排序方式： 共有6条查询结果，搜索用时 78 毫秒
1
1.
Oleg A. Trubetskoj Olga E. Trubetskaya Gaida V. Afanasieva Olga I. Reznikova Bernardo Hermosin Cesareo Saiz-Jimenez 《植物养料与土壤学杂志》1998,161(6):619-625
Humic acids (HAs) from four soils were fractionated by size exclusion chromatography (SEC) on Sephadex G-75. Three fractions were obtained in all humic acids, collected and assayed by Polyacrylamide gel electrophoresis (PAGE). The unfractionated HA from each soil was used as reference. Each chromatographic fraction formed one electrophoretic zone corresponding closely to one band of the reference sample with some admixture of the fractions preceding or following. The results indicate that fractionation of HAs by tandem SEC-PAGE can be successfully used for obtaining fractions of reduced polydispersity and different electrophoretic mobilities. Pyrolysis/methylation-gas chromatography-mass spectrometry of the full size preparations of HA and fractions with exactly defined molecular size and electrophoretic mobility showed a different distribution in humic components, mainly lipids, lignin derivatives and N-containing compounds. 相似文献
2.
Pyrolysis mass-spectra from a sample of the A1-horizon of a soil from southern Spain showed predominant peaks related to furan derivatives similar to those observed from complex polysaccharides in which not only hexoses but also pentoses and deoxyhexoses were constituent units. Smaller peaks, typical for protein materials and phenolic units, were also observed. On the other hand, typical peaks for the methoxyphenols of lignins were very small and indicated only limited amounts of undecomposed lignin residues in this soil sample. Peaks related to benzene or toluene were also very small.Humic acid samples from this soil showed much more prominent signals related to protein materials, benzene and phenolic derivatives and weaker polysaccharide-related signals than did the entire sample. Typical lignin related peaks were small or insignificant. Spectra from the grey or brown humidic acid fractions were much like those of the parent humic acid. Brown humic acid, however, showed stronger signals for nitrogen and sulphur compounds, indicating a higher content of protein-like materials in this fraction. Preparations of humic acid hydrolyzed by 6 N HCl showed in their pyrolysis products a marked increase in phenols and methoxyphenols.In its pyrogram, humin resembled humic acid, but signals for complex polysaccharides were more evident. Lignin-like materials seem not to be higher in this fraction. Hymatomelanic acid showed prominent signals related to polysaccharides and lignin. Pyrograms from the soil polysaccharides showed the characteristic pattern of a complex polysaccharide with the presence of fragments from polymers of amino acids or amino sugars. Fulvic acid spectra showed obvious dissimilarities to those from humic acid in that signals for protein, as well as those related to phenols, were low. Depending upon the isolation method, the fulvic acid preparations showed differing signals related to polysaccharide or phenolic materials. 相似文献
3.
The analysis of trace element in different kinds of waters is described, using a preconcentration technique on ion exchange loaded filter papers. The filters were analyzed employing an energy dispersive X-ray fluorescence system characterized by radioisotopic excitation sources and gas proportional or semiconductor detectors. The detection limits of the method were experimentally determined and the elemental levels in typical waters were measured. 相似文献
4.
Pyrolysis-gas chromatography-mass spectrometry was used to characterize fungal melanins and model phenolic polymers. Samples were pyrolysed at 700°C for 10 s and the low boiling-point compounds were separated on a Chromosorb 102 column. Low boiling-point compounds identified with a mass spectrometer coupled to the gas Chromatograph were very similar for peptone, a model autoxidative phenolic polymer incorporating peptone, and some fungal melanins. The major low boiling-point components from fungal melanins were related to proteins and to polysaccharides. A nitrogen-free phenolic polymer yielded very small amounts of low boiling-point pyrolysis fragments. The compounds identified appeared to be derived largely from the peptide, carbohydrate, and possibly small amounts of other aliphatic materials in the polymer structures. 相似文献
5.
6.
1