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41.
Determination of abamectin and doramectin in sheep faeces using HPLC with fluorescence detection 总被引:2,自引:0,他引:2
An analytical procedure for the determination of abamectin and/or doramectin in sheep faeces has been developed. Avermectins were extracted from sheep faeces with acetonitrile, clean-up using solid phase extraction (SPE) and analysed by high performance liquid chromatography (HPLC) with fl uorescence detection after derivatization with N-methylimidazole.The method has a low detection limit (1.0 ng/g of moist sheep faeces), low quanti fi cation limit (2.5 ng/g of moist sheep faeces), good recovery in the range 66.4-80.8% for abamectin and 67.7-85.5% for doramectin as well as good repeatability (>85%). The method is applicable to the study of the time pro fi le of excretion in sheep faeces and also for ecotoxicological studies of both avermectins. 相似文献
42.
43.
Marijana Jurić Berislav Perić Nevenka Brničević Pavica Planinić Damir Pajić Krešo Zadro Gerald Giester 《Polyhedron》2007
Two novel compounds of the formulae [{Cu(phen)2}2(μ-C2O4)][Cu(phen)2(μ-C2O4)NbO(C2O4)2]2 · 8H2O (1) and [{Cu(bpy)2}2(μ-C2O4)][Cu(bpy)2(μ-C2O4)NbO(C2O4)2]2 · 0.5bpy · 7H2O (2) (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) have been prepared and characterized by single crystal X-ray diffraction, IR spectroscopy and magnetic susceptibility measurements. The molecular structure of both 1 and 2 consists of a discrete CuIICuII oxalate-bridged dinuclear [{Cu(L)2}2(μ-C2O4)]2+ cation (A unit) and two CuIINbV oxalate-bridged dinuclear [Cu(L)2(μ-C2O4)NbO(C2O4)2]− anions (B units) (L = phen, bpy). In 1 a crystallographic inversion centre is located in the middle of the oxalate bridge of the A unit, whereas in 2 an analogous inversion centre is missing. In the A units the copper(II) atoms adopt a tetragonally elongated octahedral coordination with the equatorial planes being perpendicular to the mean planes of the oxalate bridge and parallel to each other. In both structures, similar one-dimensional motifs are generated through the ligand stacking interactions, with a difference that one free bipyridine molecule, present in 2, intercalates into one of the motifs. It is shown that the phenanthroline ligand, due to its ability of stacking through the central aromatic ring, causes longer intermolecular Cu?Cu distances than the bipyridine ligand. The magnetic susceptibility measurements (1.8–290 K) show the ferromagnetic exchange interaction between the copper(II) atoms in the A units of both compounds, with J = +5.9 cm−1 and +7.9 cm−1 for 1 and 2, respectively (J – the exchange parameter in the isotropic spin Hamiltonian HINT = −JS1 · S2). 相似文献
44.
Selective Indicator Reaction for Kinetic Determination of Traces of Manganese(II), Ribavirin and Tiazofurin 总被引:1,自引:0,他引:1
Gordana A. Milovanović Mira M. Čakar Nevenka B. Vučić Milan Jokanović 《Mikrochimica acta》2000,135(3-4):173-178
In this work it was established that, in the presence of ammonium carbonate, traces of manganese(II) catalyse the oxidation
of Nile Blue A by hydrogen peroxide, which enables its kinetic determination in the concentration range from 6.6 to 65.9 ng
cm−3, the detection limit being 8.0 × 10−2 ng cm−3. Antiviral/antitumour substances modify the catalytic activity of manganese(II): 1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide,
ribavirin, increases the catalytic effect of manganese(II), while 2-β-D-ribofuranosyl-thiazole-4-carboxamide, tiazofurin,
acts as an inhibitor. On the basis of these effects, a kinetic method for determining ribavirin concentrations from 0.5 × 10−1 to 4.0 × 10−1 μg cm−3 and tiazofurin concentrations from 0.3 to 2.6 μg cm−3 is proposed. The kinetics of the indicator reaction were studied in the presence of the substances examined, the kinetic
equations established, and the constants of the corresponding reaction rates calculated. The effect of temperature on these
reactions was also investigated. The method was applied to the determination of manganese(II) in mineral water and ribavirin
in pharmaceutical preparations.
Received December 16, 1999. Revision June 6, 2000. 相似文献
45.
Julian Küppers Patrick Becker Dr. René Jarling Dr. Marvin Dörries Dr. Nevenka Cakić Dr. Marc Schmidtmann Prof. Dr. Jens Christoffers Prof. Dr. Ralf Rabus Prof. Dr. Heinz Wilkes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4722-4731
The constitutions and absolute configurations of two previously unknown intermediates, (1S,2S,4S)-2-hydroxy-4-isopropylcyclohexane-1-carboxylate and (S)-3-isopropylpimelate, of anaerobic degradation of p-cymene in the bacterium Aromatoleum aromaticum pCyN1 are reported. These intermediates (as CoA esters) are involved in the further degradation of 4-isopropylbenzoyl-CoA formed by methyl group hydroxylation and subsequent oxidation of p-cymene. Proteogenomics indicated 4-isopropylbenzoyl-CoA degradation involves (i) a novel member of class I benzoyl-CoA reductase (BCR) as known from Thauera aromatica K172 and (ii) a modified β-oxidation pathway yielding 3-isopropylpimeloyl-CoA analogously to benzoyl-CoA degradation in Rhodopseudomonas palustris. Reference standards of all four diastereoisomers of 2-hydroxy-4-isopropylcyclohexane-1-carboxylate as well as both enantiomers of 3-isopropylpimelate were obtained by stereoselective syntheses via methyl 4-isopropyl-2-oxocyclohexane-1-carboxylate. The stereogenic center carrying the isopropyl group was established using a rhodium-catalyzed asymmetric conjugate addition. X-ray crystallography revealed that the thermodynamically most stable stereoisomer of 2-hydroxy-4-isopropylcyclohexane-1-carboxylate is formed during p-cymene degradation. Our findings imply that the reductive dearomatization of 4-isopropylbenzoyl-CoA by the BCR of A. aromaticum pCyN1 stereospecifically forms (S)-4-isopropyl-1,5-cyclohexadiene-1-carbonyl-CoA. 相似文献
46.
Nevenka Rajic Djordje Stojakovic Sanja Jevtic Natasa Zabukovec Logar Gregor Mali Venceslav Kaucic 《Journal of Thermal Analysis and Calorimetry》2010,101(3):919-924
An open-framework aluminophosphate analog of the fluorogallophosphate structure-type ULM-3 was obtained by hydrothermal crystallization of an aqueous aluminum phosphate suspension in the presence of 3-methylpropylamine (MAPA) and hydrofluoric acid. The open-framework fluorinated aluminophosphate structure was confirmed by Rietveld analysis and the 27Al, 31P, and 19F MAS NMR spectroscopy. The MAPA, located in the ten-membered ring channels, is doubly protonated to balance the negative charge of the Al3P3O12F2 2– framework. Thermogravimetric analysis data have been used to study kinetics of the thermal decomposition of MAPA. The decomposition was found to be a complex process, its activation energy varied from 177 to 259 kJ mol−1. The relatively high E values are explained by the fact that the MAPA cations are bound to the anionic framework both by electrostatic forces as well as strong N-H…O hydrogen bonds. The strength of the interactions is indirectly confirmed by the in situ high temperature X-ray diffraction analysis which shows that the MAPA decomposition leads to a phase transformation of the open-framework structure to the dense trydimite phase. 相似文献
47.
Martina Furdek Turk Ivan Senta Goran Kniewald Nevenka Mikac 《International journal of environmental analytical chemistry》2018,98(1):1-15
In this work, a simple, sensitive and affordable analytical method for the simultaneous determination of nine organotin compounds (butyltins, phenyltins and methyltins) in seawater using solid-phase extraction (SPE) and gas chromatography-pulsed flame photometric detection was developed and validated. The performance of three different SPE cartridges (Envi C18, Oasis HLB and Oasis MCX) and three elution solvents of different polarity (hexane, methanol and acetonitrile) was evaluated. The extraction parameters, such as solvent volume, presence of complexing and ion-pairing reagents, sample volume and pH and breakthrough volume, were also investigated. Tributyltin, as the organotin compound of special interest, was efficiently extracted using any of the cartridges and solvents tested. However, the simultaneous extraction of all nine organotin compounds was the most efficient using reversed-phase Envi C18 cartridge and 0.1% (w/v) tropolone in methanol as eluent. The optimised method resulted in good recovery, precision and linearity for all compounds, particularly for tri- and disubstituted species. Method detection limits ranged from 0.22 to 1.27 ng(Sn) L?1 for butyltins, 0.37 to 4.91 ng(Sn) L?1 for phenyltins and 0.45 to 1.16 ng(Sn) L?1 for methyltins. The accuracy of butyltins determination was further verified by the comparison with purchased derivatised standards. The developed method was successfully applied to the environmental samples. 相似文献
48.
Five N,N-dialkylamino acids were synthesised [4]: N,N-dimethylisoleucine (DMIL), N,N-dimethyl-alloisoleucine (DMAIL), N,N-dimethylvaline (DMV), N,N-diethyl-alanine (DEA), and N,N-diethylvaline (DEV), as well as their complexes with copper(II): Cu(DMIL)2, Cu(DMAIL)2, Cu(DMV)2, Cu(DMIL)(DMV), Cu(DEA)2, and Cu(DEV)2. UV/VIS spectra of the complexes were recorded in CH2Cl2 solutions and the ESR spectra in CH2Cl2, CD3OD, and D2O solutions. By applying the analysis of variance, ESR spectra were shown to be influenced by the solvent and substituent differences, the former effect being related to the degree of covalency of the copper-ligand bonds. The effect of the ligand's spatial configuration (diastereoisomerism) upon the ESR spectrum of the complex was demonstrated and explained. 相似文献
49.
Berislav Perić Nevenka Brničević Marijana Jurić Pavica Planinić Dubravka Matković-Čalogović 《Structural chemistry》2009,20(5):933-941
Abstract The compound [NH4][(CH3)2NH2]2[Ta(C2O4)4]·2H2O has been synthesized and characterized by elemental and TG/DTA analyses, IR spectroscopy and by the single-crystal X-ray
diffraction study. The structure comprises the [Ta(C2O4)4]3− anion, NH4
+ and [(CH3)2NH2]+ cations and crystallization water molecules. The Ta atom is octacoordinated by oxygen atoms from four bidentate oxalate groups
forming a coordination polyhedron close to the triangular dodecahedron. The charge-assisted hydrogen bonds from both cations
connect the [Ta(C2O4)4]3− anions into a three-dimensional framework.
Graphical Abstract The synthesis and properties of [NH4][(CH3)2NH2]2[Ta(C2O4)4]·2H2O, the first structurally characterized compound with the tetra(oxalato)tantalate(V) anion, is reported.
相似文献
50.
A kinetic method is proposed for the determination of propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid, based on its inhibitory effect on the acetonitrile-catalysed oxidation of Pyrocatechol Violet by hydrogen peroxide. The concentrations of 1,3-propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid determined ranged from 5.0 × 10?7 to 4.0 × 10?6 M with a relative standard deviation of up to 3.3%. The same indicator reaction can be applied to the determination of 1,3-propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid and ethylenediaminetetra-acetic acid in mixtures. Mixtures of these acids in molar ratios from 1 ∶ 4.5 to 10 ∶ 1 have been analysed. Concentrations of 1,3-propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid from 2.0 × 10?7 to 1.0 × 10?6 M and ethylenediaminetetra-acetic acid from 1.0 × 10?7 to 9.0 × 10?7 M were determined with relative standard deviations of up to 4.3 and 5.7%, respectively. The effect of foreign ions on the accuracy of these determinations was also investigated. 相似文献