A weak cation exchanger by encapsulating silica with maleic anhydride-modified polyvinyl alcohol.

A novel weak cation exchanger is described by encapsulating silica with a (or multiple) layer(s) of maleic anhydride-modified polyvinyl alcohol coating(s). The preparation method is facile and fast, which is simply performed by dipping silica particles into maleic anhydride-modified polyvinyl alcohol solution as-synthesized, then filtering and curing thermally, and finally generating a thin coating onto silica particles. Multiple layers of maleic anhydride-modified polyvinyl alcohol coatings can be generated by repeating above steps, offering an easy way to manipulate the capacity. The obtained weak cation exchanger demonstrated high separation efficiency and good selectivity toward common inorganic cations, for example, high plate count of 81 000 per meter was obtained for NH4 + . Simultaneous separation of alkali and alkaline earth metals could be achieved within 14 min under isocratic conditions.

A polyethyleneimine-functionalized polymer substrate polar stationary phase.

A polyethyleneimine (PEI)-functionalized polymer substrate polar stationary phase was prepared for hydrophilic interaction chromatography (HILIC) by grafting PEI onto poly(styrene-divinylbenzene) (PS-DVB) microspheres. The phase shows a U-shape retention profile and it exhibits typical hydrophilic characteristic when the organic solvent fraction in the mobile phase is > 60%. Hydrogen bonding, anion exchange, and hydrophobic interaction are involved in the retention mechanism. Good separation and unique selectivity for acidic, basic and neutral polar analytes were achieved. It showed extremely low column bleed (comparable to that of blank) under gradient elution mode (even to 50% fraction of water) and wide pH tollerance range (at least 1-13).

A hyperbranched polyglycerol-functionalized polymer polar stationary phase.

A polymer polar stationary phase functionalized with hyperbranched polyglycerol for hydrophilic interaction chromatography (HILIC) is described. It is prepared via surface-initiated ring-opening polymerization of hyperbranched polyglycerol onto hydrolzed poly(glycidyl methacrylate-divinylbenzene) microspheres. The capacity of the functional groups can be maniputed by repeating hyperbranch layers. The phase showed typical HILIC character with good separation performance towards tested polar analytes. It also exhibited wider pH tolerance range (e.g. at least 2 to 12) and as well negligible bleed level under gradient elution mode (even to 50% fraction of water).

A hydrolytically stable amide polar stationary phase for hydrophilic interaction chromatography.

A novel amide functionalized polar stationary phase has been described by grafting acrylamide polymer coating onto hydrolysed poly (glycidyl methacrylate-divinylbenzene) (GMA-DVB) microsphere. The grafting of acrylamide coating is performed via free radical polymerization of acrylamide with pendant double bonds of hydrolysed GMA-DVB microsphere. The obtained stationary phase (G-pAM) possesses favorable hydrophilicity, as proved by strong retention and good separation ability towards several types of model polar analytes (e.g. 71913 plates/m plate count of sucrose), and excellent hydrolytically stability, as indicated by extremely low bleed level (much superior to commercial ones, ~23.7-fold-~77.4-fold lower). Negligible baseline drift under gradient elution (water fraction even up to 50%) was observed. It also exhibits good selectivity in the separation of isomers and homologue sugars.

A polymer-based zwitterionic stationary phase for hydrophilic interaction chromatography.

We describe a novel polymer-based zwitterionic stationary phase for hydrophilic interaction chromatography (HILIC). It is prepared by chemical modification of poly (glycidyl methacrylate-divinylbenzene) (GMA-DVB) by converting epoxide groups of microsphere surface to diol groups via hydrolysis, then clicking cysteine onto the microsphere with pendant double bonds of microsphere surface via "thiol-ene" click chemistry. The phase has been characterized by scanning electron micrograph, elemental analysis and zeta potential measurement. Diol and zwitterionic group (carboxylate and amine group associated with cysteine) onto the surface of GMA-DVB microspheres make them possess good hydrophilicity, as supported by effective separation towards common polar analytes. It shows good stability at alkaline solution (e.g. pH 10) and negligible bleed (e.g. only 1.7-fold blank and ~55-fold lower than a commercial silica-based polar phase tested with the minimal bleed level). Such phase exhibits specific separation selectivity to ionic analytes and simultaneous separation of anions and cations is achieved in the retention order of I- < NO3- < Choline < Br- < Cl- < K+< Na+.

A polar stationary phase obtained by surface-initiated polymerization of hyperbranched polyglycerol onto silica.

A novel polar stationary phase for hydrophilic interaction chromatography (HILIC) is prepared by surface-initiated polymerization of hyperbranched polyglycerol onto silica. Such polymerization offers an easy way to tune the cabon load. The stationary phase showed obvious hydrogen bonding interaction and typical HILIC character, exhibiting nealy-universal separation ability towards polar analytes. Good peak shape and high separation efficiency was observed for model polar analytes, including nucleosides and nucleic bases, aromatic acids, organic bases, vitamins, saccharides, amino acids, e.g. 35,000-58,000 plate counts per meter for five water-soluble vitamins.