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V Correcher J Garcia-Guinea FJ Valle-Fuentes 《Journal of Thermal Analysis and Calorimetry》2006,83(2):439-444
In
this paper, novel results on the blue thermally stimulated luminescence (TSL)
emission of ulexite (NaCaB5O6(OH)6·5H2O)
have been studied. The four maxima appearing at 60, 110, 200 and 240°C
on the TSL glow curves of this borate could be respectively associated to:
(i) the first dehydration (NaCaB5O6(OH)6·5H2O→NaCaB5O6(OH)6·3H2O),
(ii) the creation-annihilation of the three-hydrated
phase, (iii) the Na-coordinated chains
dehydroxylation and the starting point of the alkali self-diffusion through
the lattice and (iv) the amorphisation
of the lattice. These results are fairly well correlated with the differential
thermal analyses (DTA), in situ thermal observations under environmental scanning
electron microscope (TESEM) and thermal X-ray diffraction (TXRD) techniques. 相似文献
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Marie Kjærgaard Bjørk Marie K. K. Nielsen Lotte Ø. Markussen Helene B. Klinke Kristian Linnet 《Analytical and bioanalytical chemistry》2010,396(7):2393-2401
A high-performance liquid chromatography (LC)–tandem mass spectrometry (MS/MS) method has been developed and validated for
the determination of 19 drugs of abuse and metabolites and used in whole blood. The following compounds were included: amphetamine,
methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, methamphetamine, cocaine, benzoylecgonine,
morphine, 6-acetylmorphine, codeine, methadone, buprenorphine, norbuprenorphine, ketobemidone, tramadol, O-desmethyltramadol, zaleplone, zolpidem, and zopiclone. The sample pretreatment consisted of solid-phase extraction using
mixed-mode columns (Isolute Confirm HCX). Deuterated analogues were used as internal standards for all analytes, except for
ketobemidone and O-desmethyltramadol. The analytes were separated by a methanol/ammonium formate gradient using high-performance LC (Agilent
HPLC 1100) with a 3 mm × 100 mm Varian Pursuit 3 C18 column, 3-μm particle size, and were quantified by MS/MS (Waters Quattro micro tandem quadrupole mass spectrometer) using
multiple reaction monitoring in positive mode. Two transitions were used for all analytes, except for tramadol and O-desmethyltramadol. The run time of the method was 35 min including the equilibration time. For all analytes, responses were
linear over the range investigated, with R
2 > 0.99. One-point calibration was found to be adequate by validation, thereby saving analysis of multiple calibrators. The
limits of quantification (LOQs) for the analytes ranged from 0.0005 to 0.01 mg/kg. Absolute recoveries of the analytes were
from 34 to 97%, except for zaleplone (6%). Both the interday precision and the intraday precision were less than 15% (20%
at the LOQ) for all analytes, except buprenorphine, norburprenorphine, and zaleplone (less than 18%). Accuracy (bias) was
within ±15% (±20% at the LOQ) for all analytes, except MDMA and O-desmethyltramadol (within ±19%). No ion suppression or enhancement was seen nor was suppression from coeluted analytes seen.
Matrix effects were found to be less than 23% for all analytes, except zopiclone (64%). High-concentration and low-concentration
quality control samples gave acceptable values, and the method has been tried in international proficiency test schemes with
good results. The present LC-MS/MS method provides a simple, specific, and sensitive solution for the quantification of some
of the most frequent drugs of abuse and their metabolites in whole blood. The quantification by LC-MS/MS was successfully
applied to 412 forensic cases from October 2008 to mid February 2009, where 267 cases were related to zero-tolerance traffic
legislation. 相似文献
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Juárez BH Meyns M Chanaewa A Cai Y Klinke C Weller H 《Journal of the American Chemical Society》2008,130(46):15282-15284
Insights to the mechanism of CdSe nanoparticle attachment to carbon nanotubes following the hot injection method are discussed. It was observed that the presence of water improves the nanotube coverage while Cl containing media are responsible for the shape transformation of the nanoparticles and further attachment to the carbon lattice. The experiments also show that the mechanism taking place involves the right balance of several factors, namely, low passivated nanoparticle surface, particles with well-defined crystallographic facets, and interaction with an organics-free sp2 carbon lattice. Furthermore, this procedure can be extended to cover graphene by quantum dots. 相似文献
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A new family of tetranuclear nickel cube complexes [Ni(4)L(4)(solv)(4)] (1, solv = MeOH; 2, solv = H(2)O; H(2)L = pyrazole-based tridentate {ONO} ligand) has been studied in detail, in particular by X-ray diffraction and superconducting quantum interference device (SQUID) magnetometry. Different solvates 1·H(2)O, 2·4C(3)H(6)O, 2·CH(2)Cl(2), and 2·H(2)O were obtained in crystalline form. Only small structural variations were found for the Ni-O-Ni angles of the [Ni(4)O(4)] cores of those compounds, but these slight variations have dramatic consequences for the magnetic properties. [Ni(4)L(4)(MeOH)(4)]·H(2)O (1·H(2)O) and [Ni(4)L(4)(H(2)O)(4)]·H(2)O (2·H(2)O) can be reversibly interconverted in the solid state by exposure to the respective solvent, MeOH or H(2)O, and this goes along with a switching of the spin ground state from magnetic (S(T) = 4) to diamagnetic (S(T) = 0). Likewise the (irreversible) loss of lattice solvent in [Ni(4)L(4)(H(2)O)(4)]·4C(3)H(6)O (2·4C(3)H(6)O) to give 2·2C(3)H(6)O changes the ground state from S(T) = 4 to S(T) = 0. In view of these dramatic solvatomagnetic effects for the present [Ni(4)L(4)(solv)(4)] complexes, which occur upon extrusion of lattice solvent or facile exchange of coordinated solvent molecules while keeping the robust [Ni(4)O(4)] core intact, a note of care is issued: whenever magnetic data are obtained for powdered material or for crystals that easily loose lattice solvent molecules, the magnetic properties may not necessarily reflect the situation observed in the corresponding single crystal diffraction study. Finally, a thorough analysis of the present series of complexes as well as other {Ni(4)(μ(3)-OR)(4)} cubes reported in the literature confirms that a correlation between the (Ni-O-Ni)(av) bond angle and J in [Ni(4)O(4)] cubane complexes does indeed exist. 相似文献
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