Influence of pH*-value of methanolic electrolytes on electroosmotic flow in hydrophilic coated capillaries

The dependency of EOF on the H+-concentration and the related so called pH* value of methanolic electrolytes has been examined with poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and uncoated capillaries. These results were compared with the pH dependency of EOF of these capillaries using aqueous buffers. In uncoated capillaries the dependency of EOF on the pH(*)-value is very similar for aqueous and methanolic electrolytes. The EOF increases with increasing H+-concentration and pH-hysteresis is observed. In PVA coated capillaries the EOF is strongly reduced over wide pH* or pH ranges for both methanolic electrolytes and aqueous buffers. The EOF in PEG coated capillaries is surprisingly directed to the anode with methanolic electrolytes whereas a reduced cathodic EOF is observed in aqueous electrolytes. The anodic EOF of PEG-coated capillaries in methanolic electrolytes is independent of the pH*-value. The usefulness of PEG- and PVA-coated capillaries for adjusting the EOF in non-aqueous electrolytes for the analysis of isomeric organic acids was demonstrated.     

Synthese,IR-Spektrum und Kristallstruktur von PPh4[OsCl4(NO)(NSCl)]

Synthesis, I.R. Spectrum, and Crystal Structure of PPh₄[OsCl₄(NO)(NSCl)] Molten trithiazyl chloride reacts with OsCl₃(NO) to yield a product mixture consisting mainly of S₄N₃[OsCl₄(NO)(NSCl)] and S₄N₃Cl. Extraction of this mixture with a solution of tetraphenylphosphonium chloride in dichloromethane affords green (PPh₄)₂[OsCl₅(NO)] · 2 CH₂Cl₂ and the red title compound. PPh₄[OsCl₄(NO)(NSCl)] was characterized by its IR spectrum and an X-ray crystal structure analysis (3001 independent observed reflexions, R = 0.048). Crystal data: monoclinic, space group P2₁/c, Z = 4, a = 1716, b = 1054, c = 1588 pm, β = 96.25°. The compound consists of PPh₄⊕ cations and [OsCl₄(NO)(NSCl)]? anions in which the nitrosyl and the chlorothionitrene ligands have a cis arrangement. Due to positional disorder the NO and NSCl groups are superimposed statistically in the structure model.     

(Cycloheptatrienyl)hydridotungsten Complexes

Carbonyl(cycloheptatrienyl)iodo(phosphorus donor)tungstens ([WI(C₇H₇)(CO)L]; L = P(OMe)₃, 1a ; L = P[O(i-Pr)]₃, 1b ; L = PPh₃, 1c ) were prepared from dicarbonyl(cycloheptatrienyl)iodotungsten ([WI(C₇H₇)(CO)₂)] via a carbonyl-substitution process. Similarly, bromocarbonyl(phosphorus donor)(1,2,4,6-tetramethylcycloheptatrienyl)tungstens ([WBr(Me₄C₇H₃)(CO)L]; L = P(OMe)₃, 6a ; L = P[O(i-Pr)]₃, 6b ; L = PPh₃, 6c ) were obtained from the reaction of bromodicarbonyl(1,2,4,6)-tetramethylcycloheptatrienyl)tungsten ([WBr(Me₄C₇H₃)(CO)₂]; 4 ) with L. The reduction of 1a - c , 4 , and 6a , b with sodiumdihydridobis(2-methoxyethoxy)aluminium in toluene led to stable hydrido complexes [WH(R₄C₇H₃)(CO)L] (R = H, L = P(OMe)₃, 2a ; R = H, L = P[O(i-Pr)]₃, 2b ; R = H, L = PPh₃, 2c ; R = Me, L = P(OMe)₃, 7a ; R = Me, L = P[O(i-Pr)]₃, 7b ; R = Me, L = CO, 7d ). Complexes 2a and 7b were characterized by X-ray structure analyses.     

Determination of siloxanes,silicon, and platinum in tissues of women with silicone gel-filled implants

Silicone [poly(dimethylsiloxane)] gel used in breast implants has been known to migrate through intact silicone elastomer shells, resulting in the clinically observable "gel bleed" on the implant surface. Although silicon concentrations in capsular tissues of women with silicone prostheses have been measured with element-specific silicon analyses, no silicone-specific investigation of these tissues has been performed as yet.A combination of element-specific inductively coupled plasma high-resolution isotope dilution mass spectrometry (ICP-HR-IDMS) and species-specific gas chromatography coupled mass spectrometry (GC-MS) was used to analyze silicon, platinum, and siloxanes in prosthesis capsule, muscle, and fat tissues of women (n=3) who had silicone gel-filled breast implants and in breast tissue of non-augmented women (n=3) as controls.In all tissues of augmented women, siloxanes, in particular octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were identified. Depending on the siloxane species and type of tissue analyzed, siloxane levels in the range of about 10-1,400 ng g(-1) were detected; total silicon was found in all tissue samples in the range of about 8,900-85,000 ng g(-1). Higher platinum levels ranging from 25-90 ng g(-1 )were detected in fibrin layer and fat tissue of two patients with prostheses. No siloxanes were detected in control breast tissue samples.This investigation of human tissues by a combination of element-specific and species-specific analytical techniques clearly demonstrates for the first time that platinum and siloxanes leak from prostheses and accumulate in their surrounding tissues.     

An Unprecedented Domino Double Allylsilane [3+2] Cycloaddition/Wagner–Meerwein Rearrangement/Friedel–Crafts Alkylation/Elimination Reaction Sequence Leading to a Novel Pentacyclic Ring System

A stereoselective synthesis of the disilyl derivatives 3 is achieved by the title reaction, an unprecedented Lewis acid promoted domino reaction, between the cross-conjugated dienone 1 and the allylsilanes 2 . The configurations of the five stereogenic centers of this novel ring system are established in the first step of the reaction sequence, the double [3+2] cycloaddition.     

α-Funktionelle 2-Methylphenylphosphane, 2-(HE?CH2)?C6H4?PH2 (E = O,NR, PH). II. Komplexbildungsverhalten mit den Metallcarbonylen des Cr,Mo, W

α-Functionalized 2-Methyl Phenylphosphines, 2-(HE? CH₂)? C₆H₄? PH₂ (E = O, NR, PH) II. Coordination Behaviour with Metal Carbonyles of Cr, Mo, W The preparation of different carbonyl substituted coordination compounds (M: Cr, Mo, W) of the phosphines 2-(HE? CH₂)C₆H₄? PH₂ (E = O, NPh, PH) is described. In one case, after deprotonation of a PH₂ group a phosphine/phosphide migration of a W(CO)₅ fragment is detected.     

A characterization of weighted (<Emphasis Type="Italic">LB</Emphasis>)-spaces of holomorphic functions having the dual density condition

We characterize when weighted (LB)-spaces of holomorphic functions have the dual density condition, when the weights are radial and grow logarithmically.     

Denuder sampling system for the determination of gaseous and particle-bound organic health hazardous substances

A novel denuder system for the determination of airborne hazardous organic substances is presented. A special wall coating technique allows to reuse the denuder after a regeneration procedure. The denuder system has been designed for workplace air monitoring and can be used in combination with filters and back-up adsorbents to distinguish between the gaseous and the particle-bound phase of a compound. The use of dynamically generated test gases has been enabled reliable determinations of uptake rates and adsorption capacities as well as desorption efficiencies at different conditions. The penetration of particulate matter through the denuder has been examined.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday