Fluorine-19 nuclear magnetic resonance (19F NMR) spectroscopic measurements were used to determine the chemical nature and amounts of organofluorine in dosed meat baits. Earlier work implied that sodium monofluoroacetate (compound 1080) in meat baits was broken down into other organofluorine compounds such as fluorocitrate. No chemical evidence was found for such compounds. Only monofluoroacetate was detected in the prepared 1080 bait samples. Once the baits have aged, aqueous extraction fails to recover all the added 1080. Analysis using 19F NMR confirmed that the 1080 present in the aqueous extracts of the bait is recovered by Kramer's liquid chromatography method. It was shown here that the aqueous extracts do not recover all the 1080 in the meat bait. 相似文献
The system POCl3–NaAlCl4 was investigated by measuring the conductivity and the Raman and NMR spectra (27Al, 23Na and 31P) as a function of the mol fraction x of NaAlCl4 in POCl3. Additionally, Raman spectra of POCl3 solutions of NaFeCl4, LiAlCl4, LiFeCl4, and KAlCl4 were recorded. In solutions containing Li+ or Na+ ions a liquid to solid (or jelly) phase transition was observed under certain conditions, dependent on salt concentration and temperature. Observed changes in the Raman spectra of the electrolyte solutions in comparison to the pure solvent POCl3 demonstrate the existence of interactions. Clearly, the POCl3 eigenfrequencies and hence the molecules are pertubed. The formation of [M(POCl3)4]+ complexes (M = Li, Na) can be deduced from the Raman measurements. NMR investigations support this conclusion. For assigning of Raman spectra, (Li+, K+) cation and ([FeCl4]?, [SbCl6]?) anion substitutions were employed. 相似文献
The conditions of thermal decomposition of the 3-chlorobenzoates of Y, La and the lanthanides from Ce(III) to Lu have been studied. The complexes of La, Pr(III), Sm, Eu, Gd, Tb(III) and Dy were prepared as heptahydrates, those of Ce(III) and Y as pentahydrates, that of Nd as the tetrahydrate, that of Ho as the dihydrate and those of Er, Tm, Yb and Lu as anhydrous salts. On heating, these complexes decompose in three or two stages. They first lose some water molecules and then decompose to oxides through the intermediate formation of LnOCl. Cerium(III) 3-chlorobenzoate loses its crystallization water in two stages and yields the anhydrous salt, which is then transformed directly into CeO2. All these complexes melt before decomposition in the temperature range 441–513 K. 相似文献
A theoretical study of ion hydration using the statistical thermodynamic supermolecule-continuum method is described. The cell and shell methods are used for configurational averaging. Enthalpies, free energies and entropies are calculated for Li+, Na+, K+, F– and Cl– each four coordinated with water. The results are in reasonable accord with experiment. A comparison of the site method, cell method and shell method results is presented. The supermolecule-continuum approach to solvent effects seems to be capable of accommodating essential features for the calculation of solvation energy and solvent effects on structure and properties. 相似文献
A series of N-phenyl-3-methylthiopropylamine hydrochlorides were prepared by reacting a series of anilines with methional and sodium cyanoborohydride. These were cyclized upon oxidation by N-chloro-succinimide to the corresponding N-phenyl-S-methylisothiazolidinium derivatives which were isolated as the tetraphenylborate salts. Compounds successfully prepared included the m-methyl, p-methyl, m-methoxy, and p-methoxyphenyl derivatives. 相似文献
Examinations of the extracts of 8 taxonomically-diverse marine soft-corals (Orders Gorgonaceae, Alcyonaceae and Stolonifera, Subclass Octocorallia, Phylum Cnidaria), have resulted in the isolation of 4 new sesquiterpenoids (1–4) of the germacrene type. Three previously known germacrene derivatives (5–7), and the elemane 8, have also been isolated, and complete 1H and 13C NMR assignments for these compounds are reported. 相似文献
4-[(9-Methyl-as-triazino[6,5-b]indol-3-yl)amino]-2-methyl-2-butanol ( 13 ) and the corresponding 2-methyl-3-imino derivative 12 were synthesized and tested in vitro against Rhino 2 virus. The two compounds were more active than the known triazino[5,6-b]indole 4 . 2,9-Dimethyl-3-methoxy-9H-as-triazino[6,5-b]indolium tosylate ( 21 ) and the related 3-methylthio compound 9 were prepared. Quaternary 21 formed a pseudo base, 22a , whereas quaternary 9 did not form a pseudo base. 相似文献
A new approach has been developed and tested for the urgent analysis of dioxins in samples of air-dust filters originating from catastrophe emissions. The procedure consists of a fast extraction of the sample with microwave solvent extraction (MASE) and acetone as solvent followed by a fast cleanup of the extract with normal phase coupled column liquid chromatography (LC/LC).
The multi-dimensional LC/LC system employs a 50 mm×4.6 mm i.d. column packed with 3 μm silica and a 150 mm×4.6 mm i.d. column packed with 5 μm PYE as the first and second analytical column, respectively. Iso-hexane is used on both columns to perform cleanup and dichloromethane to perform efficient back-flush elution of the compounds from the second column. The obtained polarity-based separation in the first dimension and molecular-structure based separation in the second dimension provides a fast and powerful cleanup.
Validation was done by analysing samples of homemade RIVM air-dust with aged residues (n=8, spiking level about 15 pg mg−1 per compound) of dioxins/furans and samples of reference Urban Dust SRM 1649a (n=4) with both the new approach and the existing conventional procedure and were instrumentally analyzed with capillary gas chromatography and high resolution mass spectrometric detection (GC/HRMS).
In comparison to the existing conventional procedure, the new approach reduces sample processing from several days to several hours per sample.
As regards the aged-residue air-dust samples, the new method shows a good accuracy, precision and high selectivity providing a performance in good agreement with the existing procedure. In SRM air-dust, the concentration of a few compounds obtained by the new method was below (10–50%) the certified value. 相似文献
Rhodium phthalocyanine (RhPc) was synthesized and ultra thin Langmuir-Blodgett (LB) films of RhPc were successfully fabricated. The LB film characterization was carried out using both UV-vis absorption spectra and Raman scattering. The Raman spectroscopy was carried out using 633 and 780 nm laser lines. LB films were deposited onto Ag nanoparticles to achieve the surface-enhanced pre-resonance Raman scattering (pre-SERRS) and surface-enhanced Raman scattering (SERS) for both laser lines, respectively, which allowed the characterization of the RhPc ultra thin films. The morphology of the LB RhPc neat film is extracted from micro-Raman imaging. 相似文献
Useful methodology is described for the synthesis of dehydroalanine residues (II) within peptides. The unnatural amino acid (Se)-phenylselenocysteine (I) can be incorporated into growing peptide chains via standard peptide synthesis procedures. Subsequent oxidative elimination affords a dehydroalanine at the desired position. The oxidation conditions are mild and tolerate functionalities commonly found in peptides, including variously protected cysteine residues. To illustrate its utility, cyclic lanthionines have been synthesized by this method. 相似文献