Peiyong Xin

A novel glycidyl methacrylate-based monolith with sub-micron skeletons and well-defined macropores

A series of glycidyl methacrylate-based polymer monoliths, including spherical walled structures, sub-micron skeletons, and lamellar morphologies, are reproducibly prepared by high internal phase emulsions in combination with block copolymer chemistry. The morphologies could be manipulated over a wide range by only altering the typical tri-block copolymer (Pluronic F127) concentration. The ability of the Pluronic F127 to direct supramolecular self-assembly is the main reason for the rich phase behavior exhibited such as the micellar phase (i.e., spherical micelles, wormlike micelles), the bicontinuous phase, and the lamellar phase. Equally important, the glycidyl methacrylate-based monoliths differ significantly from conventional polymer monoliths; they have sub-micron skeletons (100–1000 nm), micrometer-sized throughpores, relatively large specific surface area (161 m2 g−1), and excellent permeability (6.1 × 10−13 m2). Further, the monoliths display superiority in fast and high-throughput separation of proteins. This, together with easy fabrication makes the novel monoliths a promising alternative to commercially available monolithic supports.

Preparation of poly(N-isopropylacrylamide)-grafted polymer monolith for hydrophobic interaction chromatography of proteins

Poly(N-isopropylacrylamide)-grafted polymer monolith has been achieved using a surface-initiated atom transfer radical polymerization grafting polymerization within the pores of poly(chloromethylstyrene-divinylbenzene) macroporous monolith contained in a 100 mm x 4.6mm I.D. stainless steel column. The grafted-poly(N-isopropylacrylamide) on the surface of the grafted monolith that was used as chromatographic stationary phase showed a response to the variation of temperatures and/or salt concentrations. This study focus on its salt concentration responsive property and it has been revealed that the hydrophobicity of the grafted monolith can be adjusted by changing salt concentrations in the range of 0.05-2.0 mol/L. A variety of salts including sodium sulfate, ammonium sulfate and sodium chloride exhibited different effects on the alteration of hydrophobicity of the grafted monolith, and the effect of the salts was in the order of sodium sulfate>ammonium sulfate>sodium chloride. Based on this response to salt concentrations, the grafted monolith was applied in hydrophobic interaction chromatography of proteins, and the base-line separation of a six proteins mixture consisting of cytochrome c, myoglobin, ribonuclease A, bovine serum albumin, ovalbumin and thyroglobulin bovine was achieved by a salt gradient elution.

Preparation of poly(N-isopropylacrylamide)-grafted well-controlled 3D skeletal monolith based on E-51 epoxy resin for protein separation.

A novel type of poly(N-isopropylacrylamide) grafted E-51 epoxy-based monoliths in a 100 mm × 4.6mm I.D. stainless steel column with well-controlled three-dimensional skeletal structures has been prepared and proposed for the separation of proteins. The grafted PNIPAAm chain via surface-initiated atom transfer radical polymerization was successfully performed. The proposed method provided a new route to modify the E-51 epoxy-based monoliths for widening their applications. Meanwhile, the temperature and the salt concentration responses of the grafted monolithic columns were investigated. Under the salt gradient, six proteins were well separated in hydrophobic interaction mode. Moreover, for further confirming the application of the prepared monolith was meaningful for proteome analysis in actual system, the separation of human serum sample was performed.

A well-defined block copolymer serving as surfactants in separation of 1,4-dihydropyridines by open-tubular capillary eletrochromatography

A novel series of diblock copolymers, poly(butyl methacrylate)n‐block‐poly(glycidyl methacrylate)m [P(BMA)n‐b‐P(GMA)m], were synthesized by atom transfer radical polymerization and developed as covalent coating of capillaries. The excellent performance of this coating in separation of three 1,4‐dihydropyridines (DHPs) derivatives (amlodipine, nicardipine, nitrendipine) was achieved when the diblock copolymers self‐assembled into micelles, which was confirmed by transmission electron microscopy, dynamic light scattering, and atom force microscopy. Meanwhile, the effects of block ratio n/m, pH value, buffer concentration, and organic solvents on the separation of 1,4‐DHPs were investigated in detail. Then, the relationship between the morphologies of copolymers and the separation resolutions of 1,4‐DHPs was discussed. Furthermore, the proposed method exhibited good run‐to‐run and column‐to‐column precision with relative standard deviations of electroosmotic flow less than 3.0%. It was also validated with linearity of three 1,4‐DHPs in the range of 0.01–1.80 mM (r2 ≥ 99.7%), efficient recovery (94–103%), and good repeatability (≤ 3.8%). In addition, three 1,4‐DHPs were successfully separated in the spiked human serum sample, which indicated the potential utility of this method in biological sample analysis.