Green's function calculation of through‐bond electronic coupling in donor–bridge–acceptor model systems II: Importance factors applied to atomic sites

Importance factors, associated with the Green's function formalism, are introduced. They are applied for the determination of the relative atomic site contribution to the electronic interaction propagation in a molecular system. The calculation is performed at the Hartree–Fock (self‐consistent) level, using ab initio STO‐3G, 4‐31G, and D95 basis sets. The results are compared with those obtained from the charge densities of the appropriate molecular orbitals at the ab initio STO‐3G level. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Extraction and preconcentration of polychlorinated dibenzo-p-dioxins using the cloud-point methodology: Application to their determination in water samples by high-performance liquid chromatography

A new analytical method based on the cloud-point extraction (CPE) methodology combined with high-performance liquid chromatography is used in this study for the extraction and quantification of polychlorinated dibenzo-p-dioxins. These compounds are extracted by using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE) from different aqueous systems: fresh, brackish and sea waters. After the cloud-point extraction, which also allowed a preconcentration of the PCDDs being studied, the samples were analysed using a HPLC–UV system under the optimum chromatographic conditions. The proposed method showed very satisfactory recovery percentages for the PCDDs under study and standard deviation values lower than 2%.

The results obtained were finally compared with those found using the traditional liquid–liquid extraction method.     

Simultaneous metal adsorption on tannin resins

Vegetable tannin sorbent is evaluated as ion exchange resin using a multitracer study on the adsorption behavior of various elements. Lisiloma latisiliqua L. tannins, polycondensated into spherical pellets were chosen as sorbent resin material. Sorption evaluation of Ce, Cu(II), U(VI), Eu, Fe(III), Th, Nd as representatives of different classes of metal ions were done at different pH values. The distribution ratio of the studied elements was calculated from laboratory experiments. Tannic ion exchange material shows excellent ability for actinides and rare earth elements adsorption from waters. Using radiotracers, the number of catechins subunits involve in each tannin-metal complex was determined.     

Photoaddition of benzophenone to azaindole,synthesis of the oxetane of 7-azaindole

7-Azaindole did not react with benzophenone on irradiation. However, irradiation of benzophenone in the presence of 1-acetyl-7-azaindole produced an oxetane by cycloaddition of the ketone to the 7-azaindole 2,3-double bond. The nmr and the mass spectra of the oxetane have also been studied in some detail.     

Finite-size effects on the phase transition in a four- and six-fermion interaction model

We consider four- and six-fermion interacting models at finite temperature and density. We construct the corresponding free energies and investigate the appearance of first- and second-order phase transitions. Finite-size effects on the phase structure are investigated using methods of quantum field theory on toroidal topologies.     

New approach for the clinical monitoring of 25‐hydroxyvitamin D3 and 25‐hydroxyvitamin D2 by ultra high performance liquid chromatography with MS/MS based on the standard reference material 972

Biomarkers, 25‐hydroxyvitamin D₃ and 25‐hydroxyvitamin D₂, are important indicators of the vitamin D general status and are monitored in several pathophysiological disorders, such as osteoporosis, diabetes, heart disease, etc. A novel ultra‐HPLC with MS/MS methodology for the analysis of 25‐hydroxyvitamin D derivatives coupled with a very simple and highly rapid sample preparation step was developed. Analytical parameters obtained showed linearity (R²) above 0.999 for both vitamins with accuracies between 95.8 and 102%. The LODs were as low as 0.22 and 0.67 nmol/L for 25‐hydroxyvitamin D₃ and 25‐hydroxyvitamin D₂, respectively. Intra‐assay precision (%RSD) was lower than 4.5%, and inter‐assay precision (%RSD) was lower than 6.5%. The feasibility of the developed methodology to be applied in clinical routine analysis has been proved by its application in blood samples from non‐agenarian patients, patients with familial hypercholesterolemia and patients suffering from age‐related macular degeneration.     

Herbal medicine physical quality evaluation by thermal analysis using adapted Ozawa method

Journal of Thermal Analysis and Calorimetry - The aim of this study was to evaluate the physical quality of Tabebuia caraiba (Mart.) Bur. powder, separately in three batches of different particle...     

A New Extraction and Purification Methodology of Bowman-Birk Inhibitors from Seeds and Germinated Seeds of Macrotyloma axillare

The Macrotyloma axillare Bowman-Birk inhibitors from seeds and germinated seeds (120 h) were purified by an alternative methodology and revealed the presence of different contents of inhibitors for each treatment. Mass analyses of inhibitors, from seeds and germinated seeds, showed masses of about 7 and 8 kDa. The 120 h-germinated seed fractions presented higher activity isoforms than seeds without treatment.

     

Determination of 5‐fluorocytosine, 5‐fluorouracil,and 5‐fluorouridine in hospital wastewater by liquid chromatography–mass spectrometry

Chemotherapeutics are pharmaceutical compounds the occurrence of which in the environment is of growing concern because of the increase in treatments against cancer diseases. They can reach the aquatic ecosystems after passing through wastewater treatment plants without complete removal. One of the most frequently used chemotherapeutics is 5‐fluorouracil which exhibits a strong cytostatic effect. In this paper, an analytical methodology was developed, validated, and applied to determine 5‐fluorouracil, its precursor, 5‐fluorocytosine, and its major active metabolite, 5‐fluorouridine, in hospital wastewater samples. Due to the expected low concentrations after dilution and interferences present in such a complex matrix, a very selective and sensitive detection method is required. Moreover, an extraction method must be implemented prior to the determination in order to purify the sample extract and preconcentrate the target analytes at micrograms per liter concentration levels. Solid‐phase extraction followed by liquid chromatography with tandem mass spectrometry was the combination of choice and all included parameters were studied. Under optimized conditions for wastewater samples analysis, recoveries from 63 to 108% were obtained, while intraday and interday relative standard deviations never exceeded 20 and 25%, respectively. Limits of detection between 61 and 620 ng/L were achieved. Finally, the optimized method was applied to samples from hospital wastewater effluents.