Study of diclofenac distribution in aqueous two-phase PEG/salt/water systems

Abstract

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID). Due to its extensive use, it has been detected in various environmental compartments, where it has been shown to exert adverse effects on living organisms. This underscores the need to develop efficient and environmentally benign removal strategies. Aqueous Two-Phase Systems (ATPS) offer a promising alternative for liquid–liquid extraction without the use of organic solvents, providing a sustainable separation technique. This study evaluated the effectiveness of diclofenac extraction using ATPS. Results demonstrated that, at low drug concentrations (10 ppm), extraction yields exceeded 95% across all systems tested, regardless of whether the pH values were above or below the pK_a of diclofenac. The ATPS composed of polyethylene glycol (PEG) 1000 g mol⁻¹ at 25.5% w w⁻¹ and sodium citrate at 21.5% w w⁻¹ was identified as the most efficient, achieving an extraction efficiency of up to 99.9% and minimal mass transfer of PEG and salt between phases. UV-Vis spectroscopy analysis suggests that the drug's phase transfer occurs via hydrogen bond formation between diclofenac and PEG. The proposed method exhibits high efficiency for diclofenac recovery and stands out for its low environmental impact.