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71.
Spherical molecularly imprinted polymer particles: a promising tool for molecular recognition in capillary electrokinetic separations 总被引:2,自引:0,他引:2
De Boer T Mol R De Zeeuw RA De Jong GJ Sherrington DC Cormack PA Ensing K 《Electrophoresis》2002,23(9):1296-1300
Spherical molecularly imprinted polymer particles obtained via precipitation polymerization, were introduced as a pseudostationary phase in capillary electrophoresis (CE) to study molecular recognition. Analyses were performed via a partial filling technique using (+)-ephedrine-imprinted microspheres (100-200 nm) which were polymerized from methacrylic acid and 1,1,1-Tris(hydroxymethyl)propanetrimethacrylate using acetonitrile as the solvent. The influence of pH and the modifier content on the separation was investigated. A 0.1% w/v suspension in an aqueous 10 mM phosphate buffer (pH 2.5 with 40% acetonitrile) was hydrodynamically injected into the CE system (80% of the effective capillary length) and led to full baseline separation of racemic ephedrine within 10 min. 相似文献
72.
73.
Chromatography has been an important tool in marine laboratories. Since the 1960s, marine laboratories have been involved in the analysis of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and brominated flame retardants (BFRs). Column chromatography and liquid chromatography (LC) techniques have been used, mainly in the clean-up phase, while gas chromatography (GC) has been used extensively in the final determination of these contaminants. Developments have been observed from the use of packed GC columns, via capillary columns to the use of heart-cut multi-dimensional GC and comprehensive multi-dimensional GC. The progress made in interlaboratory studies and the availability of certified reference materials are discussed. 相似文献
74.
The charge-transfer (CT) transition of complexes involving alkylated aromatic electron donors shifts hypsochromically upon benzylic deuteration. This is attributed to hyperconjugative effects. 相似文献
75.
A simple, rapid and sensitive high-performance thin-layer chromatographic assay for the determination of epoxide hydrolase activity in rat liver homogenates is described. It is extended to the determination of a series of phenoxypropane-1,2-diols. The hydrolase assay has the advantages of using a readily available substrate, 2,3-epoxypropyl 4-methoxyphenyl ether, of multiple sample application, and of the simultaneous determination of reaction product (diol) as well as unchanged substrate (epoxide). The use of an internal standard, 4-nitroanisole, results in high sensitivity and good reproducibility of the proposed method. The limit of diol detection is 20 pmol. 相似文献
76.
Ester van den Beuken Sylvie Samson Elizabeth J. Sandoe G. Richard Stephenson 《Journal of organometallic chemistry》1997,530(1-2):251-253
The first example of an alkyne-substituted tricarbonyl(η5-cyclohexadienyl)iron(1+) complex has been prepared and the ω directing effect of the phenylethynyl substituent has been demonstrated in nucleophile addition reactions. Addition of NC− also occurs at the a position to form an unusual η1, η3-structure. 相似文献
77.
Thermal Properties of Hot-Stage Extrudates of Itraconazole and Eudragit E100. Phase separation and polymorphism 总被引:1,自引:0,他引:1
Six K. Leuner Ch. Dressman J. Verreck G. Peeters J. Blaton N. Augustijns P. Kinget R. Van den Mooter G. 《Journal of Thermal Analysis and Calorimetry》2002,68(2):591-601
Solid dispersions of itraconazole and eudragit E100 were prepared by hot-stage extrusion. Analysis of the physical structure
revealed the existence of different phases, depending on the manufacturing condition. Extrudates prepared at 453 K existed
as a molecular dispersion of itraconazole in eudragit E100 when the drug concentration did not exceed ca. 13% mass/mass. At
higher concentrations, a second phase consisting of pure glassy itraconazole emerged. In other dispersions prepared at 413
K, the second phase consisted of pure crystalline itraconazole. The difference can be attributed to the relation of the process-temperature
to the melting point. Heating of both dispersions induced cold crystallization. Extrudates prepared at 453 K showed comparable
behavior before and after milling, with the exception that unmilled dispersions with a drug load of ≥60% mass/mass recrystallized
upon heating into a polymorphic modification of itraconazole (T
m=431 K). Upon further heating the polymorph recrystallized to the stable crystalline form (T
m=441 K).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
78.
V. V. Barbakadze E. P. Kemertelidze I. Targamadze K. Mulkidzhanyan J. Kemink A. J. J. van den Berg K. J. Beukelman A. I. Usov 《Chemistry of Natural Compounds》2005,41(4):374-377
Two high-molecular-weight (>1000 kDa) water-soluble preparations were isolated from stems of Symphytum asperum and S. caucasicum. Their basic component was established as poly[hydroxy-1-carboxy-2-(3,4-dihydroxyphenyl)ethylene], analogous to that of high-molecular-weight
(>1000 kDa) preparations from roots of these same plants, using IR and NMR spectral data.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 303–305, July–August, 2005.
An erratum to this article is available at . 相似文献
79.
Tiggelaar RM Berenschot JW de Boer JH Sanders RG Gardeniers JG Oosterbroek RE van den Berg A Elwenspoek MC 《Lab on a chip》2005,5(3):326-336
In this paper the fabrication and electrical characterization of a silicon microreactor for high-temperature catalytic gas phase reactions, like Rh-catalyzed catalytic partial oxidation of methane into synthesis gas, is presented. The microreactor, realized with micromachining technologies, contains silicon nitride tubes that are suspended in a flow channel. These tubes contain metal thin films that heat the gas mixture in the channel and sense its temperature. The metal patterns are defined by using the channel geometry as a shadow mask. Furthermore, a new method to obtain Pt thin films with good adhesive properties, also at elevated temperatures, without adhesion metal is implemented in the fabrication process. Based on different experiments, it is concluded that the electrical behaviour at high temperatures of Pt thin films without adhesion layer is better than that of Pt/Ta films. Furthermore, it is found that the temperature coefficient of resistance (TCR) and the resistivity of the thin films are stable for up to tens of hours when the temperature-range during operation of the microreactor is below the so-called "burn-in" temperature. Experiments showed that the presented suspended-tube microreactors with heaters and temperature sensors of Pt thin films can be operated safely and in a stable way at temperatures up to 700 degrees C for over 20 h. This type of microreactor solves the electrical breakdown problem that was previously reported by us in flat-membrane microreactors that were operated at temperatures above 600 degrees C. 相似文献
80.
The conditional metal availability and the kinetic stability of humic substance-metal species in humic-rich waters (e.g. bog water) was characterized by means of EDTA exchange. For this purpose a combined procedure consisting of time-controlled ligand exchange by EDTA, species differentiation by a fast single-stage tangential-flow ultrafiltration (TF-UF) technique (cut-off 1 kDa) and sensitive atomic spectrometry methods (e.g. AAS, ICP-OES, TXRF) was developed. The kinetics and the yield of the EDTA exchange served as operational parameters for assessing the kinetic stability and EDTA availability of HS-metal species, respectively. Considerable fractions of natural HS-metal species studied were shown to be EDTA-inert (e.g. 31% of the total Fe, 44% of the total Al) even after long reaction times (48 h), in contrast to artificial ones formed in solutions of isolated HS. Moreover, the conditional thermodynamic stability of HS-metal complexes formed by successive loading of an aquatic reference HS (HO14) with a number of heavy metal ions (e.g. Cr(III), Cu(II), Fe(III), Mn(II), Zn(II)) was also evaluated discriminating the free metal concentrations by means of TF-UF. In addition, from the loading isotherms obtained conditional complexation capacities could be derived for the studied HS exhibiting the order Fe(III)>Cu(II)>Cr(III)>Co(II)>Mn(II). 相似文献