Determination of six quinolone residues in porcine muscle and liver by modified QuEChERS coupled with UPLC-MS/MS

The determination of quinolone residues in animal-derived foods is important for food safety control. In this study, a modified QuEChERS sample preparation combined with UPLC-MS/MS was developed for the simultaneous determination of six quinolones (norfloxacin, enoxacin, enrofloxacin, ciprofloxacin, pefloxacin, and lomefloxacin) in porcine muscle and liver. Acidified acetonitrile (0.1% formic acid) was used as the extraction solvent, and C18 was selected for dispersive solid-phase extraction cleanup. Detection was performed using electrospray ionization (ESI) in positive ion mode under multiple reaction monitoring (MRM) conditions. The six quinolones showed good linearity (r > 0.990). The limits of detection (LODs) were in the range of 0.05–0.17 μg/kg, and the limits of quantitation (LOQs) were 0.14–0.52 μg/kg. Method validation was carried out on spiked samples at concentration levels of 2.0, 10.0 and 200.0 μg/kg. Recoveries ranged from 74.8% to 106.7% with relative standard deviations (RSDs) of 1.6%-9.1%. Application of the method to market samples showed that two porcine muscle samples contained enrofloxacin at 13.7–18.7 μg/kg, which were below the regulatory limits. Overall, the results indicates that the proposed method provides a rapid and reliable analytical approach for monitoring quinolone residues in porcine tissues.