NMR imaging of the chromatographic process. Deposition and removal of gadolinium ions on a reversed-phase liquid chromatographic column

Bayer, Ernst; Baumeister, Edgar; Tallarek, Ulrich; Albert, Klaus; Guiochon, Georges

doi:10.1016/0021-9673(95)00200-7

Cited by 36 publications

(11 citation statements)

References 16 publications

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“…Any such fluctuation would warp the band profile, causing the locus of the maxima of the concentration profiles along straight lines parallel to the column axis to differ significantly from the plane. This warping of bands during their migration along a column has been reported conclusively by NMR imaging of bands of Gadolinium chelates Bayer et al, 1995).…”

Section: August 1997supporting

confidence: 64%

Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column

1997

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The use of optical fibers in a fluorescence-detection scheme permits the accurate determination of the radial distribution of the transit time, the column eficiency, and the analyte concentration at the exit of a chromatographic axialcompression column (50 mmID). The results obtained demonstrate that the column is not homogeneous, but suggest a nearly cylindrical distribution of the packing dens@. The average velocity close to the column wall is 7% lower than along its axis and the HETP 25% higher. The lack of homogeneity of the column packing is another source of band broadening not taken into account in chromatography so far. It causes the apparent HETP derived from the conventional elution chromatogram recorded on the bulk eluent to be larger than the local HETP and the band profile to be unsymmetrical with a slight tail reminiscent of kinetic tailing.from the width of the residence time distribution is much larger (Tallarek et al., 1997), since the latter includes a contribution arising from the large-scale fluctuations of the mo-S and 0 local efficiency for column 1 along two perpendicular diameters; + and corresponding data for column 2.

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Section: August 1997supporting

confidence: 64%

Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column

1997

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“…Even though most tend to ignore it, chromatographers have Ž long known that columns are not radially homogeneous Baur et al, 1998;Baur and Wightman, 1989;Bayer et al, 1989Bayer et al, , 1995Eon, 1978;Farkas et al, 1994Farkas et al, , 1996Farkas et al, , 1997Farkas and Guiochon, 1997;Guiochon et al, 1997;Horne et al, 1966; . Knox et al, 1976;Tallarek et al, 1995Tallarek et al, , 1996 .…”

Section: Introductionmentioning

confidence: 97%

“…Broyles et al, 2002 . The lower efficiency derived from measurements made by bulk detection under the same conditions is explained by the warping of the solute bands arising from the large-scale, systematic radial variation of the mobile phase Ž velocity Bayer et al, 1989Bayer et al, , 1995Farkas et al, 1997;Farkas and Guiochon, 1997;Tallarek et al, 1995Tallarek et al, , 1996Broyles et . al., 2002 .…”

Section: Introductionmentioning

confidence: 98%

“…This is true for Ž columns packed with dry Eon, 1978;Horne et al, 1966;Knox . Ž et al, 1976 or wet techniques Baur et al, 1988;Baur and Wightman, 1989;Bayer et al, 1989Bayer et al, , 1995Farkas et al, 1994Farkas et al, , 1996Farkas et al, , 1997Farkas and Guiochon, 1997;Guiochon et al, 1997; Correspondence concerning this article should be addressed to. G. Guiochon.…”

Section: Introductionmentioning

confidence: 98%

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Mechanics of column beds: I. Acquisition of the relevant parameters

2003

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The efficiency of chromatographic columns is ad®ersely affected by large-scale radial ®ariations of the packing density or ®oid ratio of the material used to prepare the bed. This heterogeneity is due to wall friction effects that take place during the preparation of the column and to seepage effects operating during the packing process and the subsequent operation of the column. The dependence of the bed's ®oid fraction on the stress applied during its consolidation was determined, as well as its permeability at ®arious stages of the consolidation process and the coefficient of friction between typical packing materials and the stainless steel wall of chromatographic columns. These results are required to de®elop and use numerical models of the ®olumetric response to axial compression of the bed and models of the coupled mechanical-seepage rheology of particulate materials.

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“…Accordingly, only small fluctuations in the column efficiency could take place and these were considered as of no consequence. This assumption has been falsified by Guiochon et al [1] in a work based on the results of earlier investigations pursued by Knox et al [2], Eon [3], Baur et al [4,5], Farkas et al [6,7], Bayer et al [8][9][10], and Fernandez et al [11]. These studies have demonstrated that particle-packed columns were not radially homogeneous but that the velocity of the mobile phase as well as the local column efficiency significantly vary across the diameter of these columns.…”

Section: Introductionmentioning

confidence: 83%

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

Abia

Mriziq

Guiochon

2009

J of Separation Science

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Using an on-column local electrochemical microdetector operated in the amperometric mode, band elution profiles were recorded at different radial locations at the exit of a 10 mm id, 100 mm long silica-based monolithic column. HETP plots were then acquired at each of these locations, and all these results were fitted to the Knox equation. This provided a spatial distribution of the values of the eddy diffusion (A), the molecular diffusion (B), and the resistance to the kinetics of mass transfer (C) terms. Results obtained indicate that the wall region yields higher A values and smaller C values than the central core region. Significant radial fluctuations of these contributions to band broadening occur throughout the exit column cross-section. This phenomenon is due to the structural radial heterogeneity of the column.

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NMR imaging of the chromatographic process. Deposition and removal of gadolinium ions on a reversed-phase liquid chromatographic column

Cited by 36 publications

References 16 publications

Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column

Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column

Mechanics of column beds: I. Acquisition of the relevant parameters

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

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