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961.
Development of an analytical procedure for determination of selected estrogens and progestagens in water samples 总被引:1,自引:0,他引:1
An analytical procedure has been developed for determination of eight selected natural and synthetic hormonal steroids in surface water and in effluent samples. Several methodological points have been investigated and are discussed; they include the choice of the solid-phase extraction sorbent, the influence of flow rate on recovery, the breakthrough volume for a given sorbent (Env+ and Oasis HLB), sample clean up, and sample storage. As regards the latter point, it was found that when no preservative was added to effluent from a sewage-treatment plant, severe loss of steroids occurred—85% of progesterone and about 30% of both estrone and estradiol were found to be degraded in 24 h. The procedure developed was applied to samples from the Seine river estuary. Sex steroids were not detected in surface water; estrone was the most commonly detected steroid in sewage-treatment plant effluent, with levels ranging from 1.8 to 8.3 ng L–1. Synthetic estrogens (ethynylestradiol and mestranol) and progestagens (levonorgestrel and norethindrone) were never detected, whatever the sampling season. Overall, for 162 out of 168 measurements levels were below the detection limits of the developed procedure. 相似文献
962.
Alain H. Roux Daniel Hétu Gérald Perron Jacques E. Desnoyers 《Journal of solution chemistry》1984,13(1):1-25
Mixed micelles can be formed in water between various pairs of hydrophobic solutes such as surfactants, alcohols and hydrocarbons. These systems can often be studied through the thermodynamic functions of transfer of one of the solutes, usually kept near infinite dilution, from water to an aqueous solution of the other solute. When mixed micelles are formed, these functions change significantly, and often go through extrema, in the region where the binary system micellizes or undergoes some microphase transition.Three main effects are responsible for the observed trends: pair-wise interactions between both solutes in the monomeric form, a distribution of the reference solute between the aqueous and micellar phases and a shift in the monomer-micelle equilibrium in the vicinity of the reference solute. Simple equations can be derived for these three effects which can account for the sign and magnitude of the observed trends using parameters which are derived for the most part from the two binary systems. 相似文献
963.
Ru-based catalysts can be used in E-selective cross metathesis (CM) reactions to synthesise various functionalised internal allylic monofluorides. 相似文献
964.
Petra Spitzer Bruno Rossi Yves Gaignet Stéphane Mabic Uwe Sudmeier 《Accreditation and quality assurance》2005,10(3):78-81
There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 S cm–1 at 25.0 °C, resistivity >1 M cm at 25.0 °C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.Milipore, Milli-Q and Elix are registered trademarks of Millipore Corporation. 相似文献
965.
Summary An extension of the multiconfigurational SCF approach for the resolution of the vibrational problem is presented; it follows the philosophy of the CASSCF method developed in Quantum Chemistry. The new method allows a more complete treatment of anharmonic mode couplings, converges much faster and gives a clearer physical insight of vibrational interactions. This is exemplified by the calculation of infrared transition moments in the H2O and D2O isotopomers of the water molecule. It is shown how this property varies with the quality of the wave function when vibrational resonances occur. A detailed analysis by means of this new VCASSCF method demonstrates the crucial importance of excited bending oscillators in the intensity of some pure stretching transitions.Boursier F.R.I.A. 相似文献
966.
Pandya SU Garçon C Chavant PY Py S Vallée Y 《Chemical communications (Cambridge, England)》2001,(18):1806-1807
The vinylzinc reagents derived from hydrozirconation of alkynes and transmetallation add readily to nitrones to yield pure (E)-N-allylhydroxylamines; some of these rearrange into O-allylhydroxylamines. 相似文献
967.
Paul Boullanger Jean-Claude Martin Grard Descotes 《Journal of heterocyclic chemistry》1975,12(1):91-93
The synthesis of 3,4,6 tri-O-benzyl-D-glucal (4) has been accomplished by direct benzylation of triacetylglucal (yield 55%) and by zinc reduction of 3,4,6-tri-O-henzyl-2-acetoxy-1-bromoglucose (yield 26%). The nmr spectra of tribenzyl- and triacetyl-D-glucal in the presence of lanthanide shift reagents were reported. 相似文献
968.
Jean-Pierre Labbé 《Mikrochimica acta》1964,52(2-4):298-316
Résumé L'auteur reprend et complète la méthode de dosage microgravimétrique du germanium à l'état de germanimolybdate de tétraphénylarsonium (F
Ge=0,02137). Dans une deuxième partie, il décrit une méthode de préparation des heptagermanates alcalins et de métagermanates de métaux bivalents à partir des solutions d'oxyde GeO2 et d'acétates métalliques. Les courbes de thermolyse et les spectres d'absorption infrarouge sont présentés. Aucun orthogermanate ne précipite des solutions aqueuses.
Mémoire en l'honneur du professeurA. A. Benedetti-Pichler. 相似文献
Summary The author resumes and completes the method for the microgravimetric determination of germanium as the germanium molybdate of tetraphenylarsonium (F Ge=0.02137). In a second part he describes a method for preparing some heptagermanates of divalent metals from solutions of the oxide GeO2 and metal acetates. The thermolysis curves and the infrared absorption curves are given. No orthogermanate precipitates from aqueous solutions.
Zusammenfassung Der Verfasser berichtet über die mikrogravimetrische Bestimmung des Germaniums als Tetraphenylarsonium-Germanium-Molybdat (F Ge=0,02137). Im zweiten Teil der Arbeit wird die Herstellung von Alkaliheptagermanat sowie von Metagermanaten bivalenter Metalle aus Germaniumoxidlösungen und Metallacetaten beschrieben. Die Thermolysekurven und IR-Absorptionsspektren werden vorgelegt. Aus wäßrigen Lösungen fällt kein Orthogermanat aus.
Mémoire en l'honneur du professeurA. A. Benedetti-Pichler. 相似文献
969.
Treatment of 2-methylphenols with chloro(diphenyl)-lambda(3)-iodane led to their regioselective dearomatizing 2-phenylation into cyclohexa-2,4-dienone derivatives via a proposed ligand coupling reaction. In the same vein of investigation, treatment of 2-methylanilines with the lambda(5)-iodane 2-iodoxybenzoic acid IBX reagent led to their regioselective dearomatization into previously undescribed ortho-quinol imines. 相似文献
970.
Céline Pascal Claude Merlet Rose-Marie Marin-Ayral Jean-Claude Tedenac Bernard Boyer 《Mikrochimica acta》2004,145(1-4):147-151
The phases formed at the interface between an intermetallic (NiAl) and a nickel base superalloy joined by combustion synthesis were investigated, particularly the eutectic phases. Owing to their small size, the characterisation of these phases using a Castaings electron microprobe encounters difficulties. The analysis volume size is generally too large to differentiate the phases from their surrounding matrix, even by using low accelerating voltage. Moreover, the eutectic phases contain boron, which is difficult to characterise by EPMA. Independently of the phases shape, the characterisation can be solved by viewing this complex system as a surrounding matrix and a multi layer system. The results of these simulations revealed the presence of two categories of borides: the eutectic boride MM2B2 (M=Mo and M=Co, Cr) and the solid solution boride [Cr1–x (Mo, W)x]B. 相似文献