A novel polymer-based zwitterionic separation material was synthesized by a two-step reaction, in which 2-hydroxyethyl methacrylate−ethylene dimethacrylate copolymer beads were first activated with epichlorohydrin, whereafter (2-dimethylamino)ethanesulfonic acid inner salt was coupled to the epoxide groups on the activated beads in a quaternizing reaction. The resulting material carried strong/strong charge zwitterionic pendant groups, whose charge properties did not change over a wide pH range. It was capable of separating inorganic anions and cations both independently and simultaneously using aqueous solutions of perchloric acid or perchlorate salts as eluent. It was found that the retention of cations and anions depended on the individual ions in the analyte, not on type of salt injected, as reported for ODS columns dynamically coated with zwitterionic detergents using water only as eluent. This study also revealed that both the concentration and the water structure related properties of the eluent ions were important for the retention of ionic species. The mechanism appears to involve the interaction of the chaotropic anion component with the quaternary ammonium group, resulting in an increasing cation-exchange capacity of the zwitterion up to a perchloric acid eluent concentration of ∼10 mM. Above this concentration the material appears to become saturated, and the retention times of both cations and anions become practically independent of the HClO4 concentration.
一种新型聚合物两性离子分离材料通过两步反应合成,其中,2-羟乙基
甲基丙烯酸酯-
乙烯二
甲基丙烯酸酯共聚物珠粒首先用
环氧氯丙烷活化,然后(2-二甲基
氨基)
乙磺酸内盐在季化反应中与活化珠粒上的环氧基团偶联。所得材料带有强/强电荷两性离子侧基,其电荷性质在宽pH范围内不会改变。它能够独立或同时分离无机阴离子和阳离子,使用
高氯酸或
高氯酸盐的
水溶液作为洗脱液。研究发现,阳离子和阴离子的保留取决于分析物中的单个离子,而不是注入的盐的类型,这与仅使用
水作为洗脱液、动态涂覆两性离子洗涤剂的ODS柱的报道一致。这项研究还表明,洗脱液离子的浓度和
水结构相关的性质对于离子种类的保留都很重要。该机制似乎涉及无定形阴离子成分与季
铵基团的相互作用,导致两性离子的阳离子交换容量增加,直至
高氯酸洗脱液浓度达到约10mM。超过该浓度,材料似乎变得饱和,阳离子和阴离子的保留时间实际上与HClO4浓度无关。