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911.
912.
A pcu network can be ordered through trigonal bipyramidal nanocages as secondary building blocks, which have the striking feature of hydrophilic affinity to the polar molecules and π-π interactions for aromatic molecules. 相似文献
913.
The first asymmetric synthesis of indole alkaloid (+)-subincanadine F was successfully accomplished with the uncommon 7-endo-trig stereoselective radical cyclization as the key step and its absolute configuration was thus assigned. 相似文献
914.
915.
Hybrid chips combing microchips with capillaries have displayed particular advantages in achieving UV-vis and mass spectroscopic detection. In this work, systematic 3-D numerical simulations have been carried out to explore the influence of junction interface cross-sectional area and ζ-potential distribution on sample band broadening in hybrid-chip electrophoresis separation. In this case, the ratio of cross-sectional area of chip to capillary channel (S(ratio) ) is used as the parameter of the variation in junction interface cross-sectional area. Theoretical simulations demonstrated that the decrease of the S(ratio) would increase the separation efficiency in the hybrid-chip-based CE with uniform ζ-potential distribution. ζ-potential distribution along the axial direction of the channel also affects mass transport in hybrid-chip-based CE. Therefore, the effect of ζ-potential distribution has been considered in the 3-D simulation. Theoretical simulation results reveal that ζ-potential distribution rather than the interface cross-sectional area variation (S(ratio) ) controls the sample band broadening and manipulates sample separation efficiency in the hybrid-chip-based CE with non-uniform ζ-potential distribution. Both the theoretical simulations and experimental results show that optimal hybrid-chip CE separation efficiency can be achieved at S(ratio) =1. 相似文献
916.
The creation of tailor-made receptors which are able to recognize molecular targets with high affinity and selectivity has
attracted much attention in the field of chemistry, physics, and biology. Molecular imprinting has proved to be an effective
technique for generating specific recognition sites in synthetic polymers. The synthesis of molecular imprinted polymers specific
for proteins and peptides has been a focus for many scientists working in the area of molecular recognition, since the creation
of synthetic polymers that can specifically recognize biomacromolecules is a very challenging but potentially extremely rewarding
work. These polymers with specificity for biological macromolecules have considerable potential for applications in the areas
of solid phase extraction, catalysis, medicine, clinical analysis, drug delivery, environmental monitoring, and sensors. In
this review, the authors discuss the developed approaches associated with the imprinting of peptides and proteins, and provide
an overview of the significant progress achieved within this field. Finally, the possible mechanism of the molecular imprinting
and recognition has been discussed. 相似文献
917.
Matrix solid-phase dispersion (MSPD) with alumina N as adsorbent has been used for extraction of para red, Sudan 1, Sudan 2, Sudan 3, and Sudan 4 dyes from egg yolk. The extracts were analyzed by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS). Mean recovery for the five dyes ranged from 63.2 to 98.6%, with CV 0.55–10.00%. One sample was confirmed to contain 0.3 mg kg?1 Sudan 4. 相似文献
918.
Zhi-Rong Tan Yao Chen Gan Zhou Shan Cao Xiang-Dong Peng Yi-Cheng Wang Xiu-Juan Peng Wei Zhang Hong-Hao Zhou 《Chromatographia》2010,72(11-12):1107-1113
A sensitive and specific liquid chromatography–electrospray ionization-tandem mass spectrometry method has been developed and validated for the identification and quantification of ursolic acid in human plasma using glycyrrhetic acid as an internal standard. The method involves extraction with methyl tert-butyl ether. The analyte was separated on a C18 column and analyzed in multiple reaction monitoring mode with a negative electrospray ionization interface using the [M–H]? ions, m/z 455.4 for ursolic acid and m/z 469.5 → m/z 425.5 for glycyrrhetic acid. The method was validated over the concentration range of 0.86–110.0 μg L?1. The intra- and inter-day precisions were less than 13.53% relative standard deviation (RSD) and the accuracy was within ?4.76% in terms of relative error (RE). The lower limit of quantification was 0.86 μg L?1 with acceptable precision and accuracy. There were almost no matrix effects. Recovery of ursolic acid from spiked drug-free plasma was higher than 68%. The method was used to study the pharmacokinetic profile of ursolic acid in human plasma after oral administration of Jieyu capsules. 相似文献
919.
<正>Poly(vinylidenefluoride-hexafluoropropylene)(PVDF-HFP) nanofiber membranes with improved hydrophilicity and protein fouling resistance via surface graft copolymerization of hydrophilic monomers were prepared.The surface modification involves atmospheric pressure glow discharge plasma(APGDP) pretreatment followed by graft copolymerization of poly(ethylene glycol) methyl ether methacrylate(PEGMA).The success of the graft modification with PEGMA on the PVDF-HFP fibrous membrane is ascertained by X-ray photoelectron spectroscopy(XPS) and attenuated total reflectance Fourier transform infrared measurements(ATR-FTIR).The hydrophilic property of the nanofiber membranes is assessed by water contact angle measurements.The results show that the PEGMA grafted PVDF-HFP nanofiber membrane has a water contact angle of 0°compared with the pristine value of 132°.The protein adsorption was effectively reduced after PEGMA grafting on the PVDF-HFP nanofiber membrane surface.The PEGMA polymer grafting density on the PVDF-HFP membrane surface is measured by the gravimetric method,and the filtration performance is characterized by the measurement of water flux.The results indicate that the water flux of the grafted PVDF-HFP fibrous membrane increases significantly with the increase of the PEGMA grafting density. 相似文献
920.
波谱分析课程教学的实践与思考 总被引:1,自引:0,他引:1
介绍作者在长期波谱分析课程教学实践的基础上,对该课程教学内容及教学方法改革的一些探索。 相似文献