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排序方式: 共有399条查询结果,搜索用时 15 毫秒
41.
Jozef Ková Jozef Tekel Magda Kurucová 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1987,184(2):96-100
Summary The method described is based on the biochemical detection of herbicides on a silica gel thin layer following their chromatographic separation. The detection reagent is a mixture of a homogenate of bean leaves (Phaseolus vulgaris) and of the redox indicator 2,6-dichloroindophenol. This chronometric determination of herbicide residues is based on the observation that dark blue inhibition zones appear on a pale yellow-green background during the exposure of the sprayed chromatoplates Silufol to light. The dark blue zones disappear again after a time, their lifetime is proportional to the amount of the herbicide in the zone.Because of the high selectivity and sensitivity of the biochemical detection this method does not require a multiple clean-up procedure, nor does it require sophisticated instrumentation. It equals gas chromatography in sensitivity and precision. The determination limit lies between 0.01 and 0.001 mg · kg–1, the average recovery rate is 85 to 90%.
Bestimmung der Herbicid-Rückstände in landwirtschaftlichen Produkten, in Lebensmitteln, im Boden und Wasser mit der chronometrischen Methode
Zusammenfassung Die Methode stützt sich auf einen biochemischen Nachweis der Herbicide auf einer Silicagel-Dünnschichtplatte nach ihrer chromatographischen Verteilung. Das Nachweisreagens ist eine Mischung aus einem Homogenat von Blättern der Bohnen (Phaseolus vulgaris, L.) und des Redoxindikators 2,6-Dichlorphenolindophenol. Die chronometrische Bestimmung der Herbicidrückstände gründet sich auf die Beobachtung, daß während der Lichtexposition der besprühten Dünnschichtplatte Silufol auf einem gelbgrünen Hintergrund dunkelblaue Inhibitionszoneu entstehen, welche nach einer bestimmten Zeit verschwinden. Die Haltbarkeitszeit der Zone ist der Menge des Herbicids in der Zone direkt proportionell.In Betracht der hohen Selektivität und Empfindlichkeit des biochemischen Nachweises benötigt die Methode keine komplizierte Reinigung der Extrakte und keine hochentwickelte Ausstattung des Labors mit Instrumenten. Die Empfindlichkeit und Genauigkeit der chronometrischen Methode ist gleich der der Gaschromatographie. Die Bestimmungsgrenze ist 0,01 bis 0,001 mg·kg–1, die Wiederfindung ist 85–90%.相似文献
42.
Susan Joseph Maria Rutkowska Mariola Jastrzêbska Helena Janik Jozef T. Haponiuk Sabu Thomas 《应用聚合物科学杂志》2003,89(4):1007-1016
Blends of polystyrene and polybutadiene were prepared by melt mixing. The melt rheology behavior of the blends was studied with a capillary rheometer. The morphology of the blends was examined with scanning electron microscopy. The levels of continuity and cocontinuity were studied by both morphology and dissolution techniques. The region of phase inversion was observed at 50 wt % polystyrene. Various theoretical models were applied to determine the region of cophase continuity and to locate the point of phase inversion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1007–1016, 2003 相似文献
43.
44.
Zoran Djuric Zoran Djinovic Zarko Lazic Jozef Piotrowski 《Journal of Electronic Materials》1988,17(3):223-228
A quantitative model of isothermal vapor phase epitaxy is proposed. It can be applied to both closed and open tube systems.
This model enables the prediction of compositional profiles of the layers grown by isothermal vapor phase epitaxy with dependence
on the growth parameters and thermodynamical data of the (Hg,Cd)Te system. The dependence of compositional profiles of the
ISOVPE layers on temperature and time of deposition, source to substrate spacing, mercury and inert gas pressures are discussed
for both solid and liquid sources. Modification of the compositional profiles by the postgrowth annealing has also been studied.
The proper choice of growth and annealing parameters makes the optimization of the profiles possible. The calculated profiles
are compared with the experimental data and a satisfactory quantitative fit is found in most cases. The possible reasons for
remaining discrepancies are discussed. 相似文献
45.
Wil?A.?M.?van Loon Jozef?P.?H.?LinssenEmail author Aagje?Legger Ruud?M.?H.?Heijmans Henk?C.?van Deventer Maurits?J.?M.?Burgering Bas?L.?van Drooge Alphons?G.?J.?Voragen 《European Food Research and Technology》2005,221(6):779-786
A new, energy efficient production process for French fries was developed and evaluated. Superheated steam (SHS) was used
for evaporation of water instead of pre-drying with air and par-frying with oil. The product was frozen by vacuum cooling.
Unfortunately, with this process it was not possible to reach the quality of conventional French fries. Sensory analysis indicated
that the main quality defect was a tough crust with a fatty appearance. Confocal Scanning Laser Microscopy showed that this
was caused by skin formation on the surface during both SHS drying and vacuum cooling. A frying step was necessary to obtain
a porous crust. A satisfactory product quality was feasible after drying with SHS instead of air. Due to the concessions made
for the product quality, the final energy reduction was limited. Nevertheless, this study has gained more insight into how
processing affects potato tissue on micro-scale and it has shown that a porous structure is essential for good quality French
fries. 相似文献
46.
Polaczek E Tomasik PJ Mazurkiewicz J Wrzalik R Stobinski L Tomasik P Lin HM 《Journal of nanoscience and nanotechnology》2005,5(3):479-483
Closed-end single-walled carbon nanotubes were wetted in aqueous solutions of monosaccharides, forming weak surface complexes, as proven by the estimation of the content of monosaccharides in complexes isolated from aqueous solutions. The complexation was confirmed by micro-Raman spectroscopy. The Gaussian 03 (Molecular Mechanics UFF method) computations of total energy of the single-walled carbon nanotube-monosaccharides inclusion and surface complexes showed that inclusion complexes should be more stable than corresponding surface complexes. Computed total energies for particular complexes pointed to a lack of preferences for the formation of complexes with either alpha- or beta-tautomers and either pyranoses or furanoses. The forms preferred in the formation of the surface complexes usually differ from these favored in the formation of the inclusion complexes. 相似文献
47.
On the basis of standards of identification of substances in the additive system of polyethylene has been performed. Different methods for separation such as adsorption thin-layer chromatography, high-performance liquid chromatography with chemically bounded phases, and gas chromatography have been used. The fir al identification has been made with mass spectrometry. The substances have been extracted from polyethylene with hexane and chloroform. 相似文献
48.
A kinetic model for the formation of acrylamide in a fructose–asparagine reaction system at initial pH 5.5 is proposed, based on an approach called multiresponse kinetic modelling. The formation of acetic acid and formic acid from the degradation of fructose and its isomer glucose was included in the proposed kinetic model. The kinetic model suggests that the effect of temperature on acrylamide formation with fructose is more due to the preceding steps with the formation of the Schiff base. The use of fructose and lower pH resulted in a higher yield of acrylamide (3%), suggesting that both can play an important role in acrylamide mitigation. Furthermore, these models have shown that, at high temperatures (120–200 °C), the Maillard reaction rapidly goes into the advanced stages, forming high amounts of organic acids and high molecular weight melanoidins. Overall, these mechanistic models provide more insight of the formation of acrylamide in a quantitative way. 相似文献
49.
Lucia Reale Jozef Kaiser Loretta Pace Antonia Lai Francesco Flora Antonella Angelosante Bruno Adele Tucci Paola Zuppella Lucia Mancini Giuliana Tromba Fabrizio Ruggieri Maria Fanelli Radomir Malina Miroslav Liška Anna Poma 《Microscopy research and technique》2010,73(6):638-649
This study is related to the application of the X‐ray dual‐energy microradiography technique together with the atomic absorption spectroscopy (AAS) for the detection of lead on Zea mays stem, ear, root, and leaf samples. To highlight the places with lead intake, the planar radiographs taken with monochromatic X‐ray radiation in absorption regime with photon energy below and above the absorption edge of a given chemical element, respectively, are analyzed and processed. To recognize the biological structures involved in the intake, the dual‐energy images with the lead signal have been compared with the optical images of the same Z. mays stem. The ear, stem, root, and leaf samples have also been analyzed with the AAS technique to measure the exact amount of the hyperaccumulated lead. The AAS measurement revealed that the highest intake occurred in the roots while the lowest in the maize ears and in the leaf. It seems there is a particular mechanism that protects the seeds and the leaves in the intake process. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc. This article was published online on 1 December 2009. An error was subsequently identified. This notice is included in the online and print version to indicate that both have been corrected 19 February 2010. 相似文献
50.