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31.
Summary A sensitive precolumn fluorescence derivatization method for low level detection of the, volatile (N-nitrosodimethylamine and N-nitrosopyrrolidine) and non-volatile N-nitrosamines (N-nitrosoproline and N-nitrosodiethanolamine) an high-performance liquid chromatography was developed. This method is based on the denitrosation of the compounds of interest by a mixture of hydrobromic acid and acetic acid to produce the corresponding secondary amines. These are, then, able to react with, a quinolizinocoumarin derivative (luminarin 9®) to form highly fluorescent labelled N-nitrosamine derivatives. The structural elucidation of the luminarin 9® derivatives of N-nitrosoproline and N-nitrosodimethylamine by way of example, were established by liquid chromatography-mass spectrometry (LC-MS) and by direct chemical ionization-mass spectrometry (CI-MS). The separation, derivatization and detection conditioins were optimized for all the studied compounds. The detection limits (signal to noise ratio=3) were between 0.4 and 1.0 pmol injected depending on the compound. The calibration graphs were linear for derivatized amounts in the range of 0.5–40 nmol for N-nitrosodimethylamine and N-nitrosopyrrolidine, 0.4–2- nmol for N-nitrosoproline and 1.0–40 nmol for N-nitrosodiethanolamine. The repeatability (RSD less than 3.5%, n=6) and reproducibility (RSD less than 4.8%, n-6) were satisfactory. 相似文献
32.
S. V. Kurbatova E. E. Finkelshtein E. A. Kolosova A. V. Kartashev S. N. Yashkin 《Journal of Structural Chemistry》2004,45(1):144-150
The potential of the structural analogy method in the topological studies of adamantane derivatives and analogs is demonstrated. The topological and structural characteristics of these compounds are calculated. Chromatographic retention indices were determined experimentally. Correlations between the topological indices and the physicochemical and chromatographic characteristics are investigated. 相似文献
33.
34.
Qiang Li Pingfan Wu Yongge Wei Hongyou Guo 《Journal of organometallic chemistry》2006,691(6):1223-1228
An organic-inorganic hybrid compound, (Bu4N)2[Mo6O18(NAr)] (Ar = p-BrC6H4) has been synthesized via the DCC dehydrating protocol of the reaction of [α-Mo8O26]4− with 4-bromoaniline hydrochloride in anhydrous acetonitrile, which has been characterized by UV-Vis spectra, 1H NMR and single crystal X-ray diffraction study. By comparing the UV-Vis spectra, which were used to monitor the reaction, the optimum preparative condition for this compound was also determined. This compound crystallizes in the monoclinic space group P21/n, which is featured in a terminal para-bromophenylimido group linked to an Mo atom of a hexamolybdate cluster by a Mo-N triply bond. In addition, there are π-π dimerization of the neighboring cluster anions though the parallel aromatic rings in their crystals. 相似文献
35.
36.
Kovácik V Bekesová S Tvaroska I Hirsch J Chmelík J 《Journal of mass spectrometry : JMS》2004,39(12):1554-1561
Fragmentation mechanisms of electrospray ionization (ESI) mass spectrometry of aldobiuronic and pseudoaldobiuronic acid derivatives were elucidated by multistage mass spectrometric (MS(n), n = 2-5) measurements of selected ions. Characteristic under the conditions of ESI-MS analysis is the production of alkali metal (Na and K) cationized adducts. The probability the of locations of Na cations in per-O-methylated compounds was proved by quantum chemical calculations, using the Jaguar program. The most probably position of alkali metal attachment is the carboxy group of the methoxycarbonyl C-5 group of the uronic acid unit. Characteristic cleavages vary according the kind of O-derivatization. In most cases they take place on the acidic part of the dimer and at the interglycosidic oxygen atom. As a result, the criteria for the differentiation of aldobiouronic and pseudoaldobiouronic acids derivatives were elucidated. 相似文献
37.
Summary A porous polymer resin loaded with hydrous zirconium oxide (Zr-gel) was evaluated as a stationary phase for the liquid chromatographic separation of disubstituted aromatic compounds. The prepared Zr-gel was used to separate disubstituted phenols andortho-substituted benzoic acid derivatives in reversed-phase mode. The retention time of catechol was greater than those of other disubstituted phenols; this implies that the Zr-gel has specificity for the phenolic hydroxyl group. The retention behavior ofortho-substituted benzoic acid derivatives on the Zr-gel was also evaluated in reversedphase mode using buffer. Phthalic acid was specifically retained in the vicinity of pH 6.0, which has been regarded as the equal adsorbic point. Similar behavior was also observed for salicylic acid, although the retention time of salicylic acid was less than that of phthalic acid. It seems that the specific retention behavior of hydrous zirconium oxide is a result of complexation with ligands such as hydroxyl and carboxyl groups. The results of this study have revealed that the retention mechanism of hydrous zirconium oxide is a combination of ion exchange and interaction based on complexation with ligands. 相似文献
38.
We have demonstrated that the readily available amido-keto compounds 5, with prearranged carbonyl and glycine moieties, under strongly basic conditions easily undergo complete and highly diastereoselective cyclization, affording a generalized and practical access to the conformationally constrained phenylserine derivatives 4. High chemical yields, virtually complete diastereoselectivity combined with the operational convenience of the experimental procedures render this method useful for preparation of these diastereomerically pure derivatives. 相似文献
39.
M. V. Alfimov S. P. Gromov O. B. Stanislavskii E. N. Ushakov O. A. Fedorova 《Russian Chemical Bulletin》1993,42(8):1385-1389
Styryl dyes containing a crown ether group and a heteroaromatic moiety with a sulfoalkylN-substituent (1a,b) undergo photocyclodimerization in acetonitrile in the presence of Mg(ClO4)2 to give only the typeA isomer of cyclobutane derivative (2a,b). The photochemical regio- and stereoselectivity of the cycloaddition is explained by self-organization of thetrans-isomers of the styryl dyes upon complexation with the Mg2+ cations into dimers with a fixed mutual arrangement of multiple bonds.For part 7, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1449–1452, August, 1993. 相似文献
40.
Zur Synthese von fungizid wirksamen Isocamphanderivaten: Synthesen in der Isocamphanreihe, 34. Mitt.
Gerhard Buchbauer Helmut Spreitzer Margarete Kneidinger 《Monatshefte für Chemie / Chemical Monthly》1990,121(6-7):549-554
Summary Some esters of isocamphenilanic acid (4) have been prepared and tested for their fungicidal and insecticidal activity. Esters of various acids with isocamphanyl ethylalcohol (5) have also been synthesized and included in the fungicidal/acaricidal/insecticidal screening programme. All esters bear a geminal dimethyl group at C-3 of the bicyclus which is important because of its shielding effect. 相似文献