Model for nonequilibrium binding and affinity chromatography: characterization of 8-hydroxyquinoline immobilized on...

This paper discusses the use of pulse techniques for analysis of zonal elution data for the determination of mass-transfer and axial dispersion constants for porous support materials with adsorption to the surface or to a surface-bonded phase. As an example, this paper considers the case of controlled pore glass (CPG) with a bonded phase that is used with microcolumns and a flow injection analysis system. For the CPG, axial dispersion in the form of eddy mixing can be described by l = 0.203, and the overall mass-transfer term, K(OL) = 3.9 x 10(-6) cm/s. Additionally, an affinity chromatography model was adapted to effectively describe systems employing CPG as the support material through modification of equations describing typical affinity chromatography systems and by inclusion of an axial dispersion term in the calculation of N. This model was used to predict breakthrough curves for cadmium adsorption by 8-hydroxyquinolinol immobilized on CPG packed in microcolumns. In general, the information from the model can be used to extract equilibrium-based constants (binding strengths and site capacities) from a nonequilibrium flow system. The data and model can also be employed in determining the performance for scaled-up extraction systems. The modified model is available in EXCEL spreadsheet format as Supporting Information.