Development of a convenient HPLC-UV screening method for six antibiotic residues in chicken meat samples: model-driven gradient optimization and sorbent-free extraction with SALLME preconcentration.

The presence of antibiotic residues in poultry meat poses a growing risk of non-compliance with maximum residue limits under international food safety regulations. However, existing screening methods to detect antibiotic overuse rely mainly on LC-MS with dispersive solid-phase extraction (dSPE) clean-up using instrumentation and sorbents that are economically inaccessible to many food-safety laboratories in resource-limited countries where such monitoring is most needed. This work develops and validates a sorbent-free, HPLC-UV multiclass screening procedure for six antibiotic residues (sulfadiazine, trimethoprim, ciprofloxacin, enrofloxacin, sulfamethoxazole and doxycycline) in chicken meat samples prior to confirmatory testing by the LC-MS technique. Three integrated methodological milestones were achieved in this work. First, mechanistic retention-time modeling equations were applied to optimize a gradient HPLC-UV separation for the studied compounds based on only six scouting runs without trial-and-error effort. Second, the extraction procedure was optimized using the Plackett-Burman screening, followed by Box-Behnken response surface design, yielding a modified QuEChERS extraction method, eliminating the dSPE step. Third, a salt-assisted liquid-liquid microextraction (SALLME) preconcentration step for the recovered analytes mitigated the sensitivity limitations of UV detection, enabling detection at food-safety-relevant concentration ranges. A robust HPLC-UV method was developed with good peak separation within 17 min using a Zorbax SB C8 column (150 × 4.6 mm, 5 µm) with a gradient system consisting of a 20 mM formate buffer (pH 3.0) and an acetonitrile-methanol (1 : 1, v/v) blend. Detection was performed using the dual-wavelength mode at 230 and 275 nm. The procedure met the linearity, repeatability and recovery validation criteria under Commission Implementing Regulation (EU) 2021/808, with recoveries of 77.7-109.2% and expanded measurement uncertainty values not exceeding 42.8%, in accordance with SANTE/11312/2021 v2. The presented sorbent-free workflow provided a validated screening platform accessible in resource-limited settings worldwide.