Partial least squares multicomponent fluorimetric determination of fluoroquinolones in human urine samples

Ternary mixtures of fluoroquinolones, with a 7-piperazinyl substituted group have been simultaneously determined in human urine samples by application of a multivariate calibration partial least squares (PLS) model. The calibration set was designed with 15 urine samples containing different concentrations of the three fluoroquinolones and 16 blank urine samples. The concentration range for the fluoroquinolones were up to 25 ng ml⁻¹ for norfloxacin (NOR), 80 ng ml⁻¹ for ofloxacin (OFLO) and 300 ng ml⁻¹ for enoxacin (ENO). The method is based on the native fluorescence emission of these compounds in sodium dodecyl sulfate (SDS) medium, at pH 4.0, when exciting at 277 nm. A selection of the emission wavelength range used for the analysis was made for each component. Intraday and interday precision values were determined. Figures of merit as selectivity, sensitivity, limit of detection (LOD) and analytical sensitivity were also calculated. Using the standard addition methodology, five urine samples from five different persons, fortified with three concentration levels of the fluoroquinolones, were analyzed. The limits of detection in urine were 10.0, 0.5 and 0.8 ng ml⁻¹ for ENO, NOR and OFLO, respectively.