STUDY OF 4-QUINOLONE ANTIBIOTICS IN BIOLOGICAL SAMPLES BY SHORT-COLUMN LIQUID-CHROMATOGRAPHY COUPLED WITH ELECTROSPRAY-IONIZATION TANDEM MASS-SPECTROMETRY

Simultaneous detection and confirmation of 15 quinolone antibiotics wa s accomplished by fast short-column liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC/MS/MS). Several physicochemical parameters such as hydrophobicity and aqueous dissocia tion constants were calculated from the structural formulas of the qui nolone drugs, and their impact on both chromatographic and mass spectr ometric behavior was studied. Additionally, a possible influence of bu lk solution pH on electrospray detection sensitivity of 4-quinolones w as investigated and compared to predictions based on solution-phase eq uilibria, A signal intensity comparison of the MH+ ions at different p H values for all 15 compounds did not reveal any pH effect, despite va riations by several orders of magnitude in equilibrium concentrations in bulk solution. To demonstrate the potential of the LC/MS/MS method, its application to trace analysis in several biological matrices such as milk, salmon, and human urine was investigated. The method was sho wn to be sensitive with detection limits down to 1 ppb in both milk an d salmon tissue. The versatility of the method was also exhibited by u tilizing it for rapid identification of urinary metabolites of ciprofl oxacin. Finally, a new complementary approach is described for confirm atory analyses of 4-quinolones by means of a quasi-MS/MS/MS technique involving in-source collision-induced dissociation. it is shown that L C/quasi-MS/MS/MS can significantly enhance structural information and, thus, the specificity of analysis for the investigated 4-quinolones.