目的 加替沙星注射液光降解产物的初步鉴定。方法 用液相色谱-质谱联用技术分离并鉴定加替沙星注射液光降解产物，以3%醋酸乙腈溶液-3%醋酸溶液（15∶85）为流动相，紫外检测波长293 nm，质谱检测为电喷雾离子化正离子方式。结果 加替沙星注射液经光照后增加了一光降解杂质峰，该杂质的相对分子质量为335；加替沙星注射液光照10 d后放置1年所产生的光降解杂质与其室温放置14个月后再光照10 d所产生的光降解杂质相同。结论 推断加替沙星注射液光降解杂质的结构为6-氟-8-甲氧基-7-（3-甲基-1-哌嗪基）-1,4-二氢-4-氧代-3-喹啉羧酸；加替沙星注射液在避光条件下保存是稳定的。

OBJECTIVE To analyse the photodegradation product of gatifloxacin injection METHODS The photodegradation product of gatifloxacin injection was analysed by RP-HPLC/electrospray ionization mass spectrometry with a Zorbax SB-C₁₈ (4.6 mm×150 mm ID, 5μm) column. The mobile phase was composed of 3% acetic acid in acetonitrile and 3% acetic acid in water (15∶85, v/v) RESULTS The molecular weight of the photodegradation product was 355，40 less than that of gatifloxacin. The photodegradation product of gatifloxacin injection which had been stored at room temperature for 1 year after 10 days′ illumination was the same as that of the injection which had been illumination for 10 days after 14 months′ storage at room temperature CONCLUSION The structure of the photodegradation product may be 6-fluoro-1,4-dihydro-8-methoxy-7-(3-methy-1-piperazinyl)-4-oxo-3-quinolinecarboxylic acid. The gatifolxacin injection was stable protected from light.