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BACKGROUND Tetracycline antibiotics are employed for human and animal health and for speeding up growth rates. However, their presence in food products and environmental waters has been a concern for some years. Therefore, a variety of sample preparation methods have been developed for the analysis of tetracycline residues in these matrices. RESULTS An electrochemically controlled solid phase microextraction based on a modified copper electrode with polyaniline/graphene oxide (PANI/GO) conductive nanocomposite was developed for the extraction of oxytetracycline, tetracycline and doxycycline before high‐performance liquid chromatography‐UV analysis. PANI/GO was synthesized by in situ chemical oxidative polymerization, characterized by scanning electron microscopy and Fourier‐transform infrared spectroscopy, and bound on the electrode using high purity conductive double‐sided adhesive carbon glue. The significant factors affecting the performance of microextraction were investigated and optimized. Under the optimized conditions [sample, 15 mL; sorbent, 10 mg; pH, 3.0; electroextraction voltage, −0.9 V; electroextraction time, 20 min; eluent (MeOH/NH3), 500 μL; and desorption time, 5 min], the limits of detection for target analytes were in the ranges 0.32–1.01 and 2.42–7.59 μg L−1 in water and milk samples, respectively. The linear ranges were 1.06–750 μg L−1 for water and 8.05–750 μg L−1 for milk samples. The intra‐day and inter‐day precisions were 2.32–3.80 and 3.29–4.25, respectively. The method was applied to the determination of analytes in milk and water samples with different fat contents, and the recoveries were obtained in the range 71–104%. CONCLUSION The developed electro‐microextraction method provides a facile, rapid, cost‐effective, sensitive and efficient promising procedure for the extraction of antibiotics in complex matrices. © 2020 Society of Chemical Industry

A novel sorbent material consisting of a copolymeric deep eutectic solvent (DES) gel doped in calcium alginate (CA) hydrogel beads was synthesized and used in a green micro-solid phase extraction of 24 pesticides in 8 nonalcoholic malt beverages. The analyses were performed by gas chromatography–mass spectrometry/selective-ion monitoring. The DES was prepared by combining thymol (Thy, thyme oil) and methacrylic acid (MAA, can be obtained from Roman chamomile oil) in a 1:1 molar ratio via the heating-stirring method. Then, it was copolymerized using ammonium persulfate as a polymerization initiator and ethylene glycol dimethacrylate (EGDMA) as a crosslinking monomer through thermally induced free-radical reaction and finally was encapsulated in CA beads. The DES was characterized by Fourier transform infrared, Fourier transform nuclear magnetic resonance, and scanning electron microscopy techniques. A comparison study indicated that t extractionhe efficiency of the modified CA with polymeric DES (CA/[poly(MAA-co-EGDMA)]:[Thy]) was 1.5–3.4-fold higher than unmodified CA hydrogel beads. The influence of significant parameters affecting extraction efficiency was optimized. The method was validated by the matrix effect, specificity, precision, limits of quantifications (0.010–0.230 μg L–1), matrix-matched calibration linearity (0.010–300 μg L–1), and determination coefficients (r 2 = 0.990–0.998). The method was successfully utilized for the detection of pesticide residues in nonalcoholic malt beverage samples, and the obtained relative recoveries were 68.2–115.6% (relative standard deviation < 10.2%). The procedure’s greenness was evaluated by the Complex Green Analytical Procedure Index and the Analytical Eco-Scale protocols. This paper is the first report on the preparation and utilization of this novel sorbent for the analysis of pesticides in nonalcoholic malt drinks.