Dispersive liquid-liquid microextraction for the determination of menthol residue in fish by GC-MS

Conventional dispersive liquid-liquid microextraction (DLLME) and low density solvent-based dispersive liquid-liquid microextraction (LDS-DLLME) were evaluated in the extraction of menthol (1R, 2S, 5R)-2-isopropyl-5-methylcyclohexanol from tilapia (Oreochromis niloticus) fillets. The nature of the extraction and disperser solvents underwent univariate analysis. The results indicated greater efficiency in the extraction of menthol when toluene was used as extraction solvent and acetone as the disperser solvent. Once the extraction and disperser solvents were set, the parameters: ionic strength and volumes of the extraction solvent and water were evaluated using the central composite design (CCD). The conditions determined as ideal were 0.1 g of sodium sulfate, 100 μL of toluene and 5 mL of water. The enrichment factor of the LDS-DLLME technique was of 80 times, the limits of detection and quantification were of 0.0539 and 0.1190 μg L− 1, respectively. The methodology developed was applied to determine menthol residues in tilapia fillets killed at different times and at different anesthesia concentrations. The results showed that the time needed for the organism of the fish to completely eliminate the menthol was > 24 h. This methodology becomes promising for the obtaining of protocols which regulate the use of menthol as an anesthetic used in aquaculture.