Minlian Zhang

On-line solid-phase extraction of ceramides from yeast with ceramide III imprinted monolith

A molecularly imprinted polymeric monolith (MIPM) was prepared by in situ polymerization using styrene, glycidyl methacrylate and methacrylic acid as monomers, divinylbenzene and triallyl isocyanurate as cross-linking agents, and ceramide III as print molecule. The texture, pore size distribution, mobile phase flow characteristic, and chromatographic performance of the MIPM and a control monolith synthesized without the print molecule were examined, respectively. The results showed that using ceramide III as print molecule significantly affected the pore structure and pore distribution of the monolith, and greatly improved the retention of ceramide III and its analogues used in cosmetics as well. The retention of ceramide III on the MIPM could be reduced by increasing the ratio of chloroform to hexane in eluting buffer. The workability of the MIPM was firstly demonstrated through the separation of a model lipid mixture containing ceramide III and ergosterol, the main sterol impurity in yeast lipid extracts. The application of the ceramide III imprinted monolith to the isolation of ceramides from yeast lipid extracts was attempted and resulted in a considerable enrichment of ceramides, as shown by FIIR analysis. This indicates the potential of ceramide III imprinted monolith synthesized in the present study in the on-line solid-phase extraction of ceramides from yeast.

Poly(glycidyl methacrylate-divinylbenzene-triallylisocyanurate) continuous-bed protein chromatography

A novel continuous bed with high dynamic adsorption capacity for protein has been developed. It is a macroporous poly(glycidyl methacrylate-divinylbenzene-triallylisocyanurate) rod prepared by in situ copolymerization in a chromatographic tube. The bed matrix contained epoxy groups, so diethylaminohydroxypropyl groups were coupled to the matrix, leading to an anion-exchange continuous bed. The component, specific surface area, and the pore structure of the bed matrix were characterized by Fourier transform infrared spectroscopy, BET method and scanning and transmission electron microscopies, respectively. The flow properties, column efficiency and the dynamic adsorption behavior of the bed were studied. The results show that the continuous bed, a ternary copolymer of glycidyl methacrylate (GMA), divinylbenzene (DVB) and triallylisocyanurate (TAIC) with a specific surface area of 56.4 m2/g, consisted of a three-dimensional structure made up of continuous clusters of microspheres (300 nm) and interconnected irregular pores. The rate of mass transfer is enhanced by the convection of the mobile phase through the pores. The dynamic adsorption isotherm of the anion-exchange column for bovine serum albumin was expressed by the Langmuir equation with a dynamic capacity as high as 76.0 mg/g. Moreover, the separation of proteins, i.e. lysozyme, hemoglobin and bovine serum albumin, is little affected by mobile-phase velocity up to 902.5 cm/h; it was completed within 5 min at 902.5 cm/h.

Cooperation of solid granule and solvent as porogenic agents Novel porogenic mode of biporous media for protein chromatography

A novel porogenic mode, cooperation of solid granule and solvent, has been introduced to prepare a biporous medium for protein chromatography. The matrix, a ternary copolymer of glycidyl methacrylate, triallylisocyanurate and divinylbenzene, was produced by a simple in situ polymerization with granules of sodium sulfate and cyclohexanol and dodecanol as porogenic agents. Functionalized with diethylamine, the resin (denoted as Resin C) was used as an anion exchanger. The pore structure, specific surface area and chromatographic properties of Resin C were determined and compared with those of the resin with only the solvents as porogen (Resin A) and the resin with only the salt granules as porogen (Resin B). The results indicated that Resin C contained regions of micropores with a maximum at approximately 55 nm and regions of macropores with a distinct maximum near 340 nm, which swelled to about 1 microm in aqueous solution. Compared with Resins A and B, the biporous medium Resin C simultaneously possessed a high specific surface area of 37.2 m2/g and a low back-pressure at mobile phase flow velocity up to 720 cm/h. The result of dynamic porosity showed that mobile phase was able to convectively flow through the macropores in Resin C. The dynamic adsorption capacity of Resin C for bovine serum albumin was as high as 57.0 mg/ml column volume (95.0 mg/g wet resin), basically identical to its static capacity, while that of Resin A was only 1.95 mg/ml column volume (3.12 mg/g wet resin), about 3% that of its static capacity. In addition, the column efficiency of Resin C was comparable to that of Resin B, but much higher than that of Resin A, indicating that the mass transfer behavior of proteins in the column was greatly improved by convective flow through the macropores.

Study on epoxy resins modified by polycarbonate polyurethanes

In this article, the structure and properties of the epoxy resin (EP) modified by polyurethane (PU) prepolymers were studied. The three types of polyurethane prepolymers, namely, polycarbonate-type PU (TPC), polyether-type PU, and polycarbonate–polyether-type PU were employed. The samples were analyzed by means of an infrared spectrometer, a differential scanning calorimeter, a scanning electron microscope, a transmission electron microscope, a scanning tunnel microscope, and a thermal gravimeter. The results show that the EP modified by TPC is of excellent thermal resistance and mechanical properties. Specifically, when the ratio of PU to EP is 10/100 (wt/wt), optimal properties are achieved.

Study on degradation mechanism of polyethylene films containing additives with metal ions at a simulated composting temperature

In this article, the degradation mechanism of PE films containing additives with metal ions at a simulated composting temperature has been studied. The hydroperoxide concentration [POOH] in the films was traced quantitatively by using the iodometric potentiometric titration, compared with Fourier transform infrared spectrometry (FTIR). The results show that [POOH] increases during the early stage of degradation, followed by a more or less flat maximum before it starts to decrease. At the same time, similar results are obtained by the FTIR analysis. Besides, it is found that the rate laws for the carbonyl index and [POOH] increases seem more complicated, instead of an exponential-type increase in the early stage of the oxidation. When they are fitted by polynomial equations, the greater the rate of degradation, the more the number and content of the high-power members in the polynomial.