文摘
Fluoroquinolone (FQ) residues in caprine milk were screened by terbium-sensitized luminescence (TSL). After extraction and cleanup using Oasis HLB columns, TSL was measured at λ ex = 300 nm and λ em = 546 nm using a 5-kg luminescence photometer. A common threshold was established at x F50–3σ F50, where x F50 and σ F50 were the mean and standard deviation, respectively, of TSL intensities of milk samples (n = 18) spiked with flumequine at 50 ng/g, its maximum residue limits (MRL) set by the European Union. Enrofloxacin, ciprofloxacin, and danofloxacin at their respective MRLs had higher TSL responses, so could be screened below their MRLs. Among 48 blind samples, each randomly spiked with one FQ at up to 200% of its MRL, 36 were screened correctly without false negative. This rapid protocol can reduce a sample pool to a small fraction for confirmation, hence improve throughput and save assay costs.