Polymethylmethacrylate open tubular ion exchange columns: nondestructive measurement of very small ion exchange capacities.
Polymethylmethacrylate open tubular ion exchange columns: nondestructive measurement of very small ion exchange capacities.
复制标题
聚甲基丙烯酸甲酯开管式离子交换柱：非常小的离子交换容量的无损测量。
DOI：
10.1021/ac4018583
复制
发表时间：
2013
影响因子：
7.4
通讯作者：
P. Dasgupta
中科院分区：
文献类型：
--
作者：
Min Zhang;Bingcheng Yang;P. Dasgupta
我们描述了一种通过在16-20 μm孔径的聚甲基丙烯酸甲酯（PMMA）毛细管上涂覆单层阴离子交换纳米颗粒来制备开放式离子交换柱的方法。将乳胶纳米颗粒静电吸附在毛细管内壁的羧酸基团上，用强碱水解酯进行预处理。研究了几种无损测量色谱柱离子交换容量（IEC）的方法：(a)强荧光离子的吸附-解吸，例如荧光素和离线荧光测定法；(b)加载弱保留离子（例如IO3(-)），强结合离子（例如Cl(-)）的正面位移，以及在线光学或电导边界检测；(c)与上述类似，但位移伴随着反应（例如酸碱滴定）。据我们所知，这是第一次用柱上滴定法来测量容量。通过使用不同的pH置换溶液，我们首次证明了pka分化离子交换容量测量的可能性。裸PMMA毛细管的阳离子交换容量约为1 pequiv/mm(2)，对水解条件的时间和温度影响较小。AS18胶乳涂布后，强碱阴离子交换容量约为10 pequiv/mm(2)，非常接近单个胶乳颗粒在表面的单层覆盖所估计的容量。所使用的乳胶含有大量的弱碱性，与强碱离子交换能力大致相同。
We describe an approach to prepare an open tubular ion exchange (OTIE) column by coating a monolayer of anion exchange nanoparticle to a 16-20 μm bore polymethylmethacrylate (PMMA) capillary. The latex nanoparticle was electrostatically attached to carboxylate groups on the inner wall of capillary, pretreated with strong base for hydrolyzing the ester. Several approaches to nondestructively measure ion exchange capacities (IEC) of the columns were examined: (a) adsorption-desorption of an intensely fluorescent ion, e.g. fluorescein, and off-line fluorometry, (b) loading a weakly retained ion (e.g., IO3(-)), frontal displacement by a strongly bound ion (e.g., Cl(-)), and online optical or conductometric boundary detection, and (c) similar to the above except displacement being accompanied by reaction (e.g., acid-base titration). To our knowledge, this is the first time on-column titration has been used to measure capacities. By using different pH displacer solutions, we demonstrate for the first time the possibility of pKa-differentiated ion exchange capacity measurements. The cation exchange capacity of bare PMMA capillaries was on the order of 1 pequiv/mm(2) with little dependence on time and temperature of hydrolysis conditions. After AS18 latex coating, the strong base anion exchange capacity was on the order of 10 pequiv/mm(2), very close to what would be estimated on the basis of monolayer coverage of the surface by individual latex particles. The latex used contained a significant, additional amount of weak base character, about the same as the strong base ion exchange capacity.