Validation of a MLC method with fluorescence detection for the determination of quinolones in urine samples by direct injection

A sensitive and robust method was developed and validated for the routine identification and quantification of five quinolones in urine samples directly injected into a micellar liquid chromatographic system without any pre-treatment step. Since the simultaneous elution of the five compounds was not resolved, two mobile phases have been proposed: (a) for ciprofloxacin and levofloxacin 0.15 M sodium dodecyl sulphate, 12.5% propanol and 0.5% triethylamine at pH 3.0 as the mobile phase and the detector at excitation wavelength 285 nm and emission wavelength 465 nm; and (b) for lomefloxacin, ofloxacin and moxifloxacin 0.05 M sodium dodecyl sulphate, 12.5% propanol and 0.5% triethylamine at pH 3.0 as the mobile phase and the detector at excitation wavelength 295 nm and emission wavelength 485 nm. Using these conditions, and in accordance with the food and drug analysis (FDA) guideline, the limit of quantification was 1 ng/mL, and the relative standard deviation and accuracy of the inter-day assay were 1.0–8.4% and 0.11–1.5%, respectively. Detection of the urinary excretion of four quinolones was followed up at 12 h after the healthy volunteers had taken the drug. No potential interference from metabolites was observed. This procedure permits the rapid and reproducible measurement of low levels of quinolones in a small amount of urine.