低功率超声增强碘帕醇氯氧化的效果和路径

研究了低功率超声(US, <38 W)对NaClO氧化非离子型碘代X射线造影剂—碘帕醇(IPM)的增强作用及机理, 考察了NaClO添加浓度和超声功率的影响, 分析并计算了体系中的主要活性物种及其贡献. 采用高效液相色谱/串联质谱(HPLC/MS/MS)对降解产物进行分析, 推测IPM的降解路径. 结果表明, 低功率US显著增强了NaClO对IPM的氧化效果, 在25 ℃, pH=5.8, NaClO浓度为0.12 mmol/L条件下, 10 mg/L IPM在60 min的降解率达到85.8%. 其中NaClO氧化、 HO·和活性氯自由基(RCSs)是US/NaClO增强IPM降解的主要原因, 自由基分析计算它们的贡献率分别为15.82%, 4.65%和79.53%. NaClO浓度在0~0.24 mmol/L范围内, IPM的降解率随NaClO浓度升高而增加, 60 min后降解率由4.75%增加到91.12%; 超声功率为28.5 W, 降解率达到最高. 在 15~45 ℃温度范围内, IPM的降解过程符合表观一级反应动力学, 反应活化能(E_a)为59.03 kJ/mol. HPLC/MS/MS共检测出5种中间产物, 结合密度泛函理论(DFT)计算结果, 初步推测了IPM在US/NaClO体系中的降解途径和机理.

Enhancement Effect of Low-power Ultrasound on Iopamidol Chlorination and the Degradation Pathway

Iopamidol（IPM）， as a widely used iodinated X-ray contrast media， was degraded by an ultrasound-enhanced chlorination process. Effects of the parameters， such as NaClO concentration， ultrasonic power， and reaction temperate on IPM degradation were investigated. The main reactive radicals and their respective contribution in IPM degradation were identified and estimated. Meanwhile the intermediates were analyzed by high performance liquid chromatography-tandem mass spectrometry（HPLC/MS/MS） as well. The results showed that IPM degradation was significantly enhanced by ultrasonic excitation of NaClO. NaClO oxidation， hydroxyl radical and reactive chlorine species were involved in IPM degradation， and their contribution for degrading 10 mg/L of IPM in the presence of 0.12 mmol/L of NaClO at pH=5.8 under 25 ℃ were 15.82%， 4.65% and 79.53%， respectively. When NaClO concentration was in the range of 0―0.24 mmol/L， an increase in NaClO concentration resulted in IPM degradation efficiency going up from 4.75% to 91.12% in 60 min. Nevertheless， the ultrasound power displayed an optimum value of 28.5 W. The degradation of IPM under the US/NaClO system within 15―45 ℃ were fitted with the first-order kinetics and the corresponding activation energy（E_a） was calculated to be 59.03 kJ/mol. Finally， five intermediates were identified by HPLC/MS/MS analysis， together with the theoretical calculation of Density functional theory（DFT）， the degradation pathway of IPM in the US/NaClO system was proposed.