Evaluation of a purge-and-trap injection system for capillary gas chromatography-microwave induced plasma-atomic emission spectrometry for the determination of volatile selenium compounds in water

A method is presented for the selective determination of the volatile selenium species dimethylselenide and dimethyldiselenide, using a commercially available purge-and-trap injection system coupled to capillary gas chromatography-microwave induced plasma-atomic emission spectrometry. The efficiency of the purging step was evaluated and the parameters affecting the purge and trap processes were optimized. The method was applied to the determination of volatile selenium compounds in lake water. Relative detection limits of 2ng/l for dimethylselenide and dimethyldiselenide, corresponding to an absolute detection limit of 10 pg, were achieved.     

Highly efficient recycling of a "sandwich" type polyoxometalate oxidation catalyst using solvent resistant nanofiltration

A "sandwich" type polyoxometalate catalyst ([MeN(n-C8H17)3]12[WZn3(ZnW9O34)2]) was very efficiently recycled by nanofiltration with almost quantitative retention, using an alpha-alumina supported mesoporous gamma-alumina membrane.     

Vesicle Phases with Semipolar Additives

We examined the influence of semipolar additives on the phase behavior of mixed zwitterionic surfactant/consurfactant systems. It is shown that in these systems with increasing concentration esters like hexylacetate (HA) and ketones like hexylmethylketone (HMK) can behave both like consurfactants and like hydrocarbons. In solutions of 200 mM tetradecyldimethylamineoxide (TDMAO)/cosurfactant the additives cause first a phase transformation from the micellar L(1) phase to a lamellar L(alpha) phase. Upon further increasing concentration, the L(alpha) phase is transformed into a microemulsion. The L(alpha) phase consists of densely packed multilamellar vesicles. The vesicles are shown by electron microscopy. The multilamellar character of the vesicles is also reflected in the conductivity of the phase. It is up to 10 times lower than the conductivity of the L(1) phase. In some systems the vesicles are transformed on rest into a multidomain stacked L(alpha) phase. It is furthermore demonstrated that the two-phase L(1)/L(alpha) region in these systems is very narrow. In situations where enough HA is added to be close to the boundary of the L(1) phase, it is shown that very small amounts of cosurfactant can transform the L(1) phase into the L(alpha) phase. In extreme situations 1 mM cosurfactant is sufficient for transforming the L(1) phase with 200 mM TDMAO into the L(alpha) phase. In the investigated systems the L(alpha) phase is a highly viscoelastic fluid in which the storage modulus is 1 order of magnitude larger than the loss modulus. Besides the conventional way to prepare samples by adding all ingredients and stirring the solution intensively, all investigated systems were additionally prepared without applying any shear forces. In a surfactant/cosurfactant solution the additive was brought into the sample by diffusion. The phase behavior of both types of samples showed fundamental differences in some cases, which give insight into the influence of shear forces on these systems. Copyright 2001 Academic Press.     

Synthese von 8-Alkylamino-8-aryl-1,2,3,4,5,6-hexathiocan-7-thionen

Zusammenfassung Durch gemeinsame Einwirkung von primären aliphat. Aminen und Schwefel auf Methylarylketone in Methanol bei Raumtemp. erhält man in meist guten Ausbeuten 8-Alkylamino-8-aryl-1,2,3,4,5,6-hexathiocan-7-thione (1a-h). Die Umsetzung von 1,4-Diacetylbenzol mit n-Propyl-bzw. n-Butylamin und Schwefel liefert Phenylen-1,4-di-hexathiocanderivate (3 a, b).Bei der Reaktion von Acetophenon mit 3-N,N-Diäthylaminopropylamin und Schwefel entstehen neben dem 8-(3-N,N-Diäthylaminopropylamino)-8-phenyl-1,2,3,4,5,6-hexathiocan-7-thion (1e) 51% einer Verbindung der Summenformel C₁₅H₂₂N₂S₂ (2), der die Struktur der (3-N,N-Diäthylaminopropylimino)-phenyldithioglyoxylsäure zugeordnet wird.1 e läßt sich durch Behandlung mit wäßr. Natriumsulfit-Lösung zu2 abbauen,2 durch Reaktion mit Schwefel wieder in1 e überführen.

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Synthesis of 8-alkylamino-8-aryl-1,2,3,4,5,6-hexathiocan-7-thiones (Joint action of elemental sulfur and gaseous ammonia upon ketones, LXXVIII: Action of sulfur and amines on acetophenone, IX)

8-Alkylamino-8-aryl-1,2,3,4,5,6-hexathiocan-7-thiones (1a toh) are obtained mostly in good yields by the concomitant action of primary aliphatic amines and sulfur upon methyl aryl ketones in methanol at room temperature. Reaction of 1,4-diacetyl benzene and sulfur with n-propylamine or n-butylamine respectively leads to phenylene-1,4-dihexathiocane derivatives (3 a, b).Besides 8-(3-N,N-diethylaminopropylamino)-8-phenyl-1,2,3,4,5,6-hexathiocan-7-thione (1 e), which is obtained by reaction of acetophenone with 3-N,N-diethylaminopropylamine and sulfur, a product with the formula C₁₅H₂₂N₂S₂ (2) is isolated in 51% yield, to which the structure (3-N,N-diethylaminopropylimino)phenyl dithioglyoxylic acid is assigned. By treatment of1 e with aqueous sodium sulfite solution2 is obtained, which can be transformed back into1 e by reaction with sulfur.

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77. Mitt.:F. Asinger, A. Saus, H. Offermanns undP. Scherberich, Ann. Chem.753, 151 (1971).

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8. Mitt.:F. Asinger, A. Saus, H. Offermanns undF. Abo Dagga, Ann. Chem.723, 119 (1969).

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Teil der DiplomarbeitJ. Hartig, Techn. Hochschule Aachen, 1969.     

Accumulation and photocytotoxicity of hypericin and analogs in two- and three-dimensional cultures of transitional cell carcinoma cells

The aim of this study was to investigate the in vitro cellular accumulation, distribution and photocytotoxic effect of hypericin in two-dimensional (2-D) and three-dimensional (3-D) cultured RT-112 transitional cell carcinoma cells of the bladder. In addition, two iodinated derivatives of hypericin were incorporated to investigate whether these analogs, with their increased lipophilicity and heavy-atom effect, display a different biological behavior and optimized photodynamic effect. The results indicate that hypericin and mono-iodohypericin behave similarly in terms of cellular accumulation, spheroidal distribution and photocytotoxic effect. In contrast, di-iodohypericin concentrated to a higher extent in monolayers and spheroids, but the accumulation was restricted to the outermost part of the spheroid. An inverse correlation therefore seems to exist between the extent of cellular uptake under 2-D conditions and the penetration of the compounds in multicellular systems. Moreover, a less pronounced photocytotoxic effect was observed for di-iodohypericin in both 2-D and 3-D cell culture systems. It can be concluded that iodinated derivatives of hypericin do not show an increased cytotoxic effect upon irradiation in either monolayers or spheroids. Moreover, this study shows that when new photosensitizers are preclinically developed, the use of 3-D cell aggregates is critical for a correct evaluation of their efficacy.     

Cytotoxicity and Antiproliferative Effect of Hypericin and Derivatives after Photosensitization

The toxicity on three human tumor cell lines (A431, HeLa and MCF7) of five phenanthroperylenequinones (hypericin and derivatives) and two perylenequinones (cercosporin and calphostin C) was investigated after photosensitization (4 J/cm²). Furthermore, the antiproliferative effect on HeLa cells was studied for the phenanthroperylenequinones. Hypericin, 2,5-dibromohypericin, 2,5,9,12-tetrabromohypericin and perylenequinones displayed a potent cytotoxic and antiproliferative effect in the nanomolar range. Hypericin dicarboxylic acid exhibited no photoactivity. In general, the antiproliferative activity correlated well with the photocytotoxicity. However, the nonphotocytotoxic compound hexamethylhypericin showed potent antiproliferative activity in the nanomolar range, probably exerting its action by protein kinase C inhibition. Without light irradiation, no cytotoxic and antiproliferative effect was observed for any photocytotoxic phenanthroperylenequinone compound. Furthermore, confocal laser microscopy revealed that the subcellular localization in A431 cells was similar for the photoactive compounds; the photosensitizers were mainly concentrated in the perinuclear region, probably corresponding with the Golgi apparatus and the endoplasmic reticulum. In addition, the accumulation of the photosensitizers in HeLa cells was investigated. All compounds except hypericin dicarboxylic acid were found to concentrate to a large extent in the cells. The compound 2,5,9,12-tetrabromohypericin seemed intrinsically more effective than hypericin since the intracellular concentration of the bromoderivative was a magnitude of order lower than that of hypericin although both compounds showed similar photobiological activity.     

Ermittlung kinetischer Parameter aus der Kurvenform für Reaktionen unter Aufheizung

Form indexes for DTA or TG curves (S _T orS _x) must be treated separately. Only forS _x can clear relations to be developed for the order of reactionn. In the rational range ofn between 0.5 and 3.0 we found for linear, exponential and hyperbolic programmes these functions were found to be of the type $$S_x = an^{0,5} + b$$ Since a low dependence on frequency factork ₀ has been established, for a linear programme the simultaneous determination ofn andk ₀ may be performed.     

Lanczos cluster expansion for non-extensive systems

A cluster expansion of the Lanczos recursion for non-extensive systems is developed based on the plaquette expansion for extensive systems, in which an auxiliary scaling parameter, Ω, plays the role of volume and introduces extensivity into the problem. Connected Hamiltonian moments of the non-extensive system are computed and introduced into the plaquette expansion in the usual way with Ω. The extensive energy is calculated for increasing orders of the expansion in 1/Ω and the ground state and mass gap of the finite few body problem recovered in the limit Ω → ∞. This new non-perturbative method is applied to the case of N bosons interacting harmonically in one dimension and the ground state energy and mass gap in the vacuum sector are calculated exactly.     

Alignment and orientation effects in resonant charge exchange from laser excited Na*(3p)

A collisional alignment and orientation study with planar symmetry is described, determining the complete density matrix for resonant charge transfer from laser excited atoms. Results are reported for the Na⁺+Na*(3p) system over the collision energy rangeE _c.m.=50?100 eV. We communicate the optimal alignment angle γ and linear polarisationP _l ⁺ of the charge cloud as well as its relative height ρ₀₀ and the angular momentumL _⊥ ⁺ transferred in the collision as a function of the scattering angle. For preparation of the sodium 3p orbital in the scattering plane (positive reflection symmetry) we observe that at small reduced scattering angles (<20 eV°) the preparation of apσ at large internuclear distances contributes most to the scattering intensity whereas at larger reduced scattering angles (>60 eV°) apπ⁺ preparation is more important. In contrast, preparation of thepπ^? orbital (perpendicular to the scattering plane) is large at small and vanishes at larger scattering angles. We conclude that orbital following cannot be assumed in this resonant charge transfer process. The angular momentum transfer is observed to be small, indicating only little coherence in the process, but shows nevertheless an interesting behaviour as a function of scattering angle.