ELECTROSPRAY MASS-SPECTROMETRIC CHARACTERIZATION OF FLUOROQUINOLONE ANTIBIOTICS - NORFLOXACIN, ENOXACIN, CIPROFLOXACIN AND OFLOXACIN

We report the electrospray (ESI) mass spectra of four fluoroquinolones, enoxacin, norfloxacin, ofloxacin and ciprofloxacin, a group of highly potent antibiotics that have not been previously characterized by this ionization technique. At low sampling cone voltage settings, 50 and 100 V, the electrospray mass spectra contained primarily molecular adduct ions. At a sampling cone voltage setting of 150 V, collisionally activated dissociation mass spectra containing structurally significant product ions were produced and accurately mass measured at a magnetic sector resolution of 3000. Gradient separation and characterization of these compounds was demonstrated by analysis using packed capillary column liquid chromatography with UV and ESI-MS detection. UV detection limits in the 1 to 2 ng range ((signal-to-noise ratio S/N) = 10:1) were estimated and interpretable mass spectra with S/N ratios in excess of 100:1 were observed for 1.5 ng of analyte during electrospray mass spectrometric analysis.