水中Mn(Ⅲ)介导的头孢哌酮钠转化机制

Mn (Ⅲ)-mediated transformation of cefoperazone sodium in water: A Proposed Transformation Mechanism

一些常见金属离子如Cu(Ⅱ)、Fe(Ⅲ)或Mn(Ⅱ)等对水中头孢菌素类抗生素(CEPs)水解具有促进作用,已有研究证实高锰酸钾/亚硫酸氢钠(PM/BS)体系生成的Mn(Ⅲ)能高效氧化去除多种有机污染物,而Mn(Ⅲ)对CEPs的转化作用尚不明确.本研究以头孢哌酮钠(CFZ)为目标化合物,考察了Mn(Ⅲ)介导对水中CEPs的转化作用,研究了PM和BS浓度、初始pH、共存组分等因素对Mn(Ⅲ)转化CFZ的影响,采用超高效液相色谱串联质谱法(UPLC-MS/MS)对CFZ的转化产物进行了分析.结果表明,当PM和BS浓度分别为5.0μmol·L-1和20μmol·L-1、反应介质为弱酸性时更有利于Mn(Ⅲ)对CFZ的转化.加入Mg2+会促进PM/BS体系对CFZ的转化,而HCO-3和腐殖酸对CFZ的转化起到抑制作用.通过加入过量焦磷酸盐得出82.2%的CFZ是由于Mn(Ⅲ)介导而降解,根据UPLC-MS/MS分析其降解产物推测,Mn(Ⅲ)介导的CFZ降解主要包括水解和氧化两条路径.该研究阐明了Mn(Ⅲ)在CEPs环境转化中的作用,对深入认识Mn物种及CEPs在环境中的转化规律提供了新的参考价值.

The cephalosporin antibiotics(CEPs) are susceptible to be hydrolyzed by common metal ions such as Cu(Ⅱ), Fe(Ⅲ) or Mn(Ⅱ) in water. It has been demonstrated that potassium permanganate/sodium bisulfite(PM/BS) system could generate Mn(Ⅲ), which could be used to remove organic contaminants efficiently, but its role in the transformation of CEPs was still unknown. In this study, Mn(Ⅲ)-mediated transformation of CEPs in aqueous solution was studied using cefoperazone sodium(CFZ) as the target compound, and the effects of PM and BS dosage, initial pH value, and the coexisting components on the degradation efficiency were investigated. CFZ degradation products were analyzed by ultrahigh performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS) method. The results showed that the favorite conditions for Mn(Ⅲ)-mediated transformation of CFZ were PM concentration as 5.0 μmol·L-1 and BS concentration 20 μmol·L-1 under weakly acidic condition. Mg2+ addition could accelerate the CFZ removal efficiency in PM/BS system, while humic acid and HCO-3 played an inhibitory role in the CFZ degradation. The contribution of Mn(Ⅲ)-mediation to CFZ degradation was up to 82.2%, which was determined by adding excessive pyrophosphate in the PM/BS system. Based on the transformation products identified by UPLC-MS/MS, Mn(Ⅲ)-mediation led to hydrolysis and oxidation of CFZ. This study elucidated the role of Mn(Ⅲ) in the environmental transformation of cephalosporin antibiotics which had not been recognized before. This new discovery further clarified our understanding of Mn species and its role in the environmental fate of cephalosporin antibiotics.