Ultrasound-assisted supramolecular deep eutectic solvent extraction coupled with salting-out separation for the determination of GABA in tea

In this work, a convenient, sensitive, and economical ultrasound assisted extraction method based on a supramolecular deep eutectic solvent (SUPRADES) was developed for the determination of γ-aminobutyric acid (GABA) in tea. In this approach, 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) served as the hydrogen-bond acceptor and malonic acid as the hydrogen-bond donor for the preparation of the DES, while ultrasound assistance was employed to intensify mass transfer. The DES composition and key process variables were systematically investigated and optimized. The effects of DES dosage, ultrasonication time, solid-to-liquid ratio, salt amount, and derivatization time were evaluated with a Box–Behnken response surface. The obtained model was highly significant (p < 0.0001) with an not significant lack of fit (p = 0.0853), affording an R² of 0.9995. Under the optimized conditions, excellent linearity was achieved over 0.5–500 µg/mL (R² = 0.9995), with a limit of detection (LOD) and limit of quantification (LOQ) of 0.27 µg/mL and 1.25 µg/mL, respectively. The method exhibited satisfactory intra /inter-day precision (RSD ≤ 2.7%) and recoveries of 85.6%–92.8%. The greenness of the developed method was assessed using two quantitative green metrics tools: analytical Eco-scale and AGREE, with analytical Eco-scale qualifying the proposed method as green. The proposed method was successfully applied to real tea samples and exhibited a limited matrix effect, offering a practical sample-preparation strategy for other complex food matrices.