Ellipsoidal particles for liquid chromatography: Fluid mechanics, efficiency and wall effects

• Published in: Journal of Chromatography A Vol. 1580; pp. 30 - 48
• Main Authors: Schure, Mark R., Maier, Robert S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 14-12-2018
• Subjects: Chromatography, Liquid - methods; Column packing; Ellipsoidal particles; Hydrodynamics; Lattice Boltzmann method; Liquid chromatography; Particle shape; Particle Size; Porosity; Pressure; Wall effects; Ellipsoidal particles; Liquid chromatography; Particle shape; Lattice Boltzmann method; Wall effects; Column packing
• ISSN: 0021-9673; 1873-3778
• DOI: 10.1016/j.chroma.2018.09.051

•Packed beds of ellipsoidal-shaped particles for liquid chromatography are explored.•Performance is enhanced over spheres when wall effects are included in capillaries.•Lattice Boltzmann fluid mechanics are used to determine chromatographic performance.•Methods for comparing spheres and ellipsoidal particles are described in details.•Separation impedance is found to be independent of the comparison method.
Ellipsoidal particles are investigated as packing media for liquid chromatography using high resolution fluid mechanics and Brownian dynamics simulations. The simulations are conducted with packed capillary columns, as well as beds with periodic boundary conditions (PBCs) to study transport in the absence of wall effects. The performance of ellipsoidal particles is evaluated over a range of aspect ratios. The definition of effective diameter used to compare sphere and ellipsoidal particle performance metrics is presented and discussed along with scaling relationships which are necessary to compare sphere and ellipsoidal particle packs.
Ellipsoidal particle packs are found to be inferior to sphere packs using PBCs to study chromatographic dispersion. The separation impedance was calculated with PBCs and shown to be approximately the same with ellipsoidal particles as those of spheres. Efficiency of ellipsoidal packs, as measured by plate height, is lower than spherical particle packs and the pressure drop is higher than sphere packs when using PBCs.
However, a smaller wall effect is shown for ellipsoidal particles when packing cylindrical capillaries. Radial variations in packing porosity and in flow within the wall region are smaller for ellipsoidal packings. The minimum reduced plate height and the separation impedance for the packed capillaries clearly demonstrate the advantages of ellipsoidal particles compared to spherical particles. This predicted performance advantage remains to be demonstrated in actual practice.