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A simple and rapid method for the simultaneous microdetermination of iodine and sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion, the iodide ions titration with 0.01 N mercuric perchlorate solution and diphenylcarbazone as indicator and the sulfate ions titration with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are in good agreement with calculated values. 相似文献
3.
Mallet CR Lu Z Fisk R Mazzeo JR Neue UD 《Rapid communications in mass spectrometry : RCM》2003,17(2):163-170
Recently, sample preparation has been considered to be the major cause of bottlenecks during high-throughput analysis. With the assistance of robotic liquid handlers and the 96-well plate format, more samples can be prepared for subsequent liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. Protein precipitation is still widely used despite potential loss of sensitivity or variable results due to ion suppression. The use of solid-phase extraction (SPE) clearly gives superior results but may not be as cost effective as protein precipitation due to the labor and material costs associated with the process. Here, a novel 96-well SPE plate is described that was designed to minimize the elution volume required for quantitative elution of analytes. The plate is packed with 2 mg of a high-capacity SPE sorbent that allows loading of up to 750 microL of plasma, while the novel design permits elution with as little as 25 microL. Therefore, the plate offers up to a 15-fold increase in sample concentration. The evaporation and reconstitution step that is typically required in SPE is avoided due to the concentrating ability of the plate. Examples of applications in drug discovery/development are shown and results are compared to protein precipitation. Excellent sensitivity and linearity are demonstrated. 相似文献
4.
A general method for the simultaneous and rapid determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds is described.The procedure is based on the combustion of the sample, containing approximately 0.005 meq of Cl or Br or I and 0.005 meq of S. by the Schöniger flask technique, using potassium hydroxide and hydrazine hydrate as absorption solution. The excess of hydrazine is eliminated with hydrogen peroxide after combustion.This method allows complete reduction of halogens to halides and oxidation of sulfur to sulfate.The halide ions are titrated with mercuric perchlorate and diphenylcarbazone as indicator; the sulfate ions with barium perchlorate and dimethylsulfonazo(III) as indicator.The results obtained are in good agreement with calculated values. 相似文献
5.
Patrizia Scafato Francesca Caprioli Laura Pisani Daniele Padula Fabrizio Santoro Giuseppe Mazzeo Sergio Abbate France Lebon Giovanna Longhi 《Tetrahedron》2013
Three forms of chiroptical spectroscopies, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) have been employed to study the configuration and conformational properties of the three molecules: (S)-3-phenylcyclopentanone, (S)-3-phenylcyclohexanone, and (S)-3-phenylcycloheptanone (including (S)-3-phenylcyclopentanone-2,2,5,5-d4 and (S)-3-phenylcyclohexanone-2,2,6,6-d4). ECD and VCD spectra in the mid-IR for the three molecular systems are marginally dependent on fine conformational details, as interpreted in terms of standard DFT computational methods, with common spectroscopic features to the three systems clearly identified. Accounting for vibronic coupling mechanisms reproduces the structuring of ECD n→π∗ band. The ORD curves are quite similar for the three types of molecules, but their interpretation highlights a crucial role played by conformations of the cycloalkanone ring in the case of (S)-3-phenylcycloheptanone. The same conclusions are reached by considering the VCD spectra in the CH-stretching region. 相似文献
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We consider the normalized Ricci flow ? t g = (ρ ? R)g with initial condition a complete metric g 0 on an open surface M where M is conformal to a punctured compact Riemann surface and g 0 has ends which are asymptotic to hyperbolic cusps. We prove that when χ(M) < 0 and ρ < 0, the flow g(t) converges exponentially to the unique complete metric of constant Gauss curvature ρ/2 in the conformal class. 相似文献
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James Isenberg Rafe Mazzeo Daniel Pollack 《Communications in Mathematical Physics》2002,231(3):529-568
We establish a general gluing theorem for constant mean curvature solutions of the vacuum Einstein constraint equations.
This allows one to take connected sums of solutions or to glue a handle (wormhole) onto any given solution. Away from this
handle region, the initial data sets we produce can be made as close as desired to the original initial data sets. These constructions
can be made either when the initial manifold is compact or asymptotically Euclidean or asymptotically hyperbolic, with suitable
corresponding conditions on the extrinsic curvature. In the compact setting a mild nondegeneracy condition is required. In
the final section of the paper, we list a number ways this construction may be used to produce new types of vacuum spacetimes.
Received: 4 October 2001 / Accepted: 26 July 2002 Published online: 29 October 2002
RID="*"
ID="*" Supported by the NSF under Grant PHY-0099373
RID="**"
ID="**" Supported by the NSF under Grant DMS-9971975 and at MSRI by NSF grant DMS-9701755
RID="***"
ID="***" Supported by the NSF under Grant DMS-9704515 相似文献
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