Large-Scale Simulation of Flow and Transport in Reconstructed HPLC-Microchip Packings

Abstract

Flow and transport in a particle-packed microchip separation channel were investigated with quantitative numerical analysis methods, comprising the generation of confined, polydisperse sphere packings by a modified Jodrey-Tory algorithm, 3D velocity field calculations by the lattice-Boltzmann method, and modeling of convective-diffusive mass transport with a random-walk particle-tracking approach. For the simulations, the exact conduit cross section, the particle-size distribution of the packing material, and the respective average interparticle porosity (packing density) of the HPLC-microchip packings was reconstructed. Large-scale simulation of flow and transport at Peclet numbers of up to Pe = 140 in the reconstructed microchip packings (containing more than 3 x 10(5) spheres) was facilitated by the efficient use of supercomputer power. Porosity distributions and fluid flow velocity profiles for the reconstructed microchip packings are presented and analyzed. Aberrations from regular geometrical conduit shape are shown to influence packing structure and, thus, porosity and velocity distributions. Simulated axial dispersion coefficients are discussed with respect to their dependence on flow velocity and bed porosity. It is shown by comparison to experimental separation efficiencies that the simulated data genuinely reflect the general dispersion behavior of the real-life HPLC-microchip packings. Differences between experiment and simulation are explained by differing morphologies of real and simulated packings (intraparticle porosity, packing structure in the corner regions).

Bed morphological features associated with an optimal slurry concentration for reproducible preparation of efficient capillary ultrahigh pressure liquid chromatography columns

“…A number of important parameters and their often-complex influences were identified and correlated with the separation efficiency. These include the width and shape of the particle size distribution (PSD) and surface properties of the particles [6, 11], the inner diameter of capillary columns [12], the conduit geometry, in particular, of HPLC microchips [25, 26], and the slurry concentration [2, 13]. Modern three-dimensional (3D) imaging techniques provide insights into the relationship between morphological properties of porous materials and their performance in targeted applications [27–31].…”

Improved particle‐packed HPLC/MS microchips for proteomic analysis

“…The analysis of complex mixtures of tryptic peptides with the HPLC/MS chips improves when optimal packing parameters and a small particle size of the stationary phase are used for the chip's noncylindrical separation channel. Based on our previous work 12, 14, 19, 21 this improvement can be rationalized by the combination of a reduced transcolumn velocity bias (due to denser chip packings which minimize the effects of wall and particularly corner regions on the bed heterogeneity) and the smaller size of the totally porous particles (which reduces intraparticle mass transfer resistance and also allows to better fill the corner regions of the chip separation channel). Both effects, i.e.…”

“…Recently, we have shown by extensive numerical simulation studies of flow and dispersion 19–21 how the density and the cross‐sectional geometry of microchip packings affect their chromatographic resolution. The cross‐sectional heterogeneity of noncylindrical particulate packings translates to an inhomogeneous flow distribution between the corner regions and the bulk and thus to increased band broadening.…”

Performance of HPLC/MS microchips in isocratic and gradient elution modes

“…lower Darcy permeabilities and interparticle porosities result in a more uniform flow profile over the cross-section of the microchip packings supposed for the shorter separation channels of the HPLC/MS chips. Our previous experiments [27] and simulations [30,32] have shown that higher packing densities reduce the influence of the corners in noncylindrical conduits. The channel corners are the locations of advanced fluid flow, and these high-porosity and high-velocity corner regions expand with increasing ε inter of the packing (decreasing packing density).…”