Determination of fluoroquinolones in human urine by liquid chromatography coupled to pneumatically assisted electrospray ionization mass spectrometry.

The fluoroquinolones are synthetic antimicrobial agents widely used in human and veterinary medicine. The aim of this work was to develop a method of characterization and determination of three widely used fluoroquinolones (norfloxacin, ciprofloxacin and ofloxacin) in human urine by liquid chromatography (LC) coupled to pneumatically assisted electrospray ionization (ESI) mass spectrometry (MS). For this purpose, the operational parameters of the electrospray interface were optimized in order to obtain the best signal stability and the highest sensitivity of the fluoroquinolones. The three fluoroquinolones studied and enrofloxacin, used as internal standard, were extracted from human urine samples by solid-phase extraction (SPE) and the previously established LC-UV method was successfully coupled with the MS system. The mass spectra obtained provide adequate information for identification purposes. Quality parameters were determined and satisfactory results were obtained. Likewise, the method detection limit was about 10 ng ml(-1) for the three fluoroquinolones studied employing selected-ion monitoring mode.