响应面法优化萃取条件用于高效液相色谱分析饮用水中痕量邻苯二甲酸二(2-乙基己基)酯及其迁移规律

应用响应面法辅助分析塑料瓶装饮用水中邻苯二甲酸二（2-乙基己基）酯（DEHP）的迁移,建立了一种快速、简便、环保的痕量塑化剂类污染物检测方法。在盐析作用下,使用正己烷涡旋萃取,经氮气浓缩后进行高效液相色谱-紫外检测。响应面最优分析法考察了盐量、涡旋时间和萃取液体积3个因素作为萃取条件对DEHP回收率的影响,得到最佳萃取条件：盐量为16 g/L、涡旋时间为90 s、萃取液体积为5.28 mL。在此实验条件下,DEHP的最大理论回收率为92.91%,实验验证值为92.97%,与理论值相差0.06%。本方法检出限为0.006 mg/L,满足中国国家标准规定的生活饮用水安全标准要求（0.008 mg/L）,在0.01~15 mg/L范围内线性关系良好（相关系数R=0.9996）。选取常见市售饮用水样品进行分析,研究了塑料包装饮用水中痕量DEHP迁移的规律。与传统的优化方法相比,响应面模型分析法综合考虑了各因素的影响,而且更加简便、低成本、对环境友好,是实现样品中微痕量污染物精准检测的重要辅助手段。     

EXISTENCE OF PERIODIC SOLUTIONS TO AN ISOTHERMAL RELATIVISTIC EULER SYSTEM

In this paper,we study the global existence of periodic solutions to an isothermal relativistic Euler system in BV space.First,we analyze some properties of the shock and rarefaction wave curves in the Riemann invariant plane.Based on these properties,we construct the approximate solutions of the isothermal relativistic Euler system with periodic initial data by using a Glimm scheme,and prove that there exists an entropy solution V（x,t）which belongs to L^∞∩ BV_loc（R × R_+...     

THE GLOBAL EXISTENCE OF BV SOLUTIONS OF THE ISENTROPIC p-SYSTEM WITH LARGE INITIAL DATA

In this paper,we study the global existence of BV solutions of the initial value problem for the isentropic p-system,where the state equation of the gas is given by P=Av^-γ.For γ> 1,the general existence result for large initial data has not been obtained.By using the Glimm scheme,Nishida,Smoller and Diperna successively obtained the global existence results for(γ-1)TV(v₀(x),u₀(x)) being small.In the present paper,by adopting a rescaling technique,we improve th...