Studies on degradation mechanism of niclosamide ethanolamine salt Ⅱ Isotopic tracing and determination of photolysis end-product

目的观察同位素示踪技术解析氯硝柳胺乙醇胺盐(nES)在水体中的稳定性及测定光解终产物CO2的变化。方法实验室配制PH5的0.05μg/Ml、PH7的0.5μg/Ml和PH9的2.5μg/MlnES溶液,采用氙灯光源作为模拟日光照射上述nES溶液,照射8、16、24、32、40、48H和72H后,分别测定nES溶液在光解管顶的气态样品,采用gASbEnCHⅡ进样针插入直接分析;液体样品则取2.5Ml注入用高纯氦吹过的密封顶空样品瓶中,用加酸泵滴加无水磷酸,30℃超声反应1H,再插入gASbEnCHⅡ进样针进行分析;与dElTAPluS/XP稳定同位素质谱仪联用测定光解产物CO2的量及碳稳定同位素。结果在氙灯光光照条件下,PH70.5μg/Ml和PH92.5μg/MlnES溶液的光解,随光照时间的增加,CO2的量也增加,并呈线性增长,72H时其产量接近nES的实际产量。同位素结果显示,随光照时间的增加,CO2的碳同位素值逐渐变负,72H时接近nES原药的碳同位素值,为-25.36±0.11,光降解已接近完全。而PH50.05μg/MlnES溶液的光解,随光照时间的增加,CO2的量也在增加,但其产量超出了nES的实际产量;同位素结果显示,随光照时间的增加,产出CO2的碳同位素值逐渐变负,但在光照16H后其产CO2的碳同位素值比nES的碳同位素值偏负。结论 nES能够在水中快速光解,终产物为CO2。Objective To analyze the stability of niclosamide ethanolamine salt(NES)in water and determine the changes of CO2,the photolysis end-product,by using the isotopic tracing technique.Methods NES was formulated into the solutions of pH 5(0.05 μg/ml),pH 7(0.5 μg/ml)and pH 9(2.5 μg/ml),respectively.The xenon gas lamp was used as the simulated sunlight.After 8,16,24,32,40,48,72 h of the illumination,the gas samples of the NES solution on the top of photolysis tube were determined by using direct insertion of GasBenchII needle.For liquid samples,2.5 ml NES solution was added into a sealed empty bottle,which was treated with high pure helium,and then anhydrous phosphoric acid was added.After ultrasonic reaction at 30 ℃ for 1 h,the GasBenchII needle was inserted for analysis.The amount of CO2 and carbon isotopic value were determined by using the GasBenchII needle combined with isotopic mass spectrometer.Results Under the illumination of xenon gas lamp,the NES solutions of pH 7 and pH 9 occurred photolysis,with the increase of illumination time,the amount of CO2 increased,showing a linear increase.At 72 h,its yield approximated to the active output of NES.The isotopic tracing results showed,with the increase of illumination time,the carbon isotope value of CO2 turned to be negative gradually,and approximately reached to the carbon isotope value(-25.36±0.11‰)of NES active ingredient at 72 h when the photolysis approximated to be completely finished.For the photolysis of pH 5 NES solution,with the increase of illumination time,the amount of CO2 increased,however,its output was more than the active output of NES.The isotopic tracing results showed,with the increase of illumination time,the carbon isotope value of CO2 turned to be negative gradually.However,after illumination for 16 h,the carbon isotope value of CO2 was more negative than that of NES.Conclusions The photolysis of NES can occur rapidly in water,and the end product is CO2.江苏省自然科学基金(BK200602);江苏省卫生厅项目(X200504

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies