Abstract：The fluorescence characteristics of norfloxacin in different pH media have been studied by spectrofluorimetry. It was found that in the neutral and alkalescent media the fluorescence signal of norfloxacin was weak, while in the acidity media the signal was very strong. The maximum fluorescence signal of norfloxacin could be obtained at pH 3.04, and the norfloxacin fluorescence emission wavelength has red-shifted 30 nm compared with the other condition. Based on this, a spectrofluorimetric method of the determination of norfoxacin in pharmaceuticals is proposed. The linear range was 0.016-0.96 μg·mL-1, the detection limit was 0.016 μg·mL-1, the RSD was 1.65%-2.86%, and the recovery was within the range of 99.7%-100.94%. At pH 3.04, norfloxacin in human urine can be well resolved by Synchronization-1st derivative fluorescence spectroscopic techniques with Δλ=90 nm, and the interference from urine blank can also be eliminated. The linear range was 0.096-3.19 μg·mL-1 for determining norfloxacin in human urine sample. The detection limit was 0.096 μg·mL-1, the recovery was within the range of 96.24%-104.4% and RSD was 0.71%-2.60%. Pharmacokinetic study of norfloxacin showed that norfloxacin reached its peak concentration in urine samples two hours after a healthy man took capsules. The method is simple, rapid and accurate with high sensitivity and good selectivity, and suitable for the determination of norfloxacin. The method was applied to analysis of norfloxacin in drugs and biological samples.
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