Fitting adsorption isotherms to the distribution data determined using packed micro-columns for high-performance liquid chromatography

Knowing the adsorption isotherms of the components of a mixture on the chro matographic system used to separate them is necessary for a better understa nding of the separation process and for the optimization of the production rate and costs in preparative high-performance liquid chromatography (HPLC) . Currently, adsorption isotherms are usually measured by frontal analysis, using conventional analytical columns. Unfortunately, this approach requir es relatively large quantities of pure compounds, and hence is expensive, e specially in the case of pure enantiomers. In this work, we investigated th e possible use of packed micro-bore and capillary HPLC columns for the dete rmination of adsorption isotherms of benzophenone, o-cresol and phenol in r eversed-phase systems and of the enantiomers of mandelic acid on a Teicopla nin chiral stationary phase. We found a reasonable agreement between the is otherm coefficients of the model compounds determined on micro-columns and on conventional analytical columns packed with the same material. Both fron tal analysis and perturbation techniques could be used for this determinati on. The consumption of pure compounds needed to determine the isotherms dec reases proportionally to the second power of the decrease in the column inn er diameter, i.e. 10 times for a micro-bore column (1 mm I.D.) and 100 time s for capillary columns (0.32 mm I.D.) with respect to 3.3 mm I.D. conventi onal columns. (C) 2001 Elsevier Science B.V. All rights reserved.