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Modeling l-dopa purification by chiral ligand-exchange chromatography

Authors

  • Nooshafarin Sanaie,

    1. Michael Smith Laboratories and Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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  • Charles A. Haynes

    Corresponding author
    1. Michael Smith Laboratories and Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
    • Michael Smith Laboratories and Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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Abstract

A model describing elution-band profiles that combines multiple chemical equilibria theory with the nonideal equilibrium–dispersion equation for solute transport is used to predict and characterize the separation of l,d-dopa by chiral ligand-exchange chromatography (CLEC). Formation constants and stoichiometries for all equilibrium complexes formed in the interstitial volume and pore liquid are taken from standard thermodynamic databases and independent potentiometric titration experiments. Formation constants for complexes formed with the stationary phase ligand (N-octyl-3-octylthio-d-valine) are determined from potentiometric titration data for a water-soluble analogue of the ligand. This set of pure thermodynamic parameters is used to calculate the spatially discretized composition of each column volume element as a function of time. The model includes a temperature-dependent pure-component parameter, determined by regression to a single elution band for the pure component, that corrects for subtle effects associated with immobilizing the N-octyl-3-octylthio-d-valine ligand onto the stationary phase. The model is shown to accurately predict elution chromatograms and separation performance as a function of key column operating variables. The model is then used to better understand the connection between chemical equilibria within the system and changes in band profiles and band separation resulting from changes in column operating conditions. © 2007 American Institute of Chemical Engineers AIChE J, 2007

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