氟喹诺酮类抗生素的表面解吸常压化学电离质谱行为研究

采用表面解吸常压化学电离质谱（DAPCI-MS）技术对5种氟喹诺酮类化合物进行多级串联质谱研究，获得了各化合物的多级质谱信息。通过比较各化合物质谱裂解途径的异同，发现在正离子检测模式下，氟喹诺酮类化合物在碰撞诱导解离过程中均产生中性丢失44 u（CO₂）、28 u（CO）、20 u（HF）、18 u（H₂O）的离子峰。如果结构中含有哌嗪环取代基，脱羧后可观察到哌嗪环的重排反应，生成丢失43 u（C₂H₃NH₂）和57 u（CH₃-CH₂-N[CDS1]CH₂）的碎片离子，这可作为“诊断”其他氟喹诺酮类化合物和结构类似物的特征。该方法无需样品预处理，不使用有机溶剂，分析速度快，是一种无污染、无毒、原位、无损的分析方法，可为痕量药物分析提供新的思路。

Analysis of Fluoroquinolones by Surface Desorption Atomospheric Pressure Chemical Ionization Mass Spectrometry

Fluoroquinolones (FQs) are the third generation of quinolones (QNs), which are one of the most important breakthrough in the field of artificially synthesis of antimicrobial agents following sulfa drugs. Because of its wide antimicrobial spectrum, strong antibacterial activity, no cross resistance side effects with other antimicrobial agents, FQs are widely used in small animal and human many kinds of infectious diseases prevention and treatment. However, with the widespread use of antibiotics, the problems of counterfeit antibiotics emerged and proliferated gradually. Therefore, it is need to develope an analytical method with high sensitive and high speed. Mass spectrometry was the development of ambient ionization techniques, which enabled the ionization of samples in their native environment without sample pretreatment. After the emergence of the pioneered technique, desorption electrospray ionization (DESI), including more than 20 direct-ionization techniques, have been developed in the past decades. Among them, desorption atmospheric pressure chemical ionization (DAPCI) is a powerful ionization technique and has been successfully applied to detect trace surface analytes without evidently injuring the sample in food security, forensic science and environmental science. In this study, the DAPCI source coupled with the linear ion trap mass spectrometer was used to investigate the fragmentation mechanism of fluroquinolones. Five compounds of fluroquinolones were analyzed using surface desorption atomospheric pressure chemical ionization mass spectrometry (DAPCI-MS) by collision induced dissociation in positive ion detection mode. The mass spectra and structures of the five fluroquinolones were compared with each other, and it was observed that fluroquinolones gave characteristic fragment ions by the neutral loss of 44 u (CO₂), 28 u (CO), 20 u (HF) and 18 u (H₂O). If compounds have piperazidine substituent, piperazine-link rearrangement can be observed after decarboxyliation, and characteristic fragment ions by the loss of the 43 u (CH₂[CDS1]CH-NH₂) and 57 u (CH₃-CH₂-N[CDS1]CH₂) were produced. All of them can be used as a “diagnosis” of other fluoroquinolone compounds and structure similar to the characteristics of the ions, which can open a way to fast analyze the FQ drugs.