Adsorptive behavior of α-lactalbumin on cation-exchange supermacroporous monolithic column

The adsorption and thermodynamics of alpha-lactalbumin onto cation-exchange continuous supermacroporous chromatographic columns were investigated. A poly(acrylamide)-based monolithic column has been produced by cryo-polymerization (cryogel), modified to an ion exchanger by grafting polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA). The ionic capacity of the hydrated cryogel was determined as 91.2 x 10(-3) mol Na+ per liter gel. The bed was characterized according to its morphology and flow properties, presenting interconnected pores ranging from 20 to 100 mu m, weak axial dispersion and height equivalent to theoretical plate (HETP) between 0.08 and 0.13 cm. Isotherm data were measured by frontal analysis at 30 degrees C and 40 degrees C, pH 2.5 and various salt concentrations (0-180 x 10(-3) mol L-1 of NaCl). A Langmuir model was fitted to equilibrium data, with a maximum adsorptive capacity (ranging from 120 to 210 mg mL(-1)) that is inversely proportional to the temperature and salt concentrations. Thermodynamic analysis based on the van't Hoff relationship shows that at the studied conditions the process was spontaneous with enthalpy-entropy compensation. Endothermic behaviors were observed in general, except at low NaCl concentrations, and was observed that the ion exchange process is entropically driven at the studied conditions. This matrix has a great potential in purification processes, presenting interesting characteristics for downstream processes. (C) 2015 Elsevier B.V. All rights reserved.