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101.
Summary The highly complex matrix of diesel particulate extracts was analyzed for nitrated polycyclic aromatic hydrocarbons (nitro-PAH)
using fused-silica capillary-column gas chromatography along with a thermionic nitrogen-phosphorus detector (TID) and high-performance
liquid chromatography followed by on-line catalytic reduction of the nitro-PAH to amino-PAH and subsequent fluorescence detection.
Positive isomer identification and quantitation of nitro-PAH are from retention times of authentic standards and their mass
spectra. The ease of nitro-PAH formation by nitration of PAH raises the question regarding the origin of these species, whether
they are produced as “native” products during the engine combustion process and/or in the exhaust, or instead, formed as the
result of chemical conversion to produce artifacts during the sampling procedure. This problem is assessed examing 1-nitropyrene-concentration
in particulates of three light-duty diesel engines for different sampling times. 1-Nitropyrene concentrations show only a
moderate increase with sampling time under average sampling conditions.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
102.
《Surface and interface analysis : SIA》2006,38(5):931-940
The initial oxidation of magnesium at oxygen partial pressures between 1.3 × 10?8 and 1.3 × 10?5 Pa and at temperatures ranging from 273 to 550 K has been investigated in situ with X‐ray photoelectron spectroscopy (XPS), ellipsometry and high resolution elastic recoil detection analysis (HERDA). Quantitative analysis of the XPS spectra showed a clear oxygen deficiency with respect to MgO for the initial oxide. HERDA measurements confirmed this relatively low oxygen content in the thin oxide layers formed. Ellipsometry measurements showed that the electronic structure of the initially formed oxide differs significantly from that of bulk MgO. The band gap values at room temperature for the oxide layers investigated are clearly smaller than the value for bulk MgO. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
103.
Microemulsions used in enhanced oil recovery are usually used in conjunction with a polymer solution that provides mobility control by reducing the permeability of the formation and/or increasing the viscosity of the injected fluid. Microemulsions, which are mixtures of at least four components — water, oil, surfactant and cosurfactant (and, usually, inorganic salts) are complex even in the absence of polymer and consequently, studies of their phenomenon tend to be phenomenological. An approach found to be useful to circumvent this has been to consider the microemulsion particles dispersed in their external phase to be macromolecules which retain their integrity when diluted with external phase or when mixed with polymers. Thus the dispersed phase components are treated as a pseudocomponent. If this approach is followed, many features of the phase diagram of polymer-microemulsion mixtures can be rationalized. It is therefore of some interest to determine whether a similar approach can be used to understand or predict the viscosity of mixtures in which a simple mixing rule for viscosities can be utilized to gain further insight into the polymer-microemulsion interaction. 相似文献
104.
Summary Clenbuterol has been determined in urine by solidphase extraction on a C18 cartridge, diazotization of the eluate with nitrite, coupling of the diazonium ion with 1-(naphthyl)ethylenediamine, and
separation of the azo dye formed by HPLC with a C18 column and a micellar mobile phase containing 0.1 M sodium dodecyl sulphate, 12%n-butanol and 0.05 M citrate buffer, pH 3. Recoveries higher than 90% were obtained by mixing the samples with a 20% 0.2 M
NaOH before extraction. Limits of detection of 51 and 6.7 ng L−1 were obtained with spectrophotometric and thermal lens spectrometric detection, respectively; respective repeatabilities
were 3.1% (5 μg mL−1) and 5.6% (0.16 μg mL−1). 相似文献
105.
P. Staszczuk J. C. Bazan M. Błachnio D. Sternik N. J. Garcia 《Journal of Thermal Analysis and Calorimetry》2006,86(1):57-68
This paper presents possible applications of thermal analysis, sorptometry
and porosimetry to study physico-chemical properties of Na- and La-montmorillonite
samples, especially for determination of total surface heterogeneity. The
quasi-isothermal thermogravimetric (Q-TG) mass loss and its first derivative
(Q-DTG) curves with respect to temperature and time obtained during programmed
liquid thermodesorption under quasi-isothermal conditions have been used to
study adsorbed layers and heterogeneous properties of the Na- and La-montmorillonites.
Calculations of the desorption energy distribution functions by analytical
procedure using mass loss Q-TG and differential mass loss Q-DTG curves of
thermodesorption under quasi-isothermal conditions of polar and non-polar
liquid vapours preadsorbed on a material surface are presented. Parameters
relating to porosity of samples were determined by sorptometry, mercury porosimetry
and atomic force microscopy (AFM). From nitrogen sorption isotherms from sorptometry
and porosimetry methods, the fractal dimensions of montmorillonites have been
calculated. Moreover, a new approach is proposed to calculate fractal dimensions
of materials obtained from Q-TG curve; this is compared with values obtained
by the above methods. The total heterogeneous properties (energy distribution
function and pore-size distribution functions) of samples studied were estimated.
The radius and pore volume of the tested samples calculated on the basis of
thermogravimetry, sorptometry and porosimetry techniques were compared and
good correlations obtained. 相似文献
106.
S. Magaz F. Migliardo D. Barreca E. Bellocco G. Lagan 《Journal of Molecular Structure》2007,840(1-3):114-118
Among disaccharides, trehalose, a naturally-occurring glass-forming disaccharide, is particularly effective in terms of its ability to preserve several organisms under stress conditions. The present work is aimed to investigate the bioprotective action of trehalose on lysozyme as a function of temperature. In order to extract quantitative information about the dimensional changes of the proteins, we performed Small Angle Neutron Scattering measurements on lysozyme/D2O solutions in absence and in presence of the disaccharide. The findings emphasise the capability of trehalose to stabilise the protein, activating aggregation processes. 相似文献
107.
Thomas F. Brodasky 《Journal of separation science》1978,1(5):239-244
Two new acyltetramic acids related to streptolydigin have been isolated from fermentations of Streptomyces lydicus. The principal members of this complex were resolved by TLC on silica gel. However, the methods of detection, permanganate spray or bioautography, were not suitable for both crude fermentation broths and purified extracts. Gas chromatography is unsuitable for the detection of either underivatized or silylated streptolydigins. High performance liquid chromatography (HPLC) particularly on triethylaminoethyl cellulose is rapid and sensitive and is the method of choice for the analysis of both crude and purified samples. Using high performance liquid chromatography, two components were detected in the complex, which are not observed using any of the other chromatographic procedures. 相似文献
108.
Methyl methacrylate and butyl methacrylate were polymerized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS). A poly(N-acetylethylenimine) (PNAEI) macromer was also included in the recipe, as a cosurfactant and a comonomer. Polymerizations were initiated by UV-irradiation. The average diameters of latex particles, obtained by STM, were in the range of 17-200 nm. The experimental data evidenced that the particle size was mainly dependent on the SDS/PNAEI ratio. Polymerization yields were around 75-85%. The synthesized copolymers have viscosity average molecular weights in the range of 2.1-2.4×106 and glass transition temperatures of 38.0-43.5°C, lower than those obtained without using PNAEI. The investigation by means of FTIR and 1H-NMR techniques revealed that PNAEI was incorporated into the nanoparticles. 相似文献
109.
Siavosh Mahboobi Andreas Sellmer Thomas Burgemeister Alexei Lyssenko Dieter Schollmeyer 《Monatshefte für Chemie / Chemical Monthly》2004,135(3):333-342
The synthesis of the naturally occurring and biologically active alkaloids 1 and 2, first isolated from the red ascidian Botryllus leachi by Duran et al. [1], is described and the structure proposed for Botryllazine B (1) is confirmed. The analytical data for 2-(p-hydroxybenzoyl)-4-(p-hydroxyphenyl)imidazole (2) are discussed and compared with the literature. With special emphasis of 1H NMR data the tautomerism of aroylimidazolemethanones is described. 相似文献
110.
S. B. Denisova E. G. Galkin V. T. Danilov Yu. I. Murinov 《Chemistry of Natural Compounds》2003,39(3):237-239
Simple sugars were isolated from the ethanol extract of Glycyrrhiza glabra L. root. The component composition of the carbohydrate fraction was established using GC-MS (gas-chromatographic separation and mass-spectrometric analysis). 相似文献