Beitr?ge zur Analytik von als Lebensmittelzusatzstoffe verwendeten Polysacchariden

Zusammenfassung Die bei der Hydrolyse von polysaccharidhaltigen Dikkungsmitteln entstehenden Monosaccharidbausteine können gaschromatographisch über die Aldonitrilacetate aufgetrennt werden. Zu diesem Zweck wird das Hydrolysat nach der Neutralisation mit einem Anionenaustauscher zur Trockene eingedampft, in Pyridin mit Hydroxylamin zu den entsprechenden Aldoximen und anschließend mit Acetanhydrid zu den Aldonitrilacetaten umgesetzt, welche in Chloroform gelöst, zur gaschromatographischen Trennung verwendet wurden. Es entsteht pro Zucker nur ein einziger Peak im Gaschromatogramm, ein großer Vorteil gegenüber früheren Verfahren, bei denen infolge der Anomerie bis zu fünf Peaks pro Zucker erhalten wurden und wodurch bei einem komplizierten Zuckergemisch die erhaltenen Gaschromatogramme sehr unübersichtlich waren.

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Analysis of polysaccharides used as food additivesIV. Gaschromatographic identification and determination of neutral components in polysaccharide-hydrolysates

Summary The monosaccharides, which are obtained by hydrolytic cleavage of the polysaccharid containing stabilisators, can be separated gaschromatographically by the way of their aldonitrilacetates. After hydrolysis, the mixtures are neutralized by an anion exchanger, evaporated to dryness, converted in pyridin with hydroxylamin to the aldoximes and hereafter with acetic anhydride to the aldonitrilacetates. Dissolved in chloroform, these compounds are used for gaschromatographic separations; only one peak is obtained for each sugar. This is a great advantage to the previous methods, where the anomeric constellations lead up of five peaks for one sugar compound and for complicated sugar mixture, it therefore was difficult to evaluate their gaschromatograms.

     

Reconstruction dynamics of recorded holograms in photochromic glass

We have investigated the dynamics of the record-erase process of holograms in photochromic glass using continuum Nd:YVO? laser radiation (λ=532 nm). A bidimensional microgrid pattern was formed and visualized in photochromic glass, and its diffraction efficiency decay versus time (during reconstruction step) gave us information (D, Δn) about the diffusion process inside the material. The recording and reconstruction processes were carried out in an off-axis setup, and the images of the reconstructed object were recorded by a CCD camera. Measurements realized on reconstructed object images using holograms recorded at a different incident power laser have shown a two-stage process involved in silver atom kinetics.     

Effect of equal channel angular pressing (ECAP) on hydrogen storage properties of commercial magnesium alloy AZ61

Cast commercial AZ61 magnesium alloys were processed through equal channel angular pressing (ECAP) and were comminuted into chips by filing with a rasp in order to measure their hydrogen storage properties. The effects of the number of ECAP passes and the processing route of ECAP on the hydrogen storage properties of AZ61 magnesium alloys were investigated. ECAP processing led to severe dynamic recrystallization and grain refinement of the AZ61 alloys. Of the analyzed samples, the AZ61 alloy processed via the Bc ECAP route with eight passes exhibited the smallest grain size, the fastest hydrogen absorption and desorption rates, and the highest gravimetric hydrogen storage capacity of 6.2 wt%.