Salt-saturated supramolecular solvent microextraction for spectrophotometric determination of curcumin in food samples

A salt-saturated supramolecular solvent-based liquid–liquid microextraction method coupled with UV–Vis spectrophotometry was developed for the sensitive determination of trace levels of curcumin in food samples. Supramolecular solvents formed from decanol and tetrahydrofuran were employed as the extraction phase, while a mixed salt system (NaCl, Mg(NO 3 ) 2 ·6H 2 O, and KNO 3 ) was used to enhance extraction efficiency through a salting-out effect. Key experimental parameters influencing extraction performance, including pH, extraction solvent volumes, mixing time, and centrifugation conditions, were optimized using Box–Behnken design combined with response surface methodology. Under optimal conditions, the proposed method exhibited a linear response over the concentration range of 1.0 µg/L − 5.0 mg/L with a limit of detection of 0.23 µg/L. An enrichment factor of 131 was achieved within a total extraction time of 6 min. The method demonstrated good precision, with relative standard deviations below 3.7%. Compared with supramolecular solvent microextraction without salt saturation, the proposed approach provided an average signal enhancement of 32.7%. The method was successfully applied to the determination of curcumin in tomato, apple and fish samples, yielding recoveries between 98.0% and 99.7%. Owing to its simplicity, rapidity, low solvent consumption, and satisfactory analytical performance, the developed method represents a green and efficient alternative for routine spectrophotometric analysis of curcumin in food matrices.