Thermodynamics and optimization of norbixin transfer processes in aqueous biphasic systems formed by polymers and organic salts.

Abstract

Partitioning of the natural dye norbixin has been studied in aqueous two-phase system (ATPS) that are formed by mixing aqueous solutions of a polymer (or copolymer) and an organicsalt (sodium tartrate or succinate). In this work, the norbixin partition coefficient (KN) was optimized, taking into account the variables of polymer concentration, salt concentration and pH. It was found that KN is highly dependent on the electrolyte nature, system hydrophobicity and TLL values. Testing produced KN values between 8 and 130, indicating the great potential of ATPS as a method for norbixin pre-concentration/purification. Thermodynamic transfer parameters (ΔtrG, ΔtrH, ΔtrS) indicate that the preferential concentration of norbixin in the top phase is favored by enthalpic and entropic contributions.