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Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

When heating vinyl polymers within the temperature gradient of 50–450° C, they are fragmented in certain temperature ranges to defined products. These products are fractionated on the TLC-layer and subsequently chromatographed. Based on the thermofractograms obtained identification of the starting material can be made. From polyvinyl esters, e.g., the corresponding acid is obtained and copolymers yield the different acids. Thermolysis of polyvinyl carbazole yields vinyl carbazole and vinyl pyrrolidone and pyrrolidone are obtained from polyvinyl pyrrolidone. Polymethacrylate is fragmented to the corresponding methacrylate, and acrylate if obtained from polyacrylate. Evaluation of the thermofractograms leads in part to new conceptions about structures and cleavage mechanisms of such polymers.

To investigate the gaseous products from the TAS-process and TFG, a coupling with gas chromatography was developed. For comparison a commercially available GC-solid sample inductor and a GC-pyrolysis device were used to verify the results. At 250°C only very small amounts of gaseous products were evolved from carbohydrates. At 300°C 18 low molecular mass compounds could be identified by gas chromatography-mass spectrometry. Larger amounts of gaseous products which cannot be condensed on the TLC-layer are formed at higher temperatures. In the usual temperature range of the TAS-procedure and TFG approximately 5% volatile compounds and 80% of compounds which can be condensed on the TLC-layer evolve from carbohydrates.

Zusammenfassung Eine Apparatur zur quantitativen Bestimmung der Löslichkeit im Mikromaßstab von Substanzen in überkritischen und verflüssigten Gasen wurde beschrieben. Hiermit konnte die Löslichkeit der Opiumalkaloide Morphin, Codein, Thebain, Papaverin und Noscapin in den Gasen Kohlendioxid, Distickstoffmonoxid und Trifluormethan ermittelt werden. Drücke zwischen 60 und 200 bar und Temperaturen zwischen 18 und 40° C wurden angewandt; die Löslichkeiten lagen je nach Alkaloid und Gas und den weiteren Bedingungen zwischen wenigenµg und einigen mg pro Normalliter.

The advantages of pH gradient layers are presented with some fluorescent dyes as examples. In chromatography, transverse to the gradient (T-gradient) indications as to the chemical structure of the substance are obtained and contaminants are easily recognized. Chromatography in the direction of the gradient leads to a focusing, especially of the accompanying substances in the upper region of the chroma togram: These layers are suitable also for the chromatography of mixtures of substances of strongly differing polarities.

A method for zinc dust distillation of 20–200 µg of substance under controlled conditions is described. The sample is heated on copper-activated zinc up to 350–450° C for several minutes in a TAS-cartridge. The resulting oxygen-free aromatic resp. the stable heterocyclic components are transferred directly to the starting point of a TLC-plate by a stream of nitrogen at 15 ml/min and identified after chromatography. Thermography is applied to study the reaction process and to determine the optimal temperature ranges. Examples of application to the groups of naphthalene-, anthracene-, phenanthrene-,tetracene- and indol derivatives are listed.

Zahlreiche Substanzen lassen sich mit überkritischen Gasen aus Proben fraktioniert abtrennen. Als Gase dienen z.B. Kohlendioxid und Distickstoffoxid im fluiden Zustand, d.h. bei Temperaturen von 40° C und Drücken zwischen 70 und 400 bar. Für derartige lösungsmittelfreie Extraktionen im analytischen Bereich wird eine Apparatur beschrieben. Sie ist direkt mit einer Auffangapparatur zur anschließenden Dünnschicht-Chromatographie gekoppelt. An 3 Beispielen mit entsprechenden Chromatogrammen werden die Möglichkeiten und Vorteile dieser neuen Kopplungsmethode demonstriert. Numerous substances can be extracted from samples by supercritical gases, e.g. either carbon dioxide or nitrous oxide in the fluid condition at temperatures of 40° C and pressures between 70 and 400 bar. An apparatus for such solvent-free extraction in the analytical field is described. It is coupled directly with a receiving apparatus for subsequent thin-layer chromatography. Three examples with corresponding chromatograms show the possibilities and advantages of this new coupling procedure.

Es werden eine Methode und ein Gerät (Testscraper) zur Ermittlung der Haft- und Abriebfestigkeit beschrieben. Die sogenannten Abriebgewichte liegen bei den selbstgestrichenen Schichten mit den handelsüblichen Kieselgelen für die DC zumeist unter 30g. Die sogenannten Kieselgel Fertigplatten zeigen dagegen Abriebgewichte, die zumeist zwischen 200 und 700 g liegen. Weiter werden eine Reihe organischer Binder zur Selbstherstellung abriebfester DC-Schichten geprüft. Gute Ergebnisse werden u.a. mit der Kunststoffdispersion Acronal und mit dem festen Polyviol erzielt.

In the TAS procedure, substances which can be separated from a sample by thermal increase of the vapour pressure can be transported to the TLC layer in different ways and with varying effectiveness. “Forced Convection” gives the lowest yields, results improve considerably with the so-called carrier gas extraction, and a carrier gas extraction in a stream of helium results in optimal yields. Nipagin®, Sudan red, Dimethyl yellow, Menadione® and Diphenyl were used as model substances. An almost quantitative thermoextraction from samples can only be achieved with amounts of less than 20 µg. Following scraping off and elution of the corresponding TLC-zones a photometric assay is carried out for quantitative determination.

A rapid method is described which permits to carry out a coupled dehydratization and sulphur resp. selenium dehydrogenation with 50–300 µg of starting material under controlled conditions. The sample is heated on a potassium hydrogen sulphate-sulphur resp. selenium mixture at preselected temperatures of between 160–400° C for several minutes in the TAS-oven resp. the Tasomat. The resulting aromatic components are transferred directly to the starting point of a TLC-plate by a stream of nitrogen at 10 ml/min and the reaction products are identified after chromatography. Thermofractography is applied to study the reaction processes and to determine the optical temperature ranges. Examples of application to the groups of sesquiterpenes, diterpenes and steroids are listed.

An overview of the solvent power of dense gases is given. The properties of these novel solvents are described and the specific advantages of carbon dioxide discussed. New qualitative and quantitative procedures for the rapid determination of solubilities are described for several interesting classes of natural substances. These include fatty oils, steroids, alkaloids, flavor and aroma substances, which documents the versatility of the new extraction procedure in many practical applications.

In this report the behaviour of a number of phenolic substances of natural and synthetic origin-e.g. monomeric phenols, defined tanning agents and their constitutional units (model substances), tanning drugs and leather-was investigated under the conditions of thermofractography (TFG), with linear increase of temperature in the range 50–450° C. The TLC conditions had to be optimized first in order to achieve the best possible identification of the phenols expected to originate during TFG. The TFG of the model substances showed varying fragmentations according to their constitutional units and their types of linkage. Regarding the thermal range of fragmentation and the phenols which appear in the thermofractograms (TFG), the assignment to the types of tanning agents in plant material has become possible. The same assignment can be made for the tanning agents which are bound in collagen (leather) by hydrogen bonds. Further, TFG gives hints about substances which have been used for finishing and dyeing leather. The figures of the thermofractograms of some natural and synthetic tanning agents are given and discussed. Unter den Bedingungen der Thermofraktographie (TFG) wurde das Verhalten einfacher Phenole, definierter Gerbstoffe und deren Bausteine (Modellsubstanzen) sowie von Gerbstoffdrogen und Ledern im linearen Temperaturanstieg von 50–450° C untersucht. Zuvor mußte die DC der zu erwartenden Phenole optimiert werden. Die Thermofraktogramme (TFG) der Modellsubstanzen zeigten die verschiedenartige Fragmentierung je nach ihren Bausteinen und deren Verknüpfung. Anhand der Thermolysebereiche und der auftretenden Phenole im TFG ist nun die Zuordnung zu einer der Gerbstoffklassen möglich geworden. Dies gelingt auch, wenn die Gerbstoffe, wie im Leder, in fester H-Brückenbindung an Kollagen vorliegen. Zusätzlich erhält man Hinweise auf die bei der Zurichtung und Färbung des Leders verwendeten Stoffe. F:ur einige wichtige natürliche und synthetische Gerbstoffe sind die TFG abgebildet und besprochen.

Direct coupling of a catalytic dehydrogenation to TLC is described. The reaction takes place according to the principle of gas phase dehydrogenation by injecting the solution of the compound to be dehydrogenized in batches into the TAS-cartridge, loaded with e.g. palladium-barium sulphate catalyst. Sample size are in the range of 20–100 µg and the reaction temperatures, depending on the compound, is between 200 and 400°C. The reaction products are carried by the solvent vapours to the thin-layer and subsequently chromatographed and identified. In given examples the dehydrogenation is applied to sesquiterpene hydrocarbons and alcohols, sesquiterpenoids of the eudesman type, abietic acid and steroids.

In “liquid chromatography” (LC), a stationary phase of microcrystalline cellulose is suitable for the separation of polyhydric alcohols such as glycerine, ethylene glycol, propane diol and butane diol when using a solvent mixture of ethyl acetate and n-propanol, saturated with approx. 15% of water. When using benzene as solvent, the monohydric alcohols C1-C5 can also be separated on the same column. Differential refractometers and micro adsorption detectors are suitable for detection.

Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Zusammenfassung 1.DerAvena-Silicagel-Krümmungstest stellt eine Modifikation desAvena-Tageslichttests nachSöding dar. Die Übertragung des zu prüfenden Wuchsstoffes auf Agarblocks erfolgt durch Kieselgel, das nach der Dünnschicht-Chromatographie (DC) aus den zu testenden Chromatogramm-Zonen ausgeschabt und über die Agarblocks geschichtet wird. Für die Kontrollen werden abgegrenzte Felder einer Kieselgel-Schicht (über Blutzucker-Pipetten) mit methanolischer Wuchsstoff-Lösung versetzt, ausgeschabt und auf Agar übertragen. Die Agarblocks werden mit dem anhaftenden Kieselgel zum Test benutzt (S. 24).2.IES ist — selbst bei ungleichmäßiger Verteilung in dem Kieselgel-Feld — nach 1/2–1stündigem Aufenthalt der Agarblocks in feuchter Kammer gleichmäßig im Agar verteilt (S. 25f.).3.Testzeiten zwischen 1,5 und 2,5 Std ergaben die beste quantitative Trennung für IES-Konzentrationen zwischen 8×10-8 und 4×10-7 in den Agarblocks, d.h. 8–40 ng Ausgangsmenge (S. 26f.).4.IES läßt sich nach DC praktisch verlustfrei auf Agarblocks übertragen (S. 30f.).5.Bei Benutzung von Kieselgel HF254-Schichten kann die Laufhöhe der zu testenden Substanz unter kurzwelligem UV-Licht ohne Sprühreagens an Hand der auftretenden Fluorescenzlöschung genau markiert werden. 0,5 µg IES sind sicher zu erkennen. Längerer Aufenthalt der Chromatogramme unter UV-Licht ist zu vermeiden. 5 min Bestrahlung mit kurzwelligem UV-Licht bedingt etwa 10% Verlust, anschließende 5 min-Bestrahlung mit langwelligem UV-Licht einen weiteren Verlust von etwa 10% an IES-Aktivität (S. 32f.).6.Bei Extraktion von IES aus Kieselgel, das mit IES-freiem Pflanzen-Diffusat oder-Extrakt versetzt war, kann nach anschließender Dünnschicht-Chromatographie des auf dem Wasserbad bei ca. 80°C eingeengten Extraktes mit einer Ausbeute von 85% gerechnet werden (S. 33f.).

Einleitend sind die Möglichkeiten und bisherigen Anwendungen der Gradient-Dünnschicht-Chromatographie kurz zusammengestellt. Die Ergebnisse dieser Technik, insbesondere der pH-Gradient-DC, waren vor Beginn dieser Arbeit noch nicht gut reproduzierbar; vor allem waren die Schichten in Bezug auf den Verlauf des pH-Gradients nicht gekennzeichnet. In der vorliegenden Arbeit werden nun Vorschriften für die reproduzierbare Herstellung fehlerfreier pH-Gradient-Schichten gegeben. Diese Schichten lassen sich durch die Angabe des pH-Wertes als Funktion des Ortes charakterisieren. Damit sind erstmals pH-Gradient-Schichten mit definierter Gradient-Ausbildung gegeben. Abschließend sind die bei der pH-Travers-Gradient-Chromatographie auf solchen Schichten erhaltenen typischen Kurvenformen einzelner Substanzklassen zusammengestellt und kurz erläutert.

Zusammenfassung Eine Apparatur und eine Methode werden beschrieben, die zur gravimetrischen Erfassung kleinster Mengen ätherischer Öle und ähnlicher Stoffe (von etwa 0,5 mg an) dienen. Die Apparatur arbeitet nach dem Prinzip der kontinuierlichen Wasserdampfdestillation mit etwa 0,5 ml Pentan (Kp. 32°C) als Vorlage. Letzteres wird später entfernt und das zurückbleibende Öl gewogen. Eine eingebaute Mikrobürette ermöglicht zusätzlich auch Bestimmungen nach der volumetrischen Methode. Hierdurch vereinigt diese Apparatur den Vorteil einer gravimetrischen Bestimmung (D. A. B. 6) mit dem der kontinuierlichen Destillation und anschließender volumetrischer Messung des ätherischen Öles (U. S. P. XIV und B. P. 1948). Abschließend wird noch auf eine einfache Methode der „reinen Dampfdestillation“ von Drogen hingewiesen.

The further development of the Thermo-Micro-Extraction, Transfer and Application Procedure (TAS) resulted in Thermofractography (TFG). The necessary apparatus for this (TASOMAT and regulating mechanisms) is desribed. In TFG a few milligrams of a sample are heated with linear rise of temperature from, e.g., 20° C–450° C. The volatile and condensable components, as well as the products of thermolysis of polymeric material, are caught continually and fractioned as the starting line of a TLC-plate. After chromatography, rapid information can thus be obtained about the components of a complex sample of mixtures which were hithertoo difficult to analyse, like e.g., chewing gum, lignins, coloured mixed textiles and fats with additives.

Summary Different ways of improving the separation effect in thin-layer chromatography are reviewed. Special attention is paid to such variable experimental conditions as chamber atmosphere, development of chromatogram, and conditions at the starting point. Discussing the evaluation of chromatograms the relationship is demonstrated between the method of detection, zone size, and structure of the substances separated. It is desirable to have three groups of revealing procedures, all of which should be highly sensitive: 1. universal procedures, 2. procedures specific for a group of substances, and 3. procedures specific for individual substances. Experimental data are presented which show that separation time can be considerably shortened by using adsorbent layers of a given particle size distribution and/or appropriate solvents. Solvents frequently used in TLC were arranged according to their migration rate and it is shown that a more or less pronounced relationship exists between this velocity and the viscosity of the solvents.

Summary Gradient techniques in chromatography are reviewed in general. Gradients can be introduced in the properties of the stationary and/or mobile phases and in the other conditions (e.g. temperature or flow rate programming). A chromatography which traverses the gradient direction yields new possibilities. This procedure has been worked out for TLC for the first time.

Zur Trennung von organischen und anorganischen Jodverbindungen werden Kieselgel HF254-Stärke-Schichten und 6 verschiedene Fließmittelgemische vorgeschlagen. Die spezifische Sichtbarmachung erfolgt durch 10 min Bestrahlung mit ungefiltertem kurzwelligem UV-Licht. Das bei dieser photochemischen Dejodierung freiwerdende Jod gibt mit Stärke die bekannte blau-violette Einschlußverbindung. Die Nachweisgrenze liegt unter 0,1 µg Jod.

Résumé L'auteur envisage les possibilités d'améliorer le pouvoir séparatif et discute plus particulièrement de la variabilité des conditions de milieu tel que l'atmosphère de la chambre, mode de développement et conditions initiales.

Zahlreiche Substanzen lassen sich mit überkritischen Gasen aus Proben fraktioniert abtrennen. Als Gase dienen z.B. Kohlendioxid und Distickstoffoxid im fluiden Zustand, d.h. bei Temperaturen von 40° C und Drücken zwischen 70 und 400 bar. Für derartige lösungsmittelfreie Extraktionen im analytischen Bereich wird eine Apparatur beschrieben. Sie ist direkt mit einer Auffangapparatur zur anschließenden Dünnschicht-Chromatographie gekoppelt. An 3 Beispielen mit entsprechenden Chromatogrammen werden die Möglichkeiten und Vorteile dieser neuen Kopplungsmethode demonstriert.

A new time-saving thermomicro separation and application technique (TAS procedure) has been described, together with the apparatus and its use. With this technique it is possible to transfer, at 50–350°, volatilizable materials from 5–50 mg samples directly onto a thin-layer chromatographic plate. A survey of applications of the technique is also given. The technique offers a simple and rapid means for the separation of drugs containing essential oils, of coumarins, xanthine derivatives, some alkaloids and acids, spices such as capsaicin and piperin, and also of diphenylderivatives, 4-Hydroxybenzoate-esters, pesticides and many other compounds.

Copyright of Zeitschrift für Lebensmittel-Untersuchung und -Forschung is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary Important properties of plant materials can be improved by treatment with carbon dioxide under pressure, followed by fast decompression. This cracking increases the swelling index of linseed by almost 20 per cent and even more if the linseed has been de-oiled by high pressure extraction. From puffedhibiscus flowers a tea infusion ca be prepared in which the value ingredients such as acids and pigments are extracted more rapidly and completely.