Die Untersuchung von Sterin-Gemischen mit Hilfe der Dünnschicht-Chromatographie

Investigation of Steroid Mixtures by Thin-Layer Chromatography A new method of thin-layer chromatography on MgO-Al₂O₃-CaSO₄-plates was developed for the separation of natural mixtures of steroids in the form of their acetates. By this method, the formation of critical pairs, which was observed till now, could be avoided and considerably better separation could be achieved. Application of this new method to various vegetable oils showed in all cases the occurence of a steroid with a Rf-value corresponding to that of cholesterol. This steroid, occuring in considerable amounts especially in palm oil, was isolated from the same in centigram amounts by preparative thin-layer chromatography and thoroughly investigated. Melting point, X-ray structural analysis, infrared- and mass-spectra, optical rotation and rotational dispersion of this substance were identical with the corresponding data of cholesterol obtained from gall-stones. Thus it was proved that cholesterol occurs in plants as well.     

Die Untersuchung von Sterin-Gemischen II: Qualitative Analyse mit Hilfe der Dünnschicht-Chromatographie

Investigation of Sterol Mixtures II: Qualitative Analysis by Thin-Layer Chromatography A basic improvement in the TLC-analysis of sterol derivatives was achieved by carrying out the separation of 3,5-dinitrobenzoates of sterols on layers containing magnesium oxide. Visualization was accomplished by quenching of fluorescence on fluorescin-containing plates. Compared to separation of acetates, as described earlier, sensitivity of detection is ten times increased. Using model mixtures, it was possible to show the pattern of separation as a function of the number of C-atoms and the number and position of double bonds.     

Analyse von Acrylnitril-Styrol-Copolymeren mit Hilfe der Pyrolyse-Gaschromatographie

Copolymers of acrylonitrile and styrene with various compositions and molecular weights have been pyrolysed at a temperature of 500°C. The degradation products have been separated by means of gaschromatography and 16 compounds were identified. The most important products are cyanic acid, acetonitrile, acrylonitrile, propionitrile, toluene, ethylbenzene and styrene. The formation of these products has been investigated quantitatively as a function of the composition of the copolymers. Plotting the quantitatively determined amount of the cyanic acid as a function of the copolymer composition a linear slope resulted. Thus a method was developed to analyse copolymers of acrylonitrile and styrene. The formed amounts of acetonitrile, acrylonitrile and propionitrile during pyrolysis are independent on the molecular weights of the copolymers.     

Kinetische Untersuchungen der Reaktionen von Methylradikalen mit Allen

Kinetic Studies of the Reactions of Methyl Radicals with Allene The addition of methyl radicals to allene has been studied in the temperature range 573…595 K. The methyl radicals were produced by thermal decomposition of azomethane. It has been shown that the additions take place with a very high selectivity at the terminal carbon atoms in allene. The rate constant k₂ of the addition can be expressed by the following Arrhenius equation:      

Quantitative Bestimmung von Phosphatidylcholin mit Hilfe der HPLC

Quantitative Determination of Phosphatidyl Choline by Means of HPLC A HPLC method for a fast quantitative determination of phosphatidyl choline in soya bean lecithine is described. The separation was carried out on Li Chrosorb SI 60. The detection took place at 206 nm. Comparing this method with the results of the up to now used choline determination by Reineckat precipitation and by statistical evaluation it could be significantly established that the HPLC method (variation coefficient 1.1) is superior to the Reineckat method (variation coefficient 2.6).