(3S)-9-Fluoro-3-methyl-10-(4-methylpiperazin-1-yl)-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazin-7-one; (S)-9-Fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine;Levofloxacin Decarboxy Impurity ; Decarboxylate Impurity;