A micellar high-performance liquid chromatography (HPLC) method has been described for simultaneous determination of ephedrine, pseudoephedrine, and methylephedrine in Ephedra Herb and two traditional Chinese preparations. The separation and determination of ephedrine, pseudoephedrine, and methylephedrine were performed using a mobile phase containing 1.75 × 10−1 mol·L−1 sodium dodecyl sulphate and 0.02 mol·L−1 potassium hydrogen phosphate with 10% (v/v) methanol at pH 3.0, running at 1.5 mL·min−1 by a Venusil XBP C18 (250 × 4.6 mm, 5 μm) column at 40 °C. The detected wavelength was set at 210 nm. The method was validated according to the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines. The main analytical parameters were linearity (r > 0.9990), intra- and inter-day precisions (relative standard deviation [RSD %], 0.33–1.63, and RSD %, 1.26–2.20, respectively), limit of quantifications [LOQs], and limit of detections [LODs] (2.6 × 10−4 and 7.8 × 10−5 mg·mL−1 for ephedrine, 6.8 × 10−4 and 2.0 × 10−4 mg·mL−1 for pseudoephedrine, and 5.0 × 10−4 and 1.5 × 10−4 mg·mL−1 for methylephedrine). RSDs of recoveries were <5.5% in the three samples. Based on the optimized chromatographic conditions and the eluted orders, a model of separation mechanism for the analytes was established. The results indicated that the proposed method was an accurate, “green” and cheap method.
Authors:K. Dong, C. Hao, A. Wang, M. Cai, and Y. Yan
The wheat storage proteins, especially the high molecular weight glutenin subunits (HMW-GS), play important roles in the determination of flour processing and bread-making quality. Compared with the traditional SDS-PAGE method, reversed-phase high-performance liquid chromatography (RP-HPLC) was shown to have many advantages for the separation and characterization of HMW-GS because of its high resolving power, repeatability and automation. In this work, HMW-GS from bread and tetraploid wheats were separated and characterized by RP-HPLC. The elution time ranking of different HMW-GS was: 1Ax > 1Bx > 1Dx > 1By > 1Dy. Several subunit pairs associated with good quality properties and those with similar mobilities on SDS-PAGE, such as 1Bx7 and 1Bx7*, 1By8 and 1By8*, 1Dx2 and 1Ax2*, 1Bx6 and 1Bx6.1, were well separated and readily identified through RP-HPLC. However, other subunit pairs, such as 1Dy10 — 1Dy12, 1Dx5 — 1By18 and 1Dx2 — 1By16, could not be adequately separated and identified by RP-HPLC, whereas they displayed different mobilities on SDS-PAGE gels. Because 1Dx5 and 1Dx2 showed different hydrophobicities, RP-HPLC could distinguish 1Dx5 + 1Dy10 and 1Dx2 + 1Dy12. A comparative analysis between RP-HPLC and SDS-PAGE showed that a combination of both methods provided more effective identification of HMW-GS in wheat quality improvement and germplasm screening.
Authors:M. Dong, J. Huang, H. Du, J. Li, S. Du, A. Luo, Y. Jiang, and C. Zhang
By substututing99Mo for the Mo in the reconstituted MoFe protein, the nuclear quadrupole interactions (NQI) of99Mo have been measured using the perturbed angular correlations (PAC). Two well-defined electric quadrupole interaction parameters have been observed. The configuration of the M-Center of the MoFe protein is identified by the quadrupole couplign constant
Q1(412(9)MHz) and the asymmetry parameter
1(0.49(5)). Other parameters, VQ2(1939(13)MHz) and
1(0.90(1)), may correspond to a deformation M—Center of MoFe protein.
Authors:W.Y. Gao, Y.W. Wang, L.M. Dong, and Z.W. Yu1
A microcalorimeter (Setaram c-80) was used
to study the thermokinetics of the hydration process of calcium phosphate
cement (CPC), a biocompatible biomaterial used in bone repair. The hydration
enthalpy was determined to be 35.8 J g–1
at 37.0°C when up to 80 mg CPC was dissolved in 2 mL of citric buffer.
In the present study, parameters related to time constants of the calorimeter
were obtained by fitting the recorded thermal curves with the function θ=Ae–?t(1– e–?2t).
The real thermogenetic curves were then retrieved with Tian function and the
transformation rate of the hydration process of CPC was found to follow the
The microstructures of the hydrated CPC were examined by scanning electron
microscopy. The nano-scale flake microstructures are due to crystallization
of calcium phosphate and they could contribute to the good biocompatibility
and high bioactivity.
Authors:Bin Dong, Christian H. Galka, Lutz H. Gade, Lifeng Chi, and René M. Williams
nanocrystals are formed by self assembly of
tetra(carboxamido)perylenes (BPP) in different solvents. The structure and the
dimensions of the nano-rods may be controlled by the choice of the
hydrogen-bond accepting capacity of the solvent (DMSO, DMF, DMAc, HMPA), by the
concentration and by the composition of solvent-mixture (by adding
hydrogen-bond donating solvents), but is independent of the surface used for
their deposition (mica, silicon, gold, glass). The different forms of
aggregation were examined by AFM and SNOM and were correlated to UV-Vis
absorption spectra of the aggregates in solution. The orientation of the
transition dipole moment of the molecules in the nanocrystals has been
determined by polarized fluorescence microscopy and, in combination with the
crystal structure of the
-Bu substituted analogue of BPP, is used to
develop a model for the internal molecular structure of the rod shaped
Authors:X.K. Wang, W.M. Dong, H.X. Zhang, and Z.Y. Tao
The distribution coefficients,Kd of 36 elements from Na to Bi on a silica were determined at pH 4, 7, 9 and in the absence and presence of fulvic acid (FA) using a multitracer technique. The multitracer solution was prepared by irradiation of Th(NO3)4 with 40Ar ion beam. The effects of pH and fulvic acid on the Kd values of 36 elements were studied. It was found that the sequences of the Kd values of alkali elements (Cs>Rb>K>Na) and of alkaline earth elements(Ba>Ca>Mg) in the absence of FA can be qualitatively explained in terms of chemical bond formation and hydration. Various effects of pH and the negative or positive effect of FA on the adsorption of 36 elements were observed and are probably related to the species of 36 elements in the aqueous solutions containing CO32–, OH–, Cl– and FA. For most of the elements studied here the Kd values are increased with increasing pH and are decreased with adding FA.