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Saturday, March 16, 2013

Radial Flow Chromatography (RFC) vs Axial Flow Chromatography (AFC)


Biotechnological processes are advancing day by day and in production scale the volume is going higher and higher, recombinant protein purification involves two or three downstream purification steps. Radial flow chromatography was first introduced for gas – solid catalytic reactions in packed bed columns.
Radial flow chromatography is used as an alternative to the axial flow chromatography which was used for preparative and large scale purification processes. In radial flow chromatography, mobile phase enters radially and enters the centre rather than axially as in the axial flow chromatography. The mobile phase enters through outside tube and merges into the center tube. As compared to the axial flow chromatography, radial flow chromatography column provides larger flow area and shorter path length. It allows higher volumetric flow rate with lower pressure.


working of radial flow chromatography


Problems of Axial Flow chromatography in scale up
Axial flow chromatography has limitation when volumes are high, especially axial flow chromatography becomes troublesome when considering for scale up processes, one of the main drawback is, in order to accommodate larger volumes increasing the column size too much is impractical. When column size is increased excessive pressure drop will be there and by resulting in compromising process resolution and yield.

Pros and Cons of Radial Flow Chromatography
  • Radial Flow Chromatography provides shorter flow path with higher cross sectional area, this has same effect as pancake like axial flow chromatographic columns.
  • RFC columns requires less floor space as compared to AFC columns.
  • Flow distribution problems are there in axial flow chromatographic columns and Radial flow chromatographic columns.
  • Due to the short flow path of RFC columns pressure drop will be minimal and can handle higher volumetric flow rates in RFC columns as compared to the AFC columns.
  • Since pressure drop is minimal, bed compression problems won’t be there even with higher flow rates.
  • RFC is good choice for affinity chromatographic separations.
  • Scale up in RFC is easy because increasing height doesn’t have much effect of flow distortion problems.
  • The main problem with RFC is the limited resolution because of its short flow path.
  • Increase in flow path in larger extent leads to flow distortion problems.
  • RFC has no use in analytical HPLC because of the limited resolution.
  • RFC is not suitable for size exclusion chromatography, since SEC depend on the flow path for the resolution.