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 organic salt (sodium tartrate or succinate). In this work, the norbixin partition coefficient ( K N ) was optimized, taking into account the variables of polymer concentration, salt concentration and pH. It was found that K N is highly dependent on the electrolyte nature, system hydrophobicity and TLL values. Testing produced K N values between 8 and 130, indicating the great potential of ATPS as a method for norbixin pre-concentration/purification. Thermodynamic transfer parameters (Δ tr G , Δ tr H , Δ tr S ) indicate that the preferential concentration of norbixin in the top phase is favored by enthalpic and entropic contributions.