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991.
Stefan Mecking 《Colloid and polymer science》2007,285(6):605-619
By contrast to traditional free radical emulsion polymerization, catalytic polymerization allows for polymer microstructure
control. In terms of polymerizable monomers, both techniques are largely complementary. Since the beginning of this decade,
an increasing number of reports on polyolefin, polybutadiene, polyalkenamer, polynorbornene, polyketone, and polyacetylene
dispersions prepared by catalytic polymerization in disperse aqueous systems has appeared. This contribution reviews the preparation
of these dispersions, their colloidal properties, particle formation mechanisms, particle morphologies, and polymer microstructures. 相似文献
992.
Molecularly imprinted polymers (MIPs) are tailor-made polymers with high selectivity for the template molecule. This selectivity arises from the synthetic procedure followed to prepare the MIP. In this work, the influence of process parameters on the preparation of vinblastine (VLB) imprinted polymers was presented. In the procedure of polymerization, VLB (0.1 mmol) was used as the template molecule and a commonly used initiator, azobisisobutyronitrile (AIBN), was employed to initiate the reaction at 60 °C. The influence of the following parameters was investigated: the moles of functional monomer (MAA, 0.3-1.0 mmol), the moles of cross-linker (EDMA, 1.5-5.0 mmol) and the porogenic solvent (toluene or acetonitrile). A mathematical method of uniform design was applied to optimize these selected parameters in order to increase the selectivity of MIP for template molecule. The experimental data were analyzed to obtain the regression model and the optimal conditions were achieved by optimization with uniform design software. The MIP was synthesized under the optimal conditions that 1.0 mmol of MAA and 5.0 mmol of EDMA copolymerized in toluene in the presence of 0.1 mmol of VLB. After removal of the template molecule, the obtained MIP was then employed as the sorbents of solid-phase extraction (SPE) to separate VLB from Catharanthus roseus extract. The results showed that the polymer exhibited high affinity to the template molecule and could separate and enrich VLB from C. roseus extract effectively. The recovery of VLB on the optimal MIP was 89.00%, which agreed closely with the predicted recovery. Therefore it is possible to further improve the nature of the polymer by optimizing the polymerization parameters with the method of uniform design. 相似文献
993.
994.
A multi-residue cation-exchange clean up procedure for basic drugs in produce of animal origin 总被引:1,自引:0,他引:1
George Stubbings Jonathan Tarbin Andrew Cooper Matthew Sharman Tim Bigwood Paul Robb 《Analytica chimica acta》2005,547(2):262-268
There is considerable interest in maximising the amount of information obtained from animal product analyses, when screening for the presence of veterinary drug residues. One of the barriers to effective multi-residue analysis to date has been a lack of effective clean up procedures to isolate a wide range of residues from the potential interferents, which may be present in both simple and complex (including processed) foods. A cation-exchange clean up has, therefore, been developed for use with acetonitrile extracts of foods, when analysing for several basic drug groups (sulfonamides, benzimidazoles, levamisole, nitroimidazoles, tranquillisers and fluroquinolones). The clean up procedure has also been shown to be effective using a modified extraction solvent for malachite green and leucomalachite green in fish.Several of the key parameters that influence analyte recovery have been investigated and in an optimised procedure, tissue/biofluid samples containing sulfonamides, benzimidazoles, levamisole, nitroimidazoles, tranquillisers and fluoroquinolones are first extracted with acetonitrile. The extract is then dried with sodium sulfate and acidified with glacial acetic acid before loading onto a Bond Elut, strong cation-exchange (SCX) solid phase extraction (SPE) cartridge. Extracts from fish containing malachite green and leucomalachite green can be cleaned up using the same SCX SPE procedure following extraction with citrate buffer/acetonitrile. Typical recoveries of drugs from low level fortified tissues using the optimised procedure lie in the range 53-104% with the exception of carazolol from pig kidney (31%), malachite green from trout (42-51%) and ciprofloxacin from chicken muscle (44%) and from egg (21%). 相似文献
995.
The enantiomeric resolution of (+/-)-ibuprofen into its enantiomers was achieved by TLC on silica gel plate using optically pure (-)-brucine as a chiral selector and acetonitrile-methanol (5:1, v/v) as the solvent system. Spots were located in an iodine chamber. The detection limit was 4.9 microg. The effect of concentration of the chiral selector, temperature and pH on resolution has been studied. 相似文献
996.
The electrochemical oxidation of methanol was investigated on a Pt–Ru–Mo catalyst with an in situ infrared reflectance spectroscopy. The electrocatalysts were prepared by an electrochemical deposition and dispersed in a conducting three-dimensional matrix of polyaniline (PAni). We observed that CO2 is produced from methanol oxidation at 350 mV vs. RHE on PAni/Pt–Ru–Mo, which is 100 mV less negative than on PAni/Pt–Ru and 200 mV less than on PAni/Pt. The results suggest that Pt–Ru–Mo is less sensitive to COADS poisoning than Pt–Ru and much more sensitive than Pt. Large differences are observed concerning the average wavenumber of ADS between Pt–Ru–Mo, Pt–Ru, and Pt. 相似文献
997.
《Tetrahedron》2004,60(4):885-891
threo and erythro diastereoisomers of the constrained amino acid (βMe)Phe can be obtained separately on a multigram scale through a three-step synthesis from the corresponding Z and E isomers of 2-phenyl-4(α-phenylethylidene)-5(4H)-oxazolone. The 5(4H)-oxazolones are readily available from acetophenone and hippuric acid. The four enantiomerically pure isomers of β-methylphenylalanine, (2R,3R)-(βMe)Phe, (2S,3S)-(βMe)Phe, (2R,3S)-(βMe)Phe and (2S,3R)-(βMe)Phe, have been prepared by HPLC resolution of the racemic precursors methyl threo (or erythro)-2-benzamide-3-phenylbutanoates. 相似文献
998.
Xiang-Hua Lai 《Tetrahedron letters》2004,45(23):4469-4472
Mono(6-(p-toluenesulfonyl))permethylated β-cyclodextrin, a versatile precursor for a wide variety of mono-functionalized permethyl β-cyclodextrins, has been generated successfully by the direct methylation of monotosylated cyclodextrin. This afforded a convenient synthesis of mono(6A-N-allylamino-6A-deoxy)permethylated β-cyclodextrin. Hydrosilylation of the chiral selector with (EtO)3SiH and reaction of the resultant reactive siloxane with pristine silica gel afforded a facile entry into a structurally well-defined chiral HPLC stationary phase. 相似文献
999.
微孔型固体偏氟乙烯-六氟丙烯共聚物电解质 总被引:4,自引:0,他引:4
将固体聚合物电解质 (Solidpolymerelectrolyte)用于锂离子电池的研究已经有 3 0年的历史[1] ,从物理角度来看 ,研究过干态型 (DrySPE)、凝胶型 (GelledSPE)和微孔型固体聚合物电解质 (PorousSPE)三大类型[2 ] ;从化学角度来看 ,研究过含氧、含氮、和含氟的等聚合物[1~ 6 ] .微孔型固体含氟聚合物电解质是近 1 0年来才开始研究并受到产业界很大关注的一种SPE .固体聚合物电解质的应用可以解决液体电解质锂离子电池的漏液问题 ,并提高其安全性 ,还可以通过使用塑料包装来减小电池的重量… 相似文献
1000.
IntroductionLanthanidecomplexeshaveattractedmuchattentionbecauseoftheirimportantapplications .1InparticularEu(III)andTb(III)canbecharacterizedbylong lived(mstimescale)andstrongluminescentelectronicallyex citedstates ,whichmakesthemimportantinanalyticalchem… 相似文献