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111.
Gavrilova AL Qin CJ Sommer RD Rheingold AL Bosnich B 《Journal of the American Chemical Society》2002,124(8):1714-1722
The di-Co(2+) complex, [Co(2+)(mu-OH)(oxapyme)Co(2+)(H(2)O)](+), contains an unsymmetrical binucleating ligand (oxapyme) which provides five- and six-coordinate metal sites when a hydroxide bridge is introduced. This complex absorbs 1 equiv of O(2) irreversibly in solution, producing an unstable di-Co(3+) oxygenated product. The oxygenated product has been studied at low temperatures, where its electronic absorption and (1)H NMR spectra were recorded. It is probable that the oxygenation reaction involves a one-site addition two-metal oxidation reaction to produce an end-on-bonded peroxide ligand at the available coordination site, giving the complex [Co(3+)(mu-OH)(oxapyme)Co(3+)(mu(1)-O(2))](+). Addition of 1 equiv of HClO(4) to this oxygenation product gives a stable peroxide complex, [Co(3+)(mu,eta(1):eta(2)-O(2))(oxapyme)Co(3+)](2+), where one of the oxygen atoms bridges the two metals and is sideways bonded to one of the metals. The formation of this stable complex involves expulsion of the OH(-) bridge. Addition of NO(2)(-) to the sideways-bonded peroxide complex leads to the formation of another stable complex, [Co(3+)(mu,eta(1):eta(1)-O(2))(oxapyme)Co(3+)(NO(2))](+), where the peroxide forms a classic di-end-on bridge to the two metals. Both of these complexes have been fully characterized. Addition of acid to this second stable dioxygen complex leads to the release of HNO(2) and the formation of the mu,eta(1):eta(2) sideways-bonded peroxide complex. 相似文献
112.
Comparative study of three immunoassays based on monoclonal antibodies for detection of the pesticide parathion-methyl in real samples 总被引:2,自引:0,他引:2
Anna Yu Kolosova Jung-Hyun Park Seon-Ja Park Won-Bo Shim Yong-Tae Lee 《Analytica chimica acta》2004,511(2):323-331
Three immunoassay systems: indirect, direct competitive enzyme-linked immunosorbent assay (IC-ELISA and DC-ELISA), fluorescence polarization immunoassay (FPIA) based on monoclonal antibodies for the detection of parathion-methyl (PM) were developed and optimized. Several PM derivatives (haptens) were conjugated to proteins and fluoresceinthiocarbamyl ethylenediamine (EDF) to obtain immunogens and competitors. The influence of immunogen and competitor structures on the assay performance was investigated. IC-ELISA was the most sensitive of all techniques developed, with a detection limit of 0.08 ng ml−1, but assay time was the longest (3.5 h per 96-well microtitre plate). DC-ELISA was easier to perform and quicker (1.5 h per 96-well microtitre plate) but less sensitive than IC-ELISA (detection limit was 0.5 ng ml−1). FPIA was the fastest and simplest (7 min per 10 samples) but the least sensitive (detection limit was 15 ng ml−1) technique. The methods were characterized by high specificity and reproducibility. The cross-reactivity for parathion-ethyl was around 30-40% for IC-ELISA and FPIA, but significantly higher (125%) for DC-ELISA. The immunoassays were applied to the analysis of PM residues in different food and environmental matrices. Methanol extracts of vegetable, fruit and soil samples were used for the analysis. Recoveries for most spiked samples averaged between 85 and 110%. The methods developed can be used for screening of food and environmental samples for PM residues without complicated clean-up. 相似文献
113.
A. Toldy P. Anna I. Csontos A. Szabó Gy. Marosi 《Polymer Degradation and Stability》2007,92(12):2223-2230
The flame retardant effect of newly synthesized phosphorus-containing reactive amine, which can be used both as crosslinking agent in epoxy resins and as a flame retardant, was investigated. The effect of montmorillonite and sepiolite additives on the fire induced degradation was compared to pristine epoxy resin. The effect of combining the organophosphorous amine with clay minerals was also studied. It could be concluded that the synthesized phosphorus-containing amine, TEDAP can substitute the traditional epoxy resin curing agents providing additionally excellent flame retardancy: the epoxy resins flame retarded this way reach 960 °C GWFI value, 33 LOI value and V-0 UL-94 rating - compared to the 550 °C GWFI value, 21 LOI value and “no rate” UL-94 classification of the reference epoxy resin. The peak of heat release was reduced to 1/10 compared to non-flame retarded resin, furthermore a shift in time was observed, which increases the time to escape in case of fire. The flame retardant performance can be further improved by incorporating clay additives: the LOI and the HRR results showed that the optimum of flame retardant effect of clay additives is around 1 mass% filler level in AH-16-TEDAP system. Applying a complex method for mechanical and structural characterization of the intumescent char it was determined that the flame retarded system forms significantly more and stronger char of better uniformity with smaller average bubble size. Incorporation of clay additives (owing to their bubble nucleating activity) results in further decrease in average bubble diameter. 相似文献
114.
Danuta M. Czakis-Sulikowska Anna Malinowska 《Monatshefte für Chemie / Chemical Monthly》1988,119(6-7):677-681
The formation ofPAN complexes in the systems:Ln(III)—PAN—alcohol—water [whereLn(III) = Pr, Nd, Sm, Eu, Gd, Tb, alcohol - ethanol andLn(III) = Eu, alcohol =n-propanol, isopropanol] was investigated by a spectrophotometric method. Equilibrium constants for the reactionLn
3++HLLnL
2++H+ (HL =PAN) and stability constants of complexesLnL
2+ are reported.
Komplexbildung einiger Seltenerdmetalle mit 1-(2-Pyridylazo)-2-naphthol (PAN) in alkoholisch-wäßrigen Lösungen
Zusammenfassung Die Bildung der Komplexe vonPAN in den SystemenLn(III)—PAN—Alkohol—Wasser [Ln(III) = Pr, Nd, Sm, Eu, Gd, Tb, Alkohol = Ethanol undLn(III) = Eu, Alkohol =n-Propanol, Isopropanol] wurde mit einer spektrophotometrischen Methode untersucht. Die Gleichgewichtskonstanten der ReaktionenLn 3++HLLnL 2++H+ (HL =PAN) und die Stabilitätskonstanten der KomplexeLnL 2+ wurden berechnet.相似文献
115.
Sabbioni C Mandrioli R Ferranti A Bugamelli F Saracino MA Forti GC Fanali S Raggi MA 《Journal of chromatography. A》2005,1081(1):65-71
Glycyrrhizin is the main active compound of Glycyrrhiza glabra root extracts; according to recent studies, glycyrrhizin and its aglycon, glycyrrhetic acid, have interesting therapeutic properties. A new capillary electrophoretic method has been developed for the separation and quantification of glycyrrhizin, beta-glycyrrhetic acid and its isomer a-glycyrrhetic acid. Separation of the analytes was achieved in less than 3 min on a fused silica capillary, by injecting the samples at the short end of the capillary (effective length: 8.5 cm). The background electrolyte was composed of pH 10.0 carbonate buffer, methanol and ethylene glycol (80/10/10) and contained 0.4% beta-cyclodextrin; indomethacin was used as the internal standard. Diode array detection was used, with quantitative assays carried out at 254 nm. Linearity was found over the 5-200 and 2.5-100 microg mL(-1) concentration ranges for glycyrrhizin and glycyrrhetic acid, respectively. This method has been applied to the determination of the analytes in different matrices (liquorice roots and commercial confectionery products), and to the purity control of beta-glycyrrhetic acid obtained from the hydrolysis of glycyrrhizin. When analysing beta-glycyrrhetic acid and its epimer in roots, the samples were purified by means of a suitable solid-phase extraction (SPE) procedure with Oasis HLB cartridges, which granted good selectivity, eliminating matrix interference. 相似文献
116.
Hofmann A Pelletier M Michot L Stradner A Schurtenberger P Kretzschmar R 《Journal of colloid and interface science》2004,271(1):163-173
Hydrous ferric oxides (HFO) are efficient sorbents for inorganic and organic pollutants and therefore have great potentials in environmental science and engineering applications. Freezing and thawing of HFO suspensions leads to the formation of dense HFO aggregates. It facilitates the handling and increases the drying rate of HFO. In this study, we used a combination of pycnometry, gas adsorption (N(2) gas, water vapor), and small-angle neutron scattering (SANS) to characterize the porosity and pore size distribution of dense HFO aggregates formed by freezing dialyzed HFO suspensions at -25 degrees C and thawing them at room temperature. The crystallinity of the HFO, which was a 2-line ferrihydrite, was not affected by this treatment. Wet sieving and laser diffraction analysis showed that the dense HFO aggregates had a unimodal size distribution with an average diameter of 235+/-35 microm. Increasing the freezing rate by cooling with liquid N(2) (-196 degrees C) resulted in much smaller aggregates with an average diameter of 20 microm. Adding NaNO(3) electrolyte to the HFO suspensions prior to freezing also resulted in the formation of smaller aggregates. The dense HFO aggregates formed at -25 degrees C had a porosity of 0.73+/-0.02 ll(-1). SANS revealed a unimodal size distribution of pores, with an average pore diameter of 2.0 nm. The diameter of the HFO crystallites was estimated by transmission electron microscopy to be 1.9+/-0.5 nm. Geometrical considerations taking into account the unit particle and average pore size suggest that the crystallites retain 1-2 layers of hydration water during the coagulation induced by freezing. Analysis by N(2) gas adsorption showed that drying the dense HFO aggregates induced a reduction in porosity by about 25% and shifted the pore size distribution to smaller diameters. Rewetting during water vapor adsorption did not induce significant changes of the aggregate structure. The specific surface area of the dry HFO aggregates was between 320 and 380 m(2)g(-1). 相似文献
117.
Anna M. Trzeciak Petr Štěpni?ka Ewa Mieczyńska 《Journal of organometallic chemistry》2005,690(13):3260-3267
The rhodium complex trans-[Rh(CO)(Hdpf-κP)(dpf-κ2O,P)] (1), (Hdpf = 1′-(diphenylphosphino)ferrocenecarboxylic acid) was used as an efficient and recyclable catalyst for 1-hexene hydroformylation producing ca. 80% of aldehydes at 10 atm CO/H2 and 80 °C. After the reaction, unchanged complex 1 was separated from the reaction mixture and used again three times with the same catalytic activity. The effect of modifying ligands, phosphines and phosphites, on the reactivity of 1 was investigated. The active catalytic systems containing 1 or trans-[Rh(CO)(L)(dpf-κ2O,P)] (2) were formed in situ from acetylacetonato rhodium(I) precursors [Rh(CO)2(acac)] (3) or [RhL(CO)(acac)] (4) and Hdpf or Medpf (L = phosphine, Medpf = methyl ester of Hdpf). 相似文献
118.
W. W. Sułkowski S. Mistarz T. Borecki M. Moczyński A. Danch J. Borek M. Maciążek Anna Sułkowska 《Journal of Thermal Analysis and Calorimetry》2006,84(1):91-97
From the TG data of rubber
granulates, different polyurethane and composites it can be seen that the
thermal decomposition for the rubber granulate and all of the composites start
above 520 K. Two major mass losses for the rubber granulates and majority
of the composites were observed and thermal decomposition is essentially complete
by ~820 K. The changes of activation energies of lower and higher temperature
decomposition, calculated according to the different equations were observed
for a priori assumed first-order reaction for devolatilisation. Differences
between determined and calculated results could suggest a possible reaction
between polyurethane agents and rubber granulate during the composites formations. 相似文献
119.
Cycloaddition reactions between vinyl ethers 3 and -quinone methides 2, thermally generated from 2-hydroxybenzyl alcohols 1, have been studied. The structure and conformational preferences of the 4-substituted 2-ethoxy-(2,3)-dihydro-2-benzopyrans 4–9 obtained, which show new interesting features, are discussed together with competitive kinetic data. The cycloaddition process is concerted and involves -quinone methides in the -configuration. The OEt- transition state seems to be preferred with ethyl vinyl ether and -1-propenyl ethyl ether, whereas with -1-propenyl ethyl ether the stereoselectivity of the cycloaddition process depends on substituents on the methylene group of the starting alcohol 1. These results are discussed in terms of and preference of the propenyl ether methyl group. 相似文献
120.
Gino Morisi Marina Patriarca Ferdinando Chiodo Anna Minoprio Antonio Menditto 《Mikrochimica acta》1996,123(1-4):281-290
Between 1992 and 1994, a new screening campaign for blood Pb monitoring in the Italian general population was carried out. Since the first campaign (started in 1978, in accomplishment of the European Community Directive 77/312/EEC) a working group of the Laboratory of Clinical Biochemistry at the Italian National Institute of Health (Istituto Superiore di Sanità), as the Reference Centre (RC), has coordinated the activity of various laboratories spread over the national territory. Appropriate quality assurance procedures, including an external quality assessment scheme (EQAS), were elaborated. Within the EQAS, three or four trials were carried out every year. Each laboratory participating in the trial analyzed eight control samples prepared from cow blood at different Pb concentrations. The results obtained by each peripheral laboratory and the RC between 1992 and 1994 have been compared by regression analysis. The same statistical method was adopted to compare the results obtained by each peripheral laboratory and the RC in the duplicate analysis of about 10 per cent of the human samples collected during the 1992–1994 monitoring campaign. There was no evidence of systematic differences between the regression lines obtained on control and human samples. In spite of the lower Pb concentration in the control samples analyzed during the 1992–1994 campaign, the analytical performance of the laboratories was better than that obtained in the previous screening campaign (1985–1986). Blood Pb levels observed in human samples collected between 1992 and 1994, confirm the downward time trend observed in the campaigns carried out in 1978–1979, 1980–1981 and 1985–1986. This study confirms that the results obtained in an EQAS are representative of the actual performance in the analysis of real (human) samples. 相似文献