The degradation of levofloxacin by bismuth vanadate (BiVO4) catalyst and visible light was carried out in aqueous solution under optimized conditions. The drug degradation was monitored by observing the change in its absorbance value (l 290 nm) using a spectrometer. Levofloxacin degraded by almost 76% in 170 min under optimized conditions and followed the first order kinetics (rate constant was 0.0089 min–1). LC-MS technique, in addition to tandem mass spectrometry, was used to elucidate the structures of the proposed transformation products/intermediates. Three main initial products were determined after 30 min of reaction (Compound I Fig. 4: (S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methylpiperazin-1yl)-[1,4]oxazino-[2,3,4-ij]quinolin-7-one, Compound IV Fig. 4: (S)-3,7-dihydro-3-methyl-10-(4-methylpiperazin-1-yl)-7-oxo-2H-[1,4]oxazino-[2,3,4-ij]quinolone-6-carboxylic acid, and Compound X Fig. 5: (S)-3,7-dihydro-9-hydroxy-3-methyl-7-oxo-10-(piperazine-1-yl)-2H-[1,4] oxazino-[2,3,4-ij]quinolone-6-carboxylic acid). Several pathways for the degradation of levofloxacin can be recognized. They involve mechanisms such as demethylation, defluorination, decarboxyl-ation, deamination, and hydroxylation resulting in the production of many different transformation products such as malonic acid, piperazine, acetaldehyde, pyridone, and methylketone.
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