NMR imaging of the chromatographic process migration and separation of bands of gadolinium chelates

Measurement of transverse and axial apparent dispersion coefficients in packed beds

“…very thin, all the parts of its profile do not reach the exit at the same time (Farkas et al, phers for decades: Why is it that the actual efficiency of real columns is so poor compared to anticipations based on the predictions of the most reliable models? 1994; Tallarek et al, 1995). This appears to cause most of the actual band spreading observed.…”

“…These methods can also be implemented for direct investigations of the three-dimensional (3-D) profile of bands migrating along a chromatographic column and in situ measurement of the apparent dispersion coefficient in any direction of a packed bed. Results obtained by NMR imaging have demonstrated the warping of chromatographic bands (Tallarek et al, 1995). On the other hand, preliminary data have shown the local values of the apparent axial and transverse dispersion coefficients to correspond to relatively low values of the local plate height, with a minimum of the relative axial plate height of the order of 1.3, or nearly half the value typically obtained with a well-packed column.…”

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

“…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 .…”

“…Knox et al, 1976;Tallarek et al, 1995Tallarek et al, , 1996 . This is true for Ž columns packed with dry Eon, 1978;Horne et al, 1966;Knox .…”

“…Ž Tallarek et al, 1995Ž Tallarek et al, , 1996 , for analytical Baur et al, 1988;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 and for preparative columns ŽFarkas et al, 1997;Farkas and Guiochon, 1997;Guiochon et . al., 1997 .…”