Vortex-assisted dispersive solid-phase extraction of tetracyclines in honey and eggs using green sulfonated carbon derived from spent coffee grounds.

Residues of tetracycline antibiotics in animal-derived foods pose significant safety risks. This study developed a novel, environmentally friendly, and highly efficient method for the extraction and analysis of tetracyclines from food matrices. This approach utilized a sulfonated carbon (SC) adsorbent synthesized from a readily available and sustainable resource: spent coffee grounds via a facile, simple, and rapid ultrasound-assisted one-pot carbonization and sulfonation method. Comprehensive characterization using FTIR, SEM, TEM-EDX, XPS, BET, and zeta potential confirmed the formation of a porous carbonaceous structure functionalized with sulfonic acid groups favorable for antibiotic adsorption. The SC was applied as an effective sorbent in vortex-assisted dispersive solid-phase extraction coupled with HPLC-UV for the determination of four tetracyclines. The developed method demonstrated linearity of 10.0-500 µg L⁻¹ (R² > 0.9892), low limits of detection (5.0 µg L⁻¹), and satisfactory precision (RSD) < 11%. The method was successfully applied to honey and eggs, yielding recoveries between 74.3% and 119.4%. This approach effectively repurposes food waste into a high-performance analytical tool, offering a rapid, sustainable, and cost-effective solution for monitoring antibiotic residues in food systems.