Modelling of the pore flow in capillary electrochromatography

Pore flow in capillary electrochromatography (CEC) on porous silica particl es has been investigated. To that end the migration behaviour of narrow pol ystyrene (PS) standards dissolved in di-methylformamide (DMF) with lithium chloride in 1 and 10 mmol/l concentration has been measured. These data hav e been compared to theoretical predictions. The latter were based on a mode l comprising cylindrical pores of varying diameter as measured experimental ly by porosimetry, while the flow in each set of pores was calculated with the expression given by Rice and Whitehead. A reasonable to good agreement between experimental and predicted data was observed, provided it was assum ed that pores of differing diameter occur in series. It was found that the flow in pores with a nominal size of 100 Angstrom can be considerable compa red to the interstitial flow, especially at 10 mmol/l ionic strength. It is concluded that pore flow within porous particles in CEC, of great importan ce for improved efficiency in both interactive and exclusion type CEC, can be predicted fairly reliably by means of the Rice and Whitehead expression. (C) 2000 Elsevier Science B.V. All rights reserved.