Isolation of essential oils from tobacco by gas co-distillation/solvent extraction

Summary The essential oils have been isolated from tobacco leaves using a simple gas co-distillation apparatus. The method involves co-distillation with water under the continuous stream of an inert gas with subsequent single solvent extraction of the distillate. The extract is analysed on GC and GC/MS in splitless injection mode without further concentration. The method was evaluated for reproducibility using n-octadecane as an internal standard. The distillation-extraction procedure was reporducible with an average deviation of ±3% for the major constituents. The present method was applied to the analyses of the essential oils of other agricultural products.Dedicated to Dr. L. S. Ettre on the occasion of his 60th birthday.     

Examination of the different procedural steps in the determination of organotin compounds in water samples

Previous animal experiments suggested that the Magos cold vapor atomic absorption spectroscopic (CVAAS) method might overestimate the concentrations of inorganic mercury (I-Hg) in the presence of methylmercury (MeHg). In the present study it is shown that this error is due to a fast degradation of MeHg during the formation of the analytical signal. For brain samples, about 5% of the total amount of MeHg in the reaction vessel is degraded to I-Hg. Speciation of Hg in aqueous solution of MeHg chloride, after purification with ionexchange chromatography using the Magos method, showed that about 9% was I-Hg. Analysis by NMR of MeHg chloride and MeHg hydroxide showed that less than 1% was in the form of I-Hg. The absolute magnitude of the error in the CVAAS method is dependent on the amounts of SnCl₂ and MeHg in the reaction vessel; however, the ratio of I-Hg to total (T-Hg) is shown to be independent of the amount of MeHg (25.5–255 ng as Hg) in the reaction vessel. A procedure for corrections is proposed, based on the results from these studies and empirical data from speciation analyses of brain tissue from MeHg-exposed rats and rabbits.     

Effects of Solar UVB Radiation on Growth, Flowering and Yield of Central and Southern European Maize Cultivars (Zea mays L.)

Abstract— Different cultivars of maize ( Zea mays L.) originating from Central and South Europe were grown from June to September 1994 for 16 weeks in two greenhouses covered with different UVB-absorbing (280–320 nm) plastic foils. Using the ambient UVB radiation level of a southern location (Portugal, 38.7°N) in one of the greenhouses as an enhanced radiation compared to the reduced radiation in the second greenhouse, an increase of about 12% of UVB was simulated. Six of the eight cultivars examined showed significant reductions in height of up to 18.9% at all developmental stages under increased UVB. In contrast to this, the fresh and dry weight as well as the leaf area was reduced under UVB only at early developmental stages, but with ongoing development the UVB stressed plants caught up. The total content of absorbing compounds of the maize cultivars was completely unaffected by UVB. A flowering delay up to a maximum of 5 days was observed under higher UVB in several cultivars. Probably due to this delay in the cob development the yield decreased to 27.7% under higher UVB at the first harvest after 12 and 14 weeks, whereas at the second harvest after 14 and 16 weeks yield reduction levelled off.     

Preparative Separation and Analysis of Complex Mixtures of Leucomycins and Desmycarosyl Leucomycins Using HPLC and Mass Spectrometry

Composition and hydrolysis products of a biotechnical available complex of macrolides were analyzed by HPLC and ESI-CID-MSⁿ. Major components are leucomycin-type antibiotics (leucomycins A₁ (5), A₇ (3), A₉ (2), 9-desoxy-9-oxo-turimycin H₃ (4) and niddamycin B (6). Hydrolysis of the complex mixture yielded 9-, 13-isoforocidins (7, 8, 9, 11) and 9-oxo-forocidin (10). A preparative separation procedure was elaborated furnishing compounds 3 - 11 for semisynthetic experiments.Prof. Dr. Udo Gräfe deceased on 14.2.2003. For obituarity see: Schlegel B (2003) J Peptide Sci 9: 661–661.     

Flotation—spectrophotometric determination of osmium with thiocyanate and methylene blue

A sensitive flotation—spectrophotometric method, based on the ion associate formed by the anionic thiocyanate complex of osmium with the basic dye methylene blue (MB) is described. The ion associate precipitates when the aqueous solution is shaken with toluene, and the separated and washed compound is dissolved in acetone. The molar absorptivity is 2.2 × 10⁵ l mol^-1 cm^-1 at 655 nm. Beer's law is obeyed. The molar ratio of Os:SCN:MB in the separated and washed ion associate is 1:6:3. Ruthenium reacts similarly. The method is applied to the determination of traces of osmium in crucible platinum after separation of osmium by distillation as tetroxide.     

Pimaricin—VIII : Structural and configurational studies by electron impact and field desorption mass spectrometry, 13C (25.2MHz) and 1H (270 MHz)-NMR spectroscopy

Attempts to obtain a molecular ion from the polyene macrolide antibiotic pimaricin by EI and FD mass spectrometry were unsuccessful The loss of carbon dioxide and a varying number of water molecules from the molecular ion made a molecular-weight determination impossible ¹³C NMR spectroscopy of N-acetylpimaricin, its dodecahydroderivative, and of HH-2, a hydrogenation-hydrogenolysis product of N-acetylpimaricin, confirmed that the antibiotic has structure 3 containing a hemi-ketalic ring and lacking an OH group at C-8. The value of the anomeric coupling constant, J_c-1-h-1, indicates that the mycosamine moiety is β-glycosidically bound to the aglycone.The structure and configuration of the antibiotic have been studied by analysis of the 270 MHz ¹H-NMR spectra of N acetylpimaricin and HH-2. By comparison of the two spectra and by extensive decoupling experiments, all signals in the spectrum of N-acetylpimaricin have been assigned to the protons in structure 3. From chemical-shift, coupling constant, and integral values, it was deduced that the mycosamine ring is pyranoid with a chair conformation, the hemi-ketal is 6 membered and occupies a chair conformation with the substituents in equatorial positions, the epoxy protons as well as the olefinic protons are trans to each other, and the antibiotic is diastereomerically pure.     

A hydrogenate of cottonseed oil as a base for suppositories

The compositions of two samples of hydrogenated cottonseed oil recommended as fatty bases for suppositories have been studied. Their physicochemical indices have been determined. Tashkent Pharmaceutical Institute, fax (3712) 56 45 04. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 459–460, July–August, 1998.     

Untersuchungen zum Dehnungsverhalten von Polybutylenterephthalat (PBT)-Folien

Zusammenfassung Anhand von Röntgenuntersuchungen wurden dehnungsund belastungsabhängige Veränderungen der PBT-Ketten-konformation untersucht. Die Faseridentitätsperiode (FIP) des PBT vergrößert sich beim Dehnen oder Belasten diskontinuierlich, der Blättchenebenenabstand verkleinert sich dagegen kontinuierlich. Die auftretenden Gitterstörungen, deren Modell diskutiert wird, werden durch Veränderungen der Kettenkonformation hervorgerufen.Die von den anderen Autoren gefundene-Struktur des PBT wurde nur bei hoch gedehnten ( = 18%) PBT-Proben nachgewiesen, kann aber zur Erklärung der Umwandlung der PBT-Kettenkonformation nicht herangezogen werden.

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Summary Stress and strain induced changes in the chain conformation of polybutylene terephthalate (PBT) were determined by X-ray measurements.The fibre identity period (FIP) increases discontinuously with stress or strain, whereas the (100) Bragg spacing (Blättchenebenenabstand) decreases continuously.Lattice distortions are due to these changes in the PBT chain conformation. A model of these lattice distortions is presented and discussed.The so-called-structure of PBT given by other authors exists only in the case of highly strained ( 18% PBT fibres.The changes in the PBT chain conformation cannot be attributed solely to the existence of the-structure.

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Mit 12 Abbildungen und 2 Tabellen     

Frequency-dependent linear response of superconducting systems

We present a density functional scheme for calculating the frequency-dependent linear response of superconductors. The central result is a set of integral equations determining the linear response of the normal and anomalous densities to external perturbations. Analytic solutions of these integral equations are obtained for homogeneous systems with separable effective interactions. For inhomogeneous superconductors, the formalism leads to a scheme for calculating the critical temperature without explicitly solving the gap equation. © 1995 John Wiley & Sons, Inc.     

[(C6H5)3P]2Ni(Me3Si?CC?SiMe3). Darstellung,Eigenschaften und Struktur des ersten stabilen Nickel(0)-Komplexes von Bis-trimethylsilylacetylen

[(C₆H₅)₃P]₂Ni(Me₃Si? C?C? SiMe₃). Preparation, Properties, and Structure of the First Stable Nickel(0) Complex with Bis(trimethylsilyl)acetylene The title compound is the first example of a nickel(0) complex with bis(trimethylsilyl)acetylene and obtained from (ph₃P)₂Ni(C₂H₄) and bis(trimethylsilyl)acetylene in tetrahydrofuran. The complex is characterized by some reactions, the i.r. spectrum and by a structural analysis with the aid of X-ray diffraction data. (ph₃P)₂Ni(Me₃Si? C?C? SiMe₃) crystallizes monoclinic in the space group C2/c with four formula units per unit cell (2468 observed, independent reflexions, R = 0.038). The cell dimensions are a = 20.927, b = 13.812, c = 14.238 Å, α = γ = 90°, β = 91.02°. The molecules are monomer in crystalls. The molecule is planar with ligands arranged trigonally about the central atome but distorted to the tetrahedral complex.