Search

A coastal marine sulfide-oxidizing autotrophic bacterium produces hydrophilic filamentous sulfur as a novel metabolic end product. Phylogenetic analysis placed the organism in the genus Arcobacter in the epsilon subdivision of the Proteobacteria . This motile vibrioid organism can be considered difficult to grow, preferring to grow under microaerophilic conditions in flowing systems in which a sulfide-oxygen gradient has been established. Purified cell cultures were maintained by using this approach. Essentially all 4′,6-diamidino-2-phenylindole dihydrochloride-stained cells in a flowing reactor system hybridized with Arcobacter -specific probes as well as with a probe specific for the sequence obtained from reactor-grown cells. The proposed provisional name for the coastal isolate is “ Candidatus Arcobacter sulfidicus.” For cells cultured in a flowing reactor system, the sulfide optimum was higher than and the CO 2 fixation activity was as high as or higher than those reported for other sulfur oxidizers, such as Thiomicrospira spp. Cells associated with filamentous sulfur material demonstrated nitrogen fixation capability. No ribulose 1,5-bisphosphate carboxylase/oxygenase could be detected on the basis of radioisotopic activity or by Western blotting techniques, suggesting an alternative pathway of CO 2 fixation. The process of microbial filamentous sulfur formation has been documented in a number of marine environments where both sulfide and oxygen are available. Filamentous sulfur formation by “ Candidatus Arcobacter sulfidicus” or similar strains may be an ecologically important process, contributing significantly to primary production in such environments.

Through a detailed optimization process, response surfaces were obtained for micro-HPLC/SCD under various reversed-phase (methanol/water) elution conditions. Linear dynamic range, correlation coefficient, response factor, and limit of detection were found to vary with mobile-phase composition. The lowest sensitivity achieved was a detectivity of 600 fg of S/s at a mobile-phase composition of 40% methanol/60% water. Application of the HPLC/SCD interface to the separation of thiocarbamates extracted from apples is presented

The use of the ozone-based sulfur chemiluminescence detector (SCD) coupled with packed column supercritical fluid chromatography (SFC) was evaluated. Optimization studies performed include the quenching effect of the CO 2 mobile phase and organic species on the chemiluminescence species (SO 2 * ) and the necessary air and hydrogen flow rates to gain maximum SCD sensitivity. Detectivities of 2 pg S/s and 1 pg S/s (S/N=3) were obtained when capillary SFC (60-nL injection) and packed column conditions (500-nL injection) were employed, respectively

The effect of modifier on solid-phase trapping efficiency in off-line supercritical fluid extraction was studied. Two types of traps-solid surface (stainless steel) and sorbent (octadecyl silica)-were studied with pure carbon diocide and 1%, 2%, 4% and 8% methanol-modified carbon dioxide. The trapping efficiency of a polarity test mix consisting of N,N-dimethylanilline, acetophenone, naphthol, decanoic acid, and n-tetracosane was studied at trap temperatures ranging from 5 to 80 o C with each fluid. For low concentrations of methanol and the ODS sorbent, trap temperatures below 20 o C were necessary for volatile (bp

Recent avenues of research have improved our understanding of the chemistry of nitrocellulose. With this in mind, a brief review of the chemistry of nitrocellulose is presented. While not comprehensive in nature, this review does point out some of the underlying characteristics of nitrocellulose which are of interest to the propellant community.

Supercritical CHF3 and methanol-modified CHF3 were compared with supercritical CO2 and methanol-modified CO2 for extraction of sulfonamides from fortified chicken liver admixed with Hydromatrix. Results showed that solvating power and selectivity were higher for supercritical and methanol-modified CHF3 than for supercritical and methanol-modified CO2. Visual observation showed that chicken liver extract obtained with methanol-modified CHF3 was cleaner than that obtained with methanol-modified CO2. Fat precipitated in the solvent trap when CO2 was used as the extraction medium. Also, simple off-line collection of fortified chicken liver extract obtained with CO2 in a solid-phase extraction cartridge (packed with either C18 or alumina) followed by phosphate buffer-methanol (50 + 50) rinse yielded an extract that required no further cleanup for analysis.

A pharmaceutical agent has been quantified in a rat feed matrix wherein sample preparation was achieved by supercritical fluid extraction. Spiking levels ranged from 0.0335% to 1.12%. Pure carbon dioxide, solid phase trapping on stainless steel with acetonitrile and liquid chromatographic assay yielded recoveries greater than 90% with relative standard deviations less than 5% in all cases except for the lowest spiking level. In this case recovery was 89.6% with an RSD of 9.6.

The applicability of coupling gas (GC) and supercritical fluid chromatography (SFC) directly to supercritical fluid extraction (SFE) is made inherently easier by the nature of the chromatographic mobile phases employed. For on-line GC analysis, the presence of the supercritical fluid (SF) carbon dioxide in the SFE/chromatographic interface is not a problem since the GC mobile phase itself is a gas. After the analyte is trapped at the head of the column and the decompressed extraction fluid is purged, thermal desorption of the analyte is begun. In SFE-SFC, the same fluid that is used for extraction is likewise used for chromatography. Even though the fluid is decompressed and exists as a gas in the interface, where extracted analyte is focused, raising the pressure and the temperature of the chromatographic mobile phase converts it into a SF once again for SFC.

Sulfamethoxazole and trimethoprim have been extracted from a drug formulation, Septra Infusion, with pure supercritical carbon dioxide. Both direct extraction of the aqueous-based matrix and indirect extraction of the formulation immobilized onto Celite were studied. Exhaustive analytical extraction was achieved when active components were less than 1.0 mg. A number of co-extractants were found, but each was blind to the HPLC/UV assay.

Ni(L)2 complexes, where L equals 2-(trifluoroacetyl) heteroaromatic anion have been prepared and characterized. 2-(Trifluoroacetyl)-picolinato anion (TFAP) gives a Ni(L)2 complex that appears to be a dimeric 5-coordinate square pyramid. The complexes Ni(4MeTFAP)2 and Ni(5MeTFAP)2 are square planar complexes while Ni(6Me-TFAP)2 is tetrahedral due to steric interference. In non-donor solvents, the complexes Ni(TFAP)2, Ni(4MeTFAP)2 and Ni(5MeTFAP)2 exhibit properties that indicate a polymer/monomer equilibrium. Ni(L)2 complexes undergo a unique gas-solid dissociation reaction with H2O and NH3 to give coordinated NH2 − and OH−.

Doping polyimides with cobalt ion causes the room temperature direct current electrical resistivity to decrease relative to the polymer alone, the reduction being most pronounced for the air-side of the cobalt modified polyimides. At a constant electrical field, resistivity for the volume, air-side and glass-side modes decreases yet further with an increase in temperature as expected for semiconductors and insulators. X-ray photoelectron spectroscopy indicates the air-side of the cobalt modified polyimides is predominantly Co3O4. The bulk resistivity of the air-side and activation energy of conduction for this surface are comparable to high purity sintered Co3O4. Charging characteristics at room temperature indicate a substantial polymer matrix contribution to both the glass-side and volume mode measurements but a negligible contribution to the air-side electrical properties. Volume electrical resistivity for similar additive levels is reduced by increasing the molecular flexibility of the host polymer.

The development of a simultaneous on-line detector for metal species separated by effective molecular size is described. A new spray chamber to facilitate this analysis in relatively high-volatility organic solvents and to serve as the interface between a liquid chromatography (LC) and an inductively coupled plasma atomic emission spectrometer (ICP-AES) is evaluated. Detection limits in toluence are comparable to those found in aqueous static operation of ICP-AES. The requirements of computer-based data output and examples of the output developed are presented. The LC-ICP interface is demonstrated by size separation of three synthetic mixtures. Two of the mixtures are iron and silicon organometallic species with different ligands attached, while the third mixture consists of approximately 20 different metals in essentially the same ligand environment.

As part of a research program to decrease the electrical resistivity of polyimide films with ionic additives a variable temperature three probe electrical resistivity measurement system has been designed and constructed. Sample temperature, electrification time, atmosphere, and measurement mode are computer controlled. As a data interpretation aid, temperature cycled analysis can be routinely performed. Surface resistivities in the range 103–1015 ohm and volume resistivities in the range 105–1018 ohm-cm are theoretically measurable under well controlled experimental conditions from room temperature to 250°. The electrical resistivity measurement system is useful for the evaluation of polymer films or films in general. Application of the system for analysis of cobalt, lithium and tin ion-modified polyimide films and some experimental considerations are presented. Correlation of the electrical measurements with differential scanning calorimetry, thermomechanical analysis, and thermogravimetric analysis is demonstrated.

Organometallic and metalloorganic compounds have been separated by size exclusion chromatography using pyridine eluent. A directly interfaced inductively coupled plasma atomic emission spectrometer was used for detection of these metal-containing species. Problems relating to the use of pyridine in the chromatography of these species are discussed. Most problems appear to be related to non-carbon-bound metal systems. The application of this technique to solvent-refined coal fractions and process solvent is presented. Evidence of solvent selectivity for some of the organically bound metals in the solvent refined coal is given.

Amelioration de la conductivite superficielle d'un polyimide contenant du cobalt en surface par codopage (lithium)

Copper(II) complexes of a related series of potentially pentadentate ligands derived from substituted salicylaldehydes and 2,2′-(aminoethyl)-sulfide, 3,3′-bis(aminopropyl)sulfide, 3,3′-bis(aminopropyl)ether and diethylenetriamine have been prepared. Elemental analysis, mass, infrared and visible spectra and magnetic susceptibility measurements have been employed in order to characterize these new compounds. The materials appear to be monomeric in the solid state exhibiting no abnormal magnetic properties at room temperature. In comparison with the visible spectra of a series of known copper(II) complexes of tetradentate ligands, the structure of these complexes is postulated to be essentially square planar. However, the possibility of weak coordination by the middle donor in some of the pentadentate ligands can not be ruled out.

The successful interfacing and utilization of fused silica capability Gas chromatography(GC) columns with Fourier transform infrared spectrometry (FTIR) can introduce difficulties not usually encountered with lower efficiency (higher capacity) GC columns. Recognition of these difficulties, however, can lead to refinement of a GC-FTIR detection system which can analyze complete samples with low nanogram detection limits. Chromatography and spectrometric considerations include lightpipe temperature, choice of same introduction, column concentration dynamic range capability, infrared data acquisition rate and spectral S/N ratio. These parameters as they relate to capability GC-FTIR method development are discussed. GC-FTIR 'identification limits' for sixteen model compounds which represent both polar and non-polar functionalities have been established employing optimized chromatographic-spectrometric parameters for complex mixture analysis.