Radial distribution of the contributions to band broadening of a silica‐based semi‐preparative monolithic column

Abia, Jude A.; Mriziq, Khaled S.; Guiochon, Georges

doi:10.1002/jssc.200800590

Cited by 10 publications

(3 citation statements)

References 23 publications

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“…This is a well-known problem, particularly for the rigid, but brittle, silica monoliths prepared with pure tetramethoxysilane . In analytical and semipreparative monolithic silica columns wall effects in general have been identified before to substantially affect the average cross-sectional plate height, and they are also known for capillary monoliths. , The lateral pore space heterogeneity and its large contribution to eddy dispersion is at present the main drawback of silica monoliths in chromatographic practice …”

Section: Resultsmentioning

confidence: 99%

Confocal Laser Scanning Microscopy Method for Quantitative Characterization of Silica Monolith Morphology

et al. 2010

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We present a fast, nondestructive, and quantitative approach to characterize the morphology of capillary silica-based monolithic columns by reconstruction from confocal laser scanning microscopy images. The method comprises column pretreatment, image acquisition, image processing, and statistical analysis of the image data. The received morphological data are chord length distributions for the bulk macropore space and skeleton of the silica monolith. The morphological information is shown to be comparable to that derived from transmission electron microscopy, but far easier to access. The approach is generally applicable to silica-based capillary columns, monolithic or particulate. It allows the rapid acquisition of hundreds of longitudinal and cross-sectional images in a single session, resolving a multitude of morphological details in the column.

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Section: Resultsmentioning

confidence: 99%

Confocal Laser Scanning Microscopy Method for Quantitative Characterization of Silica Monolith Morphology

et al. 2010

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“…However, the online version of record will be different from this version once it has been copyedited and typeset. Two notable examples where this idealized patchwork model could fall short are packed bed columns where the stacking of particles is disrupted near the side wall 13,14 , and sol-gel synthesized monolithic columns, where radial heterogeneities are present along the entire axis 15,16 . In the field of chromatography, these trans-column phenomena have been put forward as significant sources of axial dispersion in the columns being used [13][14][15][16][17] .…”

Section: Introductionmentioning

confidence: 99%

On the logarithmic nature of axial dispersion in Darcy flow through heterogeneous porous media

Huygens,

Desmet

2024

Physics of Fluids

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The present study provides novel insights in how spatial velocity variations in a heterogeneous porous medium cause the dispersion of a passive tracer. The study consists of two parts. The first part describes a series of numerical computations of the axial dispersion in the flow through heterogeneous porous media, idealized as Darcy flow through two-dimensional and three-dimensional patchwork geometries of zones with randomized permeability fields. Data on the axial dispersion were obtained using the mean age theory, which transforms the transient advection–diffusion equation into the steady-state mean age field equation, thus reducing the required computational effort by multiple orders of magnitude. This allowed to consider a sufficiently large number of randomizations to obtain a statistically representative ensemble average, as well as to consider sufficiently large systems to reduce the influence of boundary conditions. In the second part, it is shown that the relation between the axial dispersion coefficient and the velocity can be represented as a series, summing up the effect of velocity differences on all length scales, assuming the velocity differences are analogous to white noise. The sum can be closely fitted by a logarithmic law containing only two parameters with a well-defined physical meaning. A similar logarithmic dependency was also obtained by Saffman, Koch, and Brady. However, the logarithmic dependency obtained in the present work emerges from the heterogeneity of the porous medium, whereas the logarithmic dependency in the aforementioned works emerged from the no-slip boundary conditions at solid surfaces.

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“…Long ago, many authors reported that HPLC columns are radially heterogeneous to a degree. − It is probably impossible to prepare columns that are radially homogeneous. So, a strategy is needed that permits the derivation of reliable information on the actual characteristics of the radial heterogeneity of columns from the asymmetrical profiles of elution peaks.…”

mentioning

confidence: 99%

Numerical Method for the Estimation of Column Radial Heterogeneity and of the Actual Column Efficiency from Tailing Peak Profiles

Miyabe

Guiochon

2010

Anal. Chem.

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It is probably impossible to prepare high-performance liquid chromatography (HPLC) columns that have a completely homogeneous packing structure. Many reports in the literature show that the radial distributions of the mobile phase flow velocity and the local column efficiency are not flat, even in columns considered as good. A degree of radial heterogeneity seems to be a common property of all HPLC columns and an important source of peak tailing, which prevents the derivation of accurate information on chromatographic behavior from a straightforward analysis of elution peak profiles. This work reports on a numerical method developed to derive from recorded peak profiles the column efficiency at the column center, the degree of column radial heterogeneity, and the polynomial function that best represents the radial distributions of the flow velocity and the column efficiency. This numerical method was applied to two concrete examples of tailing peak profiles previously described. It was demonstrated that this numerical method is effective to estimate important parameters characterizing the radial heterogeneity of chromatographic columns.

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Radial distribution of the contributions to band broadening of a silica‐based semi‐preparative monolithic column

Cited by 10 publications

References 23 publications

Confocal Laser Scanning Microscopy Method for Quantitative Characterization of Silica Monolith Morphology

Confocal Laser Scanning Microscopy Method for Quantitative Characterization of Silica Monolith Morphology

On the logarithmic nature of axial dispersion in Darcy flow through heterogeneous porous media

Numerical Method for the Estimation of Column Radial Heterogeneity and of the Actual Column Efficiency from Tailing Peak Profiles

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