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1.
A sensitive and specific method for the determination of bencyclane in human plasma is presented. Bencyclane was extracted from human plasma with two 3-ml volumes of isooctane and was shaken for 10 min. The organic phase was separated and evaporated to dryness at 40 degrees C under a nitrogen stream. The residue was dissolved and an aliquot was injected into the gas chromatograph. The separation was performed with a DB-17 column with helium as the carrier gas. Nitrogen-selective detection was performed. The quantification was performed with the signal output. The limit of detection was 1 ng/ml. 相似文献
2.
A sensitive and specific method for the determination of fendiline in human plasma is presented. Fendiline was extracted from human plasma after the addition of phosphate buffer two times with 4 ml of n-hexane. The organic phase was separated and evaporated to dryness at 40 degrees C under a stream of nitrogen. The residue was dissolved and an aliquot was injected into the gas chromatograph. Chromatographic separation was performed with a DB-1 column with helium as carrier gas. Nitrogen-selective detection was performed. Quantification was performed with the signal output. The limit of detection was 1 ng/ml of plasma. 相似文献
3.
A computer program for comparison of the conformations of a number of related molecular structures is described. The comparisons are performed on either interatomic distances or torsion angles. The comparisons are accomplished on ordered pairs of distances or torsion angles, and the distance comparisons can be performed in a manner that allows permutation of the distance pairs being compared. The algorithm utilizes bit-string Boolean operations that allow the comparisons to be performed rapidly. The program should be useful for computer-assisted molecular modeling studies in which the viable conformers of bioactive analogues are compared in order to locate those conformers that place key substituents in the same spatial orientation. 相似文献
4.
A method for the determination of nine corticosteroids in bovine liver was developed. The liquid-liquid extraction method consisted in the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract was evaporated to dryness and the residue redissolved in acetonitrile. The removal of fats was performed with n-hexane and the acetonitrile layer was evaporated. Afterwards, analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as reagent. The recovery curves, performed at five spiking levels (different for each corticosteroid), showed that recoveries of at least 70.5% could be obtained from liver. The chemiluminescence detection gave satisfactory results with respect to sensitivity, and the LOQ ranged from 0.13 ppb for prednisolone to 8.40 ppb for betamethasone. The maximum mean RSD was 4.8% and 7.3% for intra- and inter-day assay, respectively. 相似文献
5.
Aida Contreras-Ramirez Dr. Bryan E. Tomlin Gregory S. Day Prof. Dr. Abraham Clearfield Prof. Dr. Hong-Cai Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6185-6194
Nanosized α-zirconium phenylphosphonate particles were successfully prepared by the reaction between different zirconium sources and molten phenylphosphonic acid in the absence of solvent. The resultant nanoplates exhibit particle sizes in the range of 15 to 30 nm. The use of a topotactic anion exchange method starting from α-zirconium phosphate instead resulted in the generation of 15 to 180 nm plates, while also resulting in nanoparticles with a higher degree of crystallinity. The topotactic anion exchange of the phosphate groups by phenylphosphonate groups could be performed to completion when performed in molten phenylphosphonic acid. Characterization of both the final products as well as the individual steps in the anion exchange were performed by powder XRD, fast neutron activation analysis, TGA, FTIR spectroscopy, TEM, solid-state NMR and XPS. 相似文献
6.
P Van de Vijver L Scheer J van Beijnum A Griffioen TM Hackeng 《Chemical communications (Cambridge, England)》2012,48(75):9403-9405
The use of omonasteine (Omo) in sequential peptide ligation strategies extends the scope of homocysteine (Hcy) ligation to longer, methionine-rich proteins. Hcy-to-Omo conversion can be performed on-resin, while the Omo-to-Hcy deprotection can be performed in situ after peptide ligation. This strategy was successfully applied in the synthesis of the BRD7 bromodomain. 相似文献
7.
K. C. Patrick Lee Millicent Bulls John Holmes John W. Barrier 《Applied biochemistry and biotechnology》1997,66(1):1-23
Because of the recalcitrant nature of lignocellulosic materials, it is important to pretreat the biomass in order to obtain
a suitable material for the bioconversion. In this study, two different types of pretreatments were performed. The first experiment
used a 2-gal Parr reactor operated at 140, 150,160, and 170‡C with sulfuric acid concentrations varying from 0.5 to 2%. A
second pretreatment was performed with a two-stage low-temperature process. The first-stage pretreatment was performed at
100 or 120‡C with sulfuric acid concentrations of 0.5, 2, and 5% followed by a secondstage pretreatment at 120‡C with 2% acid
concentration. The best residues for enzymatic hydrolysis and simultaneous saccharification and fermentations (SSF) came from
the higher temperature pretreatment with the Parr reactor. However, a large portion of the xylose fraction was degraded to
furfural and glucose was degraded to HMF. On the contrary, the two-stage low temperature pretreatment resulted in a very low
percentage of xylose degradation, and no glucose degradation. The residues from this two-stage pretreatment performed satisfactorily
toward the production of ethanol by SSFs. This study discusses the results obtained from these experiments. 相似文献
8.
Alexandre A.M. Lapis Jackson D. Scholten Marcos N. Eberlin 《Tetrahedron letters》2006,47(38):6775-6779
Intermolecular hydroamination or hydroarylation reactions of norbornene and cyclohexadiene performed with catalytic amounts of Brönsted or Lewis acid in ionic liquids were found to provide higher selectivity and yields than those performed in classical organic solvents. The ionic liquid increases the acidity of the media and stabilizes ionic intermediates through the formation of supramolecular aggregates. 相似文献
9.
Vapor mass flux density has been calculated on the surface of spherical droplets under almost isothermal conditions. The calculations have been performed at droplet radii corresponding to the free-molecular, intermediate, and continuum flow regimes. The study has been performed by the direct numerical solution of the Boltzmann kinetic equation. The method of characteristics has been adapted for describing transfer processes in spherically symmetric systems. The applicability of different simplified approaches to the calculation of mass flux density on droplet surface has been estimated. 相似文献
10.
de Andrade RR Rivera EC Costa AC Atala DI Maugeri Filho F Maciel Filho R 《Applied biochemistry and biotechnology》2007,137(1-12):753-763
In this work, a procedure was established to develop a mathematical model considering the effect of temperature on reaction kinetics. Experiments were performed in batch mode in temperatures from 30 to 38 degrees C. The microorganism used was Saccharomyces cerevisiae and the culture media, sugarcane molasses. The objective is to assess the difficulty in updating the kinetic parameters when there are changes in fermentation conditions. We conclude that, although the re-estimation is a time-consuming task, it is possible to accurately describe the process when there are changes in raw material composition if a re-estimation of parameters is performed. 相似文献
11.
Results of high thermal resolution microcalorimetric and dilatometric measurements performed on reducer — polytetrafluoroethylene
(M-PTFE) pyrotechnic compositions have been discussed. The materials were selected for the study because of their behaviour
in combustion tests. Two complementary thermal properties, i.e. the specific heat and coefficient of linear thermal expansion
(CLTE), have been analysed in detail. The specific heat was obtained from DSC measurements performed from −20 to 375°C. Measurements
of CLTE and linear expansion were carried out from −40 to 270°C. In both cases the measurements were performed on thermocycling
with the high thermal resolution preserved. A special attention has been paid to a two-stage phase transition occurring just
below the room temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Laura C. Oliveira Cibele B. Zamboni Edson A. Pessoa Fernanda T. Borges 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):395-398
In this investigation ions in serum, urine and kidney of Wistar rats (control group) and Wistar with Acute Renal Insufficiency
(ARI) were quantified using instrumental neutron activation analysis. The measurements in serum and urine were performed before,
during and after ischemia-induced ARI. The measurements in kidney were performed for the control and ARI groups. Also, a comparative
analysis between the concentration ratios before, during and after ARI was performed in urine and serum samples for both groups.
The variations results for Cu in serum and I in urine, before and after ischemia-induced ARI, suggest that these elements
must be also investigated in renal dysfunction. 相似文献
13.
A new inorganic ion-exchanger lanthanum tungstate has been prepared by mixing lanthanum nitrate and sodium tungstate. The refluxed product has been found to be most suitable; therefore, most of the electrochemical and ion-exchange studies were performed on this product. The material is a weak cation exchanger with a capacity of 0.80 mmol per gram. Electrochemical studies are performed by preparing a pellet of this exchanger in polystyrene; charge density and membrane potential have been calculated. The results are discussed. 相似文献
14.
C. Seccaroni N. Volante A. Rosada L. Ambrosone G. Bufalo P. Avino 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(2):277-282
The results of a study on 111 obsidian artifacts collected during an archaeological campaign performed by the University of
Siena near Sesto Fiorentino (Florence, Italy) are reported. Earlier, we used the concentration ratios among some elements
as reported in the literature to discriminate the deposit sources. Later, optimizing the characterization and for having a
more strong classification, multivariate chemiometric investigation has been performed (multivariate statistical analysis
in Principal Components and Discriminating Factor Analysis). The data obtained show three wellseparated groups connected to
the relative sites in Lipari and in Sardinia (flows A and C from Arci Mountain). 相似文献
15.
Continuous concentration of bacteria in a microfluidic flow cell using electrokinetic techniques 总被引:1,自引:0,他引:1
A novel method for the concentration of bacterial solutions is presented that implements electrokinetic techniques, zone electrophoresis (ZE) and isoelectric focusing (IEF), in a microfluidic device. The method requires low power (< 3e-5 W) and can be performed continuously on a flowing stream. The device consists of two palladium electrodes held in a flow cell constructed from layers of polymeric film held together by a pressure-sensitive adhesive. Both ZE and IEF are performed with carrier-free solutions in devices in which the electrodes are in intimate contact with the sample fluid. IEF experiments were performed using natural pH gradients; no carrier ampholyte solution was required. Experiments performed in buffer alone resulted in significant electroosmotic flow. Pretreatment of the sample chamber with bleach followed by a concentrated solution of cationic detergent effectively suppressed electroosmotic flow. 相似文献
16.
Marta Pelcová Monika Langmajerová Eliška Cvingráfová Jan Juřica Zdeněk Glatz 《Journal of separation science》2014,37(19):2785-2790
This study deals with the nonaqueous capillary electrophoretic separation of dextromethorphan and its metabolites using a methanolic background electrolyte. The optimization of separation conditions was performed in terms of the resolution of dextromethorphan and dextrorphan and the effect of separation temperature, voltage, and the characteristics of the background electrolyte were studied. Complete separation of all analytes was achieved in 40 mM ammonium acetate dissolved in methanol. Hydrodynamic injection was performed at 3 kPa for 4 s. The separation voltage was 20 kV accompanied by a low electric current. The ultraviolet detection was performed at 214 nm, the temperature of the capillary was 25°C. These conditions enabled the separation of four analytes plus the internal standard within 9 min. Further, the developed method was validated in terms of linearity, sensitivity, and repeatability. Rat liver perfusate samples were subjected to the nonaqueous capillary electrophoretic method to illustrate its applicability. 相似文献
17.
Choukourov A Biederman H Slavinska D Hanley L Grinevich A Boldyryeva H Mackova A 《The journal of physical chemistry. B》2005,109(48):23086-23095
Plasma polymerization of allylamine is performed both in continuous wave and pulsed mode. Chemical derivatization is applied to determine primary and secondary amine concentration. Primary amines are efficiently formed, but secondary amines are more abundant. A polymerization mechanism is proposed to account for the difference in amine content obtained from comparison between continuous wave and pulsed mode plasma polymerization. The AFM measurements performed on ultrathin (1-10 nm) plasma polymers confirm the continuity of films and that the film growth on silicon occurs via a layer-by-layer mechanism because no islandlike structures were detected. 相似文献
18.
Direct potentiometric determination of chloride in a flow-injection system can be performed in the presence of excess bromide, iodide, sulphide and cyanide, when potassium bromate in nitric acid is used as the carrier solution. The hydrodynamics and temperature of such a system have been examined and various oxidants and indicating electrodes investigated. The analysis can be performed at a maximum rate of 120 samples per hour. 相似文献
19.
Simulation of waterlogged archaeological woods was carried out by immersion of fir and chestnut wood samples into sea water
at different temperatures (room temperature and 40°C). The effects of metals in contact with woods were simulated by inserting
in some specimens of the two types of wood copper or iron nails, the most important metals from the archaeological point of
view. The effects of this ageing simulation on woods were studied by different characterization methods. At first we have
performed gravimetric analyses, controlling the mass increase of immersed wood in function of the time of immersion and the
temperature of the bath. Then, thermogravimetry, differential thermal analysis, differential scanning calorimetry in oxygen
flux were used. The alteration of wood was observed by means of the peak temperatures of DTA, DTG and DSC variation and by
the mass losses observed during heating, evaluated on the basis of the measured thermal data. The samples were woods powder
obtained by milling. Complementary characterization of the woods was performed by evaluating the crystallinity of cellulose
by means of X-ray powder diffraction. The change in colour of woods during ageing was checked by means of spectrophotometric
measurements in the visible region.
X-ray fluorescence was used to investigate the penetration of metals into wood samples. An artificial ageing treatment with
NaOH and O3 was also performed.
Finally, a comparison between the effects of artificial alteration realised in our specimens and natural degradation observed
in archaeological woods, was performed. 相似文献
20.
《液相色谱法及相关技术杂志》2012,35(6):1121-1137
Abstract We examined with High Performance Liquid Chromatography (HPLC) gel-filtration the aggregational behaviour of insulin during application by artificial delivery systems. The short time infusion was performed by an autosyringe pump and the long time infusion was performed by a Siemens pump. For comparison we collected samples of about l ml and determined the radioimmunological activity in order to verify the results of the HPLC gel-filtration. The chromatograms, performed at 37[ddot]C and at ambibient temperature, showed no aggregates of a higher molecular weight. We observed sedimentation only once during long time infusion, however, the immediately performed gel-filtration surprisingly showed at no time an aggregate of a higher molecular weight, but the quantity of insulin was obviously reduced. A different length of the catheter systems used did not promote the aggregational behaviour. 相似文献