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

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 (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.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► ATPS have a great potential as a method for norbixin purification. ► Norbixin transference from bottom phase to the top phase is enthalpy and entropy driven. ► Polymer hydrophobicity and anionic nature significantly influence the KN values.