In situ pH-responsive deep eutectic solvent for homogeneous liquid-liquid extraction of preservatives and an...

Preservatives and antioxidants are widely used in consumer products to inhibit microbial growth and oxidative degradation. However, their excessive use may pose potential health risks, highlighting the need for regulatory control and reliable analytical methods to ensure safety and compliance. This study aimed to develop a simple, environmentally friendly, and unified sample preparation strategy based on a pH-responsive deep eutectic solvent (pH-DES) coupled with homogeneous liquid-liquid microextraction (HLLME). The method was applied to extract six preservatives and one antioxidant from aqueous and oily matrices, followed by analysis using narrow-bore high-performance liquid chromatography with UV detection. The pH-DES was generated in situ in the sample using 4-methylcyclohexanol as the hydrogen bond acceptor and decanoic acid as the hydrogen bond donor at a 1:1molar ratio. As the pH-responsive component, decanoic acid, together with 4-methylcyclohexanol, facilitates the selective capture of target analytes through hydrogen bonding and hydrophobic interactions. The developed method exhibited satisfactory linearity in both aqueous and oily matrices and was successfully applied to 15 commercial food, pharmaceutical, and cosmetic products, yielding good recoveries (90.6-104.6%). In addition, AGREEprep evaluation confirmed the green performance of the proposed method. Overall, the in situ pH-DES-HLLME approach provides a simple and environmentally friendly strategy for the extraction of preservatives and an antioxidant from complex real-world samples.