Preparation And Application Of A Novel Zwitterionic Stationary Phase For Capillary Liquid Chromatography

Capillary liquid chromatography (CLC) has attracted the attention of researchers that study the separation of compounds in a wide variety of scientific fields, because of the adventages including simple operation, low sample consumption, little pollution of environment. Recently, the preparation of the monolithic stationary phases has gained increasing attention. The preparation and application of monolithic stationary phases in hydrophobic interation have been exploried widely. However, it seems that only limited attention has been paid to the zwitterionic ion exchange monolithic stationary phase.In the present study, a novel zwitterionic monolithic stationary phase was prepared for capillary liquid chromatography by in-situ polymerization of methacrylic acid, ethylene dimetharylate and 2-(dimethyl amino) ethyl methacrylate in the presence of porogens.The effects of polymerization conditions on column performances were experimentally examined, and the optimal conditions for preparing the columns were established.The density of positive and negative charges on the stationary phase can be affected by the pH values of mobile phase, thus the cation-anion ion-exchange modes can be converted mutually by simply adjusting the pH value of the mobile phase.A typical anion ion-exchange interaction mechanism was observed at a pH value below 6.0,and several inorganic anions including bromate, bromide, nitrite and nitrate were baseline separated at the pH value of 6.0.A typical cation ion-exchange interaction mechanism was exhibited at a pH value higher than 7.0,and several organic amines including o-diaminobenzene, p-toluidine, p-chloroaniline and p-nitroaniline were baseline separated when the mobile phase was at the pH value of 7.0 and containing 40% acetonitrile. It should be noted that both hydrophobic interaction and ion-exchange interaction contribute to retention for the organic analytes on the present stationary phase, which is undoubtedly beneficial to enhancement of the separation selectivity.The zwitterionic monolithic columns were used to the rapid determination of bromate, bromide, nitrite and nitrate in seawater samples and p-phenylene diamine in hair dye samples. The quantitative methods were evaluated in terms of linear range, precision, detection limit and recovery.