The flame atomic absorption spectrometric determination of copper, zinc, calcium, magnesium and iron in fresh eggs using a microvolume injection technique is described. The capillary tube and glass impact bead were removed from the nebulizer and a polypropylene tube was installed in the inlet of the capillary tube of the nebulizer as the interface for microvolume injection. The injection volume was 10 mul and calibration was carried out using aqueous standards. Beer's law was obeyed in the concentration ranges of 0.1-1.5, 0.1-3.0, 0.2-4.0, 0.5-4.0 and 1.0-6.0 mg 1(-1) for Cu, Zn, Ca, Mg and Fe, respectively, and the detection limits were 0.016, 0.016, 0.035, 0.010 and 0.10 mg 1(-1), respectively. The reliability of the measurements was confirmed by analyzing a certified reference material, GBW 08551 Pork Liver. The precision was 2.6, 2.9, 3.0, 1.3 and 2.5% for Cu, Zn, Ca, Mg and Fe, respectively. The recovery with the standard additions method was good, ranging from 96.2 to 100.0%. 相似文献
Previous work has shown that glucose oxidase can be immobilized on platinum to give an electrode that responds potentiometrically to glucose over the clinically useful range of about 10-250 mg glucose/100 mL. The present studies were carried out with electrochemically pretreated platinum and with gold or porous graphite substituted for the platinum support. The presence of the enzyme gave a significantly enhanced potentiometric response over that obtained with the bare support for both the pretreated platinum and the porous graphite, but not with gold. However, with platinum the potentiometric response became more negative with increasing glucose concentration. With porous graphite, the potential changed in the positive direction as the glucose concentration was increased. Hysteresis was demonstrated for the platinum-enzyme electrode. Mass transfer measurements with a rotating ring-disc electrode (RRDE) showed measurable diffusional resistances to the transport of a model electroactive compound (potassium ferrocyanide) through a matrix of immobilized enzyme attached to the disc of the RRDE. These results are part of a larger study to define the source of the potentiometric response by examining the roles of the support and the mass transfer resistances through the immobilized enzyme matrix. 相似文献
Phase behavior of the extraction system, Cyanex 923–heptane/H2SO4–H2O has been studied. The third phase appeared at different aqueous H2SO4 concentration with varying initial Cyanex 923 concentration and temperature affects its appearance. Almost all of H2SO4 and H2O are extracted into the middle phase. The H2SO4 concentration in the third phase increases with the increasing aqueous acid concentration (CH2SO4,b) while the water content first increases and then reaches a constant value at CH2SO4,b=11.3 mol l−1. In the region of CH2SO4,b higher than 5.2 mol l−1, the composition of the middle phase is only related to the equilibrium concentration of H2SO4 in the bottom phase. H2SO4 and H2O are transferred into the middle phase mainly by their coordination with Cyanex 923 when CH2SO4,b is less than 11.3 mol l−1. When CH2SO4,b is higher than 11.3 mol l−1, excess H2SO4 is solubilized into the polar layer of the aggregates. In the region considered, the extracted complex changes from C923 · H2SO4 to C923 · H2SO4 · H2O and then to C923 · (H2SO4)2 · H2O. 相似文献
Thin PVA/cobalt acetate composite fibers were prepared by using sol-gel processing and electrospinning technique.After calcination of the above precursor fibers,Co3O4 nanofibers with a diameter of 50-150 nm could be successfully obtained.The fibers were characterized by SEM,FT-IR,WAXD,respectively. 相似文献
Side-chain engineering has been demonstrated as an effective method for fine-tuning the optical, electrical, and morphological properties of organic semiconductors toward efficient organic solar cells (OSCs). In this work, three isomeric non-fullerene small molecule acceptors (SMAs), named BTP-4F-T2C8, BTP-4F-T2EH and BTP-4F-T3EH, with linear and branched alkyl chains substituted on the α or β positions of thiophene as the side chains, were synthesized and systematically investigated. The results demonstrate that the size and substitution position of alkyl side chains can greatly affect the electronic properties, molecular packing as well as crystallinity of the SMAs. After blending with donor polymer D18-Cl, the prominent device performance of 18.25% was achieved by the BTP-4F-T3EH-based solar cells, which is higher than those of the BTP-4F-T2EH-based (17.41%) and BTP-4F-T2C8-based (15.92%) ones. The enhanced performance of the BTP-4F-T3EH-based devices is attributed to its stronger crystallinity, higher electron mobility, suppressed biomolecular recombination, and the appropriate intermolecular interaction with the donor polymer. This work reveals that the side chain isomerization strategy can be a practical way in tuning the molecular packing and blend morphology for improving the performance of organic solar cells.
The synthesis and anion binding properties of new ruthenium(II) and cobalt(II) phenanthroline complexes, containing two amide
subunits are described. Evidence for anion binding in dimethyl sulfoxide (DMSO) solution was obtained from u.v.–vis titration
experiments. Results indicated that these receptors showed strong affinity for F− and AcO−, and showed weak affinity for OH− and H2PO
4−
, and showed no affinity for Cl−, Br−, I−. These receptors interacted with various anions examined through hydrogen-bond formation. 相似文献
PtRu nanoparticles supported on Vulcan XC-72 carbon and carbon nanotubes were prepared by a microwave-assisted polyol process. The catalysts were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). The PtRu nanoparticles, which were uniformly dispersed on carbon, were 2-6 nm in diameter. All PtRu/C catalysts prepared as such displayed the characteristic diffraction peaks of a Pt face-centered cubic structure, excepting that the 2theta values were shifted to slightly higher values. XPS analysis revealed that the catalysts contained mostly Pt(0) and Ru(0), with traces of Pt(II), Pt(IV), and Ru(IV). The electro-oxidation of methanol was studied by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. It was found that both PtRu/C catalysts had high and more durable electrocatalytic activities for methanol oxidation than a comparative Pt/C catalyst. Preliminary data from a direct methanol fuel cell single stack test cell using the Vulcan-carbon-supported PtRu alloy as the anode catalyst showed high power density. 相似文献