Chromatographic determination of flumequine in food samples by post-column derivatisation with terbium(III)

The potential usefulness of terbium(III) as reagent for the luminescent determination of flumequine residues in food samples has been studied using both fluorescence (FL) and time-resolved (TR) modes and both batch (B) and integrated liquid chromatography (LC)/derivatisation approaches. The system was optimised in each instance to establish the analytical features of the four methods. The dynamic ranges of the calibration graphs, obtained with standard solutions of flumequine, were (ng mL⁻¹): B-FL 0.18-600; B-TR 2.4-150; LC-FL 3.7-1000 and LC-TR 52-3000. The detection limits were also obtained giving the following values (ng mL⁻¹): B-FL 0.055; B-TR 0.7; LC-FL 1.1 and LC-TR 15. The precision, expressed as the percentage of relative standard deviation, was equal or lower than 5.1% in all instances. The LC methods, which avoid the interference of other quinolone antibiotics, were applied to the analysis of chicken muscle and liver, and whole milk samples. The sample pre-treatment only consisted of a deproteinisation step. The validation procedure for the analysis of samples was carried out using EC recommendations, and the decision limit and detection capability were calculated. The recoveries obtained ranged from 95.0% to 103.8%.