Voltammetric behavior and analytical applications of lomefloxacin, an antibacterial fluorquinolone

Lomefloxacin was reduced on a dropping mercury electrode, producing one or more peaks, depending on the pH of the aqueous medium. Coulometric measurem ents gave an experimental value of 1 electron for the main peak. Electrolys is was followed by UV spectrophotometry and liquid chromatography (LC), sho wing that a new band at 413 nm appeared for the electrolysis product in an acidic medium. Furthermore, by using UV spectrophotometry, an apparent pKa value of 6.75 +/- 0.05 was obtained for lomefloxacin corresponding to the c arboxyl moiety in the 8-position. For analytical studies, the differential pulse polarographic mode in 0.1 N HCl was selected. The repeatability and r eproducibility of the method were adequate (coefficient of variation [CV], 0.51 %), The calibration curve method was used for the lomefloxacin concent ration range of 7.0 x 10(-6) to 7.0 x 10(-5)M. The detection and quantitati on limits were 1.0 x 10(-6) and 6.9 x 10(-6)M, respectively. For purposes o f comparison, both UV spectrophotometric and LC (with UV and fluorimetric d etection) methods were developed. The polarographic method showed good sele ctivity with respect to both excipients and degradation products, The recov ery study showed a CV of <2% and an average recovery of 99.5% and it was no t necessary to treat the sample before analysis, The method was applied to the determination of the uniformity content of lomefloxacin commercial tabl ets, The polarographic method was also successfully applied to the quantita tion of lomefloxacin in urine, and the renal excretion profile was also det ermined.