Screening of Danofloxacin Residue in Bovine Tissue by Terbium-Sensitized Luminescence on C18 Sorbent Strips

Danofloxacin (DANO) residue in bovine muscle was screened at 200 ng/g by terbium-sensitized luminescence (TSL) directly measured on 10 x 6 trim C18 sorbent strips. The analyte was first adsorbed on sorbent surface by immersion in defatted homogenates. After reagent application and desiccation, TSL was directly measured on sorbent surfaces at lambda(ex) = 273 nm and lambda(em) = 546 nm. The luminescence intensity was linearly dependent on DANO concentration in the 0-1000 ng/g range (R-2 = 0.9967). A threshold was established at x(200) - 3 sigma(200), where x(200) and sigma(200) are the mean and standard deviation, respectively, of the DANO signals at 200 ng/g. Among 48 blind samples randomly fortified at 0-1000 ng/g, 45 were screened correctly and 3 negative samples were presumed positive. This simple screening protocol has the potential to significantly reduce sample numbers and hence improve sample throughput and save assay costs.