Modeling of dispersion in a polymeric chromatographic monolith

Koku, Harun
Schure, Mark R.
Lenhoff, Abraham M.
Dispersion in a commercial polymeric monolith was simulated on a sample geometry obtained by direct imaging using high-resolution electron microscopy. A parallelized random walk algorithm, implemented using a velocity field obtained previously by the lattice-Boltzmann method, was used to model mass transfer. Both point particles and probes of finite size were studied. Dispersion simulations with point particles using periodic boundaries resulted in plate heights that varied almost linearly with flow rate, at odds with the weaker dependence suggested by experimental observations and predicted by theory. This discrepancy resulted from the combined effect of the artificial symmetry in the velocity field and the periodic boundaries implemented to emulate macroscopic column lengths. Eliminating periodicity and simulating a single block length instead resulted in a functional dependence of plate heights on flow rate more in accord with experimental trends and theoretical predictions for random media. The lower values of the simulated plate heights than experimental ones are attributed in part to the presence of walls in real systems, an effect not modeled by the algorithm. On the other hand, analysis of transient dispersion coefficients and comparison of lateral particle positions at the entry and exit hinted at non-asymptotic behavior and a strong degree of correlation that was presumably a consequence of preferential high-velocity pathways in the raw sample block. Simulations with finite-sized probes resulted in particle trajectories that frequently terminated at narrow constrictions of the geometry. The amount of entrapment was predicted to increase monotonically with flow rate, evidently due to the relative contributions to transport by convection that carries particles to choke-points and diffusion that dislodges these entrapped particles. The overall effect is very similar to a flow-dependent entrapment phenomenon previously observed experimentally for adenovirus.


Modeling of flow in a polymeric chromatographic monolith
Koku, Harun; Czymmek, Kirk J.; Schure, Mark R.; Lenhoff, Abraham M. (Elsevier BV, 2011-06-03)
The flow behavior of a commercial polymeric monolith was investigated by direct numerical simulations employing the lattice-Boltzmann (LB) methodology. An explicit structural representation of the monolith was obtained by serial sectioning of a portion of the monolith and imaging by scanning electron microscopy. After image processing, the three-dimensional structure of a sample block with dimensions of 17.8 mu m x 17.8 mu m x 14.1 mu m was obtained, with uniform 18.5 nm voxel size. Flow was simulated on th...
Relation of structure to performance characteristics of monolithic and perfusive stationary phases
Trilisky, Egor I.; Koku, Harun; Czymmek, Kirk J.; Lenhoff, Abraham M. (Elsevier BV, 2009-09-04)
Commercially available polymer-based monolithic and perfusive stationary phases were evaluated for their applicability in chromatography of biologics. Information on bed geometry, including that from electron microscopy (EM), was used to interpret and predict accessible volumes, binding capacities, and pressure drops. For preparative purification of biologics up to at least 7 nm in diameter, monoliths and perfusive resins are inferior to conventional stationary phases due to their low binding capacities (20...
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Secondary structure of proteins have been predicted using neural networks (NN) from their Fourier transform infrared spectra. Leave-one-out approach has been used to demonstrate the applicability of the method. A form of cross-validation is used to train NN to prevent the overfitting problem. Multiple neural network outputs are averaged to reduce the variance of predictions. The networks realized have been tested and rms errors of 7.7% for alpha -helix, 6.4% for beta -sheet and 4.8% for turns have been achi...
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Polarization properties of the fluorescence from a pair of identical molecules coupled electronically are examined on the basis of a stochastic Liouville equation formalism developed in 1979 by Rahman, Knox and Kenkre. The time development of polarization is calculated for random ensembles of rigid molecule pairs under initial conditions that represent either selective excitation or broad-band coherent excitation. We hold that the applicability of the Forster mechanism is not limited to cases of weak coupli...
Morphology and optical properties of thin silica films containing bimetallic Ag/Au nanoparticles
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We have studied the optical spectra in the UV and visible regions, the morphology by scanning electron microscopy (SEM), and the X-ray photoelectron spectra (XPS) of bimetallic Ag/Au nanoparticles incorporated into transparent silicate films in the sol-gel transition stage. The bimetallic nanoparticles, obtained by a combination of photoreduction and thermal reduction, form structures of the alloy or core-shell type.
Citation Formats
H. Koku, M. R. Schure, and A. M. Lenhoff, “Modeling of dispersion in a polymeric chromatographic monolith,” JOURNAL OF CHROMATOGRAPHY A, pp. 55–63, 2012, Accessed: 00, 2020. [Online]. Available: