One-step phase separation and magnetic retrieval of switchable natural deep eutectic solvents via Fe3O4@CA composites for rapid extraction of illegal non-steroidal anti-inflammatory drugs in herbal extracts

A novel microextraction method based on switchable natural deep eutectic solvents (SNADES) was developed for the determination of illicitly added non-steroidal anti-inflammatory drugs (NSAIDs) in herbal extracts, enabling one-step phase separation and magnetic retrieval of the extractant. The addition of ammonia solution induces the reversible transition of the hydrophobic SNADES (menthol:decanoic acid = 1:1) to a hydrophilic state, thereby significantly enhancing the extraction efficiency of the target analytes. Citric acid-modified Fe 3 O 4 composites (Fe 3 O 4 @CA) were employed to achieve rapid phase separation and efficient magnetic retrieval of the SNADES phase. After systematic optimization, the optimal conditions were established as 30 μL of SNADES, 70 mg of citric acid, 4 mg of Fe 3 O 4 , an extraction time of 4 min, and 100 μL of acetonitrile for desorption. Under the optimal conditions, four NSAIDs (flurbiprofen, diclofenac sodium, ibuprofen, and ketoprofen) exhibited good linearity over the concentration range of 0.1–20 μg/mL, with correlation coefficients (R 2 ) ≥ 0.993. The method provided relative recoveries of 93.7–109.2 % for the target analytes, with relative standard deviations (RSDs) ≤ 9.7 %. The limits of detection were in the range of 0.016–0.036 μg/mL. Spiked recovery experiments in real herbal extracts confirmed the method's accuracy (96.0–112.3 %), demonstrating that the proposed approach provides a rapid, efficient, and green sample preparation strategy for the screening of illicit synthetic drugs in herbal products.