Norfloxacin Glutamate

A simple, precise, stability-indicating reversed-phase high-performance liquid chromatographic method for norfloxacin glutamate and norfloxacin glucuronate in liquid and solid dosage forms is described. Chloronitrodiazepine was used as the internal standard. The eluent used with a C18 bonded phase column was methanol-water-diethylamine (50:50:0.4, v/v/v) (pH* 5.5). The effects of the eluent pH*, the ratio of methanol to water, and the quantity of diethylamine on the retention times of the sample and internal standard were investigated. The method showed good linearity in the range 1-45 micrograms ml-1 for norfloxacin. Solid samples were ground, dissolved in the eluent, filtered, and then determined by this method. Liquid samples were dissolved in the same solvent. The average recoveries of norfloxacin glutamate and norfloxacin glucuronate in their simulated preparations were 99.5% for solid products and 99.8% for liquid products. The method was applied to the study of the thermal stability of the drugs by following the degradation of norfloxacin glutamate and glucuronate in the four products in accelerated tests at 37-80 degrees C for up to 3 months. Shelf-lives at 25 degrees C of the four products were predicted from the results assuming zero- and first-order kinetics of decomposition, and were at least 1.5 years for liquid products and 2 years for solid products.