A 'zero length' criterion for ZLC chromatography

The usual approach to mathematically modelling the zero length column (ZLC) has been to treat the column as being physically short enough for the carr ier phase to be considered well mixed. This work presents an evaluation of this assumption for a sorbent bed of arbitrary length using a systematic co mparison of the standard model to a plug flow model. The case of finite dis persion was modelled and shown to be intermediate to the two extremes. Usin g this comparison, a criterion was developed by which the two cases can be considered identical for practical purposes. It was shown that the axial fl ow pattern in the sorbent bed may be disregarded when the dimensionless par ameter L > 15, assuming that interstitial fluid holdup is negligible. The u sual ZLC analysis may then be applied for extracting diffusion and adsorpti on parameters from the desorption curve. (C) 2000 Elsevier Science Ltd. All rights reserved.