腐植酸与环丙沙星结合机制的多维光谱学解析研究

Multi-spectroscopic Investigation on Mechanism of Binding Interaction between Humic Acid and Ciprofloxacin

本工作研究了水环境中残留喹诺酮类抗生素环丙沙星(ciprofloxacin,CIP)与溶解有机物(dissolvedorganicmatter,DOM)腐植酸(humic acid,HA)的结合作用机理.采用三维荧光、傅里叶红外光谱、二维相关光谱和液体核磁共振氢谱等技术进行表征分析.结果表明,CIP和HA的结合作用会产生明显的荧光淬灭现象,且在6 h后结合开始趋于平衡.结合作用与HA表面的羟基、羧基以及酮基等官能团相关,而CIP分子哌嗪环上的H质子是参与结合的主要位点.此外,影响因素实验表明,离子强度(ionic strength,IS)对结合作用影响较小,而pH对其影响较大,且在pH=5时荧光淬灭率最高.荧光淬灭率与金属离子价态呈现正相关.通过研究水体中CIP和HA的相互作用,对于监测研究天然水体中残留抗生素的迁移和转化提供理论依据.

In this paper,the mechanism of the binding interaction between residual ciprofloxacin(CIP)and dissolved organic matter humic acid(HA)in natural water environment was systematically investigated.Various spectral analysis technologies,including the three-dimensional excitation-emission matrix spectra,fourier transform infrared(FTIR)spectra,two-dimensional correlation spectra(2D-COS)and liquid nuclear magnetic resonance(^(1)H NMR)spectra techniques,were adopted to reveal the mechanism of the binding interaction between CIP and HA.The results suggested that the binding interaction between CIP and HA resulted in significant fluorescence quenching,and the binding interaction tended to balance after 6 h monitored by ultraviolet(UV)differential spectroscopy.Based on the FTIR analysis,the hydroxyl,carboxyl and ketone groups of HA were the main contributors to the binding interaction,and the results of 2D-COS indicated that the ketone groups preferentially participated in binding interaction compared to carboxyl groups.The H protons on the piperazine ring of CIP were identified as the main binding sites by the 1H NMR,and the comparison of fluorescence quenching rate of other fluoroquinolone antibiotics(norfloxacin and levofloxacin)with similar structures also verified that the piperazine ring played a crucial role in binding interaction.Additionally,the influence of ionic strength(IS,range 0.001—0.1)on the binding interaction was ignorable compared with pH.The fluorescence quenching rates increased firstly and then decreased with the increase of pH(range 3—11),and the fluorescence quenching rate was up to 70%at pH 5.Moreover,the fluorescence quenching rates were positively correlated with the valence state of metal ions(order of influence followed:Al^(3+)>Zn^(2+),Co^(2+),NH_(4)^(+),Ca^(2+)>Mn^(2+),Na^(+),K^(+)).This study provides the theoretical basis and effective detection technologies for monitoring the migration and transformation of residual antibiotics in the natural water environment.