Spectrum Characteristic and Variation Mechanism of Ofloxacin under Different Acid-Basic Conditions

The structural morphology and spectra characteristic of ofloxacin (OFL) was strongly affected by the pH. In strong acidic solutions, OFL molecule exists as strong cation to achieve a weaker intensity. When the pH value increased to 3-4, OFL molecule exists as zwitterions, which is the strongest fluorescence form to have maximum intensity; the maximum exciting and emission wavelength of OFL were 298 and 508 nm, respectively. Along with the increase in neutral pH value, OFL molecule exists as weak anion, fluorescence and UV spectra changed, the intensity decreased, the maximum exciting and emission wavelength of OFL were 290 and 467 nm, the UV absorbance wavelength blue-shifted 5-7 nm; under basic condition, OFL molecule exists in anion ion form, and fluorescence and UV intensity and decreases with pH increasing , but spectrum remains constant. OFL molecular spectrum is stable and achieved the maximum intensity under the pH of 3-4.