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Open Tubular Hydrodynamic Chromatography (OTHDC) is currently limited by two shortcomings, namely the low selectivity and the large values of the Height Equivalent of the Theoretical Plate (HETP) caused by the Taylor-Aris dispersion. Recently, these authors and co-workers, (Biagioni and Cerbelli, 2022) have shown the possibility to contain the Taylor-Aris effect by inducing transversal velocity components superimposed to the main pressure-driven axial flow in a square channel. It was found that the separation efficiency can be enhanced by a 50-fold factor introducing a transversal DC-electroosmotic flow characterized by two symmetrical vortices. Considering the significant improvement obtained, the possibility to increase the efficiency of OTHDC by inducing different transversal flows is here investigated. Different transversal flows can be generated by placing electrode pairs in different configurations along the walls of the channel and by treating the walls with different coatings that make them charged or uncharged. It is found that all the types of transversal flows studied can improve the separation efficiency of OTHDC. The best performance is provided by the transversal flow characterized by four symmetrical vortices, which yield an improvement of the separation efficiency by a factor of up to one hundred times compared to standard OTHDC in the range of operating conditions considered. |
