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991.
Hsieh Y Wang G Wang Y Chackalamannil S Brisson JM Ng K Korfmacher WA 《Rapid communications in mass spectrometry : RCM》2002,16(10):944-950
An ultrafast bioanalytical method using monolithic column high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) was evaluated for the simultaneous determination of a drug discovery compound and its metabolite in plasma. Baseline separation of the two compounds was achieved with run times of 24 or 30 s under isocratic or gradient conditions, respectively. The monolithic column HPLC/MS/MS system offers shorter chromatographic run times by increasing flow rate without sacrificing separation power for the drug candidate and its biotransformation product (metabolite). In this work, the necessity for adequate chromatographic resolution was demonstrated because the quantitative determination of the drug-related metabolism product was otherwise hampered by interference from the dosed drug compound. The chromatographic performance of a monolithic silica rod column as a function of HPLC flow rates was investigated with a mixture of the drug component and its synthetic metabolite. The assay reliability of the monolithic column HPLC/MS/MS system was checked for matrix ionization suppression using the post-column infusion technique. The proposed methods were successfully applied to the analysis of study rat plasma samples for the simultaneous quantitation of both the dosed drug and its metabolite. The analytical results obtained by the proposed monolithic column methods and the 'standard' silica particle-packed HPLC column method were in good agreement, within 10% error. 相似文献
992.
Summary A simple procedure for the amperometric determination of lead, mercury, cadmium and thallium in theg range by titration with EDTA is described. Using 0.5 ml of the test solution and 10–5
M EDTA, the minimum quantity of these metal ions that can be determined is about 1 ppm. The accuracy is within ±5%.
Spurenanalyse toxischer Metalle. I.Bestimmung von Pb, Hg, Cd und Tl durch amperometrische Titration
Zusammenfassung Ein einfaches Verfahren zur amperometrischen Bestimmung von Mikrogrammengen Pb, Hg, Cd und Tl durch Titration mit ÄDTA wurde beschrieben. Bei Verwendung von 0,5 ml Probelösung und 10–5 M ÄDTA-Lösung können die genannten Metallionen in der Größenordnung von 1 ppm bestimmt werden. Die Genauigkeit beträgt ±5%.相似文献
993.
Introduced in this article is fabrication of an integrated capillary for the applications of electrochemical detection in capillary electrophoresis. The separation section, voltage decoupler, and working electrode were composed into a single section of capillary. The porous decoupler was constructed by HF etching till the thickness of the capillary wall less than 20 μm. The working electrode was prepared by sputtering Au-films on the outlet of the capillary. The integration of the separation capillary with a complete detection assembly improves the convenience for the routine application of electrochemical measurements in capillary electrophoresis. For a 100-μm-i.d. capillary, the theoretical plate number of catechol and the migration time reproducibility can reach 120,000 and 1.9% RSD, respectively. The linear range exceeds 3 order of magnitude and the detection limit is lower than 0.65 μM. 相似文献
994.
The force acting on a porous spheroidal floc having a nonhomogeneous structure in a uniform flow field is evaluated theoretically. Here, the floc is simulated by an entity having a two-layer type of structure, and its porous nature is mimicked by varying the relative magnitudes of the permeabilities of its inner and outer layers. The results of numerical simulation reveal that, for the same volume-averaged permeability, the drag coefficient of a spheroidal floc with a nonhomogeneous structure is much larger than that of a floc with a homogeneous structure for both prolate and oblate spheroids. This is true regardless of the relative magnitudes of the permeability of the inner layer and that of the outer layer. While the drag coefficient of a homogeneous prolate is the same as that of a homogeneous oblate the drag coefficient of a nonhomogeneous prolate is larger than that of a nonhomogeneous oblate. For the same volume-averaged size, the more nonhomogeneous the structure of a spheroidal floc the easier for the relation between the drag coefficient and the Reynolds number to deviate from a Stokes-law-like relation. For a fixed volume-averaged permeability, the effective drag coefficient increases with the increase in the ratio (polar radius of inner layer/polar radius of floc), regardless of whether its inner layer is less permeable than its outer layer or not. 相似文献
995.
A new vanadium(IV) silicate, Rb(2)(VO)(Si(4)O(10)).xH(2)O (x approximately 0.1), has been synthesized by a high-temperature, high-pressure hydrothermal method. It crystallizes in the tetragonal space group I4(1)md (No. 109) with a = 12.2225(7) A, c = 7.7948(6) A, and Z = 4. The structure consists of spiral chains of corner-sharing SiO(4) tetrahedra linked to neighboring chains via corner sharing to form a 3-D silicate framework which delimits channels to accommodate the VO(2+) groups. The Rb(+) ions are located in the cavities within the silicate framework. Magnetic susceptibility confirms the valence of vanadium. A partially occupied lattice water site is confirmed by IR and solid state (1)H NMR spectroscopy. The structure of the title compound is considerably different from those of the synthetic silicate K(2)(VO)(Si(4)O(10)).H(2)O and the two polymorphs of the natural mineral Ca(VO)(Si(4)O(10)).4H(2)O, although they have identical framework stoichiometry. 相似文献
996.
Studies on the Formosan Soft Corals I-Cytotoxic Cembrane Diterpenes from Sarcophyton Trocheliophorum
Yang-Chang Wu Pei-Wen Hsieh Chang-Yih Duh Shang-Kwei Wang Keryea Soong Lee-Shing Fang 《中国化学会会志》1992,39(4):355-357
Two cytotoxic cembranoid diterpenes, (+)-isosarcophytoxide (1) and ( + )-isosarcophine (2), were isolated from the soft coral Sarcophyton trocheliophorum by cytotoxicity-guided fractionation. These two compounds demonstrated potent cytotoxicity against P-388 and HL-60 cells. 相似文献
997.
We report concentration methods for the analysis of small solutes by capillary electrophoresis in conjunction with laser-induced native fluorescence using a Nd:YAG laser. After injecting samples, poly(ethylene oxide) (PEO) in the anode reservoir entered a capillary filled with Tris-borate buffer. When migrating in PEO solution, the analytes slowed down and stacked at the interface between the sample zone and PEO solution. As a result, the limits of detection (LODs) down to 8 pM for 2-naphthalenesulfonic acid and 70 pM for L-tryptophan have been achieved when injecting at 30 cm height for 120 s and 230 s, respectively. Such low LODs are partially due to the effects of NaCl in the samples and PEO on the fluorescence characteristics of the analytes. In addition, the concentrations of NaCl and PEO have great impacts on the migration of the analytes and electroosmotic flow, thereby affecting resolution and speed. Without pretreatment, the determinations of five important markers in urine samples and two acids in a cerebrospinal fluid sample have been performed separately, with the relative standard deviations of the concentrations less than 3.6%. Furthermore, by applying a short plug of low-pH buffer after injection, the analysis of greater volumes of the urine sample has been carried out, resulting in detecting more peaks. 相似文献
998.
999.
For links of 3 components, such as Borromean rings, which escape the detection of Gauss linking, we define and compute combinatorically and explicitly the higher linking. And as in perturbative quantum field theory, this higher linking is presented as a sum of Chern–Simons–Witten configuration space integrals. 相似文献
1000.
This paper studies coordinated decisions in a decentralized supply chain that consists of one Original Equipment Manufacturer (OEM), one manufacturer, and one distributor, and possesses uncertainties at both demand and supply sides. These uncertainties emerge, respectively, from random demand the distributor faces and randomness of capacity with which the OEM processes the manufacturer’s outsourced quantity. Sharing supply and demand uncertainty information along the supply chain enables us to develop three models with different coordination efforts—the OEM and manufacturer coordination, the manufacturer and distributor coordination, and the OEM, manufacturer, and distributor coordination—and quantify the coordinated decisions in these three models. Our analysis of these coordination models suggests that coordinating with the OEM improves the manufacturer’s probability of meeting downstream demand and his expected profit, yet coordinating with the manufacturer is not necessarily beneficial to the OEM when downstream coordination is lacking. 相似文献