Research Of Degradation Mechanism Of Fluoroquinolone Antibiotics In Advanced Oxidation Processes By Mass Spectrometry

With the increasing use of pharmaceuticals and personal care products?PPCPs?,PPCPs are widely distributed in rivers,lakes,groundwater and the marine environment and their concentration is gradually increasing.Fluoroquinolone antibiotics which belong to PPCPs,were widely used.The cumulative and “pseudo-persistent” of fluoroquinolone antibiotics in the environment poses a serious threat to the environment and biological safety.Advanced oxidation processes are emerging organic pollutant treatment technology in recent years,which can effectively degrade antibiotic compounds and has a good application prospect.However,at present,the mechanism of degradation of organic pollutants by advanced oxidation processes is generally in off-line ways,which leads to incomplete information capture and unclear mechanism,restricting the improvement of organic pollutant degradation technology.Therefore,it is of great significance to establish a new method for real-time and online monitoring the degradation process of organic pollutants by advanced oxidation processes and to clarify the degradation mechanism of organic pollutants,so as to improve the degradation efficiency of organic pollutants and promote the practical application of advanced oxidation technology.Ambient ionization mass spectrometry has the characteristics of real-time,in-situ desorption and ionization of samples,which has been widely used in the real-time and on-line study of chemical reaction mechanism.In this paper,illumination-assisted droplet spray ionization mass spectrometry?IA-DSI-MS?based on the droplet spray ionization mass spectrometry was built,and the degradation mechanism of fluoroquinolone antibiotics by persulfate oxidation was studied by this IA-DSI-MS method.Based on the IA-DSI-MS system,the concentration of PMS and Fe²⁺ in Ultraviolet/Peroxymonosulfate/Fe²⁺(UV/PMS/Fe²⁺)were optimized,and the total optimum experimental conditions was determined.Then,with the optimal experimental conditions,IA-DSI-MS system was used to monitor the degradation process of fluoroquinolone antibiotics in UV/PMS/Fe²⁺ system in a real-time and on-line way.High resolution mass spectrometry and tandem mass spectrometry be used to analyze the intermediates captured during the reaction,for both determining the molecular composition and molecular structure of the intermediates.Radical quenching and active species capture experiments were carried out to investigate the types of active species generated in the UV/PMS/Fe²⁺ system.Based on the information of reaction intermediates obtained above and the time trend of intermediate products in the reaction process,the path of degradation of fluoroquinolone antibiotics in IA-DSI-MS with UV/PMS/Fe²⁺ system can be deduced,and the degradation mechanism will be clarified as well.In this paper,SO₄^·-and ·OH exist in UV/Fe²⁺/PMS without ¹O₂ which proved by radical quenching and active material capture experiments?The degradation of fluoroquinolone antibiotics in UV/PMS/Fe²⁺ system in a real-time and on-line way is monitored by using the IA-DSI-MS.And about 50 intermediates can be captured during the degradation of ciprofloxacin and norfloxacin,15 new intermediates are first proposed.It is found that the degradation reaction of fluoroquinolones in UV/PMS/Fe²⁺ system is mainly the cleavage and hydroxylation of piperazine ring,and there is no defluorination reaction.Besides,alkyl groups on the quinolone ring also have certain influence on degradation products,and no ring splitting reaction of quinolone ring occurs.This paper provides a real-time and on-line monitoring method for the mechanism study of organic pollutants degradation by the advanced oxidation processes.It can accurately and reliably capture the information of reaction intermediates in the process of reaction.And it is of great significance to improve the efficiency and methods of organic pollutants degradation by the advanced oxidation processes.