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81.
Various ways of application of radial electric field for the control of electrokinetic potential and EOF in a home-made device for CE are presented. The device comprises three high-voltage power supplies, which are used to form a radial electric field across the fused-silica capillary wall. One power supply provides the internal electric field - a driving force for electrophoretic migration of charged analytes and for the EOF. Two power supplies are connected to the ends of the outer low-conductivity polymeric coating, which is formed by the dispersion of insoluble conductive copolymer of aniline and p-phenylendiamine in polystyrene matrix (dissolved in N-methylpyrrolidone) attached to the original outer polyimide coating of the capillary. They are able to constitute the external longitudinal electric field with variable values of electric potential at both ends of the outer coating. The potential gradient between the external and internal electric field is perpendicular to the capillary wall and forms a radial electric field across the capillary wall, which affects the electrokinetic potential at the solid-liquid interface and EOF inside the capillary. The developed device and methodology has been applied for the analysis of both chiral and achiral molecules such as terbutaline enantiomers and oligopeptides (diglycine and triglycine). The effect of magnitude, orientation, and different ways of application of the radial electric field on the flow rate of the EOF and on the speed, efficiency, and resolution of CZE separations of the above analytes in the internally noncoated fused-silica capillaries have been evaluated. 相似文献
82.
B. Evrard P. Bertholet M. Gueders M. Piette G. Piel D. Cataldo L. Delattre 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):303-308
Ro 28-2653 is a new synthetic inhibitor of matrix metalloproteinases. The ability of these enzymes to degrade various components
of the extracellular matrix seems to play a major role in tumors progression and is potentially effective against bronchial
remodeling in asthma and BPCO. Ro 28-2653 is very poorly soluble in water. This low solubility estimated at about 0.56 μg/ml
in water at 25 °C gives rise to difficulties in pharmaceutical formulation of oral, injectable or nebulizable solutions. The
purpose of our study is to prepare and to characterize inclusion complexes between Ro 28-2653 and cyclodextrins and to investigate
the biopharmaceutical repercussion of the inclusion of the active substance.
The complex formation was investigated by phase solubility studies. 1H-NMR spectroscopy and molecular modeling studies were carried out to elucidate the structure of the inclusion complex between
Ro 28-2653 and cyclodextrin. Oral, intravenous and nebulizable solutions of Ro 28-2653 were developed with cyclodextrin. The
in vivo studies were performed on healthy sheep for the pharmacokinetic evaluation of the oral and intravenous formulations
while the nebulization of the complex solution was studied by using an asthma model in mouse. 相似文献
83.
The radiolysis of β(−)pinene has been studied at five different radiation dose, namely at 50, 100, 150, 300 and 600 kGy with
a dose rate of 2.2 kGy/h. At lower radiation dose, β(−)pinene showed a reduction of the optical activity, hence, the expected
radioracemization appeared predominant. At higher radiation dose, an opposite and unexpected trend was observed: the optical
activity increased almost linearly with the radiation dose. The increase of [α]D of radiolyzed β(−)pinene was due to the formation oligomers, mainly a dimer and/or a trimer of β(−)pinene which remain soluble
in the monomer but which displayed a higher optical activity than the starting monomer, contributing to the increase in the
specific optical rotation. Simultaneously to the formation of the dimer/trimer the radiolysis of β(−)pinene induced also its
polymerization into a poly(β(−)pinene) resin which was insoluble in the monomer and which was characterized by a high structural
order and by the preservation of the chiral centers so that it showed an enhanced specific optical rotation which is ≈2 times
that of the monomer. It is shown that poly(β(−)pinene) radiopolymer can be easily racemized in presence of a Friedel-Crafts
catalyst. The kinetics of β(−)pinene radiation-induced oligomerization and polymerization can be described by a pseudofirst
order rate constant k = 1.9·10−7·s−1. The radiation chemical yield for the same reaction is G = 1.93·10−6 mol/J. The work shows that also the radiation-induced polymerization of chiral monomers may be a tool for the preservation
and amplification of the optical activity of the monomer with implications for abiotic mechanisms of chiral amplification. 相似文献
84.
F. Cataldo 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(1):107-113
The terpenes α-(+)-pinene, and α-(−)pinene have been radiolyzed at radiation doses of 150, 300 and 600 kGy. The radiolyzed
samples have been analyzed by FT-IR spectroscopy and polarimetry. Both α-(+)-, α-(−)-pinenes show a linear trend to radioracemization
as a function of the radiation dose administered ≈2.5·10−3 [α]D/kGy. The solvent fractionation and the liquid chromatographic analysis (HPLC) of the radiolyzed samples shows that both α-pinene
enantiomers produce ocimene and dipentene together with minor quantities of other products and a resin. The kinetics of α-pinene
decomposition under radiolytic conditions can be described by a pseudofirst order rate constant k∼5.3·10−7s−1 while the radiation chemical yield for the same reaction has a G = 5.0 molecules/100 eV, so that about 30% of the original α-pinene is converted into other products at 600 kGy. 相似文献
85.
86.
87.
Mandrioli R Musenga A Ferranti A Lasaponara SS Fanali S Raggi MA 《Journal of separation science》2005,28(9-10):966-972
A micellar electrokinetic chromatographic method was developed and applied for the first time to the separation and quantification of the main components of cloves, namely eugenol and beta-caryophyllene. The analytes were separated in less than ten minutes in an unmodified fused silica capillary (effective length: 40.0 cm) using a background electrolyte composed of 25 mM carbonate buffer (pH 10.0) and 60 mM sodium dodecylsulfate. Analyte concentrations were determined in clove oil and in methanolic clove extracts after simple sequential dilution with methanol and background electrolyte, and the resulting electropherograms showed no interference due to other components. Precision assays gave satisfactory results, with mean standard deviation of peak areas lower than 4.7% (lower than 1.5% for migration times). The eugenol content of a commercial clove oil was about 70% (RSD% = 3.2), while that of beta-caryophyllene was about 15% (RSD% = 4.2); in clove extracts, on the other hand, eugenol was approximately 15% (RSD% = 4.7) and beta-caryophyllene 4% (RSD% = 5.1). Accuracy was also good (mean recovery >98%). 相似文献
88.
Aurore Fraix Vanna Torrisi Giovanni Marletta Salvatore Sortino Placido G. Mineo Gaetano A. Tomaselli 《Supramolecular chemistry》2016,28(5-6):485-492
AbstractA poly(p-phenyleneethynylene) polymer (PCF[5]), bearing two π-rich cone-like calix[5]arene cavities (assembling cores) attached to a rigid p-phenyleneethynylene spacer, was synthesised by a Pd-catalysed cross-coupling reaction. UV–vis absorption and fluorescence spectroscopies combined with dynamic light scattering measurements provide evidence for the self-assembly of PCF[5] (homopolytopic host molecule) with a complementary C60 fulleropyrrolidine (C60-Pyr) guest in solution, in the construction of a supramolecular polymer network. Atomic force microscopy analysis of PCF[5]/C60-Pyr highlights the formation of a bicontinuous network consisting of a uniform distribution of prominent structures, within a polymeric background forming a biphasic structure. 相似文献
89.
Reduction of enantiopure N-p-toluenesulfinyl ketimines derived from 2-pyridyl ketones affords N-p-toluenesulfinyl amines with good yields and diastereoselectivities. 相似文献
90.
[reaction: see text] Ytterbium triflate was shown to be an effective catalyst in promoting the synthesis of either isopropyl esters or free alpha-hydroxy-arylacetic acids from substituted aromatic glyoxals and aryl methyl ketones, respectively. The reaction to provide acids starting from differently substituted ketones was carried out by an environmentally friendly method using an aqueous medium as a solvent and giving the adducts in 78-99% yield without any further purification after the usual workup. 相似文献