Synthesis and application of polyoxometalate ionic liquid-coated ZnO nanoflowers for efficient extraction of tetracycline residues in food and environmental samples

Abstract

Monitoring of antibiotic residues in foodstuffs is essential to ensure consumer safety. Among these antibiotics, tetracyclines (TCs) are the most widely used veterinary drugs, and their residues pose serious health risks. A novel sorbent material consisting of zinc oxide modified with a polyoxometalate-based ionic liquid (POM-IL@ZnO) was applied in dispersive micro-solid phase extraction (D-µSPE) coupled with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) for the determination of tetracyclines, namely oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC), in complex food and water samples. The morphology, crystallinity, thermal stability, and structural characteristics of POM-IL@ZnO were characterized using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR). Systematic optimization was performed by evaluating key extraction parameters, including sorbent recyclability, eluent type and volume, extraction time, pH, and adsorbent amount. The developed method achieved maximum recoveries of 99.8%, low limits of detection (0.026–0.067 µg mL⁻¹) and quantification (0.080–0.210 µg mL⁻¹), excellent linearity (R² ≥ 0.998), a linear range of 10–1000 µg mL⁻¹, and relative standard deviation (RSD) values ranging from 1.8% to 6.0%. The POM-IL@ZnO sorbent-based D-µSPE method demonstrates strong potential for routine food safety analysis as a rapid, sensitive, and environmentally friendly approach for determining tetracycline residues. The performance of the developed method was compared with previously reported SPE-based methods.