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71.
氧弹燃烧灰化法测定有机物中磷 总被引:1,自引:0,他引:1
用氧弹燃烧法灰化有机物进行元素测定,操作简便,快速,无污染,该方法用于有机物中磷的分析,结果可靠。 相似文献
72.
73.
Extracting organotin compounds (OTC) from soils is difficult due to the high cation exchange and complexation capacity of soils, and little information about OTC in soils is available. In this study, a new extraction method, combining 1 M CaCl2, 0.1% tropolone, and glacial acetic acid was developed. Recoveries of mono-substituted OTC from spiked plant litter, and soil samples were improved substantially to 40% compared to classical glacial acetic acid extraction commonly used in sedimentology, yielding <10% recovery in C-rich soil samples. Simultaneously, the recovery of other OTC, trimethyllead and monomethylmercury was satisfactory. The recoveries of most species from the spiked litter, upland and wetland soils exceeded 70%. The new method extracted much more organometallics from unspiked organic soils and litter than microwave- and ultrasound-assisted extraction and accelerated solvent extraction, most likely due to exchange of organometallics from the solid phase by Ca2+. The method is simple, highly efficient and with low contamination. Together with GC-ICP-mass spectrometry, the method allows the detection of these organometallics in the pg g−1 range and it is particularly suitable for soil and plant materials with low organometallics contents. 相似文献
74.
6-(Perfluoroalkyl)salicylates were prepared by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 3-ethoxy-1-(perfluoroalkyl)prop-2-en-1-ones. 相似文献
75.
Fourier-transform infrared (FTIR) spectroscopy has been a major point of development in many wine laboratories in recent years. It enables almost instant analysis of several properties of wine, usually with very good precision and accurate results. Nevertheless, validation procedures should not be forgotten and should be fully performed. Recovery experiments were performed by spiking wine samples with different amounts of organic acids (tartaric, malic, lactic, acetic and citric—the most prominent in wines). After FTIR analysis of the total acidity and of each organic acid concentration, recoveries were calculated. For total acidity recovery results were, in general, good and very close to 100% (64–111%). On the other hand, for individual organic acid concentrations, the recovery results were lower than 100% (11–73%) for all spiking additions. These results could be explained by spectroscopic interferences between the organic acids. Because they have similar infrared spectra, it is not easy to distinguish between them and, therefore, to achieve accurate calibration. When total acidity, with a different infrared spectrum from the other abundant compounds in the wine, was taken as a single property the recovery results were acceptable. 相似文献
76.
Summary The cation-exchange behaviour of Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II), Fe(III), Sc(III), Y(III), Eu(III), Dy(III), Ho(III), Yb(III), Ti(IV) and Nb(V) in malate media at various concentrations and pH, was studied with Dowex 50 WX8 resin (200–400 mesh) in the ammonium form. Separation of Fe(III)/Cu(II), Fe(III)/Cu(II)/Zn(II), Fe(III)/Co(II)/Mn(II), Cu(II)/Ni(II)/Mn(II), Fe(III)/Cu(II)/Co(II)/Mn(II), Fe(III)/Cu(II)/Ni(II)/Cd(II), Yb(III)/Eu(III), Sc(III)/Y(III),Sc(III)/Yb(III)/Dy(III) and Nb(V)/Yb(III)/Ho(III) has been achieved, among others.This work was supported by C.N.R. of Italy. 相似文献
77.
Summary Organic acids, such as lactic, malic and citric acids, are involved in primary metabolism of all living organisms. Their presence in food products contributes to the flavour and their equilibrium with inorganic cations defines to a large extent the acidity of the food preparations. A resin cation-exchanger device, normally used for separating amino-acids, can be adapted for characterizing 10 organic acids: formic, propionic, fumaric, succinic, lactic, malic tartaric, citric, and oxalic. Two monitoring systems were used, one of them based on specific iron III salt coloration with hydroxy-acids. 相似文献
78.
79.
《Arabian Journal of Chemistry》2020,13(8):6568-6579
In this work, the sol–gel technique was used to prepare a new organic–inorganic hybrid from Epoxidized Natural Rubber (ENR-50) and Titanium dioxide (TiO2) by blending different content of titania precursors (10, 30, and 50 wt%) with an ENR-50 matrix. A wide range of analyses was conducted to understand the nature of this hybrid and also to evaluate its potential uses in applications required high refractive index such as micro optical and optoelectronic devices. Results indicated that the ring-opening reaction of epoxide groups in ENR-50 increased with the increase of titania content in the hybrid resulting a strong bonding between titania and ENR-50 through TiOC bond, which was observed in FTIR spectrum at 1027–1028 cm−1. It is also observed a slight decrease in the intensity of the amorphous peak along with a new crystalline peak appeared at 2θ = 23 and 27° due to the crystalline nature of titania. The hybrids showed three thermal degradation steps in the range of temperature 76 to 769 °C due to the existence of the Ti moieties with the mixture of polymer chains, which in turn shifted the Tg at 24.3, 26.9 and 28.1 °C for the hybrid at 10, 30, and 50 wt% TiO2 compared to the Tg of ENR-50 at −18.4 °C respectively. The morphology of the ENR-50 showed clear changes during of the synthesis of ENR-50/TiO2 hybrids, these changes were proven by SEM, TEM, and AFM analyses. Uv–Vis results showed that the higher wavelength peak at 293 nm has shifted to 296, 298 and 300 nm for the hybrid at 10, 30, and 50 wt% TiO2 respectively due to the strong interaction between titania precursors and ENR-50 matrix. Furthermore, the hybrids showed good optical transparency in the visible light range. 相似文献
80.
P. J. Oefner A. H. Lanziner G. Bonn O. Bobleter 《Monatshefte für Chemie / Chemical Monthly》1992,123(6-7):547-556
Summary Chromatographic analysis of the degradation ofD-xylose either in plain water or aqueous sulfuric acid at temperatures ranging from 180 – 220°C gave up to 50 mol% of furfural. Activation energies did not differ significantly between reactions in plain water (E
a
=119.4 kJ/mol), 0.001M H2SO4 (E
a
=120.6 kJ/mol), 0.01M H2SO4 (E
a
=130.8 kJ/mol), and 0.1M H2SO4 (E
a
=120.7 kJ/mol). However, under alkaline conditions the activation energy was only 63.7 kJ/mol, indicating a different reaction mechanism. Isotachophoretic analyses revealed the formation of pyruvic, formic, glycolic, lactic, and acetic acid. While the relative yields of these acids ranged from 0.8 to 7% under hydrothermal and acidic conditions, 10 – 23% were obtained in alkaline degradation.
Quantitative Studien zur Bildung von Furfural und organischen Säuren während des hydrothermalen, sauren und alkalischen Abbaues vonD-Xylose
Zusammenfassung Die chromatographische Analyse des Abbaues vonD-Xylose in reinem Wasser und Schwefelsäure bei Temperaturen von 180 – 220°C ergab die Bildung von bis zu 50 mol% Furfural. In bezug auf die Aktivierungsenergie zeigten sich keine signifikanten Unterschiede zwischen dem Abbau vonD-Xylose in reinem Wasser (E a =119.4 kJ/mol), 0.001M H2SO4 (E a =120.6 kJ/mol), 0.01M H2SO4 (E a =130.8 kJ/mol), and 0.1M H2SO4 (E a =120.7 kJ/mol). Unter alkalischen Bedingungen hingegen betrug die Aktivierungsenergie nur 63.7 kJ/mol. Dies weist auf einen unterschiedlichen Reaktionsmechanismus hin. Ferner konnte mittels Isotachophorese die Bildung von Brenztraubensäure, Ameisensäure, Glycolsäure, Milchsäure und Essigsäure nachgewiesen werden. Während sich die relativen Ausbeuten in Wasser und Schwefelsäure zwischen 0.8 und 7% bewegten, betrugen sie unter alkalischen Bedingungen 10 bis 23%.相似文献