabricated GC columns, such as trapezoidal cross-sections, non-uniform stationary phase, and temperature gradients. This paper reports a 3D finite-element model for the chemical separation process in microfabricated GC columns using COMSOL. The model incorporates gas flow, diffusion, partition, and temperature effects, enabling quantitative assessment of the separation performance of microfabricated GC columns with different stationary phase coating topologies and temperature gradients. To address the tremendous computational burden in such a 3D model, this paper investigates methods of providing proper meshing and dimensional scaling. For validation purposes, the implemented model was first applied to a conventional capillary GC column and showed good matches to both the analytical calculation and experimental results. Next, the model was used to assess microfabricated columns with a trapezoidal cross-section and different stationary phase coating topologies. The results showed that, for the cases under consideration, a single-side-coated column provides only a 33% lower separation resolution compared to a double-side-coated column, and a parabolic stationary phase profile provides only a 12% lower separation resolution compared to a uniform profile. The model also indicated that temperature gradients have a negligible impact on separation performance. [ABSTRACT FROM AUTHOR]