Detection of VX contamination in soil through solid-phase microextraction sampling and gas chromatography/mass spectrometry of the VX degradation product bis(diisopropylaminoethyl)disulfide

A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) sampling and analysis method was developed for bis(diisopropylaminoethyl)disulfide (a degradation product of the nerve agent VX) in soil. A 30-min sampling time with a polydimethylsiloxane-coated fiber and high temperature alkaline hydrolysis allowed detection with 1.0 microg of VX spiked per g of agricultural soil. The method was successfully used in the field with portable GC-MS instrumentation. This method is relatively rapid (less than 1 h), avoids the use of complex preparation steps, and enhances analyst safety through limited use of solvents and decontamination of the soil before sampling.     

Novel methyl helianthrones as photosensitizers: synthesis and biological evaluation

A combination of light, oxygen and a photosensitizer is used to induce death of cancer cells by photodynamic therapy. In this study, we have synthesized several new methyl helianthrone derivatives and compared their phototoxicity with that of hypericin. In contrast to hypericin, methyl helianthrones are soluble in aqueous solutions and have a broad range of light absorbance, which allows the use of polychromatic light. Structural modifications of methyl helianthrone demonstrated that substitution of hydrogen atoms of methyl helianthrone at Positions 2 and 5 with Br atoms or methylation of its phenolic hydroxyls, significantly increases the corresponding singlet oxygen quantum yield and their phototoxicity toward alphaT3-1, M2R and LNCaP cells. The phototoxicity of some of these compounds was similar to that of hypericin. Methyl helianthrones, like hypericin, accumulated mainly in the perinuclear region as evident by confocal microscopy. Irradiation of cells pretreated with methyl helianthrone derivatives generates intracellular reactive oxygen species and lipid free radicals, as shown by a fluorescentic probe and electron paramagnetic resonance methods, respectively. The phototoxicity of these methyl helianthrones as well as their ability to oxidize membrane lipids were significantly decreased on addition of specific Type-II inhibitors, suggesting the involvement of singlet oxygen as the main oxidant.     

Bestimmung geringer Uranmengen nach Konzentrierung durch Extraktion und Anionenaustausch in einem tri-n-octylphoshinoxidhaltigen Lösungsmittelsystem

Zusammenfassung Auf Grund systematischer Untersuchungen des Verhaltens von Uran in verschiedenen wäßrig-organischen, Tri-n-octylphosphinoxid (TOPO) enthaltenden Lösungsmittelsystemen gegenüber verschiedenen Anionenformen des stark basischen Anionenaustauschers Dowex 1, X 8 wurde eine Methode zur Abtrennung des Urans entwickelt. Bei diesem Verfahren wird das Uran aus einer ascorbin-säurehaltigen, 1-n salzsauren Lösung mit 0,1-m TOPO in Diäthyläther extrahiert und aus einem Gemisch aus 50 Vol. % Äther (0,1-m an TOPO), 45 Vol. % Methylglykol und 5 Vol. % 12-n Salzsäure am Ionenaustauscher (Chloridform) adsorbiert. Nach Elution mit 1-n Salzsäure wird das Uran entweder fluorimetrisch oder spektrophotometrisch nach der Thiocyanatmethode bestimmt. Mit diesem Anionenaustauschverfahren ist eine Abtrennung des Urans von allen, seine fluorimetrische oder spektrophotometrische Bestimmung störenden Ionen und auch vom TOPO selbst möglich. Besonders wurde auf die spektrophotometrische Bestimmung des Urans bei Anwesenheit großer Molybdänmengen eingegangen und eine Methode zur Abtrennung dieses Elementes entwickelt.

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Determination of small amounts of uranium after concentrating through extraction and anionic exchange in a solvent agent system containing tri-n-octylphosphine oxide

Summary A method has been developed for the separation of uranium that is based on systematic studies of the behavior of uranium in various water-organic solvent systems containing tri-n-octylphosphine oxide (TOPO) towards various anion forms of the strongly basic anion exchanger Dowex 1, X 8. In this procedure, the uranium is extracted from a 1N hydrochlorid acid solution containing ascorbic acid into diethyl ether and adsorbed from a mixture consisting of 50 vol.% ether (0.1N in TOPO), 45 vol.% methylglycol and5 vol.% 12N hydrochloric acid on the ion exchanger (chlorid form). Following elution with 1M hydrochloric acid, the uranium is determined either fluorimetrically or spectrophotometrically by the thiocyanate method. By means of this anion exchange procedure, it is possible above all to separate the uranium from all ions interfering with its fluorimetric or spectrophotometric determination and also from TOPO itself. In particular, consideration is given to the spectrophotometric determination of the uranium in the presence of larger amounts of molybdenum, and a method was worked out for the removal of this element.

     

In situ NMR observation of mono- and binuclear rhodium dihydride complexes using parahydrogen-induced polarization

Starting from the binuclear complex [RhCl(NBD)]2 (NBD = 2,5-norbornadiene) in the presence of the phosphines L = PMe3, PMe2Ph, PMePh2, PEt3, PEt2Ph, PEtPh2, or P(n-butyl)3, various mononuclear dihydrides of the type Rh(H)2CIL3, i.e., those of the homogeneous hydrogenation catalysts RhCIL3, have been obtained upon addition of parahydrogen, and their 1H NMR spectra have been investigated using parahydrogen-induced polarization (PHIP). Furthermore, the two binuclear complexes (H)(Cl)Rh(PMe3)2(mu-Cl)(mu-H)Rh(PMe3) and (H)(Cl)Rh(PMe2Ph)2(mu-Cl)(mu-H)Rh(PMe2Ph) have been detected and characterized by means of this in situ NMR method. Analogous complexes with trifluoroacetate instead of chloride, i.e., Rh(H)2(CF3COO)L3, have been generated in situ starting from Rh(NBD)(acac) in the presence of trifluoroacetic acid in combination with the phosphines L = PPh3, PEt2Ph, PEt3, and P(n-butyl)3, and their 1H NMR parameters have been determined.     

Flexible sorption and transformation behavior in a microporous metal-organic framework

Crystals of the metal-organic framework material Ni(2)(4,4'-bipyridine)(3)(NO(3))(4) (A) have been grown by reaction of Ni(NO(3))(2).6H(2)O and 4,4'-bipyridine in methanol solution. Single-crystal X-ray diffraction experiments show that the ladder structure of the framework is maintained after desolvation of the material, resulting in the production of a porous solid stable to 215(4) degrees C. Powder X-ray diffraction has been employed to confirm the bulk purity and temperature stability of this material. The crystal structure indicates that the pore window has an area of 12.3 A(2). However, sorption experiments show these windows will admit toluene, which has a minimum cross-sectional area of 26.6 A(2), with no significant change in the structure. Monte Carlo docking calculations show that toluene can be accommodated within the large pores of the structure. Exposure of the related microporous material Ni(2)(4,4'-bipyridine)(3)(NO(3))(4).2C(2)H(5)OH (B) to methanol vapor causes a guest-driven solid-state transformation to A which is observed using powder X-ray diffraction. This structural rearrangement proceeds directly from crystalline B to crystalline A and is complete in less than 1 day. Mechanisms for the transformation are proposed which require breaking of at least one in six of the covalent bonds that confer rigidity on the framework.     

Photometrische Bestimmung von Antimon in Eisen und Stahl

Zusammenfassung Zur Bestimmung von 2,5–100 ppm Sb in Eisen, unlegierten und niedrig legierten Stählen sowie in Automatenstählen wird das Antimon zuerst in 2 Stufen vorisoliert mit Hilfe der Spurenfällung mit Mangan(IV)-oxidhydrat als Spurenfänger und anschließender Jodidextraktion. Nach der Rückextraktion erfolgt die photometrische Bestimmung mit Methylfluoron in der wäßrigen Phase. Der relative Fehler beträgt ±5%, der Zeitbedarf für eine Einzelbestimmung 1,5 h.Herrn H. Sifirin danke ich für die sorgfältige Durchführung der Versuche.     

Photometrische Bestimmung von Antimon mit Methylfluoron

Zusammenfassung Es wird eine Arbeitsvorschrift zur photometrischen Bestimmung kleiner Mengen Antimon mit Methylfluoron beschrieben. Die günstigsten Arbeitsbedingungen und die Störung durch Fremdionen werden untersucht. Das Extinktionsmaximum liegt bei 530 nm. Die photometrische Bestimmung wird bei 495 nm durchgeführt. Das Beersche Gesetz ist im Bereich von 0,2– 4 g Sb/ml erfüllt, die Bestimmungsgrenze liegt bei 0,21 g Sb/ml · cm. Der Zeitbedarf einer Einzelbestimmung beträgt 15–20 min.Für die sorgfältige Durchführung der zahlreichen Versuche sprechen wir Herrn H. Siffrin unseren Dank aus.     

Restricted rotation about partial C,N double bonds

The restricted rotation about the partial C,N double bond in 2-chloro-6-NR₂-pyran-4-ones is discussed in the light of NMR spectroscopic data and theoretical calculations.Ab initio calculations at the HF/6-31G^* level were carried out using a continuum model to take solvent effects into account. The delocalization of-electron density [described by natural bond orbital analysis (NBO)] was applied to determine the degree of conjugation in the ground state (GS) and in the transition state (TS) for the restricted rotation of the compounds studied. The reason for the different barriers to rotation of the NR₂ substituents (pyrrolidino > dimethylamino > morpholidino > piperidino) at the 2-chloro-pyran-4-one ring appears to be the different steric hindrance of the NR₂ substituents in the GS for the restricted rotation.