Characterization of radial and axial heterogeneities of chromatographic columns by flow reversal

Flow-Reversal Experiments with Macromolecules to Measure Column End Efficiency and Bed Heterogeneity

“…The insulin peaks observed after flow-reversal are definitely narrower and more symmetrical than the peaks obtained without reversing the flow. For small molecules, the band compression effect was found to be less [6,8]. The molecular diffusivity of macromolecules is much smaller than that of small molecules.…”

“…Gritti et al [8] designed a custom-made low-dispersion system made of two small-volume optical detection cells placed immediately before and after the column. They applied the flow-reversal technique to determine radial and axial structural heterogeneities of packed chromatographic beds.…”

Methods to determine the kinetic performance limit of contemporary chromatographic techniques

“…It was observed previously that these assumption are not always valid as a clear variation of plate height with column length [79] and diameter [80] were observed. More detailed discussion regarding axial heterogeneities of chromatographic beds can be found in [81]. The reasons for these variations are manifold and a detailed discussion is outside the scope of this work.…”

“…In addition, these ends consist of a conical structure, flow distributor, and/or frit that can all contribute significantly to the total column dispersion for short narrow bore columns [82–84]. Finally, due to relaxation of packing stress and the inevitable presence of a column wall, radial variations in packing density occur that have a column length dependent contribution to the plate height [81,85,86]. Some of these effect can counter each other as, for example a longer column experiences a larger contribution from these trans‐column velocity differences, but should be less influenced by variations in packing density at the column ends and the presence of the frit and flow distributor.…”

Extra-column band broadening effects in contemporary liquid chromatography: Causes and solutions

“…In very recent work, Gritti [47] and Felinger and Tanaka [48] observed that the dispersion occurring in the particle retaining frits as well as in the bore and distributor cone of the column end-fittings can be as high as 1 L 2 , which is of the same order as the dispersion experienced by a non-retained marker in the 2.1x50mm column packed with 2.7m core-shell particles [48]. As a consequence, the notion "extracolumn" to denote the dispersion losses that occur outside the actual chromatographic (and hence useful) part of the system is maybe not even the most appropriate term.…”