Determination of the Thermodynamic Behavior of a Therapeutic Peptide in Overloading Conditions in Gradient Elution Chromatography

Abstract

The aim of this work is to model the adsorption behavior of a cyclic octapeptide, octreotide, in reversed-phase gradient elution liquid chromatography. Adsorption isotherms of the peptide were firstly determined in isocratic conditions, using different peptide concentrations and compositions of the mobile phase (mixtures with different percentage of organic modifier, ranging from 23 to 28% v/v). Inverse Method (IM) was applied to determine the parameters describing the isotherm equation for every composition of mobile phase considered. Then, the isotherm parameters have been correlated to the amount of organic modifier in the mobile phase, through the Linear Solvent Strength model (LSS). In the end, it was possible to predict the chromatographic behavior of the cyclic octapeptide in overloading gradient conditions, the knowledge of which can be useful when scaling the method in preparative conditions.