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Sample Composition (sample + composition)
Selected AbstractsSPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: Comparison of direct injection to SPE-MEKCELECTROPHORESIS, Issue 21 2008Rade Injac Abstract A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco® LC-8, LC-18, LC-SCX, and LC-WCX, as well as StrataÔ-X and X-C). DOX was determined on a 56,cm (effective length 50,cm)×50,,m id fused-silica capillary. The BGE was 20,mM borate buffer, pH 9.3, containing 80,mM SDS and 7.5%,v/v of methanol (30,s×50,mbar), and the temperature and voltage were 25°C and 30,kV, respectively. The analytical wavelength was set at 210,nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1,,g/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80,mM of SDS, 10%,v/v of methanol and 40,mM borate buffer (pH 9.3; 30,s×50,mbar; 25°C; 30,kV; 350,nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition. [source] Micro freef-low IEF enhanced by active cooling and functionalized gelsELECTROPHORESIS, Issue 24 2006Jacob W. Albrecht Abstract Rapid free-flow IEF is achieved in a microfluidic device by separating the electrodes from the focusing region with porous buffer regions. Moving the electrodes outside enables the use of large electric fields without the detrimental effects of bubble formation in the active region. The anode and cathode porous buffer regions, which are formed by acrylamide functionalized with immobilized pH groups, allow ion transport while providing buffering capacity. Thermoelectric cooling mitigates the effects of Joule heating on sample focusing at high field strengths (,500,V/cm). This localized cooling was observed to increase device performance. Rapid focusing of low-molecular-weight pI markers and Protein G,mouse IgG complexes demonstrate the versatility of the technique. Simulations provide insight into and predict device performance based on a well-defined sample composition. [source] Bauxite manufacturing residues from Gardanne (France) and Portovesme (Italy) exert different patterns of pollution and toxicity to sea urchin embryosENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2002Giovanni Pagano Abstract This study was designed to investigate the composition and toxicity of solid residues from bauxite manufacturing plants. Soil and dust samples were collected in the proximity of two bauxite plants (Gardanne, France, and Portovesme, Italy). Samples were analyzed for their content of some selected inorganic contaminants by means of inductively coupled plasma optical emission spectroscopy (ICP-OES) either following acid digestion procedures or by seawater release of soluble components. Toxicity was tested by sea urchin bioassays to evaluate a set of toxicity endpoints including acute embryotoxicity, developmental defects, changes in sperm fertilization success, transmissible damage from sperm to the offspring, and cytogenetic abnormalities. Inorganic analysis showed two distinct sets of inorganic contaminants in Gardanne versus Portovesme, including Al, Cr, Cu, Fe, Mn, Pb, Ti, and Zn; sample composition (seawater-soluble cotaminants) and toxicity showed a noteworthy association. The most severe toxicity to embryogenesis and to sperm fertilization success was exerted by some Portovesme samples (0.03,0.5% w/v), with a significant association between toxicity and dose-related seawater release of Zn, Pb, and Mn. Seawater extraction of a toxic dust sample (G20) from the Gardanne factory showed increasing seawater release of Al, Fe, and Mn; the G20 sample, at the level of 0.5%, affected both developing sea urchin embryos and sperm (offspring quality). Soil samples around the Gardanne factory showed the highest frequency of toxic soil sites eastward from the factory. The present data point to solid deposition from bauxite plants as a potential subject of environmental health concern. The results suggest that extraction methods for evaluating the toxicity of complex mixtures should be based on the environmental availability of mixture components. The differences in sample toxicity among the tested sites, however, suggest possible site-to-site variability in geochemical and/or technological parameters. [source] Quantitative trace element imaging using PIXE and the nuclear microprobeINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2000C. G. Ryan Abstract The X-ray spectra of pure elements, excited using MeV energy beam of protons from the nuclear microprobe, have known spectra signatures. This makes X-ray spectra for more complex mixtures amenable to decomposition into contributions from the component elements. By devising this procedure as a matrix operation that transforms directly from spectrum vector to elemental concentration vector, the decomposition can be performed very efficiently enabling the real-time projection of the component element signals. In the case of a raster-scanned beam, with data that contain position information for each X-ray event, this approach enables the real-time projection of component element spatial distribution images. This paper describes the matrix transform approach called dynamic analysis (DA), which enables on-line real-time imaging of major and trace elements using proton-induced X-ray emission (PIXE). The method also provides off-line iterative yield corrections to these images to compensate for changing sample composition across an image area. The resulting images are quantitative in two respects: (1) they resolve the pure element components and strongly reject interferences from other elements and (2) they can be directly interrogated for sample composition at each pixel, over areas, or along lines across the image area, with accuracy comparable to microanalytical point analysis methods. The paper describes the DA method, presents tests, and discusses its application to quantitative major and trace element imaging in geology. © 2001 John Wiley & Sons, Inc. Int J Imaging Syst Technol 11, 219,230, 2000 [source] Direct exposure electron ionization mass spectrometry and gas chromatography/mass spectrometry techniques to study organic coatings on archaeological amphoraeJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2005Maria Perla Colombini Abstract Two different analytical approaches, direct exposure electron ionization mass spectrometry (DE-MS) and gas chromatography/mass spectrometry (GC/MS), were compared in a study of archaeological resinous materials. DE-MS was found to be an efficient fingerprinting tool for the fast screening of organic archaeological samples and for providing information on the major components. GC/MS appeared to be more efficient in unravelling the sample composition at a molecular level, despite the long analysis time and the need for a wet chemical pretreatment. Both procedures were applied to characterize the organic material present as coatings in Roman and Egyptian amphorae. DE-MS successfully identified abietanic compounds, hence a diterpenic resinous material could be identified and its degree of oxidation assessed. GC/MS enabled us to identify dehydroabietic acid, 7-oxodehydroabietic acid, 15-hydroxy-7-oxodehydroabietic acid, 15-hydroxydehydroabietic acid, retene, tetrahydroretene, norabietatriene, norabietatetraene and methyl dehydroabietate. These oxidized and aromatized abietanes provided evidence that the amphorae examined were waterproofed with a pitch produced from resinous wood of plants from the Pinaceae family. The chemometric evaluation of the GC/MS data highlighted significant chemical differences between the pitches found in the two archaeological sites, basically related to differences in the production techniques of the materials and in their degradation pathways. Copyright © 2005 John Wiley & Sons, Ltd. [source] What determines the value of life? a meta-analysisJOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 2 2002Janusz R. Mrozek A large literature has developed in which labor market contracts are used to estimate the value of a statistical life (VSL). Reported estimates of the VSL vary substantially, from less than $100,000 to more than $25 million. This research uses meta-analysis to quantitatively assess the VSL literature. Results from existing studies are pooled to identify the systematic relationships between VSL estimates and each study's particular features, such as the sample composition and research methods. This meta-analysis suggests that a VSL range of approximately $1.5 million to $2.5 million (in 1998 dollars) is what can be reasonably inferred from past labor-market studies when "best practice" assumptions are invoked. This range is considerably below many previous qualitative reviews of this literature. © 2002 by the Association for Public Policy Analysis and Management. [source] The interdependence of wavelength, redundancy and dose in sulfur SAD experimentsACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2008Michele Cianci In the last decade, the popularity of sulfur SAD anomalous dispersion experiments has spread rapidly among synchrotron users as a quick and streamlined way of solving the phase problem in macromolecular crystallography. On beamline 10 at SRS (Daresbury Laboratory, UK), a versatile design has allowed test data sets to be collected at six wavelengths between 0.979 and 2.290,Å in order to evaluate the importance and the interdependence of experimental variables such as the Bijvoet ratio, wavelength, resolution limit, data redundancy and absorbed X-ray dose in the sample per data set. All the samples used in the experiments were high-quality hen egg-white lysozyme crystals. X-radiation damage was found to affect disulfide bridges after the crystals had been given a total dose of 0.20 × 107,Gy. However, with such a total dose, it was still possible in all cases to find a strategy to collect data sets to determine the sulfur substructure and produce good-quality phases by choosing an optimum combination of wavelength, exposure time and redundancy. A ,|,ano|/,(,ano), greater than 1.5 for all resolution shells was a necessary requirement for successful sulfur SAD substructure location. Provided this is achieved, it seems possible to find an optimum compromise between wavelength, redundancy and dose to provide phasing information. The choice of the wavelength should then follow the sample composition and the diffracting properties of the crystal. For strongly diffracting crystals, wavelengths equal or shorter than 1.540,Å can be selected to capture the available data (provided the Bijvoet ratio is reasonable), while a longer wavelength, to gain as high a Bijvoet ratio as possible, must be used for more weakly diffracting crystals. These results suggest that an approach to a sulfur SAD experiment based on a complete description of the crystal system and the instrument for data collection is useful. [source] Geochemistry and petrography of basalt grindstones from the Karak Plateau, central JordanGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 1 2004Brandon G. Watts Seventeen basalt grindstone fragments from central Jordan's Karak Plateau were studied. Most of these artifacts are vesicular or amygdaloidal with calcite as the dominant mineral filling the voids. The major minerals are olivine (with iddingsite rims), plagioclase, clinopyroxene, magnetite, and apatite. Glass is present in some samples. One basalt fragment is quite different in appearance and composition and may have come from flows closer to the Dead Sea. Grindstone fragment compositions plot in the tephrite-basanite and basalt fields. A plot of the concentrations of niobium, zirconium, and yttrium reveal that the sample compositions plot in the "within-plate alkali basalt" and "within-plate tholeiite" fields. The acquisition of basalts for preparing such implements appears to have been random. Some may have been introduced through trade and migration. Archaeological and environmental studies on the Karak Plateau are urgently needed because Jordan's population growth and economic development are destroying many sites and their environmental contexts. © 2004 Wiley Periodicals, Inc. [source] A solid-state NMR study of phase structure, molecular interactions, and mobility in blends of citric acid and paracetamolJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2009S. Schantz Abstract Citric acid anhydrate (CAA) and paracetamol (PARA), prepared as crystalline physical mixtures and as amorphous blends, were studied using 13C solid-state cross polarization magic angle spinning (CPMAS) NMR. Amorphous blends showed significant line broadening from the conformational distribution as compared to the crystalline samples. Also, chemical shift variations were observed between crystalline and amorphous blends, which were attributed to differences in intermolecular interactions. Averaging of proton rotating-frame spin-lattice relaxation times (T1,) probed via different 13C sites in the amorphous blends confirmed molecular level mixing. For some, initially amorphous, sample compositions the onset of crystallization was evident directly from spectra and from the significantly longer T1, relaxations. Thus, crystallization caused phase separation with properties of the two phases resembling those of pure CAA and PARA, respectively. 13C spectra of amorphous 50/50 (w/w, %) CAA/PARA recorded from above the glass transition temperature broadened as the temperature increased to a maximum at T,,,Tg,+,33 K. This was the result of a dynamic interference between the line narrowing techniques being applied and the time scale of molecular reorientation in the miscible melt. The derived average correlation time was found to correspond well with previous results from melt rheology. We conclude that the underlying reasons for physical instability (i.e., crystallization from the miscible melt, including molecular interactions and dynamics) of this class of amorphous binary mixtures can be effectively evaluated using NMR spectroscopy. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1862,1870, 2009 [source] | |||||||||||||