Dispersion of Magnetic Graphene Oxide Nanoparticles Coated with a Deep Eutectic Solvent Using Ultrasound Assistance for Preconcentration of Methadone in Biological and Water Samples Followed by GC-FID and GC-MS

Magnetic graphene nanoparticles coated with a new deep eutectic solvent (FeO@GO-DES) were developed for efficient preconcentration of methadone. The extracted methadone was then analyzed by gas chromatography-flame ionization detection (GC-FID) or gas chromatography-mass spectrometry (GC-MS). FeO@GO-DES were characterized by Fourier transform IR and X-ray diffraction techniques. Ultrasound was used to enhance the dispersion of the sorbent, with a high extraction recovery. Some parameters affecting the extraction recovery, such as pH, type of deep eutectic solvent, sample volume, amount of sorbent, extraction time, and type of eluent, were investigated. Under optimum conditions, the method developed was linear in the concentration range from 3 to 45,000 μg L for GC-FID and from 0.1 to 500 μg L for GC-MS, with a detection limit of 0.8 μg L for GC-FID and 0.03 μg L for GC-MS. The relative standard deviations (n = 6) as the intraday and interday precisions of the methadone spike at a concentration of 100 μg L were 5.8% and 8.4% respectively for GC-FID. The preconcentration factor was 250. Relative recoveries from spiked plasma, urine, and water samples ranged from 95.1% to 101.5%.