Recebido em 7/7/09; aceito em 25/11/09; publicado na web em 23/3/10The objective of this research was to develop and validate an alternative analytical method for quantitative determination of levofloxacin in tablets and injection preparations. The calibration curves were linear over a concentration range from 3.0 to 8.0 μg mL -1. The relative standard deviation was below 1.0% for both formulations and average recovery was 101.42 ± 0.45% and 100.34 ± 0.85% for tablets and injection formulations, respectively. The limit of detection and limit of quantitation were 0.08 and 0.25 μg mL -1 , respectively. It was concluded that the developed method is suitable for the quality control of levofloxacin in pharmaceuticals formulations.Keywords: fluoroquinolone; UV spectrophotometry; quality control.
INTRODUCTIONQuinolones are antimicrobials, structurally related to nalidixic acid, which were made available for clinical use in urinary infections, since 1960s.1,2 They are used in human and veterinary medicine, especially in animal breeding area.1,2 Considerable amounts of quinolones are widely used under field conditions (in poultry, swine, and cattle production), both in the treatment of infections and as growth promoters.1 The bactericidal activity of levofloxacin is mediated by the inhibition of DNA gyrase (topoisomerase II) and topoisomerase IV, essential enzymes involved in bacterial DNA replication, transcription, repair and recombination. , is presented as white to light yellow needlelike crystals, that melt at approximately 226 ºC. Its solubility is nearly constant from pH 0.6 to 5.8 (100.0 mg mL -1 ). Above pH 5.8, solubility increases sharply, reaching a maximum of 272 mg mL -1 at pH 6.7, beyond which it decreases to a minimum of 50.0 mg mL -1 . 5 Levofloxacin is the quinolone of choice for airway infections, being active against several types of pathogens. 1,2,4,6 Various analytical methods have been reported in scientific literature for the analysis of levofloxacin in pharmaceutical formulation and/or biological fluids including high-performance liquid-chromatography with UV detection (HPLC-UV), 7 vibrational spectroscopy, 8 spectrofluorimetry (SF), 9 colorimetric spectrophotometry (CS), 9,10 spectrophotometry by ion-pair complex (CIPS), [10][11][12] and UV spectrophotometry (UVS).
13Most spectrophotometric methods in the literature for analysis of levofloxacin is based on the formation of ion-complexes, 10-12 which use dye as Eriochrome black, 12 bromophenol blue, bromocresol green, 10,12 eosin, merbromin 11 and chromogenic reagent such as Folin-Ciocalteau.
12The addition of these substances usually increases the cost of analysis and sample preparation is time consuming. Besides cost, toxicity of reagents and solvents used in the analysis should also be considered. Exposure to merbromin even at low concentrations and short exposure time can cause poisoning. The complexes formed normally need extraction with organic solvents, for example, chloroform, 10,12 which in addition to further increase the cost of analys...
