Direct immersion single drop microextraction with hydrophobic deep eutectic solvent for the isolation of β-lactams and tetracyclines from milk.

The hydrophobic deep eutectic solvent (HDES) consisting of thymol and coumarin was used as an extraction medium during the isolation of the veterinary antibiotics from group tetracyclines (lymecycline LYM, oxytetracycline OTC, tetracycline TC) and β-lactams (amoxicillin AMS, ampicillin AMP). The use of deep eutectic solvents in miniaturized liquid-liquid extraction ensures the elaboration of a procedure consistent with the rules of green analytical chemistry. Single drop microextraction (SDME) technique enabling a radical reduction of HDES volume was developed for isolation of tetracyclines and β-lactams antibiotics from the bovine milk samples. The obtained microextracts were analyzed followed by the liquid chromatography method connected with tandem mass spectrometry (LC-MS/MS). The linear concentration range (1.10-8 mol L-1-7.10-5 mol L-1) of the studied compounds for elaborated HDES-SDME-LC-MS/MS method enables their determination in milk samples according to the normalized values (EU Regulation 37/2010).