Sensitive Determination of Fluoroquinolone Antibiotics in Milk Samples Using Time‐Resolved Methodology

Abstract

The potential application of terbium(III) as a general reagent for the luminescent determination of fluoroquinolone residues in milk samples is studied. Ten fluoroquinolones with different functional groups have been chosen for this purpose. Using time‐resolved methodology and 278 and 545 nm as excitation and emission wavelengths, most of the fluoroquinolones assayed give intense luminescence in the presence of terbium(III), which can be useful for screening purposes. Ciprofloxacin, which is the major metabolite of enrofloxacin, one of the fluoroquinolones used in veterinary medicine, has been taken as fluoroquinolone model for the optimization of the method, which has been developed in the presence of the anionic surfactant sodium dodecylsulfate (SDS), which protects the chelate from non‐radiative processes. The dynamic range of the calibration graph was 0.5–1000 ng mL−1 and the calculated detection limit was 0.14 ng mL−1. Similar results were obtained for most of the other fluoroquinolones assayed. The precision, expressed as relative standard deviation, was lower than 5%. The method is very fast and only requires the simple deproteinization of milk samples with acetonitrile, obtaining analytical recoveries that ranged from 91.9% to 110.5%.